This PDF file contains the front matter associated with SPIE Proceedings Volume 8785, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

Hartmann and Shack-Hartmann, instead of measuring the wavefront deformations directly they measure the wavefront slopes, which are equivalent to the ray transverse aberrations. Numerous different integration methods had been described in the literature to obtain the wavefront deformations from these measurements. Basically, they can be classified in two different categories, i.e., model and zonal. In this work we briefly describe a modal method to integrate Hartmann, and Shack-Hartmann patterns. Using orthogonal wavefront slope aberration polynomials, instead of the commonly used Zernike polynomials for the wavefront deformations.

The study of diffusion in a crowded and complex environment, such as inside a cell or within a porous medium, is of fundamental importance for science and technology. Combining blinking holographic optical tweezers and sub-pixel video microscopy permits one to study Brownian motion in confined geometries. In this work, in particular, we have studied the Brownian motion of two colloidal particles interacting hydrodynamically with each other. The proximity between the two microspheres induces a space-dependence in the particles diffusion coefficient and, therefore, a spurious drift. We measure this drift and evaluate the magnitude of the spurious force associated with it. We present the optoelectronic tools employed in the experiment and we discuss the experimental results.

One of the major issues in the modeling of subwavelength optical materials resides in how to compute the effective properties of such media. An efficient technique must be able to describe appropriately the electromagnetic response of the overall structure. Within this context, this work is focused on the calculation of effective parameters of metallic silver nanowires embedded in alumina background. An algorithm based on modal propagation is considered in order to estimate the refractive index at the visible spectrum. The resonances obtained in the computing model are compared to the predictions of analytical Bruggeman and Maxell-Garnett theories and analyzed by regarding excitation of surface modes at the metal-dielectric interface.

Solar-pumped solid-state lasers are promising for renewable extreme-temperature material processing and space power applications. An efficient Fresnel lens solar laser pumping approach is proposed here. The incoming solar power is firstly collected and concentrated by four 800 mm x 800 mm square Fresnel lenses and redirected by four plane mirrors to a central focal spot of 12 mm FWHM diameter, attaining 443 W concentrated solar power. Secondly for further concentration, both a set of four aspherical lenses and a fused silica sphere are positioned in the focal zone. Both side-pumping and end-pumping are achieved simultaneously for a 7 mm diameter by 12 mm length Nd:YAG single-crystal rod mounted within the sphere. Since there is no strong pump radiation absorption within the central core zone of the rod, thermal lensing effect is also minimized with the proposed scheme. A 600 mm length plane-plane resonant cavity is used to extract 1064 nm laser emission efficiently. Optimum pumping parameters and solar laser output powers are found through ZEMAX non-sequential ray-tracing and LASCAD laser cavity analysis. By taking into account 16 % of spectrum overlap between the 1.0 % Nd:YAG absorption spectrum and the solar spectrum, 183 W absorbed solar power is assumed in ZEMAX numerical analysis. Considering a round trip loss of 1.32 % for the resonant cavity, 45.2 W laser power is numerically attained through LASCAD software, corresponding to 17.7 W/m² collection efficiency. The proposed pumping scheme presents an excellent compromise between the laser output power and its beam quality.

Optical or vision-based navigation is an enabling technology for satellite autonomous navigation associated to different navigation approaches such as cruising, fly-by, terrain relative navigation, landing, rendezvous and docking between spacecrafts, rigidity of multi-satellite constellations. Since 2001, in many different ESA projects, the author and his team (at INETI and currently at FCUL) have been associated to most of the developments of the optical components of autonomous navigation, in cooperation with space primes or GNC subsystems suppliers. A unique experience related to seemingly simple photonic concepts associated to computational vision, photonic noises, camera tradeoffs and system concepts has emerged, and deserves a synthesis especially because some of these concepts are being implemented in the ESA Proba 3 mission and ESA is currently updating the technology in view of forthcoming planetary missions to Jupiter, Jupiter moons and asteroids. It is important to note that the US have already flown several missions relying on autonomous navigation and that NASA experience is at least one decade old. System approaches, sources of difficulty, some tradeoffs in both (and between) hardware and software, critical interface issues between the imaging and GNC (Guidance, Navigation and Control) subsystems, image processing techniques, utilization of apriori or to be estimated information, uncertainties, simulation of the imaging chain and non-cooperative environments will be addressed synthetically for both passive (optical) and active (lidar) systems.

ESPRESSO is a fibre-fed, cross-dispersed, high-resolution, echelle spectrograph. Being the first purpose of ESPRESSO to develop a competitive and innovative high-resolution spectrograph to fully exploit the VLT (Very Large Telescope), and allow new science, it is important to develop the VLT array concept bearing in mind the need to obtain the highest stability, while preserving its best efficiency. This high-resolution ultra-stable spectrograph will be installed in the VLT at the Combined Coudé Laboratory (CCL), fed by four Coudé Trains, which brings the light from the Nasmyth platforms of the four VLT Unit Telescopes to the CCL. ESPRESSO will combine the efficiency of modern echelle spectrograph with extreme radial-velocity precision. It will achieve a gain of two magnitudes with respect to its predecessor HARPS, and the instrumental radial-velocity precision will be improved to reach cm/s level. Thanks to its ability of combining incoherently the light of the 4 UTs, ESPRESSO will offer new possibilities in various fields of astronomy. The Coudé Train is composed of a set of prisms and lenses to deliver a pupil and an image in the CCL, including an Atmospheric Dispersion Compensator. In this paper, we present the optical design of the Coudé Trains, the opto-mechanical concept, the required control, the main characteristics and expected performances.

We report on the design and installation of a spectrometer system for monitoring solar radiation in Cochabamba, Bolivia. Both the light intensity and the spectral distribution affect the power produced by a photovoltaic device. Local variations in the solar spectrum (especially compared to the AM1.5 standard) may have important implications for device optimization and energy yield estimation. The spectrometer system, based on an Ocean Optics USB4000 (300-900nm) spectrometer, was designed to increase functionality. Typically systems only record the global horizontal radiation. Our system moves a fiber-optic cable 0-90 degrees and takes measurements in 9 degree increments. Additionally, a shadow band allows measurement of the diffuse component of the radiation at each position. The electronic controls utilize an Arduino UNO microcontroller to synchronizes the movement of two PAP bipolar (stepper) motors with the activation of the spectrometer via an external trigger. The spectrometer was factory calibrated for wavelength and calibrated for absolute irradiance using a Sellarnet SL1-Cal light source. We present preliminary results from data taken March-June, 2013, and comment on implications for PV devices in Cochabamba.

We report on the observation of a Zeeman shift (order of 100 MHz) of the Doppler-broadened D₂ transition of both ⁸⁵Rb and ⁸⁷Rb isotopes via transmission through a 400 nm diameter optical nanofiber in the presence of a DC magnetic field. Linearly-polarized light propagating in the nanofiber is analyzed as a superposition of two orthogonally circularly polarized orientations, σ+ and σ-. In the absence of the magnetic field, the absorption of these polarizations by the atomic vapor, via the evanescent field at the waist of the nanofiber, is degenerate. When a weak magnetic field is applied parallel to the propagating light, this degeneracy is lifted and relative shifts in the resonance frequencies are detected. Typical linear shift rates of 1.6 MHz/G and -2.0 MHz/G were observed. We also demonstrate a dichroic atomic vapor laser lock line shape by monitoring the real-time subtraction of the two magnetically-shifted absorption spectra. This is particularly interesting for magneto-optical experiments as it could be directly implemented for diode laser frequencystabilization.

Optical parametric chirped pulse amplification (OPCPA) is currently one of the leading techniques for the generation of ultra-powerful laser pulses, from the multi-terawatt to the petawatt range, with extremely high peak intensities. A properly designed OPCPA setup is able to provide gain over bandwidths extending hundreds of nanometers in the visible and near-infrared, allowing the generation of high-quality, energetic, few-cycle pulses. In this paper we describe the design and performance of a compact laser amplifier that makes use of noncollinear, ultrabroadband amplification in the nonlinear crystal yttrium-calcium oxyborate (YCOB). The pump and the supercontinuum seed pulses are generated from a common diode-pumped amplifier, ensuring their optical synchronization. This laser will be used as a source of ultrashort (~20 fs), energetic (~20 mJ), tunable pulses in the near infrared.

A novel solar laser uniformly pumped by six Fresnel lenses is proposed here. The incident solar radiation is firstly collected and concentrated by six 0.8 m diameter Fresnel lenses and then reflected by other six plane mirrors to a central focal zone, where a laser head is mounted. About 2.5 kW solar power with 3.5 W/mm² peak solar flux can be achieved in the focal zone. The laser head is composed of a fused silica six-sphere type secondary concentrator that further compresses the concentrated solar power from the six Fresnel lenses-plane mirrors to a core-doped YAG Nd³⁺:YAG ceramic disk. Optimum pumping parameters and solar laser output powers are found through ZEMAX non-sequential ray-tracing and LASCAD laser cavity analysis, respectively. The laser resonant cavity is formed by a PR 1064 nm output coupler and a HR 1064 nm plane reflector. An 8 mm diameter central hole is drilled through the six-sphere type concentrator to allow the extraction of laser power from the disk. Since only 16 % of the useful solar power is absorbed by the Nd:YAG medium, for 950 W/m² of terrestrial solar irradiation, the effective solar pump power of 456 W is assumed in ray-tracing analysis. 72.2 W of multimode laser power is predicted for an 8 mm diameter gain medium embedded within a conical undoped YAG cladding, reaching the collection efficiency of 24.1 W/m². M² = 16.6 is numerically calculated, corresponding to the brightness figure of merit of 0.26 W. A near uniform absorbed pump profile is achieved.

The technology of liquid crystal panels (LCP) is very mature and can be applied in many different areas in which the modulation of an input light beam is needed. LCP can be used to modulate amplitude, phase or polarization state of the input beam, being the phase modulation the most important. For this reason parallel aligned LCP are the most recommended for most applications. In this paper we review a method for the characterization of these devices, especially when temporal fluctuations are present. Next we revise several applications in different fields: a) A point diffraction interferometer with phase shifting capabilities is demonstrated and applied to the recording of digital holograms that can focus, digitally, the different planes of a 3D object; b) Different techniques to obtain superresolution imaging beyond the diffraction limit of the aperture, or the geometrical limitation imposed by the pixilation of the CCD device are shown, and c) the construction of Stokes and Mueller polarimeters with different types of LCP are also shown.

Digital holographic microscopy (DHM) provides a non-destructive measurement technique based on calculation of optical path length changes of the sample under study. If the changes are caused by refractive index variations within a constant physical thickness, the technique results in the precise measurement of the refractive index . In this paper, DHM is utilized to map the refractive index over a wide surface of a T-shaped micro channel. The micro channel is filled up by a solution of two chemical reactant fluids. In some chemical reactions the refractive index of the resultant may be highly different from the refractive indices of the reactants. Using microinjection pumps methane and water as reactants are injected into the channel at the same flow rates. Changes in optical path ways are measured by live recording the digital holograms during the fluids interaction for all the field of view pixels. The holograms are recorded by a detector and post processed by a computer in order to reconstruct the phase profile changes though angular spectrum propagation method. The changes in the refractive indices that take place during the reaction process, are viewed by the detector and are calculated and mapped for the T channel and Y channel.

Since antiquity, human gait has been studied to understand human movement, the kind of gait, in some cases, can cause musculoskeletal disorders or other health problems; in addition, also from antiquity, anthropometry has been important for the design of human items such as workspaces, tools, garments, among others. Nowadays, thanks to the development of optics and electronics, more accurate studies of gait and anthropometry can be developed. This work will describe the most important parameters for gait analysis, anthropometry and the optical systems used.

To obtain a good compromise between collection efficiency and brightness figure of merit of solar-pumped lasers, a new side-pumping scheme is proposed. Firstly the solar radiations are collected and concentrated by six 700 mm diameter Fresnel lenses. The concentrated solar radiations are subsequently reflected by six plane folding mirrors with 95% reflectivity, into a common focal spot. This allows the concentration of 1740 W solar power with about 6.4 W/mm² peak solar flux. A secondary concentrator is composed of six aspheric fused silica lenses, positioned around a 40 mm radius fused silica sphere, compressing all the concentrated solar radiation from the six Fresnel lenses into an 8 mm diameter by 9 mm length Nd:YAG single-crystal rod. By positioning the spherical concentrator slightly above the aspherical lenses, a more uniform absorption profile is achieved. Mechanical support with a water cooling system ensures an efficient cooling to the laser medium. Optimal laser parameters are found through ZEMAX™ and LASCAD™ numerical analysis software. Only 16% of the solar power is absorbed by Nd:YAG medium. Solar laser power of 42.6 W is numerically calculated, reaching a collection efficiency of 18.5 W/m². For a 400 mm plane-concave resonance cavity with –5m radius of curvature, M² _x = M² _y = 22 beam quality factors are numerically predicted. A near uniform pump absorption profile can be achieved by increasing the number of Fresnel lens and folding mirrors.

Glucose is the main energy source for the human body. The concentration of blood glucose is regulated by several hormones including both antagonists: insulin and glucagon. The quantification of glucose in the blood is used for diagnosing metabolic disorders of carbohydrates, such as diabetes, idiopathic hypoglycemia and pancreatic diseases. Currently, the methodology used for this determination is the enzymatic colorimetric with spectrophotometric. This study aimed to validate the use of measurements of nonlinear optical properties of plasma glucose via the Z-Scan technique. For this we used samples of calibrator patterns that simulate commercial samples of patients (ELITech ©). Besides calibrators, serum glucose levels within acceptable reference values (normal control serum - Brazilian Society of Clinical Pathology and Laboratory Medicine) and also overestimated (pathological control serum - Brazilian Society of Clinical Pathology and Laboratory Medicine) were used in the methodology proposal. Calibrator dilutions were performed and determined by the Z-Scan technique for the preparation of calibration curve. In conclusion, Z-Scan method can be used to determinate glucose levels in biological samples with enzymatic colorimetric reaction and also to apply the same quality control parameters used in biochemistry clinical.

This article reports the construction of a portable, low-cost LIBS (Light Induced Breakdown Spectroscopy) system for use in the Bolivian mining industry for the qualitative and quantitative analysis of the composition of mineral samples. The device consists of a portable laser, a medium-resolution spectrometer and an optomechanical light collection system. The laser developed for the device is a YAG:Nd+++ with an estimated power output of 10 MW/cm2. Weighing approximately 3 kg and powered by lithium ion batteries, it is easily carried and can be used in remote locations. The spectrometer has a resolution of 0.3 nm allowing the detection fine spectral features, while its range of 80 nm is broad enough to simultaneously show many of the principal spectral lines of the element of interest. A monochromatic CCD camera was used as the detector of the spectrometer and was fitted with an external trigger to coordinate the camera frames with the firing of the laser. The light emitted by the plasma is collected with a photographic objective and is transmitted to the spectrometer via a fiber optics cable. A mechanical system was incorporated to make, both the laser beam and the receptor positionable. In the preliminary tests of the prototype, a LIBS spectrum of a Bolivian copper coin was obtained. Analysis showed that the spectral lines obtained coincide with those of a copper reference spectrum and demonstrate the capacity of the device to perform qualitative analysis of materials.

Spectroscopy diagnostic techniques have applications in such diverse areas as mechanical and aerospace engineering, physical chemistry, optics, food and pharmaceutical industries. However, the technological state-of-the-art spectrometers do not allow very fast processes to be evaluated or controlled. This ability is crucial in the optimization of industrial processes (welding, burning flames, spark ignition, pulsed radiolysis…) where more theoretical-experimental analysis should be performed. The INSCAN project aims to overcome this technological limitation, to satisfy needs in academia and industrial markets, by developing a compact spectrometer with focal lengths less than 200 mm, taking into account three important aspects: acquisition rate of approximately 10 kHz spectra, spectral resolution on the order of 0.1 nm and operating in the spectral range 200 nm to 700 nm. Initial work is described on the optical design of the device and several possible approaches to achieve the specifications are considered. To guide the first order design, we relate the optical linewidth, spectral bandwidth and imaging properties to component characteristics. The symmetrical Czerny-Turner optical mount was chosen for its flexibility and elaborated using ZEMAX. Predictions made based on the simulated system are compared with calibration and characterization measurements on an experimental test bench used to refine the model assumptions.

We present a new method of measure of the roughness based on the analysis of the texture of speckle pattern on the surface. Images of speckle pattern over the surface are captured by means of a simple configuration using a laser, beam expander, and a camera charge coupled device (CCD). Using the properties of the normalized covariance function that we obtained from the image of the speckle through the inverse Fourier transform, we relate the values of the normalized covariance function. We compare the results obtained with a confocal microscope and co-occurrence matrices method. This method can be considered as a noncontact surface profiling method that is easy to implement and can be used during the manufacturing process.

Phase distribution may be determined by measuring only the intensity distributions along the optical axis via the Transport of Intensity Equation (TIE). TIE has been a viable alternative to interferometry techniques for experimental conditions where those techniques perform poorly. These conditions are either because of the requirement one applies on the spatial and temporal coherence of the optical source or because of sensitivity and resolution issues. Optical testing is crucial in applications using manufactured optical elements. In this paper, we developed a method and experimental realizations capable to use both Shake-Hartman wavefront sensing (SHWS) and TIE method for testing transparent and reflective optical surfaces. The integration of TIE and SHWS has the advantage for obtaining high spatial resolution and wide dynamic range which cannot be obtained using only one of those methods. We showed that the retrieved phase profile and quantified surface variations of unknown samples from both methods are in very good agreement with each other.

We present an absolute distance measurement concept based on pulse frequency repetition (PRF) sweep with a mode-locked laser diode. This technique requires a Michelson interferometer, a mode-locked laser source and a cross-correlation detector. The role of the cross-correlator is to analyze the state of superposition of a pair of pulses, one travelling over the reference arm of the interferometer, the other, corresponding to the measuring arm, travelling from the apparatus to the target and reflected back. Using two distinct laser pulse repetition frequency and knowing the cross-correlation peak position at reference arm of the interferometer for each frequency, it’s possible to obtain the length of the measuring arm, i.e., a distance measuring. The main techniques for performing pulse correlation are based in 2nd order effects over second harmonic crystal (SHG) or a two-photon absorption (TPA) process in a semiconductor junction. Both SHG and TPA methods require reasonably high pulse energies to achieve fair signal to noise ratios. The use Degree of Polarization (DOP) technique for cross-correlation detection allows the use of optical powers as low as -60 dBm. Such high sensitivity can be very convenient for low energy pulse sources such is the case of high frequency mode-locked laser diodes. The DOP technique can however limit the maximum measurement range, constrained by the loss of coherence of the laser source for longer distances. In this paper we present the first results of this measurement concept, based in the DOP correlator, discussing the main limitations of this technique for long distance measurements.

In this work, we present a method to visualize the air flow of two circular micro-nozzles with different diameters. The supersonic flow in the nozzle was observed using the Z-schlieren technique and the shock wave patterns were clearly identified. The refraction index of the supersonic flow was obtained using an integration form of the refraction index gradient measured experimentally. We make the comparison between the results obtained for two different nozzle diameters.

This paper presents the development of an installation for proves for characterization by fluorescence of micrometer and nanometer particles supported on the trapping and manipulation by optical trapping technique (optical tweezers). The system features an laser operating at 480 nm, CCD camera for image acquisition, Thor Labs micrometric table X, Y, Z for the movement of the sample and the trap in the visual field. The design includes the use of intensity modulated optical trap, with the option of being used in pulsed, opening up possibilities for the use of resonant phenomena optomechanical type for particle capture.

Classical multilayer filters are optically homogeneous in each layer of the surface coatings. Diffraction gratings and photonic crystals used in the filters have micro- and nanoscale inhomogeneities. An optical filter consisting of sheet transparent substrate with thin-film grating layers on both surfaces is developed. Macroscopic gratings of submillimeter widths are formed by directionally transmissive strips, alternating with absorptive, reflective, or scattering strips. Their relative position on input and output surfaces provides angular selectivity of light transmission – part of the radiation that has passed through input gratings is blocked additionally by output gratings depending on incidence angle. Graphicanalytical calculation method determines the influence of optical and geometric parameters of alternating strips on angular characteristics of transmission. Characteristics are broken lines with areas of decreasing or increasing transmission, which practically linear for the angles up to approximately 60°, with further increase in the angles, the lines are curved more because of sinusoidal dependence under Snell's law. Results of graphic-analytical calculations are confirmed experimentally. Preset the desired dependence of transmission is adjusted considering reflection (Fresnel formulas) and absorption (Bouguer-Lambert law). The adjusted dependence is approximated to a broken line taking into account obtained regularities. Finally, all parameters of alternating strips of gratings are chosen. Thus at pre-known trajectory of light source relative to the filter pre-adapted angular selective regulation of its light transmission is provided. Architectural glazing to control the transmitted solar radiation without special redirecting devices and provide invisibility through window at predetermined angles is the most promising area of application.

In this work an image encryption-decryption system is developed using Gyrator transform (GT) and Jigsaw transform (JT). The encryption system uses two successive GTs and JTs, in order to convert a real image to a real noisy encrypted image. The decryption system is an inverse system with respect to the encryption system. The real image to be encrypted is preprocessed with the purpose of obtaining a real encrypted image, this real encrypted image has the same size as the original image to be encrypted and it is much more convenient for either its storage or transmission. The JT is applied to eliminate the random phase mask used in many encryption systems based on double random phase mask and to increase the security of the encryption-decryption system proposed in this work. Finally, in order to verify the performance of the encryption-decryption system, a digital algorithm was developed. There are four keys used in the encryption-decryption algorithm, which are constituted by the two GTs rotation angles and the two random permutations used in the JTs; all these keys have to be correct for a proper recovery of the original image in the decryption system.

A new method for double image encryption based on the fractional Hartley transform (FrHT) and the Arnold transform (AT) is proposed in this work. The encryption method encodes the first input image in amplitude and the second input image is encoded in phase, in order to define a complex image. This complex image is successively four times transformed using FrHT and AT, and the resulting complex image represents the encrypted image. The decryption method is the same method as the encryption method applied in the inverse sense. The AT is a process of image shearing and stitching in which pixels of the image are rearranged. This AT is used in the encryption method with the purpose of spreading the information content of the two input images onto the encrypted image and to increase the security of the encrypted image. The fractional orders of the FrHTs and the parameters of the ATs correspond to the keys of the encryption-decryption method. Only when all of those keys are correct in the decryption method, the two original images can be recovered. We present digital results that confirm our approach.

In this paper, we propose the design of a robotic system to semi-automatically align components in the Ronchi test; the robotic system will align the Ronchi tester with the surface being tested. In this work, we present the control system design of a rail system with two degrees of freedom, which allows semiautomatic alignment of the Ronchi tester with the surface in production. Informative visual markings (IVM) are used to achieve this [1]. The IVM help locate the system coordinates of the optical surface with respect to the basic system coordinates of the rail system. Quantification of the alignment is performed using the value of non-integer interference order, which is calculated to generate the simulated ronchigram which more closely resembles the experimental ronchigram [2].

On the basis of the second order irradiance-moments formalism some relations between the normalized weighted average of the Gouy phase shift and the spatial structure of partially coherent beams have been investigated.

We present the results of the amplitude diffraction pattern produced by two circular apertures. It was found that on the Fraunhofer plane there are is a diffraction pattern with an elliptical geometry with a Bessel-like spatial distribution modulated by Young fringes. The model was experimentally confirmed using circular apertures illuminated with a Helium-Neon laser and propagating to either the divergent Fresnel zone and the Fraunhofer plane using an achromatic cemented doublet as transforming lens.

This work seeks to determine the age of a fruit from observation of its dynamic speckle pattern. A mobile speckle pattern originates on the fruit's surface due to the interference of the wavefronts reflected from moving scatterers. For this work we analyzed two series of photographs of a strawberry speckle pattern, at different stages of ripening, acquired with a CMOS camera. The first day, we took ten photographs at an interval of one second. The same procedure was repeated the next day. From each series of images we extracted several statistical descriptors of pixel-to-pixel gray level variation during the observation time. By comparing these values from the first to the second day we noticed a diminution of the speckle activity. This decay demonstrated that after only one day the ripening process of the strawberry can be detected by dynamic speckle pattern analysis. For this study we employed a simple new algorithm to process the data obtained from the photographs. This algorithm allows defining a global mobility index that indicates the evolution of the fruit's ripening.

We experimentally investigate the synchronous response of two fiber-optic coupled optoelectronic circuit oscillators based on resonant tunneling diodes (RTDs). The fiber-optic synchronization link employs injection of a periodic oscillating optical modulated signal generated by a master RTD-laser diode (LD) oscillator to a slave RTD-photodetector (PD) oscillator. The synchronous regimes were evaluated as a function of frequency detuning and optical injection strength. The results show the slave RTD-PD oscillator follows the frequency and noise characteristics of the master RTD-LD oscillator resulting in two oscillators with similar phase noise characteristics exhibiting single side band phase noise levels below -100 dBc/Hz at 1 MHz offset from the carrier frequency. Optical synchronization of RTD-based optoelectronic circuit oscillators have many applications spanning from sensing, to microwave generation, and data transmission.

Nowadays, there is a demand for more efficient opto-mechanical mounts which allow for the implementation of robust optical arrays in a quick and simple fashion. That is to say, mounts are needed which facilitate alignment of the optical components in order to perform the desired movements of each component. Optical testing systems available in the market today are costly, heavy and sometimes require multiple kits depending on the dimensions of the optical components. In this paper, we present the design and analysis of a mechanical system with some interchangeable basic mounts which allow for the application of both Ronchi and Fizeau tests for the evaluation of concave reflective surfaces with a diameter of 2 to 10 cm. The mechanical system design is done using the methodology of product design process, while the analysis is performed using the commercial software SolidWorks.

A modulator fundamental part of Mach Zhender interferometer is studied. This interferometer has applications such as a sensor or spectral analyzer. The modulator was designed on a SOI substrate comprising a dual capacitor structure that allows the electro optical modulation through the overlap of the plasma dispersion effect (variations of the free carriers density due to electric field induced carrier depletion) with the guidewave mode that induce the change of the effective refractive index. The modulator is excited by a tension ramp between 0 and 2V yielding performance exceeding 7 GHz.

Vacuum thermal evaporation has, for some time now, been the principal method for the deposition of thin films, given, among other aspects, its simplicity, flexibility, and relatively low cost. Therefore, the development of models attempting to predict the deposition patterns of given thin film materials in different locations of a vacuum evaporation chamber are arguably important. With this in mind, we have designed one of such models for the thermal evaporation process of magnesium fluoride (MgF₂), a common material used in optical thin films, originating from a tungsten boat source. For this we took several deposition samples in glass slide substrates at different locations in the vacuum chamber, considering as independent variables the mean deposition rate, and the axial and vertical distances of the source to the substrate. After a careful analysis by matrix method from the spectral transmittance data of the samples, while providing as output data the spectral transmittance, as well as the physical thickness of the films, both as functions of the aforementioned variables, the virtual surface of the source was determined.

Photoassociation is a possible route for the formation of chemical bonds. In this process, the binding of colliding atoms can be induced by means of a laser field. Photoassociation has been studied in the ultracold regime and also with temperatures well above millikelvins in the thermal energy domain, which is a situation commonly encountered in the laboratory. A photoassociation mechanism can be envisioned based on the use of infrared pulses to drive a transition from free colliding atoms on the electronic ground state to form a molecule directly on that state. This work takes a step in this direction, investigating the laser-pulse-driven formation of heteronuclear diatomic molecules in a thermal gas of atoms including rotational effects. Based on the assumption of full system controllability, the maximum possible photoassociation yield is deduced. The photoassociation probability is calculated as a function of the laser parameters for different temperatures. Additionally, the photoassociation yield induced by subpicosecond pulses of a priori fixed shape is compared to the maximum possible yield.

This paper develops and implements, can experimental method to characterize the process of splice optical fibers by fusion for determine the quality thereof. The procedure utilizes the Bragg diffraction law, allowing spectrally decomposed emitted light in the fusion splicing process. The experimental mounting used a diffraction grating to refract light, a video camera that allows capturing the image sequences during the complete process of fusion splicing, later and with the aid of the computational tool MATLAB is performed all the segmentation process, filtering, correlation and analysis of images obtained.

This paper presents a simple method for manufacturing fiber tapered through elongation, by the combination of heating with a butane torch and controlled stretch. Reducing the diameter of the multimode fiber of 100 microns to 10 microns, the displacement of the fiber is performed through bipolar stepping motors with one driver L293B and one PIC16F628A microcontroller for controlling movement. The system allows control of the desired fiber diameter up to 10 microns; the results are seen in a microscope and a rule of separation 2.5μm micrometer to calculate the diameter of the fiber.

To measure the angular response of radiometers developed in the laboratory, an automated system was assembled and characterized. The main light source is a QTH lamp of 1000W and for UV radiometers a Hg(Xe) lamp of 500W. The light beam has a useful diameter of 40 mm, a half divergence of 10mrad and the spatial uniformity is better than 97%. Errors up to 5% at large angles were estimated for misalignments of 1° in the positioning of the radiometers . In this work details of the system and results of measurements obtained with radiometers developed in the laboratory and with commercial ones are presented.

Public and private lighting account for a relevant share of the overall electric power consumption worldwide. The pressing need of reducing the carbon dioxide emissions as well as of lowering the lumen•hour price tag has fostered the search for alternative lighting technologies to substitute for the incandescent and gas-discharge based lamps. The most successful approach to date, solid-state lighting, is already finding its way into the public lighting market, very often helped by substantial public investments and support. LED-based sources have distinct advantages: under controlled coditions their efficacy equals or surpasses that of conventional solutions, their small source size allows for an efficient collimation of the lightbeam (delivering the photons where they are actually needed and reducing lightspill on the surrounding areas), and they can be switched and/or dimmed on demand at very high rates, thus allowing for a taylored schedule of lighting. However, energy savings and carbon dioxide reduction are not the only crucial issues faced by present day lighting. A growing body of research has shown the significance of the spectral composition of light when it comes to assess the detrimental effects of artificial light-at-night (ALAN). The potential ALAN blueshift associated to the deployment of LED-based lighting systems has raised sensible concerns about its scientific, cultural, ecological and public health consequences, which can be further amplified if an increased light consumption is produced due to the rebound effect. This contribution addresses some of the challenges that these issues pose to the Optics and Photonics community.

We present an experimental method to characterize a liquid-crystal variable retarder (LCVR). In addition, experimental results using LCVR’s to measure the four Stokes parameters of a light beam simultaneously are presented. We use known waveplates (half-wave and quarter-wave) as devices to provide controlled polarization states to the Stokes polarimeter, and we use the measured Stokes parameters as functions of the orientation of the axes of the waveplates as an indication of the quality of the polarimeter. Also, we present results of simulations for comparison.

This paper shows the design and implementation of a fiber optic sensor for detecting and identifying wavelengths in the visible range. The system consists of a diffuse optical fiber, a conventional laser diode 650nm, 2.5mW of power, an ambient light sensor LX1972, a PIC 18F2550 and LCD screen for viewing. The principle used in the detection of the lambda is based on specular reflection and absorption. The optoelectronic device designed and built used the absorption and reflection properties of the material under study, having as active optical medium a bifurcated optical fiber, which is optically coupled to an ambient light sensor, which makes the conversion of light signals to electricas, procedure performed by a microcontroller, which acquires and processes the signal. To verify correct operation of the assembly were utilized the color cards of sewing thread and nail polish as samples for analysis. This optoelectronic device can be used in many applications such as quality control of industrial processes, classification of corks or bottle caps, color quality of textiles, sugar solutions, polymers and food among others.

Metallic structures made of ribbed iron bars (ADN-420) are of common use in sheds and supporting structures. Usually, trusses are constructed with many pieces of ribbed iron bars, combined together through a welding process. Although ribbed iron manufacturers do not recommend this type of structure it is still frequently used. The main weakness of these trusses is the welding point because ribbed iron is not a material suitable for welding. This work presents results obtained from an analysis of welding points between ribbed iron bars extracted from a collapsed truss, by means of conventional (optical) and digital holographic interferometry (HI and DHI, respectively). The experiments were divided in two different series of studies. The first series were performed by HI on metallographic samples while the second series were done by DHI on different welding points. These results were complemented by metallographic analysis made in an external laboratory. DHI indicated that the bars did not have important failures but evidenced defects in one of the welding points under analysis. This information together with metallographic results allowed inferring that the collapse was probably due to an error in the design of the structure, since the iron bars were out of standard compliance.

We report the recording of nearly 35% diffraction efficiency holograms of photorefractive nature in Bi₂TeO₅ crystals, using 633 nm wavelength laser beams. Holographic techniques showed that a slow and a fast holograms arise, the latter based on electrons and the former based on positively charged carriers. We also measured the quantum efficiency for photoelectron generation and the characteristic diffusion (L_D) and Debye (l_s) lengths of these holograms and verified that L_D and l_s are modified as the light intensity onto the crystal increases, in agreement with previously reported theoretical prediction and experimental results but on other photorefractive material.

A method to create homogenous polarized light based on non-quadrature amplitude modulation is proposed. This method consists in the addition of two fields out of phase different from mπ and in the variation of their amplitudes only for obtaining a resulting field modulated in both phase and amplitude. This principle is used to modulate the vertical component in both phase and amplitude, while the horizontal component is varied in amplitude only keeping constant its phase, thus any amplitude relation and phase difference between components can be created and therefore any polarization state could be obtained. A theoretical model will be shown, and it will be sustained with numerical simulations of several polarization examples.

A new method to create elliptically polarized light based on the quadrature amplitude modulation is proposed. This method begins from an unpolarized light and does not use any classical methods, as for instance those using polarizers and retarders or also by refraction, scattering, dichroism or birefringence effects. This method is based on the amplitude modulation of two optical waves in quadrature in order to modulate the field in amplitude and phase. With this idea, we show that any amplitude relation and relative phase difference between components can be created and therefore any polarization state can be carried out. A theoretical model will be shown, and it will be sustained with numerical simulations of several polarization examples

This paper reports a packaging and calibration procedure for surface mounting of fiber Bragg grating (FBG) sensors to measure strain in rocks. The packaging of FBG sensors is performed with glass fiber and polyester resin, and then subjected to tensile loads in order to obtain strength and deformability parameters, necessaries to assess the mechanical performance of the sensor packaging. For a specific package, an optimal curing condition has been found, showing good repeatability and adaptability for non-planar surfaces, such as occurs in rock engineering. The successfully packaged sensors and electrical strain gages were attached to standard rock specimens of gabbro. Longitudinal and transversal strains under compression loads were measured with both techniques, showing that response of FBG sensors is linear and reliable. An analytical model is used to characterize the influences of rock substrate and FBG packaging in strain transmission. As a result, we obtained a sensor packaging for non-planar and complex natural material under acceptable sensitivity suitable for very small strains as occurs in hard rocks.

Increment of the axial region of ablation in a micromachining process is demonstrated when a refractive lens (RL) is replaced by a diffractive lens (DL). The depth of focus of a DL and a RL with the same numerical aperture are compared. For ultrashort pulses, the broadband spectrum of the laser together with the chromatic aberrations associated to the DL made its ablation region greater than the one corresponding to a RL. We measure experimentally the tridimensional ablation region for both types of lenses with 100 fs and 30 fs pulses. This study is expected to be promising to alleviate the mechanical tolerances in femtosecond micromachining with diffractive optical elements (DOEs).

We demonstrate the utilization of Dammann lenses encoded onto a spatial light modulator (SLM) for triggering nonlinear effects. For continuous illumination Dammann lenses generate a multifocal pattern characterized by a set of N foci diffraction orders, all with the same intensity. We theoretically show that for pulses shorter than 100 femtosecond (fs) the effects of chromatic aberrations influence the uniformity of the generated pattern. Multifocal second harmonic generation (SHG) and on-axis multiple filamentation are produced and actively controlled in β-BaB₂O₄ (BBO) and fused silica samples, respectively, with an amplified Ti:Sapphire femtosecond laser (30 fs at FWHM). Our proposal allows us to dynamically control both the quantity of foci and the distance among them. The output diffraction pattern is in good agreement with theoretical calculations. The measured spectra at the rear face of the supercontinuum sample for different separation among foci are also provided. The potential of this technique is very promising in different fields of nonlinear optics or in applications of in-depth materials microprocessing.

Knowledge of propagation, transmission and reflection properties of space- and time-limited beams is relevant to the classical description of electromagnetic field modes in laser and other optoelectronic devices. For many reasons, Gaussian beams have been the most widely studied; for instance, they correspond to the fundamental mode in cylindrical or rectangular resonators, and they are often desirable at the output of amplifiers. To describe the behavior of beams with a Gaussian amplitude profile, the usual method consists of making an approximation in Maxwell equations, such that the solution of the approximate equations is a Gaussian beam. In this work we propose a different method to study Gaussian beams in active media, describing the beam by a continuous spectrum (spatial or temporal) of plane waves. We consider active media far from saturation, i.e. the gain is independent of the electric field amplitude. As a first step in the study of propagation, transmission and reflection of pulses through thin layers of active media, we analyze the properties of the transmitted beam in the case of a thin slab with gain between two isotropic transparent semi-infinite media, assuming normal incidence of a two-dimensional, space- or time-limited gaussian beam.

We report the qualitative testing of a spherical concave surface with deformation coefficients based on the null-screen principles. The design of cylindrical null screen with curved grid is described; its image, which is formed by reflection on the test surface, becomes an exact square grid if the surface is perfect. Any departure from this geometry is indicative of defects on the surface. In contrast to others tests, here the whole surface is tested at once. The surface under test is 140 mm in diameter and a radius of curvature of 97 mm. The surface is testing during the manufacturing process; departures from the design surface will be analyzed and discussed.

A recently developed numerical method is used to calculate the double-scattered Mueller matrices for scattering of vector-electromagnetic waves from rough surfaces. The method is based on a modified version of the Kirchhoff approximation and is valid for surfaces with vertical walls and for any surface material. Calculations are performed for the case of a single groove and a single rib on silicon and gold surfaces and results are compared to published experimental results. The calculated results of the 16 elements of the Mueller matrix as functions of the scatter angle show good qualitative agreement with the experimental results for the groove cases. Results for the rib cases show poorer agreement, possibly due to variations from the optimum parameters of the surface structure.

Tracking of wet foam ageing by means of dynamic laser speckle and an optical flow sensor is presented. Using a computer optical mouse, like an optical flow sensor, a strong negative correlation between the average speed of the cursor and the coarsening of bubble was found. We used microscopic images to demonstrate that decreasing of speed is related with increasing of bubble size. The proposed setup allows sensitive measures, is not very expensive and highly portable.

We describe the control of a piezoelectric device (PZT), mounted in an interferential microscope (IM) to introduce phase steps by mean of modifications light optical path, which is reflected from a sample surface. Both the piezoelectric control as the interferogram acquisitions from the interferometry system are made in a program designed in LabVIEW®. The program gives a stepped voltage by means PZT controller to a piezoelectric; causing deformation of the piezoelectric which in turn produces a shift in the surface mounted over it, resulting in a shift in the fringes pattern, besides the program controls a camera for acquiring an image at each voltage change. We use image processing to measure the displacement of the fringes finding out the position of the pixels which have a maximum of intensity, the first interferogram is set as a reference, in the following images the position of the pixel higher intensity is moving to fill the following pixel position with major intensity pixel of reference interferogram. Between two consecutive maximum and minimum of interference, the phase difference is 2π, then we can obtain the phase-shifting for each voltage change as well as the voltage needed to introduce a 2π phase-shifting in the fringe pattern, and finally obtain interferograms with a constant phase-shifting to reconstruct surface shape of thin films.

Fiber Bragg Grating sensors (FBG) have a great resistance to embedding processes. This property is very useful for monitoring parameters at inaccessible places. Embedded fiber optic sensors into composites have been studied for a long time, but embedding a fiber sensor into metallic structure is beginning to study. Recently, this has raised interest due to embedded FBG in the metallic structure provide capabilities for controlling parameters of the structural health status and also information about their own process of deterioration. The embedding process of the FBG sensors involves the fusion of structural metallic material. During this process, very high temperatures are achieved that could damage the Bragg grating or the silica fiber. To protect the sensor during the embedding process, a fiber coating is made with a metallic material with a high melting point. In this paper we study three different techniques for coating a FBG sensor: physical vapour deposition (PVD), electroless deposition and electroplating. This paper describes the experimental procedure for coating metallic fiber optic sensors and the optical characterization.

An analysis has been made of the stability of the images generated by electronic autostereoscopic 3D displays, studying the time course of the photometric and colorimetric parameters. The measurements were made on the basis of the procedure recommended in the European guideline EN 61747-6 for the characterization of electronic liquid-crystal displays (LCD). The study uses 3 different models of autostereoscopic 3D displays of different sizes and numbers of pixels, taking the measurements with a spectroradiometer (model PR-670 SpectraScan of PhotoResearch). For each of the displays, the time course is shown for the tristimulus values and the chromaticity coordinates in the XYZ CIE 1931 system and values from the time periods required to reach stable values of these parameters are presented. For the analysis of how the procedure recommended in the guideline EN 61747-6 for 2D displays influenced the results, and for the adaption of the procedure to the characterization of 3D displays, the experimental conditions of the standard procedure were varied, making the stability analysis in the two ocular channels (RE and LE) of the 3D mode and comparing the results with those corresponding to the 2D. The results of our study show that the stabilization time of a autostereoscopic 3D display with parallax barrier technology depends on the tristimulus value analysed (X, Y, Z) as well as on the presentation mode (2D, 3D); furthermore, it was found that whether the 3D mode is used depends on the ocular channel evaluated (RE, LE).

Spectroradiometric measurements have been made for the experimental characterization of the RGB channels of autostereoscopic 3D displays, giving results for different measurement angles with respect to the normal direction of the plane of the display. In the study, 2 different models of autostereoscopic 3D displays of different sizes and resolutions were used, making measurements with a spectroradiometer (model PR-670 SpectraScan of PhotoResearch). From the measurements made, goniometric results were recorded for luminance contrast, and the fundamental hypotheses have been evaluated for the characterization of the displays: independence of the RGB channels and their constancy. The results show that the display with the lower angle variability in the contrast-ratio value and constancy of the chromaticity coordinates nevertheless presented the greatest additivity deviations with the measurement angle. For both displays, when the parameters evaluated were taken into account, lower angle variability consistently resulted in the 2D mode than in the 3D mode.

Traditionally, ultrasonic ranging sensors emit pulse trains. The distance traveled by the received signal is calculated from its delay with respect to the emitted signal. There are different strategies to encode the signal in order to determine the delay. In this paper we present a method for encoding amplitude that encodes the amplitude of a signal formed by rectangular pulse trains whose frequency is 40 kHz. The pulse amplitude is encoded in a binary manner according to a pseudorandom sequence. Owing to that the emitted signal is formed by pulse trains whose amplitude is modulated, the impulse response of the designed system generates sinusoidal pulse trains whose amplitude is variable. The proposed strategy uses the phase of signal to position temporally each pulse trains. This positioning has higher precision than the sampling time of the signal.

In this work, theory and experiment describe the performance of a surface profile measurement device based on optical heterodyne interferometry are presented. The object and reference beams propagating through the interferometer are obtained by single-pass through an acousto-optic modulator. The diffraction orders 0 and the Doppler-shifted +1 (object and reference beams, respectively) are manipulated to propagate collinearly towards the interferometer output where a fast photodetector is placed to collect the irradiance. The modulated optical signal is Fourier transformed using a data acquisition card and RF communications software. The peak centered at the acousto-optic frequency in the power spectrum is filtered and averaged. The irregularities on the surface of the reflective sample are proportional to the height of this peak. The profile of a reflective blazed grating has been sketched by translating laterally the sample using a nanopositioning system. Experimental results are compared to the measurement done with a scanning electron microscope. There has been found a good agreement between both methods.

A new optical security system for image encryption based on a nonlinear joint transform correlator (JTC) and Fresnel transform is proposed. A lensless optical encryption system, which is a simplified version of previous JTCbased encryption systems, produces a complex distribution in the Fresnel domain, whose intensity is captured by a power-law sensor and nonlinearly modified to yield the real-valued encrypted image. The nonlinearity plays an essential role in the decryption system which, in turn, contains an optical fractional Fourier transform to retrieve the primary image. The security system proposed in this work is a novel extension of the conventional JTC-based encryption system from the Fourier domain to the Fresnel domain. Additional advantages of the proposed system are: simplification of the optical setup, alleviated alignment requirements, and an additional key (the propagation distance) that improves security. Numerical simulations verify the validity of this new optical security system.

A SLM has been experimentally characterized in terms of amplitude modulation versus the gray level distribution (input signal) electronically addressed to the pixelated display in two conditions: input constant with time, and time variant input with increasing frame rate. The SLM considered in this work was a twisted nematic liquid crystal display manufactured by CRL (XGA2 model) that operates on the transmitted light. The influence of some technical specifications such as gamma correction, brightness and contrast of this SLM have been considered as well.

Schiff bases in general are important molecules from several aspects. They are compounds with a functional group that contains a carbon-nitrogen double bond with the nitrogen atom connected to an aryl or alkyl group, not hydrogen. Imines are crucial synthetic intermediates, they do have biological role and the salicylidene types may exibit thermocromic or photocromic properties. These latter two are connected to structural features, i.e., to the possibility of proton transfer complex formation. In this work, the Z-Scan technique is used to measure the nonlinear optical properties of p-bromo-benzylidene aniline substituted. All compounds display absorption bands in the range between 250 and 440 nm, being transparent in the near infrared region. Under 405 nm milliseconds excitation, the nonlinear optical process of p-bromo-benzylidene aniline substituted in DMSO solutions is caused by laser heating. The optical nonlinearity is proportional to the value of linear absorption and depends on substituent and his position.

Dispersion is a quite important parameter in optical fiber systems, mainly in pulsed lasers where the temporal width of the pulses are affected by this factor. There are many interferometric arrangements to evaluate this parameter and generally, these systems vary the wavelength to obtain information about the refractive index dependency n(λ), which is contained in the interferogram phase. However, this makes the system quite slow and it requires tunable light sources with a narrow bandwidth. In this work we propose an alternative method to measure dispersion and we present the results of measurements of special optical fibers, such as microstructured, Er doped, Yb doped, and Er/Yb doped fibers, among others. The experimental arrangement consists of a Mach-Zehnder interferometer, where the fiber under test is located in one of its arms while the air is employed as the reference arm. In order to determine the n(λ) dependency, a wide spectrum light source in the wavelength range of interest was used together with an optical spectrum analyzer. The phase information was evaluated from the measured interferogram. The obtained dispersion values were in agreement with those reported by the fabricant and they were used to calibrate the system in order to obtain non reported values.

Reflectance measurements in interurban-road typical pavements are essential for traffic security. The reflectance of interurban-road pavements presents high variability due to such variables as climatic and atmospheric conditions and the presence of foreign materials on the road (e.g. dirt, fuel or oil). For this reason, the recording of real-time measurements for these kinds of pavements is a complex task. However, its critical importance in traffic safety demands precise measurements under all the possible conditions. In this context, the use of remote-sensing systems working in the radar spectral range is of great interest. With active sensors that receive their own radar signal, the reflectance measurements made by the remote-sensing system are not influenced by the atmospheric conditions. In this work, we present a radar-based methodology to develop real-time measurements of the reflectance in typical interurban-road pavements. We are engaged in extending this new method to study the reflectance of interurban-road pavements within the visible spectrum.

We present a parallel polarizing phase shifting interferometer based in a Double Cyclic Shear Interferometer (DCSI) to analyze transparent samples. The system itself has the advantage of retrieve the derivative phase data map directly and ,due of its configuration itself, it presents betters stability against external configurations than other types of interferometers. The DCSI generates two π-shifted interferograms, which are recorded by the camera in a single-shot. The optical phase is processed by the four-step algorithm. Related simulations and experimental results obtained for transparent samples are also presented.

Electronic Speckle Pattern Interferometry (ESPI) and Shearography (ESPSI) techniques have been used in the field of non-destructive testing for a long time, providing accuracy, and allowing whole field analysis of pure deformation (ESPI) or the gradient of deformation (ESPSI). One of the major weaknesses of this two techniques is linked to speckle de-correlation. When the deformation process produces a displacement greater than a certain proportion of the speckle size, there is a severe loss of coherence which limits the application of these techniques to processes with strong or fast deformations. In order to avoid this limitation, the use of a dynamically updated reference frame is tested in this work. First, in ESPI and ESPSI setups, a metacrylathe bar is used as specimen for testing procedures, and finally a human jaw bone will be used in an ESPSI setup. One basic and regular-shaped object, the bar, and a structurally 3D complex structure, the human jaw bone, with complex elastic properties are the samples to test.

A faster and robust generalized phase-shifting interferometry suitable to automatic real-time applications is presented. The proposal is based on the parameter estimation by the least squares method. The algorithm can retrieve the wrapped phase from two or more phase shifted interferograms with unknown phase steps between 0 and π rad. Moreover, by the multiple or single parameter estimation approach of this algorithm, interferograms with variable visibility both spatial and temporally can be processed, overcoming the restrictions and drawbacks from usual variable spatial visibility approaches. By both computer simulation and a optical experiment, the algorithm's feasibility is illustrated.

The fringe-pattern normalization method by parameter estimation is used to relieve the critical filter's requirements in the Fourier transform method for phase demodulation. By the normalization procedure, the zero order spectrum is suppressed allowing a straightforward filtering in the Fourier transform method. Thus, the filtering procedure is carried out by the simple half-plane filter. The benefits of this Fourier normalized-fringe analysis scheme are tested by both computer simulation and optical experiments.

Phenolic resin boards (PRB) are wood substitutes that comprises of a thick core exclusively made of phenolic resin covered by a thin sheet of melamine resin imitating the aspect of natural wood. The use of these materials in furniture and in construction industry has proliferated during last years. Boards made of phenolic resins are dense, hard and very difficult to cut using band saws, disc saws, or milling cutters. Nevertheless, these difficulties can be overcome by means of laser cutting, which is one of the most firmly established techniques for separating materials. This is due to the great advantages of this technique over traditional cutting methods, such as its versatility and flexibility that allow effective cutting. Nevertheless, charring of the cut edge surface caused by laser induced thermal degradation degrades the cut quality under non-optimized processing conditions. In this research work the viability and quality of CO₂ laser cutting process of phenolic resin boards and wood particleboard panels has been evaluated. The present work validates the cut of phenolic resin boards by CO₂ lasers using a high laser power and elevated cutting speeds. Moreover, this process involves a serious health hazard since the combustion and decomposition of wood may produce fumes and vapors, which can be toxic and carcinogenic according to the International Chemical Safety Cards (ICSC). Therefore, this work was complemented by the assessment of the potential toxicity of the condensed residues formed on the cut edges, and assessment of the chemistry of the generated fumes by chromatography.

Rapid prototyping based on laser cladding is an additive manufacturing (AM) process based on the overlapping of cladding tracks to produce functional components. Powder or wire are fed into a melting pool created using laser radiation as a heat source and the relative movement between the beam and the work piece makes possible to generate pieces layer-by-layer. This technique can be applied for any material which can be melted and the components can be manufactured directly according to a computer aided design (CAD) model. Additive manufacturing is particularly interesting to produce titanium components because, in this case, the loss of material produced by subtractive manufacturing methods is highly costly. Moreover, titanium and its alloys are widely used in biomedical, aircraft, chemical and marine industries due to their biocompatibility, excellent corrosion resistance and superior strength-to-weight ratio. In this research work, a near-infrared laser delivering a maximum power of 500W is used to produce pure titanium thin parts. Dimensions and surface morphology are characterized using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), the hardness by nanoindentation and the composition by X-Ray Diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDS). The aim of this work is to establish the conditions under which satisfactory properties are obtained and to understand the relationship between microstructure/properties and deposition parameters.

In this paper we study wave propagation type Flat Topped through nonlinear optical fibers using as mathematical tool nonlinear equation schrödinger. In this paper we propose to perform a mathematical expansion of a Flat Topped pulse and express it as a combination of Gaussian functions where it is necessary to solve the dynamic equation numerically using the method of Split Step Fourier.

The aim of this paper is to evaluate the influence of the working parameters in the micro-machining process of stainless steel 316L by means of 355 nm Nd:YVO₄ nanosecond laser. Our target is the surface modification of metallic bioimplants to favour osseointegration. Well organized structures, like a matrix of drilling holes or a pattern of grooves, were created in the metallic surface by means of different treatments in which both laser parameters and irradiation schemes were varied. Processed metal surfaces were characterized by confocal microscopy and scanning electron microscopy SEM. The results allowed us to establish the most adequate processing parameters to generate textured micro-features in a range suitable for biomedical applications

In this work we studied the color dependence with a horizontal-viewing angle and colorimetric characterization of two liquid-crystal displays (LCD) using two different backlighting: Cold Cathode Fluorescent Lamps (CCFLs) and light-emitting diodes (LEDs). The LCDs studied had identical resolution, size, and technology (TFT – thin film transistor). The colorimetric measurements were made with the spectroradiometer SpectraScan PR-650 following the procedure recommended in the European guideline EN 61747-6. For each display, we measured at the centre of the screen the chromaticity coordinates at horizontal viewing angles of 0, 20, 40, 60 and 80 degrees for the achromatic (A), red (R), green (G) and blue (B) channels. Results showed a greater color-gamut area for the display with LED backlight, compared with the CCFL backlight, showing a greater range of colors perceptible by human vision. This color-gamut area diminished with viewing angle for both displays. Higher differences between trends for viewing angles were observed in the LED-backlight, especially for the R- and G-channels, demonstrating a higher variability of the chromaticity coordinates with viewing angle. The best additivity was reached by the LED-backlight display (a lower error percentage). LED-backlight display provided better color performance of visualization.

In this paper we present an experimental characterization of a highly nonlinear silica fiber. It includes the determination of the fiber effective nonlinear parameter using the nonlinear four-wave mixing process. From the experimental results, a value γ = 10.6 W⁻¹ km⁻¹ has been obtained for the nonlinear parameter in the co-polarized case, which was reduced to γ = 9.4 W⁻¹ km⁻¹ in the case of a decorrelated state of polarization between pump and signal waves. A threshold power of 17.8mW was found for the stimulated Brillouin scattering process. A Raman gain curve extending over a frequency range of 25 THz, with a peak value shifted by 13.1 THz from the pump frequency, was also measured.

We report a detailed characterization of the spatial resolution provided by different two-photon absorption spectroscopy techniques used in plasma diagnostics: two-photon absorption laser induced fluorescence (TALIF) and two-photon optogalvanic spectroscopy. Well-understood and characterized spatial resolution has especial importance for a precise control of experimental conditions, and absolute measurements. Beam profiles recorded with high resolution allow calculating the beam propagation and irradiance distribution in the beams overlap, the resulting fluorescence and ionization yield, and the corresponding spatial resolution.

In this work, white light interferometry is applied to perform wavelength calibration of a dispersive spectrometer .The relation between wavelength and position in the spectrometer detector is obtained from the wavelength-dependent phase difference at the output of the interferometer. In the proposed method, no suppositions are made about the spectrum of the illumination source; it is only required to make a simple assumption about dispersion in the spectrometer to be measured and to perform a Taylor expansion of the phase difference. A sample of calibration of a home-made spectrometer serves to discuss different issues that affect the calibration.

The optimized design of microstructured optical fibers (MOFs) for supercontinuum generation is investigated. The dependence of the group velocity dispersion and effective mode area on wavelength is analyzed. We consider first the case of a conventional MOF with a hexagonal pattern of air holes. In addition, we propose a new design, corresponding to a layered spiral microstructured optical fiber (LS-MOF). By changing appropriately its three parameters, it is possible to shift the zero dispersion wavelength to visible and near-infrared regions, as well as to achieve a very high nonlinearity near this wavelength. Supercontinuum generation is simulated in a LS-MOF with optimized design .

We present a method of femtosecond pulse shaping in the deep ultraviolet (DUV, 266 nm) by four-wave-mixing of temporally shaped 800 nm pulses and their second-harmonic in a thin isotropic transparent Kerr-type medium. Numerical solutions of the two-dimensional nonlinear propagation equations for this process have been obtained for double-gaussian and flat-top shapes using a dedicated code developed within our group. These results show that it is possible to obtain double-gaussian and flat-top DUV pulses depending on the relative delay between pump and idler pulses, with significant efficiency and with time durations in the range of those of the pump pulses.

The inclusion of the permanent dipole moments and the solvent on the optical conventional Bloch equations (OCBE) allowed us to obtain analytical expressions for the optical properties of a two-level molecular system. We employed the methodology developed by Colmenares et al.¹, in which they model the collisional effect of the solvent through a stochastical function, ξ(t) = ω₀ + σ(t), so the OCBE become a set of coupled integro-differential stochastical equations that we solved, up to third order in the incident field, employing the perturbation theory. Once obtained the analytical expressions for the density matrix elements, macroscopic polarization and effective susceptibility of the system, we studied the optical properties derived in the frequency space, inside and outside the rotating wave approximation.

Advanced modulation formats are an emerging area since they allow reducing the symbol rate while encoding more bits per symbol. This allows higher spectral efficiencies. In addition, we can achieve higher data rates using lower-speed equipment like in all-optical format conversion systems, an important step for the development of systems with high transmission rates. In this paper we study the impact of some impairments found in all-optical advanced format conversions based on cross phase modulation (XPM) on a highly nonlinear fiber (HNLF), such as amplified spontaneous emission (ASE), nonlinear fiber length and group velocity dispersion (GVD), and analyze its performance based on error vector magnitude (EVM) for different bitrate transmissions. This simulation study is applied on earlier proposed phase modulated format conversion where n nonreturn-to-zero on-off keying (NRZ-OOK) channels at 10 Gb/s are converted into a return-to-zero m phase shift keying (RZ-mPSK) at 20Gb/s. We extend the work with simulations and show the results for n NRZ-OOK channels at 20Gb/s, 40 Gb/s and 50Gb/s to RZ-PSK at 40Gb/s, 80 Gb/s and 100Gb/s, respectively.

Time resolution limited dynamic measurements show the need for improved techniques to access ultrafast demagnetisation processes on the sub-10 femtosecond timescale. We have constructed a state-of- the-art time-resolved magneto-optic Kerr effect (TR-MOKE) apparatus for the observation of ultrafast demagnetization and precessional dynamics in ferromagnetic materials. Our system can operate well below the current ranges used by most researchers (typically in the region of 40 fs). Using current ultrafast optical methods of pulse compression, designed to obtain unprecedented temporal resolution, we have developed a dual-colour pump-probe technique: This enables us to attain an ultimate resolution in the 12 fs range, the spectral range being split between pump and probe beams. We have demonstrated that the system has the capacity for ultrafast demagnetization measurements using a GdFeCo thin film. Future developments will employ the full spectral range in both pump and probe branches to reach an expected temporal resolution in the vicinity of 6 fs, corresponding to few-cycle pulses.

The generation of configurable multipulses by advanced MOPA fiber lasers is opening new possibilities in materials processing, showing improvements in efficiency and quality while benefiting from the advantages of competitively priced fiber lasers. We show examples of the configuration capability and control of multipulses of a 20W MOPA pulsed fiber laser at 1.06μm, having and M² of 1.3. The multipulses consist of user-defined bursts of short pulses, with burst durations ranging from 10ns up to 1000ns, frequencies up to tens of MHz within the burst, with individual pulses in the 10ns to 200ns range and with up to 12kW peak power. Multipulse repetition frequency is controlled externally from single shot up to few MHz, with the possibility of real-time switching between different multipulses.

This work studies the spatial propagation of the four-wave mixing signal of a molecular system with two electronic levels immersed in a thermal bath. Using the optical Bloch-Maxwell equations, we present three approximations, two of them are analytical solutions and the other is a numerical approach, where the effects of the variation of pump intensity through the optical path are considered. Also, we compare these results with the analogous in absence of the thermal reservoir and it is shown that the stochastic effect induced by the solvent, due to the experimental conditions as relaxation times, concentration of the solution and optical frequencies of the pumps, diminishes the intensity responses compared with the same in absence of the bath.

In this paper we present an active GRadient-INdex (GRIN) beam shaper with gain for Gaussian to flat-top beam conversion. This extra-cavity beam shaper is based in the proper design of an active GRIN selfoc rod microlens in order to perform the beam shaping operation. General condition for obtaining beam shaping by active GRIN rod microlenses is shown. Irradiance evolution through the active material for a laser beam operating at 1550 nm and 1.25 mm beam half-width is simulated and the shaping length in each case is determined. The active GRIN beam shaper is sensitive to deviations from design laser parameters such as wavelength and beam diameter, what can have great influence on the output flat-top beam quality. Variations on the design length of the shaper due to fabrication process errors can also emerge on unwanted output irradiance profiles. Here we analyze the sensitivity of the active GRIN beam shaper to the wavelength and beam half-width of the input Gaussian beam, as well as to the length of the GRIN rod lens in order to design a beam shaper that meets requirements within an acceptable tolerance. In this way, flatness quality of the output irradiance profile is examined. For the active beam shaper reported, microlens thickness, input wavelength and beam half-width tolerances are 10%, 10% and 5%, respectively.

We investigate the nonlinear refraction induced by a train of ultrashort laser pulses (repetition rate 80.75MHz) in a set of ionic liquids: [EMIM][BF₄], [BMIM] [BF₄], [HMIM] [BF₄], [OMIM] [BF₄] and [DMIM] [BF₄]. Due to the high repetition rate, linear absorption processes are developed which cause a non local increase of temperature that generates an inhomogeneous and non local spatial variation of the refractive index. This effect is known as thermal refraction. The goal of this work is to characterize by z-scan the induced changes in the refractive index at λ=810nm and to determine the thermooptic coefficient of this liquids at this wavelength

Optical vortices are employed in optical trapping applications for their ability to set microparticles into rotation. Devil’s Vortex Lenses have high diffraction efficiency and it is possible to take advantage of their particular volumetric focal structure to design versatile and efficient optical tweezers. In this communication, we report a simple design procedure, involving arrays of Devil’s Vortex-Lenses implemented in a programmable Spatial Light Modulator, for generating spatial distributions of optical vortices. In our approach, the preferred position and topological charge value can be assigned to each vortex in the structure, tuning the desired angular momentum. We have demonstrated the generation of 3D optical vortex distributions through arrays of Devil’s Vortex-Lenses, including configurations with charges and momenta of opposite sign. Our experimental results present an excellent agreement with the simulations we have developed.

The mid-infrared radiation produced by CO2 lasers is being widely used to produce long period fiber gratings (LPFG) with several advantages over other methods. Several techniques can be used to irradiate the fiber in order to produce the necessary effect. Using a cylindrical lens to create a line of light or scanning of a spot over the fiber are the most common approaches. Usually, the period is produced either by a translation stage moving perpendicular to the incident beam or by using a two mirrors scanner that inscribes the entire period directly on the fiber. In both cases, the synchronization between the laser and the moving elements is critical. Also, when using a two mirrors scanner, the dimension of the LPFG is limited by the focusing lens diameter and its focal length. All this become critical when one needs to increase the LPFG’s length or reduce its period. The later usually implies shorter laser emission times, which is limited by the laser emission physics (at least for cheap low power CW lasers). In order to overcome the disadvantages of each method, a combined approach is presented and analyzed. A mirror scans vertically the beam over a cylindrical lens and a translation stage moves the fiber to create the different periods. The laser keeps emitting during the complete process increasing laser power stability and thus, improving grating homogeneity. To guarantee the synchronization between the translation table and the one mirror scanner, special hardware and software was created.

The use of CO₂ lasers in the production of optical fiber sensors is a well proven application, especially in writing long period fiber gratings. The mid-infrared radiation (MIR) emitted by these lasers is highly absorbed by the glass optical fibers commonly used as fiber-based sensors, and the consequent heating easily leads to melting. Making use of this advantage, the application of this radiation in the tapering of optical fibers is demonstrated. A continuous wave emission CO₂ laser is used in short duration pulses, a cylindrical lens focuses the beam on the fiber and a small weight produces the effect of pulling the fiber. The resulting tapers’ characteristics (length, degree of symmetry and central diameter, or waist) are analyzed as well as the influence of the operational parameters involved in the process (laser power, pulse duration and number of pulses). The potential of this technique is demonstrated with special attention to its use in the development of optical fiber-based sensors.

In the present work holographic interferometric beating to produce digital moiré like patterns in a well controlled digital Fourier transform holographic experiment are reported. A simple implementation of digital Fourier transform holographic setup is used to produce these patterns. This setup allows us to control some parameters like incident angle of reference beams and spatial frequency of the interferometric beating patterns. The moiré like patterns could be promising to some optical interferometric applications, including profilometry and other opto-mechanical applications.

In the present paper we describe the holographic interferometric beating to produce dynamic photorefractive moiré-like patterns with two or more variation directions. It has been experimentally obtained by the superposition of two sinusoidal gratings with slightly different pitches for each direction of fringe variation obtained. These dynamic moiré-like patterns are induced in the volume of the Bi₁₂TiO₂₀ (BTO) crystal sample used as dynamic holographic medium. The Fourier transform profilometry method is applied using two or more moiré fringe patterns with different direction of variations, simultaneously or not, projected onto an object surface.

The experimental setup developed to stabilize a red diode laser using a mode-locking technique with a reference gas cell is presented. This system has an external cavity diode laser (ECDL) in a Littrow configuration and is used to calibrate gauge blocks. The electronic controller limits the bandwidth of the laser and does not allow the setup to establish the wavelength of the tuned iodine transition, which is needed to calculate the gauge block values. To solve this limitation, we have set up a laser wavemeter based on a two-beam scanning Michelson interferometer. The unknown wavelength is determined from the ratio of the number of fringes obtained by the He-Ne reference laser and our ECDL. This technique measures the laser wavelength with an accuracy of 1ppm. As the resolution of the system is influenced by the optical path length, the stability of the reference laser and the phase ratio of both lasers, an electronic Vernier counter is used to improve the accuracy of these values below 1ppm. The uncertainty evaluation is also presented.

We present results on time-resolved transillumination imaging by using the cumulant expansion solution to the transport equation for temporal extrapolation. The resolution study involves measuring the edge response function (ERF) for a mask embedded in a liquid phantom at near-IR wavelengths, obtaining the integration-time-dependent resolution for different phantom widths and verifying this spatial resolution by resolving two objects inside the phantom. We also present results on the values of different parameters of the phantom materials and the feasibility of this method to characterize the absorption and scattering coefficients of a turbid medium.

The variation of colors in microscopy systems can be quite critical for some users. To address this problem, a study is conducted to analyze how different factors such as size of the sample, intensity of the microscope’s light source and the characteristics of the material like chroma and saturation can affect the color appearance through the eyepiece of the microscope. To study the changes in colors considering these factors, the spectral reflectance of 24 colors of GretagMacbeth Classic ColorChecker® and Mini ColorChecker® which are placed under a Nikon ECLIPSE MA200 microscope®² using dark filed and bright field illuminations which result in different intensity levels, is measured using a spectroradiometer®³ which was placed in front of the eyepiece of the microscope. The results are compared with the original data from N. Ohta¹. The evaluation is done by observing the shift in colors in the CIE 1931 Chromaticity Diagram and the CIELAB space, also by applying a wide set of color-difference formulas, namely: CIELAB, CMC, BFD, CIE94, CIEDE2000, DIN99d and DIN99b. Furthermore, to emphasize on the color regions in which the highest difference is observed, the authors have obtained the results from another microscope; Olympus SZX10®⁴, which in this case the measurement is done by mounting the spectroradiometer to the camera port of the microscope. The experiment leads to some interesting results, among which is the consistency in the highest difference observed considering different factors or how the change in saturation of the samples of the same hue can affect the results.

We design tellurite and As₂S₃-based chalcogenide tapered photonic crystal fibers (TPCF) for broadband mid-infrared coherent supercontinuum (SC) generation in the few optical-cycle-regime. By injecting pre-chirped femtosecond pulses, the soliton self-compression is optimized and then, we show the generation of more than one octave-spanning SC spectra with low input pulse energies in both TPCF having 8 mm-length.

Recent advances in the acquisition of in-vivo high resolution retinal images through the use of Adaptive Optics (AO) have allowed the identification of cellular structures such as cones and rods, in and out of the fovea, in such a way that their histological characteristics can be studied in-vivo and later compared to data obtained post-mortem. In this work, an algorithm is proposed for the detection of photoreceptors; it consists of two stages: Early Cell Detection (ECD), to detect all candidate cells, and Refinement of Cell Detection (RCD), to reduce over-detection of photoreceptors. The algorithm has been tested using synthetic and real images, the latter acquired with an Adaptive Optics Scanning Light Ophthalmoscope (AOSLO). The proposed algorithm was compared against the one developed by Li and Roorda, and both algorithms were tested on synthetic and real images, yielding similar algorithm performance on both kinds of images when they had only cones; however, the algorithm developed by Li and Roorda, when applied to real images having cones and rods, identifies photoreceptors in vascular tissue, in addition to showing low rod detection.

In this paper, we describe a new method to identify the spots and to obtain the coordinates for the centroids from a Hartmann and Hartmann-Shack screen test when some noise and reflection errors are present using an independent dynamic thresholding method. The proposed algorithm is a robust one, working with almost no interactive operation. It proved to be good for noise removal in the presence of relatively high noise with low and uneven contrast and spot reflections. The process involves the binarization of the image through a thresholding operation. Subsequently, a data segmentation algorithm is used for spot identification. The spot identification and indexing is performed independently. Finally, the coordinates of each centroid are obtained using an appropriate masking for each spot. To test the procedure we used first synthetic images obtained from some specified functions and later we used a Hartmanngram image from a human cornea.

An optical fiber trap operates by radiation pressure and transverse force gradient while conventional optical trap operates on longitudinal gradient to trap particles. This subtle difference translates into easy setup and many advantages over conventional single-beam optical tweezers. In this work, we present a brief review of the current situation of fiber optic trap and their applications. Subsequently, we discuss the effect of radiation pressure on micro-organic and inorganic particles. Using a single optical fiber, radiation pressure transfers movement to the micro-particles, so velocity and acceleration are quantified. After that, micro particles are trapped, but now using two optical fibers. Finally, we discuss the results and problems involved with this research.

Many models and methods commonly used in colorimetry have been incorporated to the study and knowledge of the colorimetric properties in the reflection color holograms; these methods have reported the possibilities of color reproduction in holograms. One method is based in calculating the color differences between the CIE-L*a*b* coordinates of the original object compared to the same values obtained for the reconstructed hologram; these values are calculated through the measurement of the spectral composition of the light in the reproduced hologram which are made with spectrometers. Other methods are based in the use of cameras for the color measurement, although, they are not commonly used for that ending in holography. This work presents the results of a comparative study between the use of spectrometers and RGB digital cameras for the color measurement in holograms. The diffraction efficiency of the holograms for a GretagMacbeth Colorchecker samples is measured through a spectrometer and their CIE-L*a*b* coordinates are calculated; the color differences are also calculated by taking as theoretical values the coordinates of the original object. A similar procedure is made by capturing the reconstructed images of the hologram through a CMOSRGB camera, which requires a linearizing and characterizing procedure. The RGB coordinates of the original object are compared with the RGB coordinates of the reproduced hologram too.

Correct metrological calibration is the key to avoiding the main systematic error sources in an interferometer configuration in order to obtain high resolutions and repeatability. The calibration procedure can consist of the acquisition of two fringe patterns with a known phase shift between them, which means the correct adjustment of this phase difference fits the system. Differential phase shifting algorithms, built by combining two known phase shifting algorithms in a non-linear way, obtain this phase difference directly. In this sense, the two-dimensional characteristic polynomial is an innovative tool for qualitatively characterizing the properties of the differential phase shifting algorithms and, particularly, for determining the accuracy of the system. In previous works, it was demonstrated that sensitivities are inherited from precursor phase shifting algorithms. This mechanism of error propagation allows us to design new differential phase shifting algorithms according to standard requirements in each system in order to cancel or at least minimize this known source of errors.

In this research paper briefly describes the design and construction of an optical voltage transducer measurement based on the effect electro - optical Pockels. The equipment is designed to operate in electric transmission lines 110 kV AC. It then describes the electrical tests performed on transformer to actual operating conditions. In the design and construction of the optical transformer used a photorefractive crystal Bi₄Ge₃O₂₀ (BGO), which was used because of its high sensitivity to changes in the electric field as a light source is used a laser diode with a wavelength of 670 nm. Presents the results of performance tests on potential levels appropriate to the optical laboratory. In the second part of this work was subjected to optical transformer operating voltage levels of 110 kV ac in this test the voltage was applied gradually until the operating voltage. Team performance was satisfactory.

As digital holographic microscopy (DHM) uses microscope objectives (MO) for enlarging the sample, some associated effects that are not present in optical microscopy have to be considered as quantitative phase imaging (QPI) is regarded. The remaining phase curvature introduced by the MO, which does not affect the optical microscopes, plays a determinant role in the performance of the DHM. In this contribution a thorough analysis of the physical parameters that control the appropriate utilization of MOs in DHM is presented. The analysis is carried for QPI. We study the sample phase perturbations that the MO phase curvature introduces. An analysis of the regular ways as these phase anomalies are removed is presented. The study is supported by means of numerical modeling and experimental results.

Conventional (analog) holographic interferometry (HI) has been used as a powerful technique in optical metrology since sixties of XX century. However, its practical applications have been constrained because of the cumbersome procedures required for holographic material development. Digital holography has brought significant simplifications due to digital capture of holograms and their further numerical reconstruction and manipulation of reconstructed phases and amplitudes. These features are the fundamentals of double exposure digital holographic interferometry which nowadays is used in such applications as industrial inspection, medical imaging, microscopy and metrology. However another very popular HI technique, namely real time holographic interferometry has not been demonstrated in its digital version. In this paper we propose the experimental-numerical method which allows for real-time DHI implementation. In the first stage a set of digital phase shifted holograms of an object in an initial condition is captured and the phase of an object wavefront in the hologram plane is calculated. This phase is used to address a spatial light modulator, which generates the initial object wavefront. This wavefront (after proper SLM calibration) propagates toward an object and interfere with an actual object wavefront giving real-time interference fringes. The procedure works correctly in the case when CCD camera and SLM LCOS pixel sizes are the same. Usually it is not the case. Therefore we had proposed two different methods which allow the overcome of this mismatch pixel problem. The first one compensates for lateral magnification and the second one is based on re-sampling of a captured phase. The methods are compared through numerical simulations and with experimental data. Finally, the implications of setting up the experiment with the object reference phase compensated by the two approaches are analyzed and the changes in an object are monitored in real time by DHI.

The characterization of the superficial topography of a thin film, obtained from an interferometer installed in our Optics Laboratory, is done using bi-dimensional images of its surface overlaid with interference fringes (interferogram¹). These images differ among them only by a constant variation of the optical phase². The total number of images to acquire depends on the image processing algorithm to apply; this algorithm allows to determine the value of the phase introduced by the surface form.

Optical antennas serve as light detectors in the infrared when coupled to transducers. Distributed bolometers have been proposed and positively demostrated to produce an electric signal when light is inciding on it. These devices can be easily fabricated using only one e-beam lithography step. However, the choice of the material used to fabricate the antennas is of great importance to enhance the performance of these devices. In this contribution we present an optimized distributed bolometer. The auxiliary elmentes analyzed to provide the maximum possible response. This analysis is made using a multiphysics approach taking into account the electromagnetic and thermal domains.

The recent introduction of color digital lensless holographic microscopy (CDLHM) has shown the possibility of imaging microscopic specimens at full color without the need of lenses. Owing to the simplicity, robustness, and compactness of the digital lensless holographic microscopes (DLHM), they have been presented as the ideal candidates to being developed into portable holographic microscopes. However, in the case of CDLHM the utilization of three independent lasers hinders the portability option for this microscope. In this contribution an alternative to reduce the complexity of CDLHM aimed to recover the portability of this microscopy technology is presented. A super-bright white-light light-emitting diode (LED) is spectrally and spatially filtered to produce the needed illumination by CDLHM to work. CDLHM with LED illumination is used to image at full color a section of the head of a drosophila melanogaster fly (fruit fly). The LED-CDLHM method shows the capability of imaging objects of 2μm size in comparison with the micrometer resolution reported for LASER-CDLHM.

The effects of illumination variations in digital images are a trend topic of the pattern recognition field. The luminance information of the objects help to classify them, however the environment illumination could cause a lot of problem if the system is not illumination invariant. Some applications of this topic include image and video quality, biometrics classification, etc. In this work an illumination analysis for a digital system invariant to position and rotation based on Fourier transform, Bessel masks, one-dimensional signatures and linear correlations are presented. The digital system was tested using a reference database of 21 fossil diatoms images of gray-scale and 307 x 307 pixels. The digital system has shown an excellent performance in the classification of 60,480 problem images which have different non-homogeneous illumination.

We present an alternative description of nonlinear cross-phase modulation based on the kinetic equation for photons. The most relevant feature of this new approach is that phase itself is completely ignored. Formal exact solutions and approximate analytical solutions are discussed. Experimental measurements of cross-phase modulation of two-color ultrashort laser pulses propagating in a highly nonlinear photonic crystal fiber reveal a good agreement with the analytical results.

In order to obtain a clearer interpretation of the Intensity Transport Equation (ITE), in this work, we propose an algorithm to solve it for some particular wavefronts and its corresponding intensity distributions. By simulating intensity distributions in some planes, the ITE is turns into a Poisson equation with Neumann boundary conditions. The Poisson equation is solved by means of the iterative algorithm SOR (Simultaneous Over-Relaxation).

The determination of the optical parameters are important for remote sensing and aircraft, in this case allow the difference between a cloud composed solely of water and water plus ash. Therefore, this research is intended to determine the optical properties of the ash four active volcanoes, by studying the spectral resolution reflectance interpreting the results in the approximation of Kubelka - Munk equation through the transfer equation radiative. The results allow classifying these ashes depending on their place of origin.

A new formulation of the laws of reflection of light based on the particle model is presented, and it is shown the equivalence between the new and the classic formulations. The proposed formulation has a significant educational value, as it allows drawing analogies between the phenomena of light reflection and elastic collisions, which are very well known by students. The proposed formulation is: “If at one point on a surface whose orientation in space is defined by a unit vector k, strikes an incident ray corresponding to a plane wave (propagating through a homogeneous and isotropic medium) whose direction of propagation coincides with that from a unit vector u_i [expressed in terms of its components with respect to an orthonormal coordinate system, with one of its axis coinciding with the direction of k (u_i = u_ix i + u_iy j + u_iz k)], it will be reflected so that the unit vector whose direction coincides with that from the reflected ray, u_r, will only differ from the unit vector whose direction coincides with that from the incident ray, in the change of the sign of the component in the direction of k (u_r = u_ix i + u_iy j - u_iz k)”. Stated in everyday language, is equivalent of saying that the reflection of light occurs as if the photons underwent perfectly elastic collisions with the surface in question. As an example, this formulation is applied for the resolution of the classic reflection problem of the three plane mirrors forming a trirectangular trihedron.

In this work we studied the symmetry properties of the Rayleigh-type optical mixing signal, of a two-level molecular system immersed in a thermal bath and irradiated by a classical electromagnetic field. Taking into account that the solvent produces an inhomogeneous displacement of the Bohr frequency and, employing a cumulant expansion to solve the stochastical equations derived, we obtained the mean values of the coherence, populations and susceptibilities Fourier components of the molecular system, from the optical stochastical Bloch equations (OSBE). These symmetry properties are used to show the dependence of the spectra with the frequency shifts of the incident fields, and we obtained that the inclusion of the thermal bath diminishes the intensity response as well it promotes the loss of the symmetry properties, compared with the same results in absence of the bath.

Dynamic speckle laser (DLS) technique has been applied to the analysis of different biological systems, inorganic materials and industrial processes. In this paper, we use this technique to analyze the hygroscopic properties of different types of porcelain and papers for electrotechnical purposes. Experimental speckle results showed different behavior depending on physicochemical and textural properties of the samples.

Coal composition is popularly characterized in terms of macerals which are the microscopically recognizable individual constituents of coal; petrographic studies are mainly used for determining coal quality, coking properties and composition or coal rank (Taylor et al., 1998); maceral analysis can be carried out using manual and automated techniques, although both have drawbacks. Manual analysis is time consuming and unavoidably subjective, especially when comparing results of different analysts. Automated analysis is one possible alternative to manual analysis but is not without its difficulties, especially when resolving the various macerals from each other and from the support media used to suspend the coal in a polished block; the smallest microscopically recognizable entities in coal are called macerals, they are analogous to minerals in rocks. However they differ since minerals have an homogeneous chemistry and an orderly internal structure. Coal macerals are distinguished by their optical characteristics of color, relief of the polished surface, morphology, reflectance and fluorescence. A coal reflectogram (histogram) provides the reflectance distribution of coal sample in the form of a frequency histogram, the present work aims to study the macerals histograms in order to implemented this tool in petrographic analysis and coal characterization.

Stability in a fringe pattern is a necessary condition in interferometric processes, such as holography, and not always is enough the use of passive stabilization systems, like holographic tables, in particular, when perturbations are caused by thermal or acoustic variations. For these cases, active systems are required. In this work it is presented the implementation of a control system for interferometric fringes stabilization. The interferometric arrangement characteristics are also discussed, which permits to act independently over each of the interferometer's arms by means of two piezoelectric actuators that change the length of the optical path of light that goes through, in order to perturb the system and simultaneously compensate this perturbation in real time. It is also shown that the proposed system allows evaluating the control system's performance subjected to diverse perturbations, and it is shown how remote access was given to the implemented platform.

There are many studies focuses on self-assembled films characterization, photochromic material (spiropyran) had been electrosattached to different enzymes, and in this work we used these spiropyran characteristics to immobilized glucose oxidase. The aim of this work is establish a protocol to build an optical device that shows absorption changes when an enzyme is immobilized and characterized the devise through FTIR and UV/Vis spectroscopy and Atomic Force and Scanning Electron Microscopy. We use different methods such as self-assembled monolayers and the activation reaction by carbodiimide. Corning of quartz was used as matrix, clean solution (1:1 MeOH:HCl, H₂SO₄) was used to prepared the matrix, 1% silane solution was prepared to functionalized the surface, and a solution prepared with spiropyran (C₁₉H₁₈N₂O₃), EDC (C₅H₁₁N=C=NC₆H₁₁), NHS (C₄H₅NO₃), HEPES (C₈H₁₈N₂O₄S) and glucose oxidase from Aspergillus niger was the last step to immobilized this enzyme. Three steps to build it, the first step was cleaned the matrix, the next step was functionalized the surface with silane material, this step allows to modified the surfaces, to prepared to attach the spiropyran. The bonds found from the FTIR spectra to silanized step and the functionalized step (spiropyran attached). That indicated that FTIR and AFM techniques are available to characterized and identify absorption, morphology of a devise modified with spiropyran, that allows attach some biological material, in this case glucose oxidase, the absorption changes and morphological changes are the evidence of immobilization successful.

The target of this communication is to present a method for tailoring the complex amplitude and the polarization at the entrance pupil of a high numerical aperture objective lens in order to obtain focused fields with transverse circular polarization at any plane. Analytical expressions within the framework of the Richards-Wolf vectorial model are derived and some numerical results are presented.

In this work we show a new technique for sub-structured Ronchi rulings generation and the calculation of the irradiance profile produced by this ruling. Commonly, these rulings are used to increase the spatial resolution in the Ronchi test and allow us to observe smaller surface defects. To generate the sub-structured Ronchi ruling we propose a combination of several classical Ronchi rulings with different frequency, in order to calculate the irradiance profile generated by the substructured Ronchi ruling, we propose a combination of the irradiance profile generated by each combined classical Ronchi ruling. The comparison of synthetic and experimental Ronchigrams of spherical surfaces are shown. We found that the proposed method can reproduce reliably the experimental irradiance profile.

This work arises based on the idea proposed by Millered et al. in 2004, where they show how to get in one shot interferograms with phase shift using a mask with micro-polarizers, in this work we pretend to obtain phase shift in localized areas of an interferogram using the properties of polarization and the pixelated configuration of a liquid crystal display (LCD) for testing optical surfaces. In this work we describes the process of characterization of a liquid crystal display CRL Opto and XGA2P01 model, which is introduced in one arm of a Twyman Green interferometer. Finally we show the experimental interferograms with phase shifts which are caused by different gray levels displayed in the LCD.

Nonlinear optical and electronic properties of nanosized metal particles have drawn considerable attention because of their strong and size-dependent plasmon resonance absorption. In a metal nanoparticle system such as gold dispersed in a transparent matrix, an absorption peak due to surface plasmon resonance is usually observed in the visible spectral region. Metal nanoparticles are of special interest as nonlinear materials for optical switching and computing because of their relatively large third-order nonlinearity (χ3) and ultrafast response time. The purpose of this study was to analyze the nonlinear optical properties of biosynthesized gold nanoparticles. The samples were prepared by biosynthesis method using yeast extract as reducing agent and the nonlinear optical properties of the nanoparticles were investigated using a single beam Z-scan technique with a beam power of 20 mW and operated at wavelength of 514 nm. The reaction between metal ions and yeast extracts were monitored by UV–visible spectra of Au nanoparticles in aqueous solution with different pH (3-6). The surface plasmon peak position was shifted from 528 nm to 573 nm, according to of pH variation 4 to 6. The average particle size was calculated by the absorption peak position using the Fernig method, from 42 to 103 nm. The z-scan curves showed a negative nonlocal nonlinear refractive index with a magnitude dependent on the nanoparticle size.

A method to design Ronchi-Hartmann null screens for improved alignment in the testing of fast concave conic mirrors is presented. The designs of these null screens are based on knowledge of the caustic by reflection.

Since light emitting diodes have undergone a huge development in the last decades, they are achieving a widespread use in almost every activity substituting older light sources. The properties of the light emitting diodes such as their size, efficiency, wavelength of the emitted radiation, among others, have turn these devices into an increasingly applied solution for different applications. Some applications require a proper design of the illumination patterns. Here, it is presented a design solution for the radiation pattern of the light emitting diode using as the approximation the cone equation. Also, a method to design specific irradiance distributions using a certain number of diodes is discussed.

The Optical Vortex Metrology is based on the possibility of characterizing, through topological and morphological parameters, each one of the vortices existing in the phase of the optical field, or in a pseudo-phase obtained by means of the Hibert, Reisz or Laguerre-Gauss transforms. On this basis, it is possible tracking and pairing the homologous vortices. Then, the locations and relative displacements between the homologous vortices are determined with sub-pixel precision. Because of the statistical nature of the measurements, their quality is determined, among other factors, by the amount of available vortices per unit area. In this work, it is proposed to use the internal modulation of the speckles to generate a significant increase in the vortex density, which can be achieved by employing a double aperture pupil optical system. Simulations of the speckle distributions are presented to analyze the increase of the vortex density as a function of the distance between the apertures, and to evaluate the influence of the increment of this density in the quality of uniform in-plane displacements measurements. The results corresponding to modulated speckles are compared with those obtained with a single aperture.

In this work we report the fabrication and electro-optical characterization of CdS thin films using glycine as complexing agent with ammonia and ammonia free buffer by the Chemical Bath Deposition (CBD) method. The CdS thin films were grown at different temperatures of 50, 60, 70 and 80 °C in a thermal water bath. The morphology of these films was determined using atomic force microscopy; the resultant films were homogeneous, well adhered to the substrate, and specularly reflecting with a varying color depending on the deposition temperature. Transmittance and reflectance measurements of thermally treated CdS films were carried to study the effect of the ammonia buffer on its optical properties and bandgap. The crystallinity of the CdS thin films was determined by means of X Ray diffraction measurements. Therefore, for this study, an ammonia-free complexing agent has been taken for the deposition of CdS. Among different methods, which are being used for the preparation of CdS films, Chemical Bath Deposition (CBD) is the most attractive due to its low cost, easy to handle and large possibilities regarding doping and deposition on various substrates. In particular it can be used to easily obtain field effect devices by depositing CdS thin films over a SiO2/Si substrate. Heterostructures with interesting physical properties can be imagined, realized and tested in this way.. Structures CdS/PbS also were realized and have shown good solar cell characteristics.

Quantum teleportation has attracted much attention from both theorists and experimenters in the last decade. The emergence of new protocols and their actual implementation have even motivated the development of new quantum optical schemes. A key issue when teleporting a quantum state is establishing the quantum channel between sender and receiver stations, usually done by manipulating an auxiliary bipartite entangled state. The purpose of the present work is to study quantum teleportation processes in which that state is an entangled bipartite photon-added state, and the Adhikari et. al. continuous-variable quantum teleportation protocol is applied. Photon-added states can be generated using different experimental techniques, such as parametric down-conversion in a nonlinear crystal, and conditioned parametric amplification. These states are relevant because they exhibit generalized non-classical features for all orders of creation and annihilation operators, and may even show phase squeezing and sub-Poissonian distribution statistics. We study, the dependence of the fidelity of the teleported states and their photon number statistic as a function of the higher-order squeezing, and the higher-order sub-Poissonian statistic.

In this work, it is study thermoluminescent phenomena (TL) optically stimulated with UV radiation in Silicon Rich Oxide (SRO) nanostructured thin films. The experimental samples used were thin films of this composite deposited by Low Pressure Chemical Vapor Deposition (LPCVD) over a n-type silicon substrate, this samples were fabricated using different flow ratios of precursory gases silane and nitrous oxide R₀=SiH₄/N₂O during the deposition and were given posterior thermal treatment which gave place to the formation of different sized nanoparticles, that are attributed to the luminescent activation mechanism in this material. The silicon excess was controlled by the ratio of the gases used in the deposition process and in this way SRO films with 12, 8 and 6% silicon excess were obtained. The glow-curves experimentally obtained were submitted to analysis using different models in order to obtain important thermoluminescent parameters. The luminescence spectra of SRO show two wavelength regions of emission; one in the blue part and one in the red part of the emission spectrum. The emission in the blue part is related to defects in the SiO lattice. About the origin of the red luminescence there is still a controversy. One model assumes that the red luminescence stems from Si nano particles and another model assumes that defects at the interface of SiO bulk with the Si nano particle are responsible for the red luminescence. Finally is intended to provide favorable conditions for the development of a UV dosimeter with this material.

For a optics and spectroscopy laboratory that generated plasma from a lasers systems, it is important to know in detail the shape of the intensity distribution in the spot of the laser, for that reason it performed the characterization of the radiation from lasers CW (continuous) gas, solid state and semiconductor, where experimentally obtained information of the intensity distribution of the beam, the measurement of the radius of the spot, the beam profile and divergence of the same from a diagnostic device that is based on a CCD sensor. Images were obtained from Spot of the lasers by said sensor and were processed and analyzed by 2 dimensional graphs that yielded information on the intensity profile of the radiation optic lasers and also be presented the spot shape in detail, in order to ensure the quality of the laser systems and can select lasers devices that are capable of performing highly accurate experimental researches which have significant scientific or simply can perform ablation procedures without risk of affecting the material.

Colour-difference formulas are tools employed in colour industries for objective pass/fail decisions of manufactured products. These objective decisions are based on instrumental colour measurements which must reliably predict the subjective colour-difference evaluations performed by observers’ panels. In a previous paper we have tested the performance of different colour-difference formulas using the datasets employed at the development of the last CIErecommended colour-difference formula CIEDE2000, and we found that the AUDI2000 colour-difference formula for solid (homogeneous) colours performed reasonably well, despite the colour pairs in these datasets were not similar to those typically employed in the automotive industry (CIE Publication x038:2013, 465-469). Here we have tested again AUDI2000 together with 11 advanced colour-difference formulas (CIELUV, CIELAB, CMC, BFD, CIE94, CIEDE2000, CAM02-UCS, CAM02-SCD, DIN99d, DIN99b, OSA-GP-Euclidean) for three visual datasets we may consider particularly useful to the automotive industry because of different reasons: 1) 828 metallic colour pairs used to develop the highly reliable RIT-DuPont dataset (Color Res. Appl. 35, 274-283, 2010); 2) printed samples conforming 893 colour pairs with threshold colour differences (J. Opt. Soc. Am. A 29, 883-891, 2012); 3) 150 colour pairs in a tolerance dataset proposed by AUDI. To measure the relative merits of the different tested colour-difference formulas, we employed the STRESS index (J. Opt. Soc. Am. A 24, 1823-1829, 2007), assuming a 95% confidence level. For datasets 1) and 2), AUDI2000 was in the group of the best colour-difference formulas with no significant differences with respect to CIE94, CIEDE2000, CAM02-UCS, DIN99b and DIN99d formulas. For dataset 3) AUDI2000 provided the best results, being statistically significantly better than all other tested colour-difference formulas.

Quantum discord measures the fraction of the pair-wise mutual information that is locally inaccessible in a multipartite system. Nonzero quantum discord has interesting and significant applications because although non-zero entanglement guarantees the existence of quantum correlation in a bipartite quantum system, zero entanglement does not guarantee the absence of a quantum correlation. On the other hand, many quantum optics systems can be described as deformed quantum oscillators. In this work, we investigate the quantum discord of bipartite entangled nonlinear coherent states, in the context of the so-called f-deformed coherent states algebra. To calculate the quantum discord, we consider quasi- Werner mixed states bases on bipartite entangled f-deformed coherent states. Two explicit analytic expressions are derived for the quantum discord of two different nonlinear deformed coherent states. The first one considers deformed coherent states obtained as eigenstates of the annihilation deformed operator, and the second one is obtained by using a deformed displacement operator. We compare the quantum discord of those states, when the nonlinear deformation function is either associated with the SU(1,1) coherent states in the Gilmore-Perelomov or Barut-Girardello representations, respectively.

Among many applications quantum weak measurements have been shown to be important in exploring fundamental physics issues, such as the experimental violation of the Heisenberg uncertainty relation and the Hardy paradox, and have also technological implications in quantum optics, quantum metrology and quantum communications, where the precision of the measurement is as important as the precision of quantum state preparation. The theory of weak measurement can be formulated using the pre-and post-selected quantum systems, as well as using the weak measurement operator formalism. In this work, we study the quantum discord (QD) of quasi-Werner mixed states based on bipartite entangled coherent states using the weak measurements operator, instead of the projective measurement operators. We then compare the quantum discord for both kinds of measurement operators, in terms of the entanglement quality, the latter being measured using the concept of concurrence. It’s found greater quantum correlations using the weak measurement operators.

Many digital image applications like digitization of cultural heritage for preservation purposes operate with compressed files in one or more image observing steps. For this kind of applications JPEG compression is one of the most widely used. Compression level, final file size and quality loss are parameters that must be managed optimally. Although this loss can be monitored by means of objective image quality measurements, the real challenge is to know how it can be related with the perceived image quality by observers. A pictorial image has been degraded by two different procedures. The first, applying different levels of low pass filtering by convolving the image with progressively broad Gauss kernels. The second, saving the original file to a series of JPEG compression levels. In both cases, the objective image quality measurement is done by analysis of the image power spectrum. In order to obtain a measure of the perceived image quality, both series of degraded images are displayed on a computer screen organized in random pairs. The observers are compelled to choose the best image of each pair. Finally, a ranking is established applying Thurstone scaling method. Results obtained by both measurements are compared between them and with other objective measurement method as the Slanted Edge Test.

A goniophotometer to characterize the angular distribution of the averaged luminous intensity of LEDs has been developed at Optics Institute of CSIC. Distributions of for four low-power LEDs transfer standards (red, blue, green and white) for luminous flux and luminous intensity are shown. A proper characterization of the angular luminous intensity distribution allows measurement uncertainties to be better determined. The instrument has got a photometer placed on a ruled optical bench to vary the source-detector distance and a CCD camera to carry out the alignment of the LEDs respect to the centre of geometrical reference system. Measurements were taken at a distance of 316 mm (condition A of the CIE) to different LEDs by varying the polar angle between 0° and 90° with a step of 5° and the azimuth angle between 0° and 180° with a step of around 11°. The red LED is the most Lambertian, whereas the blue, green and white LEDs have a different behavior. Finally, to identify systematic errors, a comparison with the measurements of a similar goniophotometer in Physikalisch-Technische Bundesanstalt (PTB) was carried out.

This paper describes the design and fabrication of a system for acquisition and image processing to control the removal of thorns nopal vegetable (Opuntia ficus indica) in an automated machine that uses pulses of a laser of Nd: YAG. The areolas, areas where thorns grow on the bark of the Nopal, are located applying segmentation algorithms to the images obtained by a CCD. Once the position of the areolas is known, coordinates are sent to a motors system that controls the laser to interact with all areolas and remove the thorns of the nopal. The electronic system comprises a video decoder, memory for image and software storage, and digital signal processor for system control. The firmware programmed tasks on acquisition, preprocessing, segmentation, recognition and interpretation of the areolas. This system achievement identifying areolas and generating table of coordinates of them, which will be send the motor galvo system that controls the laser for removal

The miniaturization of photonic components in integrated optic waveguide devices to microscale platform has attracted enormous attention from the researchers and entrepreneurs. In this paper, we present and report a comparative study of photonic integrated planar waveguide based couplers using a mathematical model based on sinusoidal mode simple effective index method (SEIM). The basic photonic integrated components such as directional coupler (DC), two mode interference (TMI) coupler and multimode interference (MMI) coupler have been designed and fabricated using the versatile SiON waveguide technology (SiON as the waveguide core material using silica waveguide). The experimental results have been compared with the SEIM based theoretical results and further verified with the commercially available software tool based on beam propagation method (BPM). With a focus towards device compactness, particular emphasis is placed on device geometry in an endeavour to achieve the same. In this direction, the theoretical and experimental results obtained have been compared with tooth shaped grating assisted geometry for these photonic components. It is found that the grating assisted structures have the beat length ~0.5 times lower than that of the conventional geometry. Further it is seen that the beat length of TMI coupler is smaller compared to the DC and MMI coupler.

We present a proposal for an experiment in which birrefringence induced in a material is measured using weak quantum measurements. It is known that birrefringence can be induced in optical crystals, liquid crystal arrays and the so called photonic crystals by applying a DC field. The standard weak measurement analisys was applied to find the tolerance for the angular positioning of the polarizers used in the experiment.

Status of binocular vision is evaluated using binoculars and accommodative tests. The results of these tests allow the optometrist to decide or the type of lenses has to be prescribed or whether a vision therapy is required. The aim of this work is to check the accuracy of the measurement of the relative amplitude of accommodation. Relative accommodation amplitude assesses the ability to increase or decrease the accommodation when convergence demand is constant. The eye must be neutralized to take the measurement. Because the test is situated at a distance of 40 cm, it is considered that the convergence is 2'5 am and the accommodation 2'50 D. However, this assumption could lead to important errors in ammetropic subjects due to the eye after neutralization accommodates in the image produced by the lens forms and converges in the position of the effective binocular object [1]. Therefore, it is necessary to set measurement conditions in which the accommodative and convergence stimulus are the same for all subjects. Furthermore, the lenses added on the neutralization to determine the relative amplitude of accommodation do not correspond to the dioptric value of relaxation and stimulation of the eye accommodation. To obtain this value a more precise calculation has to be performed.

A fluorene based copolymer was synthesized for electroluminescent application. To the main chain of polymer the nitrogen heterocyclic, 1H-pyrazolo[3,4-b]quinoxaline, unit was introduced. The incorporation of this derivative tuned the emission from the blue to yellow-green one. A simple, single layered device was fabricated with the configuration ITO/PEDOT/co-poly-FLU-PQX/Ca/Mg.

In this work, we present a novel Panoramic Fringe Projection system (PFP) to retrieve the three-dimensional topography of quasi-cylindrical objects along their full length and around the entire circumference. The proposed procedure uses a 45° concave conical mirror to project a circular sinusoidal fringe pattern onto a specimen placed coaxially to the mirror and at the same time to image the modulated fringe pattern diffused from the object surface. In order to obtain the required sensitivity, an axicon is used to create a divergent fringe pattern with constant pitch. By processing the phase map, information on the radius over the full 360° surface of the sample can be obtained by using a single-view series of images captured from a single camera. To verify the feasibility of the PFP technique, a tubular sample with shape discontinuities has been tested. The proposed method demonstrated to be able to retrieve the accurate topography of quasi-axial-symmetric samples with complex geometries for a large variety of applications.

Hydrogen doped amorphous silicon carbide layers were grown by radiofrequency magnetron sputtering technique using a gas mixture of Ar and H₂. The film thickness, the refractive index and the absorption coefficient of the films were obtained by means of optical transmittance in the UV/VIS/NIR spectral region. In order to study the effect of the hydrogen doping on the optical properties of the layers, a constant hydrogen flux was used during the deposition process. The optical bandgap was calculated using different models of the fundamental absorption region. First, a good linear dependency in the Tauc-plot was observed from which the bandgap could be calculated. Second, the E₀₄ iso-absorption optical gap was extracted. Finally, the Urbach rule was used to determine the Urbach energy and the Urbach focus of the films. In order to correlate the bandgap variation with further thermal annealing temperatures and the out diffusion of hydrogen, the vibrational properties of the different bonds were studied through FTIR measurements. Such spectra present the Si-H, the Si-CH_n and Si-C bonds. Finally, the material exhibited an enhancement of the optical bandgap when doped with hydrogen. And moreover, a critical annealing temperature is found for which the bandgap reached its maximum value in both cases, doped and undoped samples.

To improve the efficiency of Nd³⁺-doped YAG solar laser, cross-pumped Cr³⁺ and Nd³⁺ co-doped YAG ceramic material has attracted more attentions in recent years. The sensitizer Cr³⁺ ions have broad absorption bands in the visible region. Despite the interests in Cr:Nd:YAG ceramic medium, researchers have achieved significant laser efficiencies with different Nd:YAG single-crystal rods. While it is clear about the effectiveness of Nd:YAG single-crystal rods for solar laser operation, there still exist some concerns about the advantages of Cr:Nd:YAG ceramics in solar-pumped lasers. A 0.9 m diameter Fresnel lens is used as an economical solar collector. A 4 mm diameter, 25 mm length 1.0 at% Nd:YAG single-crystal rod and a 0.1 at% Cr: 1.0 at% Nd:YAG ceramic rod are pumped alternatively within a conical cavity through a secondary concentrator. With the Nd:YAG rod, the maximum laser power is 12.3 W, corresponding to 19.3 W/m² collection efficiency. With the Cr:Nd:YAG ceramic rod, the maximum laser power is 13.5 W, corresponding to 21.2 W/m² collection efficiency. This result is, to the best of our knowledge, the highest collection efficiency achieved with Cr:Nd:YAG ceramic medium. There is also a 109% increase in slope efficiency. In summary, we have experimentally observed a moderate, but not significant, advantage of Cr:Nd:YAG ceramics over Nd:YAG single-crystal medium in both solar laser conversion and slope efficiency.