This PDF file contains the front matter associated with SPIE Proceedings Volume 10100, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

The design of two pumping schemes for mid-IR lasers based on photonic crystal fibers (PCFs) is illustrated. The PCFs considered in both pumping schemes are made of dysprosium-doped chalcogenide glass Dy³⁺:Ga₅Ge₂₀Sb₁₀S₆₅. The two optical sources are accurately simulated by taking into account the spectroscopic parameters measured on a rare earth-doped glass sample. A home-made numerical model based on power propagation equations and solving the ion population rate equations of the rare earth is developed and employed to perform a feasibility investigation. The first pumping scheme is based on optical power pumping at 1700 nm wavelength and allows beam emission close to 4400 nm wavelength, the efficiency is increased till about η = 22% by integrating a suitable optical amplifier after the laser cavity. The second pumping scheme exploits two pump beams at the wavelengths close to 2800 nm and 4100 nm and enables a laser emission close to 4400 nm wavelength with an efficiency higher than η = 30%. Both these sources could promote a number of promising applications in different areas such as satellite remote sensing, laser surgery, chemical/biological spectroscopy and mid-IR optical communication.

A significant issue for holmium-doped fiber lasers (HoDFLs) operating near 2 μm is multiphonon quenching due to the high phonon energy ~1100 cm^-1 of the silica host, which complicates power scaling due to reduced lifetimes and increased heating. Nanoparticle (NP) doping is a new technique where the structure surrounding the Ho ions is developed chemically prior to doping into the silica core. We have incorporated Ho³⁺ ions into various NPs, such as LaF₃, Al₂O₃ and Lu₂O₃, to shield them from the silica glass matrix. Results indicate slightly longer lifetimes with Ho:LaF₃ NPs and the possibility of further improvement with oxide NPs. We report the first of lasing in a Ho:Lu₂O₃ NP-doped fiber pumped at 1.95 μm and operating at 2.09 μm with a record slope efficiency of 85.2%.

Single crystal fibers are currently being developed for high power single frequency lasers in 1-2 µm region. Crystal fibers offer several advantages over traditional glass fibers such as silica fiber due to their higher thermal conductivity and higher stimulated Brillouin scattering (SBS) thresholds, along with excellent environmental stability and higher doping concentrations. Yb3+ and Ho3+ doped single crystal YAG fibers with diameters down to 17 µm and lengths >1m long have been grown using our state-of-the-art Laser Heated Pedestal Growth system. Single and double cladded rare earth doped crystal fibers have been fabricated using glasses where optical and physical properties were precisely matched to the core single crystal fiber. We also show successful fabrication of all crystalline core/clad fibers where thermal and optical properties are superior over glass based fibers. Various fabrication methods, optical characterization and gain measurements on these clad fibers will be reported.

This work presents a comparative study of the random lasing performance of several Nd-based stoichiometric compounds, including threshold and absolute slope efficiencies together with a discussion about the fundamental parameters which control the random laser operation in this kind of compounds.

Nano-colloids and nano-crystals doped with ions of rare-earth elements have recently attracted a lot of attention in the scientific community due to their potential applications as biomarkers, fluorescent inks, gain media for lasers and optical amplifiers. Many rare-earth doped materials of different compositions, shapes and size distribution have been prepared by different synthetic methods, such as chemical vapor deposition, sol-gel process, micro-emulsion techniques, gas phase condensation methods, hydrothermal methods and laser ablation. In this paper micro-crystalline powder of the rare-earthdoped compound NaYF₄:Yb³⁺, Er³⁺ was synthesized using a simple wet process followed by baking in open air. Under 980 nm diode laser excitation strong fluorescence in the 100 nm band around 1531-nm peak was observed from the synthesized micro-powder. The micro-powder was pulverized using a ball mill and prepared in the form of nano-colloids in different liquids. The particle size of the obtained nano-colloids was measured using an atomic force microscope and a dynamic light scatterometer. The size of the nano-particles was close to 100-nm. The nano-colloids were utilized as a filling media in capillary optical amplifiers and lasers. The gain of a 7-cm-long capillary optical amplifier (150-micron inner diameter) was as high as 6 dB at 200 mW pump power. The synthesized nano-colloids and the active optical components using them can be potentially used in optical communication, signal processing, optical computing, and other applications.

Co2+:II-VI chalcogenide (e.g. ZnSe, ZnS) crystals exhibit broad emission in the 3-4µm spectral range with absorption peaks at ~0.75µm, ~1.5µm, and ~2.9µm which can be used for excitation. Laser oscillation of Fe2+ with wavelength ~4µm has been demonstrated at 14K in Co:Fe:ZnSe/ZnS under energy transfer from Co2+ ions. However, recent efforts in obtaining laser oscillation in Co2+:ZnSe/ZnS crystals have been unsuccessful. This can potentially be explained by excited state absorption at the 4T2(F)→4T1(F) transition. In addition, the laser oscillation in Co:Fe:ZnSe/ZnS co-doped crystals was only observed at temperatures under 21K. We report measurements of Co:ZnSe/ZnS absorption and emission at room temperature and 14K as well as estimates of excited state absorption from these measurements. Also, the results of experiments showed increase of absorption at 2.94µm under alexandrite laser excitation in Co:ZnS, which could result from excited state absorption. The lifetime of induced absorption was ~100µs, which is close to the ~200µs lifetime of the 4T2 level. The model of excited state absorption at low temperature predicts strong absorption over the emission spectrum of Co2+ in ZnSe, which can explain the negative lasing results. The loss of laser oscillation in co-doped crystals with increased temperature can be explained by the broadening of excited state absorption of Co2+. The spectroscopic measurements of the excited state absorption spectrum of Co:ZnSe/ZnS will be presented at the conference.

At the nanoscale, the ZnGa₂O₄ spinel doped with chromium (III) is an interesting material for in vivo optical imaging due to its bright red persistent luminescence after UV and visible excitation. Moreover its persistent luminescent properties can be improved with the incorporation of bismuth (III) as a co-dopant without any structure changes. The nanoparticles are synthesized by soft chemistry using microwave heating in aqueous media. These very small sized nanophosphors (around 10 nm) present interesting long lasting persistent luminescence after annealing at 1000°C and they can be excited both under UV and under visible LED excitation. In this work we try to understand the mechanisms of the persistent luminescent properties of such nanomaterials. Thermoluminescence is performed to investigate trapping and detrapping processes as well as trap distribution. The chromium local environment is studied by Electron Paramagnetic Resonance. ⁷¹Ga Nuclear Magnetic Resonance is used to get information on the gallium ions repartition (tetrahedral or octahedral site) in the structure. Comparison of optical properties versus local structure increases the understanding of the persistent luminescence mechanism and gives insights to the new modalities for their use as nanoprobes for in vivo imaging.

Rare earths in glass matrices are promising for active optical devices as amplifiers and lasers. Emission originating from d-f transitions in sol-gel glass has not been studied very often, while those based on f-f transitions were widely utilized. However, d-f emission in rare earths is very important because of their strong oscillator strength and broad emission widths suitable for the application to scintillators and solid-state lasers. Co-doping of aluminum in sol-gel synthesis was known to be effective for the emission enhancement of trivalent terbium and europium. Recently, we applied aluminum co-doping to cerium and europium systems in sol-gel glass to succeed in the observation of strong blue light emission originating from d-f transitions. Glass samples were prepared with conventional sol-gel process where tetramethylorthosilicate was hydrolyzed in the mixture of water, ethanol and dimethylformamide with nitric acid catalyst. After adding cerium nitrate and aluminum nitrate, the solution experienced drying followed by calcination at 1,050°C under air environment. When molar ratio of cerium to silicon was adjusted at 0.1% and Al concentration was varied in 0.1 ~ 2.0%, transparent glass products showed bright and broad blue photoluminescence under UV illumination. The fluorescence lifetimes were found to be about 50 ~ 90 ns, indicating that the emission was due to d-f transitions. Considering the simplicity of the process, blue phosphors based on sol-gel glass will be very promising for future applications.

One key parameter in the race toward ever-higher power fiber lasers remains the rare earth doped optical core quality. Modern Large Mode Area (LMA) fibers require a fine radial control of the core refractive index (RI) close to the silica level. These low RI are achieved with multi-component materials that cannot be readily obtained using conventional solution doping based Modified Chemical Vapor Deposition (MCVD) technology. This paper presents a study of such optical material obtained through a full-vapor phase Surface Plasma Chemical Vapor Deposition (SPCVD). The SPCVD process generates straight glassy films on the inner surface of a thermally regulated synthetic silica tube under vacuum. The first part of the presented results points out the feasibility of ytterbium-doped aluminosilicate fibers by this process. In the second part we describe the challenge controlling the refractive index throughout the core diameter when using volatile fluorine to create efficient LMA fiber profiles. It has been demonstrated that it is possible to counter-act the loss of fluorine at the center of the core by adjusting the core composition locally. Our materials yielded, when used in optical fibers with numerical apertures ranging from 0.07 to 0.09, power conversion efficiency up to 76% and low background losses below 20 dB/km at 1100nm. Photodarkening has been measured to be similar to equivalent MCVD based fibers. The use of cerium as a co-dopant allowed for a complete mitigation of this laser lifetime detrimental effect. The SPCVD process enables high capacity preforms and is particularly versatile when it comes to radial tailoring of both rare earth doping level and RI. Large core diameter preforms - up to 4mm - were successfully produced.

An ytterbium (Yb) doped polarizing fiber is demonstrated. The fiber offers the opportunity to build all-fiber lasers with single polarization output and without the need for free-space polarizing components. Traditional single polarization fiber lasers utilize polarization-maintaining (PM) gain fiber with a single polarization stimulation signal. Whilst this results in an approximation to a single polarization laser, the spontaneous emission from the unstimulated polarization state limits the polarization extinction ratio (PER). The PER is further limited as the stimulated signal is prone to crosstalk. Furthermore, controlling amplitude modulation of the stimulated signal is critical for maximizing the peak power of an optical pulse, particularly for high energy lasers. If light is allowed to leak in to the unstimulated axis it will travel at a different velocity to the stimulated axis and can cross-couple back into the signal axis, creating an interference effect which leads to amplitude modulation on the signal pulse. Single-polarization Yb-doped fiber ensures that light on the fast axis is constantly attenuated; ensuring that light on the unstimulated axis cannot propagate and thus cannot degrade the PER or create amplitude modulation. In this paper we report on, to the best of our knowledge, the first demonstration of a single polarization Yb-doped bowtie optical fiber manufactured using a combination of Modified Chemical Vapor Deposition (MCVD) and rare-earth solution doping technology. The fiber has a single-polarization window of 80nm at the operating wavelength of 1060nm and a PER of >18dB. The fabrication and characterization of the fiber is reported.

The development of materials showing efficient red-emitting persistent luminescence is still an ongoing challenge. As it shows red emission, around 613 nm, Pr³⁺ remains a good candidate for such application. Indeed, the transition from its ¹D₂ excited state to its ³H₄ ground state is responsible of the red emission. In this paper the effect of Na substitution in NaNbO₃:Pr³⁺ by K or Li cations in term of Metal-to-Metal Charge Transfer (MMCT) band position and its possible effect on persistent luminescence properties were investigated. MMCT energy shows increasing tendency with increasing average distance between A site (A = Li, Na, K, Pr) of perovskite. The most intense (efficient) photoluminescence was observed under MMCT excitation in Li_0.03Na_0.97NbO₃:Pr³⁺. The relaxation pathways were discussed based on the configurational coordinate model.

Frequency up-conversion is a technique for the generation of high energy photon from two or more lower energy photons. Although many up-conversion techniques have been demonstrated such as parametric up-conversion or multi-photon absorption, their conversion efficiencies become negligible for high-order up-conversion. Alternatively, in thermal emission very high temperatures are needed for reasonable efficiencies and the emission is spectrally broad rendering this up-conversion method impractical for most applications. We present a new efficient extreme up-conversion method for generating NIR and visible wavelengths using CW LWIR laser by non-thermal-equilibrium excitation through spontaneous reduction of the chemical potential. In this method we exploit the high chemical potential of the pump specific modes to excite the vibronic states of the host, subsequently transferring the energy to chosen emitters, resulting in narrow non-thermal steady-state emission. All while, only residual energy contributes to material's temperature, thus keeping it at a comparably low temperature. We experimentally demonstrate 7, 10, 13, 16, and 20-fold up-conversion at external efficiency of up to 4%, exceeding black-body radiation of the bulk temperature. Furthermore, we present energy transfer between emitters, a phenomenon in contrast to thermal emission, showing the photoluminescence behavior of this method. We use CW CO2 laser (10.6m) to excite silica vibronic states and transfer the energy to rare-earth emitters at the NIR and visible spectrum. This new outlook on up-conversion via energy transfer paves the way for developing new light sources and new methods of imaging and detection with high efficiencies.

We have developed a highly stable electro-optic KTa1-xNbxO3 (KTN) deflector by enhancing electron transportation through KTN crystal. The amount of current is increased with 405-nm light irradiation to rapidly generate a stable refractive-index change, which induces deflection. The deflection angle is set at 160 mrad within tens of seconds and is kept at that angle for 3,000 hours. The developed deflector has been applied to a wavelength-swept light source to measure the thickness of Si wafers with a 3.6-mm optical length. The precision of 0.1-μm has been continuously achieved corresponding to the stability of the KTN deflector.

In this paper, we present an ultra-fast and high-contrast optical shutter with applications in atomic clock assemblies, integrated photonic systems, communication hardware, etc. The shutter design exploits the total light absorption phenomenon in a thin phase change (PC) material placed over a metal layer. The shutter switches between ON and OFF states by changing PC material phase and thus its refractive index. The PC material used in this work is Germanium Telluride (GeTe), a group IV-VI chalcogenide compound, which exhibits good optical contrast when switching from amorphous to crystalline state and vice versa. The stable phase changing behavior and reliability of GeTe and GeSbTe (GST) have been verified in optical memories and RF switches. Here, GeTe is used as it has a lower extinction coefficient in near-IR regions compared to GST. GeTe can be thermally transitioned between two phases by applying electrical pulses to an integrated heater. The memory behavior of GeTe results in zero static power consumption which is useful in applications requiring long time periods between switching activities. We previously demonstrated a meta-surface employing GeTe in sub-wavelength slits with >14 dB isolation at 1.5 μm by exciting the surface plasmon polariton and localized slit resonances. In this work, strong interference effects in a thin layer of GeTe over a gold mirror result in near total light absorption of up to 40 dB (21 dB measured) in the amorphous phase of the shutter at 780 nm with much less fabrication complexity. The optical loss at the shutter ON state is less than 1.5 dB. A nickel chrome (NiCr) heater provides the Joule heating energy required to achieve the crystallographic phase change. The measured switching speed is 2 μs.

LiDAR has become a critical requirement for Advanved Driver Assistance Systems (ADAS) as the automotive industry moves towards improved driver safety and autonomous cars. Silicon Photomultipliers (SiPM) and Single Photon Avalanche Diodes (SPAD) sensors are emerging as the most promising sensor technology for long range, >100m, direct time-of-flight LiDAR that needs to function in bright daylight and with low reflectance targets. SensL is developing a new range of SiPM, the R-Series, that have improved detection efficiency at longer wavelengths used in LiDAR. In parallel to the sensor development, SensL is working to understand the fundamental advantages SiPM and SPAD sensor arrays provide long-range, ADAS LiDAR systems. It will be shown that to achieve long range LiDAR with eye-safe lasers, a sensor with single photon sensitivity is required. This is due to the low number of returned photons from distances greater than 100m. When ambient daylight conditions are taken into account, the small returned signal at these distances can be easily lost in the noise and histogramming multiple laser pulses will be shown to provide the only method which allows for accurate time of flight ranging operation. The histogramming technique and the architecture used to implement it will be described. A portable long-range LiDAR demonstrator using SiPM sensors has been developed and will be presented including range accuracy versus distance and low reflective targets. This will be compared to a detailed Monte Carlo model which will be shown to accurately describes SiPM and SPAD array operation in LiDAR ranging.

An acousto-optic tunable filter (AOTF) is an all solid-state robust device with no-moving parts that has been used in the development of hyperspectral imagers from the ultraviolet to the longwave infrared. Such a device is fabricated by bonding a piezoelectric transducer on a specially cut prism in a birefringent crystal. When a radio frequency (RF) signal is applied to the transducer, a diffraction grating is set up in the crystal with grating period determined by the applied RF and the diffracted wavelength depends upon the applied RF and the prism parameters. When broadband white light is incident on the prism input facet, two orthogonally polarized diffracted beams at a specific wavelength with a narrow bandpass are transmitted for each applied RF. The transmitted wavelength can be tuned by varying the applied RF and this is used in a hyperspectral imager design. The spectral response of the transmitted intensity from an AOTF with a rectangular transducer has a sinc² distribution with a main lobe and a large number of sidelobes. In general, in hyperspectral imaging applications the light leakage from the sidelobes is not taken into account. When imaging is carried out for a scene with a laser or an intense source of light, the spectral images are affected by the light transmitted through these sidelobes away from the main lobe. We have carried out a detailed study of light transmitted through the sidelobes of a TeO₂ AOTF with a rectangular transducer operating in the shortwave infrared (SWIR) region from 0.9 to 1.7 μm. The AOTF imaging system used a telecentric confocal optics that compensates for AOTF aberrations, which are severe at high sidelobe operation. We used a 16-channel RF driver with independent amplitude and frequency control. By switching off specific RF signals applied to the AOTF, we measured the detailed sidelobe structure for the transmitted intensity by analyzing the spectral images and compared it with theoretical prediction. Here we present our experimental setup and results.

Since an immersion grating provides n (n: refractive index of its material) times higher spectral resolution compared to a conventional reflective grating of the same size, an immersion grating is a powerful optical device for the infrared high-resolution spectrometer. Recently a high-resolution spectrometer in the infrared wavelength range is increasing the importance increasingly for observations of relating with H₂O, NHx, NOx and organic molecules. Higher spectral resolution allows us to detect weak lines without spectral line confusion. On the other hands, there is no practical immersion grating for high-resolution spectrometer except Si immersion grating by anisotropic etching. It was very difficult for a fragile IR crystal to manufacture a diffraction grating precisely by machining. Our original free-forming machine has accuracy of a few nano-meter in positioning and stability. We succeeded in fabricating immersion gratings with three kinds of materials. Three materials are CdZnTe, germanium and InP, each refractive index is about 2.7, 4.0 and 3.2 respectively. By combining these devices, a spectrometer with immersion grating is realizable in the wavelength range of 1.5-20um. Thereby, the realization of these immersion gratings has led to a dramatic improvement in the operability and performance of next generation high-performance spectrometer. In this paper, we report performance of our immersion gratings and other possibility.

Detecting, counting, and sizing nanoparticles is a key problem in biomedical, environmental, and materials synthesis fields. Here we demonstrate a cost-effective and high-performance approach that uses wide-field microscopy enabled by the combination of inline lensfree holography, pixel super-resolution, and vapor-condensed nano-scale lenses (nanolenses). These nanolenses are composed of liquid polyethylene glycol (PEG) that self-assembles in situ around particles of interest. A nanolens around each particle generates a more substantial phase shift than the native object alone, making it more easily detectible in the imaging system. This latest generation of lensfree holographic microscope incorporates more precise temperature control and utilizes a hermetically sealed chamber allowing for a controlled, repeatable environment for simultaneous hologram measurements and nanolens formation. To further enhance the sensitivity of our system, we have compared the performance of two different pixel super-resolution algorithms: shiftand- add and gradient descent. It was found that the gradient descent approach provides the highest resolution. Detection and localization results for 1 μm, 400 nm, and 100 nm particles are presented.

Three types of Fiber Bragg gratings (FBGs) were inscribed in H₂-loaded and H₂-free fiber with phase mask using 800nm femtosecond (fs) laser, ultraviolet (UV) excimer laser respectively. Their reflection spectra regenerating procedure were observed under different annealing temperature and the models of regeneration process as well as annealing temperature and time were established. Experiments and model fitting show that there were definite regeneration temperature threshold for fs FBGs written in H₂-free fiber, H₂-loaded fiber and UV FBGs in H₂-loaded fiber. The temperature sensing characteristic of RFBGs were investigated and compared experimentally under ultra-wide temperature range.

Luminescence properties of Pr³⁺ and Dy³⁺ doped GaGeSbSe(S) vitreous systems have been studied. The synthesis process to obtain homogeneous glasses has been determined and fibers have been successfully drawn from the produced preforms and characterized. Fibers show a mid-IR luminescence matching with the CO₂ absorption band at 4.3 μm and can be used in an environmental monitoring sensor for the CO₂ underground storage. The luminescence and glasses properties have been investigated on bulk samples and fibers in order to improve the efficiency of an optical CO₂ sensor prototype operating from high to low concentration, down to the ppm level.

In this work we report a detailed spectroscopic study of the near-infrared to visible upconversion luminescence in Erdoped lanthanum oxysulfide crystal powders after excitation of level ⁴I_9/2. The analysis of the decay curves of the upconversion emission indicates that energy transfer upconversion is the main mechanism responsible for the green (⁴S_3/2) and red (⁴F_9/2) upconversion luminescence. The temperature dependence of the green upconverted emission from the two thermally coupled ²H_11/2 and ⁴S_3/2 levels has been analyzed in the 230 K- 300 K temperature range in order to check its availability as a temperature sensor.

For the first time, we perform a theoretical investigation into the operation of a multilayer nanocomposite based optical fibre surface plasmon resonance hydrogen sensor. The sensor consists of Pd nanoparticles embedded in host material of Ta₂O₅ over a thin continuous film of Ag, in place of a small unclad section of the fibre core. We compare the operation of this device to a sensor employing an individual multilayer based sensing stack (Ag/Ta₂O₅/Pd) by measuring the normalised output power through the fibre, and the sensor sensitivity. A much smaller modulation layer thickness is required in the NC structure in order to achieve the same spectral shift of the resonance location as compared to the IM based structure, thus indicating a faster response time. In both sensor types, sensitivity increased to a maximum with increasing modulation material thickness, beyond which it began to fall off. The NC based structure operated with overall higher sensitivity than the IM structure.

Chalcogenide integrated optic (IO) waveguides operating in the mid-wave infrared (MWIR) are of interest for a variety of applications. They are potentially useful in compact MWIR laser sources for applications such as gas sensing and infrared countermeasures. Most work on chalcogenide integrated optics to date, however, has focused on arsenic sulfide, As₂S₃, or glasses with similar compositions. These glasses are known to suffer from a host of photo-induced effects including photo-darkening, photo-induced crystallization, and low optical damage thresholds. Furthermore, they can typically accept only low concentration of rare earth dopants without clustering or crystallization. Gallium lanthanum sulfide (GLS) is an alternative chalcogenide glass with great potential for use in IO devices operating in the MWIR. Like As₂S₃, GLS exhibits a large transparency window in the MWIR and high optical nonlinearity, but it does not suffer from the same type of photo-induced effects. High rare earth dopant concentrations without clustering are possible in GLS because rare earth ions substitute for lanthanum ions in the glass matrix. IO waveguides have previously been fabricated in GLS by several methods. Formerly, it was hypothesized that patterning GLS via reactive ion etching (RIE) was impossible do the presence of lanthanum and rare earth dopant ions, but we present results for GLS waveguides fabricated via RIE. In addition, we demonstrate 2.7 μm emission from Er³⁺-doped GLS waveguides resulting from erbium’s ⁴I_11/2→⁴I_13/2 transition.

We report on the design and manufacturing parameters of waveguiding structures of anisotropic nonlinear crystals that are employed for harmonic conversions, using Adhesive-Free Bonding (AFB®). This technology enables a full range of predetermined refractive index differences that are essential for the design of single mode or low-mode propagation with high efficiency in anisotropic nonlinear crystals which in turn results in compact frequency conversion systems. Examples of nonlinear optical waveguides include periodically bonded walk-off corrected nonlinear optical waveguides and periodically poled waveguide components, such as lithium triborate (LBO), beta barium borate (β-BBO), lithium niobate (LN), potassium titanyl phosphate (KTP), zinc germanium phosphide (ZGP) and silver selenogallate (AGSE). Simulation of planar LN waveguide shows that when the electric field vector E lies in the k-c plane, the power flow is directed precisely along the propagation direction, demonstrating waveguiding effect in the planar waveguide.

Employment of anisotropic nonlinear optical waveguides, for example in combination with AFB® crystalline fiber waveguides (CFW), provides access to the design of a number of novel high power and high efficiency light sources spanning the range of wavelengths from deep ultraviolet (as short as ~200 nm) to mid-infrared (as long as about 18 μm). To our knowledge, the technique is the only generally applicable one because most often there are no compatible cladding crystals available to nonlinear optical cores, especially not with an engineer-able refractive index difference and large mode area.

Engineering a low-cost graphene- based opto-electronic device is a challenging task to accomplish via a single-step fabrication process. Recently scientists have started focusing on the development and use of a laser-based method for efficient reduction of graphene oxide (GO) films at low-temperature. Our proposed technique utilizes a laser beam for non thermal reduction of solution processed GO layers onto film substrates. Compared to other reduction techniques, it is a single-step, facile, time consuming, non-contact operation, environment-friendly, patternable, low cost, and can be performed at room temperature in ambient atmosphere without affecting the integrity of either the physical properties or the lattice of graphene. Laser scribed reduced graphene (LSRG) is shown to be successfully produced and selectively patterned from the direct laser irradiation of graphite oxide films under ambient conditions. In addition, by varying the laser's intensity, power, and irradiation treatments, the electrical properties of LSRG can be accurately attune over five orders of magnitude of conductivity. Feature has proven difficulty with other methods. This credible, scalable approach is mask-free, does not require certain expensive chemical reduction agents, and can be performed at ambient conditions starting from aqueous graphene oxide flakes. The non thermal nature of this method combined with its scalability and simplicity, makes it very attractive for the manufacturing of future generation large-volume graphene-based opto/electronics.

An interferometric method has been developed and employed at Onyx Optics, Inc. to accurately measure the thermal conductivity of laser-active crystals as function of dopant concentration or inactive materials such as single crystals, optical ceramics and glasses relative to a standard of assumed to be known thermal conductivity [1]. This technique can also provide information on heat transfer resistance at the interface between two materials in close thermal contact.

While the technique appears generally applicable to composites between optically homogeneous materials, we report on thermal conductivities and heat transfer coefficients of selected adhesive-free bond (AFB®) laser composites. Single crystal bars and AFB bonded crystal doublets with the combinations of various rare-earth (Nd³⁺, Yb³⁺, Er³⁺, and Tm³⁺ trivalent ion doped YAG, and un-doped YAG have been fabricated with the AFB technique. By loading the test sample in a vacuum cryostat, with a precisely controlled heat load at one end of the doublets, the temperature distribution inside the single crystal or the composite samples can been precisely mapped by measuring the optical path difference interferometrically, given the material’s thermal-optical properties. No measurable heat transfer resistance can be identified for the AFB interfaces between low-concentration doped YAG and un-doped YAG. For the heavily doped RE³⁺:YAG, for example, 10% Yb:YAG, the thermal conductivity measured in our experiment is 8.3 W/m•K, using the thermal conductivity of undoped YAG reported in [1] as basis. The thermal transfer resistance of the AFB interface with un-doped YAG, if there is any at the AFB interface, could be less than 1.29×10^-6 m²•K/W.

We present an overview of the fabrication process and characterization of germanate, germanate-tellurite and tellurite microstructured fibers or step-index fibers with different index contrasts. For microstructured fibers, we exploit the generated SC for methane spectroscopy measurements in the mid-infrared by means of the supercontinuum absorption spectroscopy technique. We demonstrate also an ageing process of microstructured fibers in ambient atmosphere. For stepindex fibers, several compatible core/cladding glasses were explored for fiber manufacturing with a dehydration process, allowing the drawing of low-OH tellurite fibers. We report both numerical and experimental demonstrations supercontinuum (SC) generation in these fibers. Finally we report our latest results in the generation of SC until 5.3 μm in a step-index tellurite fiber.

Graded index (GRIN) optical materials and novel lens offer numerous benefits for infrared applications, where selection of conventional materials is limited. For optical systems that must perform over wide spectral regions, the reduction of size weight and complexity can be achieved through the use of GRIN elements. At the Naval Research Laboratory (NRL) we are developing new technologies for IR gradient index (IR-GRIN) optical materials. This paper will present the latest progress in the development of these materials including their design space guidelines, fabrication, metrology, optics characterization, and preliminary imaging demonstration.

In this paper, the possibility to fasten the amorphization process of chalcogenide glasses by mechanical alloying is described. Several ways were investigated to optimize the time of milling permitting a faster production and also avoiding a higher contamination. Thus, the influence of gallium addition which could act as a solvent because of its low melting point and its low vapor pressure has been studied. Then, two conventional ways of milling were compared using a PM100 planetary grinder and a SPEX MILL 8000D, which present two different ways of rotation. Finally, the pollution by WC during mechanical alloying and by carbon during sintering has been investigated by LMS measurements.

There is a strong desire to reduce size and weight of single and multiband IR imaging systems in ISR operations on hand-held, helmet mounted or airborne platforms. Current systems are limited by bulky optics. We have recently developed a large number of new optical materials based on chalcogenide glasses which transmit in SWIR to LWIR wavelength region that fill up the glass map for multispectral optics and vary in refractive index from 2.38 to 3.17. They show a large spread in dispersion (Abbe number) and offer some unique solutions for multispectral optics designs. These glasses were specifically designed to have comparable glass molding temperatures and thermal properties to be able to laminate and co-mold the optics and reduce the number of air-glass interfaces (lower Fresnel reflection losses). These new NRL glasses also have negative or very low positive dn/dT making it easier to athermalize the optical system. This presentation will cover discussions on the new optical materials, multispectral designs, fabrication and characterization of new optics.

SCHOTT has introduced IRG 27, a classic chalcogenide glass (As₂S₃), possessing transparency from approximately 0.65 μm to well into the long-wavelength IR (> 10 μm). Additionally, this glass exhibits an extremely small thermo-optic (dn/dT) value for most of its transparency range, a critical attribute in certain applications. Relatively low density and a good thermal expansion match to aluminum are further useful characteristics of IRG 27.

We investigated the temperature characteristics of a modularized semiconductor optical amplifier (SOA) utilizing InAs/AlGaAs quantum dot (QD) in the active layer operating at C-band (1.53μm–1.56μm). It has been reported by many literatures on physics that QDs are superior at energy efficiency and leads to less thermal energy generation. By changing the temperature of the Peltier element inside the module from 20℃ to 80℃, we measured the difference in the gain at each input power and injection current. The QD-SOA we measured was utilizing InAs QD in active layer and the laminated structure had 20 layers having 20nm of intermediate layers which refers to the width between QDs. When the input power was -50 dBm, we successfully confirmed more than 10 dB at the Peltier element temperature of 70℃ by injecting a current larger than 400 mA. In addition, we obtained a maximum gain of 20.68 dB at the center wavelength and a constant gain of approximately 15 dB at other Peltier element temperatures. It can be concluded from the output of the experiment that this QD-SOA can be put to use in optical communication in several situations where the temperature ranges between 20℃ to 80℃. This involves a new approach towards the application of QD amplifiers in the field of optical fiber communications.

Several holographic and interferometric applications would benefit significantly from a diode laser based coherent light source near 633 nm. For this purpose a laser diode based on an AlGaAs/AlGaInP structure for emission in the red spectral range was developed. The laser chip features a ridge waveguide and a DBR surface grating at the rear side with a peak reflectivity at 633 nm. The laser was mounted in a butterfly-style package for temperature stabilization. The beam emitted by the laser diode was shaped with two cylindrical micro-lenses and passed through a custom-built CdMnTebased micro-optical isolator. The beam behind the isolator was coupled into a polarization maintaining (PM) single-mode fiber using an aspherical lens. The optical output power of the fiber was about 1.7 mW at 100 mA.

High reflection dielectric distributed Bragg reflector (DBR) can be used with high Q optical cavity to narrow down the spectrum optical source, for experimental quantum electro-dynamics, etc. To construct a free space optical cavity for a local oscillator of the state-of-the-art optical frequency standards, concave mirrors are used as one of the end mirrors of the cavity. Usually, the high reflection DBR is fabricated by depositing dielectric materials on a glass substrate. However, the ultimate stability of the optical cavity is limited by the thermal noise of dielectric DBR. To overcome this problem, a crystalline DBR was proposed to stabilize the optical cavity, which can reduce thermal noise. In this study, we fabricated crystalline DBR by GaAs/AlAs compound semiconductor on a concave GaAs substrate. Although a traditional semiconductor substrate has atomically flat surface, we fabricated a concave surface with a curvature radius of 1000 mm on the GaAs substrate by optical quality polishing. Then, we carried out wet etching and introduced it in vacuum chamber for molecular beam epitaxy (MBE). In the MBE growth chamber, we carried out thermal cleaning with As4 at a substrate temperature of 600°C. Next, the GaAs/AlAs DBR structure was grown at 580°C. The evaluation of surface roughness was conducted by atomic force microscopy, which showed a roughness of 0.165 nm in 1 × 1 um measurement such that a very smooth surface can be obtained.

The integration of silicon photomultiplier (SiPM) and frontend electronics in a suitable optoelectronic CMOS process is a promising approach to increase the versatility of single-photon avalanche diode (SPAD)-based singlephoton detectors. By integrating readout amplifiers, the device output capacitance can be reduced to minimize the waveform tail, which is especially important for large area detectors (>10 × 10mm²). Possible architectures include a single readout amplifier for the whole detector, which reduces the output capacitance to 1:1 pF at minimal reduction in detector active area. On the other hand, including a readout amplifier in every SiPM cell would greatly improve the total output capacitance by minimizing the influence of metal routing parasitic capacitance, but requiring a prohibitive amount of detector area. As tradeoff, the proposed detector features one readout amplifier for each column of the detector matrix to allow for a moderate reduction in output capacitance while allowing the electronics to be placed in the periphery of the active detector area. The presented detector with a total size of 1.7 ♦ 1.0mm² features 400 cells with a 50 μm pitch, where the signal of each column of 20 SiPM cells is summed in a readout channel. The 20 readout channels are subsequently summed into one output channel, to allow the device to be used as a drop-in replacement for commonly used analog SiPMs.

At the 940 nm wavelength, solar background irradiance is relatively low and device-mounted monochromatic LED emission can be used to illuminate and assess the shape, distance, and optical properties of objects. We report here NIR imaging that outperforms existing CMOS sensors by achieving record 42% quantum efficiency at 940 nm for a 1.1 μm pixel. The rationally engineered material properties of QuantumFilm allow tuning of the spectral response to the desired wavelength to achieve quantum efficiency that exceeds 40%. In addition, the combination of high QE with QuantumFilm’s distinctive film-based electronic global shutter mechanism allows for extremely low illumination power and therefore lowers time-averaged system power when imaging with active illumination.

We present the possibility to tailor the optical properties of 1D photonic structures by using more than two materials and by clustering the high refractive index (hRI) layer in the structures. In particular, we show that: i) with a photonic crystal made of i different materials, the photonic band gap splits in i-1 bands; ii) with a proper choice of the layer thickness, disordered photonic structures made with a high number of layers show periodic transmission peaks; iii) when the size of the hRI layer clusters, randomly distributed within the low refractive index layers, follows a power law distribution, the total light transmission follows a sigmoidal function. Furthermore, we discuss the fabrication aspects to realize the above mentioned photonic structures.

Chalcogenide glasses are known for their large transparency in the mid-infrared (Mid-IR) and their high nonlinear optical properties. Indeed, chalcogenide glasses can present a high non-linear coefficient (n2), 100 to 1000 times larger than for silica glass, depending on the composition. An original way to obtain fibers is to design microstructured optical fibers (MOFs). These fibers present unique optical properties thanks to the high degree of freedom in the design of their geometrical structure. Various chalcogenide MOFs operating in the mid-IR range have been elaborated in order to associate the high nonlinear properties of these glasses and the original MOF properties. Different glass compositions and different designs have been achieved depending on the intended application. Indeed, chalcogenide MOFs might lead to new devices with unique optical properties in the Mid-IR domain like multimode or endlessly single mode transmission of light, small or large mode area fibers, non-linear properties for wavelength conversion or generation of supercontinuum sources. In the 1-12 µm window, single mode fibers, polarization maintaining fibers and exposed core fibers have been realized for Gaussian beams propagation and sensors applications. In this context, different applications such as Brillouin laser, all optical demultiplexing, mid-IR supercontinuum generation, quantum cascade laser pigtailing and mid-IR spectroscopy will be exposed.

Monoclinic HfO₂ nanoparticles (9 - 45 nm) are synthesized using a sol-gel method and optically characterized using transmission- and angle-dependent reflection spectroscopy in the mid- to far-infrared. A detailed HfO₂ identification of the infrared-active phonon modes is presented; consistent with previously reported thin film values, and in excellent agreement with density functional perturbation theory calculations. An anomaly is observed in both reflection and transmission measurements, at 556 cm^-1 that is not attributed to the optical phonon modes. Numerical models indicate that this measured anomaly is in the spectral region of a localized surface phonon polariton mode. The results of this work suggest that HfO₂ nanoparticles could enable new mid- and far-infrared materials and devices with engineered optical properties.

With all-normal-dispersion fibers, highly coherent supercontinuum (SC) can be obtained, which has several applications. Traditional air-hole photonic crystal fibers encountered some limitations for such light emission. In this study, all solid composite fibers with a silica glass cladding and a yttria-alumino-silicate glass core were fabricated, which were designed for flat coherent SCs. We achieved a flat normal dispersion in this composite fiber. Flat SCs were experimentally demonstrated with different pump conditions. The simulated SC spectra coincided well with the experimental results. It also indicated that a coherent SC with more than one octave can be obtained with higher input power.

As optical fiber is being used in much harsher environments than traditional telecommunications (e.g. distributed temperature sensing at elevated temperatures) understanding its mechanical properties at high temperatures is urgently needed. As a continuation of our previous work on high temperature strength of silica optical fiber, we report our results in fatigue behavior of polyimide coated silica optical fiber at 300°C in this paper. Fiber fatigue is the degradation in strength caused by a stress dependent chemical reaction between water vapor and the surface of the silica glass. In contrast to the published data on degradation in mechanical properties of silica optical fiber at elevated temperatures, our observations indicate a negligible decrease in strength along with unchanged, n-value, (fatigue resistant factor) at 300°C. To determine the n value, we tested tensile strength of the fiber using four different strain rates while the subject under test was at 300°C. The results indicate that the polyimide coating on the silica glass fiber continues to serve as an effective water vapor barrier at 300°C. These results will be compared with data available for room temperature performance of this silica/polyimide combination and possible failure mechanisms will be discussed.

A simple, esy-to-use and physically meaningful analytical model is developed for the evaluation of the critical (Euler) force for a dual-coated fiber-optic connector. The obtained results can be used in the analysis and physical (mechanical) design of connectors of the type in question. The general concepts are illustrated by a practical numerical example.

In the article it is shown how lightweight a primary mirror of a space telescope can be made by using new material silicon carbide. The article includes theoretical calculations made with the help of software. The main aim of calculations is to get lightweight mirror with small optical surface deflections. The mirror diameter is more than 1 m.

We report here the design of a new chalcogenide hybrid microstructured optical fiber (HMOF) with a buffer layer around the core and its potential performance of tailoring chromatic dispersion and supercontinuum (SC) generation. The new chalcogenide HMOF has an AsSe₂ core. The refractive index difference Δn between the AsSe₂ core and cladding material is supposed to be 0.3. The fiber microstructure and the Δn between the core and buffer materials are designed in order to obtain broad anomalous dispersion regimes with near-zero and flattened chromatic dispersion profiles for broadband SC generation. Moreover, the suppression of chromatic dispersion fluctuation caused by fiber transverse geometry variation is investigated. By using the proposed chalcogenide buffer-embed HMOFs, the calculation shows that near-zero and flattened anomalous chromatic dispersion regimes from 4.5 μm can be obtained. When the variation of fiber structure occurs for ±1, ±5 and ±10 %, the chromatic dispersion fluctuation can be greatly suppressed. In addition, the calculation shows that a broad SC spectrum from 2.5 to more than 16.0 μm can be obtained when a 0.9-cmlong section of the new chalcogenide buffer-embed HMOF is pumped at 5.0 μm by a femtosecond laser with 1-kW peak power.

We demonstrate the effects of stimulated Raman scattering (SRS) in the all-solid-core chalcogenide microstructured optical fibers (MOFs) with AsSe₂ core and As₂S₅ cladding, which are fabricated by the rod-in-tube drawing technique. The core diameters of the MOFs are ~6.3 (Fiber I), 3.0 (Fiber II), 2.6 (Fiber III) and 2.2 (Fiber IV) μm, respectively. The chromatic dispersion of the fundamental mode in Fibers I-IV is simulated by the full-vectorial mode solver technique. The first-order Stokes wave is investigated in the fibers with different core diameters pumped by the picosecond pulses at 1958 nm. In Fiber I, no obvious Raman peak is observed with the pump power increasing, because the effective nonlinearity is not high. In Fiber II, a Raman Stokes peak at ~2065 nm begins to emerge at the pump power of 110 mW. The conversion efficiency is as weak as -36.6 dB at 150 mW pumping. In Fiber III, the first-order Raman peak at ~2060 nm begins to emerge at 40 mW pumping. The conversion efficiency is -15.0 dB, which is 21.6 dB higher than that in Fiber II. In Fiber IV, the Stokes peak at 2070 nm begins to appear at 56 mW pumping. The maximum conversion efficiency of the first-order Stokes wave is obtained in the MOF with the core diameter of 2.6 μm. The evolution of the first-order Stokes wave with pump power and fiber length is investigated. This is the first demonstration of Raman effects in the AsSe₂-As₂S₅ MOF, to the best of our knowledge.

The objective of the paper was to demonstrate feasibility of a chemical (ammonia) sensor using dye-doped polymer nanocomposite with upconversion phosphor nano-particles. The micro-crystalline powder of upconversion rare-earth phosphor NaYF₄:Yb³⁺, Er³⁺ was synthesized using a simple wet process followed up by baking in open air. The powder was reduced into nano-colloid with 100-nm nano-particles using the ball milling process. The nano-colloid was added to the solution of polymer poly(methyl methacrylate) known as PMMA. Additionally, a pH indicator dye (Phenol Red or Bromothymol Blue) was dissolved in polymer solution. The dye-doped polymer nanocomposite films were deposited on substrates using the dipping process followed by baking in order to evaporate the solvent. The deposited nano-photonic sensor film had bright green upconversion fluorescence with a spectral peak at 540 nm attributed to the nano-photonic rare-earth phosphor pumped with a 980 nm infrared diode laser. The spectrum of green emission matched the absorption band of the indicator dye exposed to ammonia. When the film was exposed to ammonia, it demonstrated an optical response in the form of the drop of intensity of green radiation measured with a silicon photodiode power meter. The sensitivity of the developed chemical sensor was close to 0.4% ammonia in air, and the response time was close to 5 minutes.

This work reports the fabrication of a PMMA-based spherical microlens array (MLA), targeting application of Shack-Hartmann wavefront sensor for lens characterization. The array present 10 by 10 elements, with f-number f/# = f/10 (1 mm diameter, 10 mm focal length). The fabrication method employs a computer-controlled mechanical indentation for the fabrication of an insert mold, and subsequent replication by injection molding on PMMA. After replication and de-molding, the PMMA surface containing the negative of the phase profile of the lens array was evaluated by optical profilometry technique, in terms of the surface quality as well as the replication fidelity. The RMS surface roughness level of approximately (λ/10) was found, considering operation in the visible range of spectrum. Optical characterization was based on the evaluation of the sharpness, FWHM, and maximum intensity, I_MAX, values associated to the profiles of each of the 100 generated light spots, obtained in the back focal plane of the MLA. An average sharpness of FWHM^AVG = 13.9 ± 8% μm, and average maximum intensity of I_MAX ^AVG = 0.72 ± 7% a.u. was obtained.

In this work optical spectroscopic characterization was performed in a Er-doped phosphate glass matrix PAN (P2O5-Al2O3-Na2CO3). Due to its high phonon energy, only the 1550 nm emission band was observed. Therefore, we have applied the normalized lifetime thermal lens technique in order to determine the luminescence quantum efficiency of this emission. These results were compared with that obtained with the standard Judd-Ofelt calculations. Besides absorption spectra, emission spectra as also obtained. Therefore, the gain coefficient spectra could be evaluated for different population inversions. Finally, figures of merit for the optical amplifiers were estimated and compared with others Er-doped materials.

In this work, we have used a Ti³⁺:Safira laser tuned at 803nm to performed time-resolved measurements using the Z-scan technique to characterize the nonlinear optical properties of phosphate glasses. The glass matrices, labeled PAN (P₂O₅-Al₂O₃-Na₂CO₃) and PANK (P₂O₅-Al₂O₃- Na₂O-K₂O), were doped with increasing Nd³⁺ concentration, ranging from 0.5 to 5 wt%. For both systems, we have seen that the optical nonlinearity has a linear dependence with the doping ion concentration. Therefore, we propose a new approach to obtain the parameters Δα and Δσ. All results obtained are in good agreement with others found in the literature.

The spectroscopic properties of rare earth ions in many different hosts have been investigated, including surveys of Nd³⁺ in silicate, phosphate, fluorophosphates and fluoride glasses. Some of the thermal-optical properties of materials are influenced by temperature change, such as thermal diffusivity, specific heat and luminescence quantum efficiency. In this work the luminescence quantum efficiency of PANK: Nd³⁺, as a function of temperature (80- 480 K), was investigated using the normalized lifetime thermal lens technique. This system presents high quantum efficiency at low Nd³⁺ concentration and at ambient temperature, ~100%, which decrease as temperature increase. Below room temperature the effects are not in accord with the maximum value of η, which must be unity.

Sodium borate glass embedded with Tb³⁺, Sm³⁺ and Dy³⁺ was made by the melt quenching technique. The resulting glass is highly transparent. Absorption, and emission spectral measurements are performed. Under a diode laser excitation the glass emitted warm white light. Lifetimes of the excited levels are measured. CIE color co-ordinates and color temperature are measured.

For present-day optical communication systems, the commonly used normal-incidence photodetectors suffer from the tradeoff between bandwidth and quantum efficiency. Such a tradeoff is especially adverse for long wavelength communication systems operating at higher data rates. For example, the maximum responsivity for a commercially available 25 Gbps photodetector operating at 1310 nm wavelength is limited to less than 0.8 A/W. In this work, we design and demonstrate a high-speed, backside-incidence, critically-coupled Ge on SOI photodetector operating at 1310 nm while maintaining a high quantum efficiency. Our device is fabricated with RPCVD epitaxy, i-line lithography, silicide contact, and Al metal wire, which are fully compatible with the state-of-art CMOS process technology. With our epitaxial scheme and surface passivation method, a low bulk (surface) dark current density of 13 mA/cm² (0.79 μA/cm) is measured from a ~ 700 nm thick Ge p-i-n device at -1 V bias. The responsivity at 1310 nm wavelength is measured to be 0.87 A/W, and the 3dB optical bandwidth of a 20 μm diameter device is measured to be 26 GHz. Our high-speed, backside-incidence, critically-coupled Ge on SOI photodetector may serve as a high-performance and low-cost solution for next generation high-speed optical receivers, and its benefit of decoupling bandwidth and quantum efficiency is especially prominent at higher data rates such as 40 Gbps and beyond.

We successfully synthesized Er³⁺-Yb³⁺ doped cubic phase NaYF₄ nanocrystals by a facile solvethermal method. The average size of the as-prepared nanocrystals was about 12 nm based on the observation of scanning electron microscope and transmission electron microscope. NaYF₄/SiO₂ nanoparticles were prepared. The thickness of shell layer was about 7 nm. The as-prepared samples were annealed at different temperature. The cubic phase NaYF₄ did not transit to hexagonal phase, but to amorphous phase as the annealing temperature increased to 700 °C. When temperature further increased to 1100 °C, the amorphous NaYF₄ reacted with SiO₂ shell and formed a new phase, NaYSiO₄. Under the excitation by a 976 nm laser, the Er³⁺-Yb³⁺ doped NaYF₄, NaYF₄/SiO₂, and NaYSiO₄ nanoparticles showed intense visible upconversion emissions. Since the host materials changed from fluoride crystals to amorphous fluoride, then to silicate crystals, the spectral profiles were different. Fluorescent lifetimes obtained from decay curves were applied to analyze the multi-phonon relaxation processes in different hosts. The Er³⁺-doped upconversion phosphors will be useful for light converting in solar cell applications in the future.

Stimulated Raman scattering is an attractive nonlinear optical process that produces the power transfer from a given frequency to one or several down-shifted Stokes beams [1-4]. It is becoming an exciting issue because of the wide application, ranging from sensors, slow light generation to Raman amplifiers and lasers [5-11]. Ever since Stolen et al. first reported it in 1972[3], SRS has been successfully demonstrated based on various fiber structures and fiber materials [12-24]. Moreover, in optical fibers with sufficiently high Raman gain and pump power, multiple-order cascaded Raman shift can be generated, which has already been observed in silica, tellurite and chalcogenide optical fibers [18, 25-28]. However, relatively few researches concerning this have been carried out on fluoride fibers, although they have high transparency from the ultraviolet (UV) region to the mid-infrared (MIR) region up to ~8 μm. In this work, we demonstrated fourth-order cascaded Raman shift in a birefringence ZrF₄‒BaF₂‒LaF₃‒AlF₃‒NaF (ZBLAN) fluoride fiber. To the best of our knowledge, this is the first demonstration of fourth-order cascaded Raman shift in fluoride fibers. The pump source was a picosecond laser with the center wavelength of 1064 nm. At the average pump power of ~7W, fourth-order cascaded Raman shift was observed if the pump pulse was polarized to the slow axis, and only third-order cascaded Raman shift was obtained if the pump pulse was polarized to the fast axis. Furthermore, the generalized nonlinear Schrödinger equation (GNLSE) was used to simulate the cascaded Raman shift generation process, and the results were in good agreement with the experiments.

The supercontinuum generation and rogue wave generation in a step-index chalcogenide fiber are numerically investigated by solving the generalized nonlinear Schrödinger equation. Two noise models have been used to model the noise of the pump laser pulses to investigate the consistency of the noise modeling in rogue wave generation. First noise model is 0.1% amplitude noise which has been used in the report of rogue wave generation. Second noise model is the widely used one-photon-per-mode-noise and phase diffusion-noise. The results show that these two commonly used noise models have a good consistency in the simulations of rogue wave generation. The results also show that if the pump laser pulses carry more noise, the chance of a rogue wave with a high peak power becomes higher. This is harmful to the SC generation by using picosecond lasers in the chalcogenide fibers.

We experimentally demonstrate mid-infrared supercontinuum (SC) generation in chalcogenide multi-step index fibers (MSIF) pumped by a femtosecond laser. The fabricated chalcogenide MSIF is composed of a high refractive index core (C1) in the center, which is enclosed by a lower refractive index core layer (C2) and an outer cladding. This fiber structure is advantageous to tailor the chromatic dispersion with higher freedom and to keep the effective mode area small at long wavelengths. The high refractive index core, low refractive index core, and the outer cladding materials are As₂Se₃, AsSe₂ and As₂S₅, respectively. When the diameter of C1 and C2 are 7.8 and 30 μm, respectively, the zerodispersion wavelength (ZDW) of the fiber is 12.5 μm. The chromatic dispersion profile is near-zero and flattened within the range of ±20 ps/km/nm in the wavelength range from 4 to 17 μm and a broad normal dispersion region is obtained in the wavelength range shorter than the ZDW. In practice, a 2.8 cm long fiber is pumped at 10 μm by using a femtosecond laser whose pulse width is ~200 fs. The SC generation extending from 2 to 14 μm is obtained. Most of its spectrum is in the normal dispersion region of the fiber. These results are promising for the highly coherent mid-infrared SC generation.

The design, fabrication and testing of hollow Grism and Constant Deviation prisms is shown. Application in the measurement of temperature is done.

Black silicon is surface modification by reactive ion etching that creates a forest of silicon micro-spikes and increases surface area of the sample. When the spikes’ height exceed an optical wavelength, light is trapped on the surface through multiple pathway scattering, increasing the optical absorption of visible and near infrared radiation. Cerium oxide (CeO₂) is believed to have good photoactivity, and finds many applications including photoelectrolysis. However, the large band gap limits the efficiency of the water splitting process. We suggest black silicon surfaces as substrates for CeO₂ sputter coating to increase photon-material interaction. An additional catalytic layer of platinum is deposited to create highly energetic electrons as a result of plasmonic resonance and enhances incident photon to current efficiency (IPCE). The difference of surface current for laser on and off condition is found to be 32 times higher in a nanolayered coated black silicon sample as compared to flat silicon. The resistance of flat silicon substrate was 11 Ω for laser-off state, decreasing to 9 Ω when the laser was turned on. On the other hand, the black silicon substrate sample had a higher resistance of 70 Ω in dark which decreased to 1.5 Ω for laser on state.

Integrated optical Mach-Zehnder interferometer (IO-MZI) has been widely researched for various usage including for biosensor application. However, the success rate of IO-MZI pattern transfer has been low using the conventional multidevelopment process. One of the main factors is the particle contamination due to the practice of reused developer bath. In this work, an innovative single development process had been proposed with the utilization of the same conventional set-up but with a different protocol. The concept of this method is the estimation of total development time based on the calculated development rate. By doing so, the development process can be completed with only one immersion of the substrate in the developer bath. Besides, the manipulation of development rate by varying exposure time in this work also had revealed the possibility of manipulation of line-width based on the exposure time. In short, the proposed single development process has increased the success rate of IO-MZI pattern transfer from 30% (multi-development method) to 90%.

In this paper, double frequency spacing of multi-wavelength Brillouin Raman fiber laser utilizing eight-shaped structure in conjunction with Raman amplifier is simulated and demonstrated using Optisys software. Double frequency multiwavelength Brillouin Raman fiber laser is one of the solution for single frequency spacing channel de-multiplexing from narrow single spacing in the communication systems. The eight-shaped structure has the ability to produce lower noise and double frequency spacing. The 7 km of single mode fiber acting as a nonlinear medium for the generation of Stimulated Brillouin Scattering and Stimulated Raman Scattering. As a results, the optimum results are recorded at 1450 nm of RP power at 22 dBm and 1550 nm of BP power at 20 dBm. These parameters provide a high output peak power, gain and average OSNR. The highest peak power of Stokes 1 is recorded at 90% of coupling ratio which is 29.88 dBm. It is found that the maximum gain and average OSNR of about 1.23 dB and 63.74 dB.