Testing the human body’s reaction to hypoxia (including the one generated by high altitude) is important in aeronautic medicine. This paper presents a method of monitoring blood oxygenation during experimental hypoxia using hyperspectral imaging (HSI) and a spectral unmixing model based on a modified Beer–Lambert law. A total of 20 healthy volunteers (males) aged 25 to 60 years were included in this study. A line-scan HSI system was used to acquire images of the faces of the subjects. The method generated oxyhemoglobin and deoxyhemoglobin distribution maps from the foreheads of the subjects at 5 and 10 min of hypoxia and after recovery in a high oxygen breathing mixture. The method also generated oxygen saturation maps that were validated using pulse oximetry. An interesting pattern of desaturation on the forehead was discovered during the study, showing one of the advantages of using HSI for skin oxygenation monitoring in hypoxic conditions. This could bring new insight into the physiological response to high altitude and may become a step forward in air crew testing.
The paper presents the results obtained in simulation of a Superstructure Fiber Bragg Grating (SFBG) torsion sensor. The SFBG sensor simulation points to an improved smart composite or metallic parts design to be operated under torsion loads in various applications. SFBG sensor simulation consists of correlating the fiber deformation under applied mechanical loads with the modified FBG characteristic reflection spectrum considering the polarization mode variations. The analyzed SFBG is developed by the selective deposition of on-fiber periodic metal thin films on regular FBGs. The torsion mechanical loads induced shifts in the characteristic reflection spectrum of Bragg wavelength and side bands are analyzed. For obtaining information about an optimal structure of SFBG sensor, simulation is performed for four commercially available photosensitive single mode silica optical fibers having different geometric and optical characteristics, mainly core and clad refractive index values. It is considered that, by using an UV writing technique, Brag gratings are induced into the simulated SFBG. Simulations are performed considering different geometric characteristics of the shaft used as mechanical mount of SFBG. The simulation results are in fairly good agreement with the experimental ones reported in literature.
Results obtained by FEM analysis of a smart mechanical part manufactured of reinforced composite materials with embedded long period grating fiber sensors (LPGFS) used for operation monitoring are presented. Fiber smart reinforced composite materials because of their fundamental importance across a broad range of industrial applications, as aerospace industry. The main purpose of the performed numerical analysis consists in final improved design of composite mechanical components providing a feedback useful for further automation of the whole system. The performed numerical analysis is pointing to a correlation of composite material internal mechanical loads applied to LPGFS with the NIR absorption bands peak wavelength shifts. One main idea of the performed numerical analysis relies on the observed fact that a LPGFS embedded inside a composite material undergoes mechanical loads created by the micro scale roughness of the composite fiber network. The effect of this mechanical load consists in bending of the LPGFS. The shifting towards IR and broadening of absorption bands appeared in the LPGFS transmission spectra is modeled according to this observation using the coupled mode approach.
This study aimed to evaluate the concept of using high-resolution optical coherence tomography (OCT) imaging to rapidly assess surgical specimens and determine if cancer positive margins were left behind in the surgical bed. A mouse model of breast cancer was used in this study. Surgical specimens from 30 animals were investigated with OCT and automated interpretation of the OCT images was performed and tested against histopathology findings. Specimens from 10 animals were used to build a training set of OCT images, while the remaining 20 specimens were used for a validation set of images. The validation study showed that automated interpretation of OCT images can differentiate tissue types and detect cancer positive margins with at least 81% sensitivity and 89% specificity. The findings of this pilot study suggest that OCT imaging of surgical specimens and automated interpretation of OCT data may enable in the future real-time feedback to the surgeon about margin status in patients with breast cancer, and potentially with other types of cancers. Currently, such feedback is not provided and if positive margins are left behind, patients have to undergo another surgical procedure. Therefore, this approach can have a potentially high impact on breast surgery outcome.
To preserve urban vegetation land cover quality and mitigate its degradation is an important task for urban planning and
environmental management of Bucharest metropolitan area in Romania. Since vegetation land cover dynamics directly
affect the urban landscape characteristics and air quality, remote sensing represents an effective tool for vegetation land
cover quality assessment at regional scale. In particular, the use of satellite-based vegetation indices, like the NDVI
(Normalized Difference Vegetation Index), can provide important information when evaluating Urban Vegetation Cover
Quality (UVCQ) patterns in urban areas, which represents one of the most sensitive landscape components to urban
environmental degradation. This paper proposes an approach for the regional-scale assessment of UVCQ by means of an
NDVI-based (functional) indicator using freely available time series MODIS Terra/Aqua (Moderate Resolution Imaging
Spectroradiometer) satellite data. As a case study, Bucharest metropolitan area landscape experiencing climate and
anthropogenic changes, increasing human pressure and high vulnerability to degradation was chosen. As UVCQ
indicator, the NDVI-based vegetation cover classification was produced by means of unsupervised multivariate statistical
techniques and compared with spatio-temporal changes during 2002-2012 period, statistical indicators, and field data
related to land cover management observed in the study area. Results demonstrate that the obtained remotely sensed
vegetation land cover characterization can be effectively considered as a proxy of the UVCQ status of the examined area.
Due to the large availability over time and low cost of satellite images, the proposed approach can be applied to wider
urban/periurban regions, to monitor vegetation quality and indirectly control vegetation land degradation.
Various aspects of distributed feedback fiber laser sensors, their interaction with environment and their possible applications are investigated by numerically solving coupled-mode equations system describing the laser field propagation. The developed numerical analysis has the aim to better understand the DFB-FL itself and its interaction with environment in order to be operated as a sensor. The main idea consists in finding out how various environment parameters modify the coefficients of coupled-mode equations describing the laser field propagation through the DFBFL structure.
Numerical simulation results obtained in investigating the generation of laser pulses with 1.55 μm wavelength generated by an Er3+, Er3+-Yb3+ or Cr3+-Yb3+-Er3+ laser or fiber laser oscillator operated in passive optical Q-switching regime are presented. Three types of passive optical Q-switch cell are investigated: the usual one based on Co2+ or UO2 embedded in different hosts; the second consisting of Co2+ nano-crystals. The spectroscopic characteristics of these Q-switch cells are analyzed and correlated with criteria obtained with a numerical simulation procedure based on solving a rate equation system.
Climate variability and change are risk factors for climate sensitive activities such as forestry. Managing these risks requires “climate knowledge”, i.e. a sound understanding of causes and consequences of climate variability and knowledge of potential management options that are suitable in light of the climatic risks posed. Thresholding based on biophysical variables derived from time series satellite data is a new approach to classifying forest land cover via remote sensing through use of Normalized Difference Vegetation Index –NDVI and Enhanced vegetation Index- EVI. This paper aims to assess spatio-temporal forest changes through applied time-series Landsat TM, ETM, MODIS Terra/Aqua and IKONOS satellite remote sensing data of Cernica forest area near Bucharest, Romania, during 1990-2011 period. Additional forest biophysical parameter Land Surface Temperature/Emissivity - LST was considered in this paper. This information is complemented by in-situ monitoring data (field measurements, data collection) together with modeling tools (theoretical developments, mathematical and bio-geophysical parameterization, statistics of the main urban structures in their interdependency) and spatial analysis methods.
Numerical simulation results obtained in investigating laser paint removal from different metal substrates, mainly aluminum and aluminum alloys, are presented. The main purpose of the developed simulation model is to define the laser installation specifications required for an operation that does not affect the substrate on which the paint is deposited. This is an important laser application in aeronautical industry. The developed simulation model considers transverse laser beam intensity distribution and, consequently, the temperature distribution in the processed mechanical component.
Spectral patterns of different forest land cover can identify certain pollution compounds, and water stress conditions
based on the interaction of photons with the molecular structure of the forest target structure. Based on such methods, the objective of this research was to evaluate and characterize selected forest test area Baneasa- Tunari located in the Northern part of Bucharest metropolitan region, Romania, where the climate and anthropogenic stressors endanger natural and economical values of environment. Based on time-series Landsat TM, ETM, MODIS Terra/Aqua and IKONOS satellite data have been investigated urban forest land cover and forest biophysical parameters (Normalized Difference Vegetation Index- NDVI and Leaf Area Index- LAI) changes over 1990- 2011 period of time. Accuracy of image processing results (spectral classification) was confirmed through in-situ spectroradiometrical analysis of reflectance spectra with portable GER 2600 spectroradiometer.
Preliminary results obtained in investigating a plane electromagnetic wave incident on a metal nanowire grating formed on a dielectric substrate, using FEM, are presented. The numerically simulated model is developed considering Cu, Au, Ag or other metal nanowire having a diameter of 40 nm - 800 nm, formed on dielectric substrates with a refractive index between 1.4 and 2.4. The transmission and reflection coefficients for refraction, specular reflection and first order diffraction are computed. The cases of dielectric substrate with metallic layers of different thicknesses deposited on the opposite side are also investigated.
This paper presents the results obtained in analyzing a quasi-cw flash-lamp pumped high power Nd:YAG slab laser
oscillator/two stages amplifier operated in passive optical Q-switching regime using LiF:F2- crystals with an improved design. A numerical simulation method based on laser rate equation is developed for theoretical analysis of a passively Q-switched Nd:YAG slab laser system. A comparison of simulation results with experimental data is also presented to certify the viability of the developed theoretical analysis method. Laser pulses output energy of 330 mJ at a FWHM time duration of 50-75 ns and at a repetition frequency of 10 – 25 kHz (pps) are reported and numerical simulation of these experimental results are presented pointing to the output parameters stability.
The main environmental issues affecting the broad acceptability of NPP (Nuclear Power Plant) are the emission of
radioactive materials, the generation of radioactive and heat waste, and the potential for nuclear accidents. Satellite
remote sensing is an important tool for spatio-temporal analysis and surveillance of environment, thermal heat waste of waters being a major concern in many coastal ecosystems involving nuclear power plants, as sharp changes in water
temperature can significantly affect the distribution and physiology of aquatic biota and contribute to global warming. The thermal plume signature in the NPP hydrological system in TIR (Thermal Infrared) spectral bands of Landsat TM and ETM TIR band 6, ASTER, and MODIS TIR bands time series satellite have been used for WST (Water Surface Temperature) detection, mapping and monitoring. As a test case the methodology was applied for NPP Cernavoda, Romania during period of 1990-2011 years. Thermal discharge from two nuclear reactors cooling is dissipated as waste heat in Danube-Black -Sea Channel and Danube River. If during the winter thermal plume is localized to an area of a few km of NPP, the temperature difference between the plume and non-plume areas being about 1.5 oC, during summer and fall, is a larger thermal plume up to 5- 6 km far along Danube Black Sea Channel, the temperature change being of about 1.0 oC.
The preliminary numerical simulation results obtained in the analysis of a landmine detection system based on laser
excitation of acoustic - seismic waves in the soil and observing its surface vibration above the embedded landmine are
presented. The presented numerical simulations comprise three main parts: 1) Laser oscillator and laser beam
propagation and absorption in soil; a laser oscillator operated in Q-switched regime is considered; different laser
wavelengths are investigated. 2) Acoustic - seismic wave generation by absorption in soil of laser pulse energy; 3)
Evaluation of acoustic - seismic wave generation by the buried in soil landmine; 4) Comparison of Distributed Feed-
Back Fiber Laser (DFB-FL) and Laser Doppler Vibrometer (LDV) detector used for soil vibrations evaluation. The
above mentioned numerical simulation is dedicated for evaluation of an integrated portable detection system.
As climatic variability and anthropogenic stressors are growing up continuously, must be defined the proper criteria for
forest vegetation assessment. In order to characterize current and future state of forest vegetation satellite imagery is a
very useful tool. Vegetation can be distinguished using remote sensing data from most other (mainly inorganic) materials
by virtue of its notable absorption in the red and blue segments of the visible spectrum, its higher green reflectance and,
especially, its very strong reflectance in the near-IR. Vegetation reflectance has variations with sun zenith angle, view
zenith angle, and terrain slope angle. To provide corrections of these effects, for visible and near-infrared light, was used
a developed a simple physical model of vegetation reflectance, by assuming homogeneous and closed vegetation canopy
with randomly oriented leaves. A simple physical model of forest vegetation reflectance was applied and validated for
Cernica forested area, near Bucharest town through two ASTER satellite data , acquired within minutes from one
another ,a nadir and off-nadir for band 3 lying in the near infra red, most radiance differences between the two scenes can
be attributed to the BRDF effect. Other satellite data MODIS, Landsat TM and ETM as well as, IKONOS have been
used for different NDVI and classification analysis.
Due to significant anthropogenic changes that have occurred in the last several decades in Bucharest city's landscape,
urbanization has become an important factor affecting urban surface parameters, hence in the surface-atmosphere
interaction processes, with a great potential to alter the local climate. Land use and land cover (LULC) influence a
variety of processes important in characterizing urban /periurban biophysical parameters' quality, including aerosol
deposition rates, biogenic emissions, albedo, surface temperatures, climatic parameters and other.
Analysis of surface biophysical parameters changes in urban/periurban areas of Bucharest town based on multi-spectral
and multi-temporal satellite imagery (Landsat TM, ETM and IKONOS) for 1989 - 2009 period provides the most
reliable technique of environmental monitoring regarding the net radiation and heat fluxes associated with urbanization
at the regional scale. Investigation of radiation properties, energy balance and heat fluxes is based on information derived
from various satellite sensors and in-situ monitoring data, linked to numerical models and quantitative biophysical
information extracted from spatially distributed NDVI-data and net radiation. This study attempts to provide
environmental awareness to urban planners suggesting that future changes in urban land cover could substantially affect
climate by altering biophysical land-atmosphere interactions.
Urban areas are currently among the most rapidly changing types of land cover on the planet. Remote sensing imagery
can provide a timely and synoptic view of urban land cover, as well as a means to monitor change in urbanizing
landscapes and to compare urban environments globally. To understand the ecology of urban systems, it is necessary to
quantify the spatial and temporal patterns of urbanization, which often requires dynamic modeling and spatial analysis.
Based on Spectral Mixture Analysis, this paper aims to provide a spatio-temporal analysis of urban structure for
Bucharest urban area based on multi-spectral and multi-temporal satellite imagery (LANDSAT TM, ETM; MODIS,
IKONOS) over 1989 - 2007 period. Accurate maps of urban tree and other surface cover types can provide critical
information to better understand urban ecosystems and help improve environmental quality and human health in urban
areas.
Environmental monitoring is essential information routinely required by the mining industry and regulators to
demonstrate that the environment is not adversely impacted by exploration and mining. New mining technologies can
not only exploit low-grade ores but also produce high volumes of tailings as mining wastes. Satellite remote sensing
imagery provided by Landsat TM and ETM sensors is an important investigation tool of mining waste cover screening,
mapping and monitoring at local and regional scales of areas containing multiple sources of mining-related heavy metals.
By this, satellite remote sensing data can help to rapidly assess the dimension of mining waste risk and therefore better
manage such a geohazard as well as for remediation programs.
Based on Landsat TM, ETM satellite data over 1989-2007 period, was possible to be achieved a discrimination between
weathered materials and other prone to acidification as well as to perform a spatio temporal landcover change detection
analysis in some mining waste areas in Maramures County, Romania. Accuracy of image processing results
(mineralogical classification) was confirmed through ground sampling and analysis of reflectance spectra with portable
GER 2600 spectroradiometer.
Light transport is currently used clinically both as a therapeutic tool and as a diagnostic tool. A concern in all these cases
is the difficulty of knowing which regions of the tissues are sufficiently illuminated for therapeutic results, or from which
regions the collected fluorescence was emitted. Development of optical models that explain the observed scattering
properties of soft biological tissues is of considerable interest. Such modeling can give how the scattering properties are
influenced by the numbers, sizes and arrangements of the tissue structure. In this article we give a brief overview of the
laser light transport in tissue and also discuss some representative applications of tissue optics for biomedical
applications.
Generally, the beam distribution in the tissue in interaction with a pulsed laser is defined by the optical properties
(effective scattering and absorption coefficient). A special Er:YAG device used for blood sampling without any pain is
presented. Our device emitting on 2940 nm has a special function. It can give four energy levels for four types of skin.
At 3000 nm there is an absorption peak in water, and the absorption in tissue is intense and the vaporization is immediate
and superficial without surrounding damages. Additionally, the very short duration of the pulse (a few hundred
microseconds) avoids the phenomenon of thermal diffusion.
The main component of the free electron laser is the undulator. Besides the numerical computation approach of the
magnetic field generated by the undulator current, the other possibility is the analogic simulation. Such an approach is
more intuitive and also enables a validation of the numerical simulation. The undulator consists of a Huygens wires
stack. In each wire of the stack the current circulates alternatively from a wire to another. The magnetic field
mathematical model for a wire uses operations like multiplications, divisions, radicals, trigonometric functions and
integrations. These operations were simulated by using an harmonic oscilator (using MC1458 amplifiers), analog
multipliers (AD633) and integrators (using MC1458 amplifiers).
To solve some microsurgical procedures in the anterior and posterior chambers using the photo disruptive effect, a
special Nd:YAG nanosecond laser device is presented. The Nd:YAG laser is q-switched (Cr4+:YAG). The laser beam is
expanded. After expansion, the laser beam is passed through a circular variable filter which is rotated by a processor,
allowing energy to be set at any value in the range of 0.5-10 mJ. Two infrared LED-phototransistor pairs are used to
position the filter. The laser beam is focused by the objective at 150 microns behind the object plane to avoid the damage
of the Intraocular Lens.
Generally, the beam distribution in the tissue in interaction with a pulsed laser is defined by optical properties (effective
scattering and absorption coefficient). In 2900 nm range, the effective scattering coefficient is much smaller than the
absorption coefficient. An Er:YAG skin puncher is presented. Thermal action of a laser beam can be described as one of
three types: hyperthermia, coagulation and volatilization, depending on the degree and the duration of tissue heating. We
are interested in the volatilization process that means a loss of material. The various constituents of the tissue disappear
in smoke at above 1000C in a relatively short time of around one tenth of a second. At the edges of the volatilization zone
there is a region of coagulation necrosis. In presented case of an Er:YAG laser operating in a free generation mode, the
mechanical effects can result from explosive vaporization. When the exposure time of the laser is lower than the
characteristic time of the thermal diffusion in the tissue, it produces a thermal containment with an accumulation of heat
without diffusion and an explosive vaporization of the target. The Er:YAG laser device has the pulse length of about 160
microseconds and four emitted energy levels. This device is used to punch the skin for blood sampling for different kinds
of analysis. The front panel of the device has four keys to select the desired energy according to the skin type.
The study of dynamics of spatial solitons in nonlinear and unidimesional fotonic crystals, with a periodical and nonlinear
fotonic network which is generated by Dirac function is presented. Are analysed comparisons and differences which
appear in development of periodical models describes by nonlinear Schrödinger equation. Also, is developed theory of
couple models for periodical modulation of refractive index.
Fudamental theory of spatial solitons are based to obtain discrete nonlinear Schrödinger equation with analyze of
stationary solutions on discrete models.
The Nd:YAG solid state laser can be used in ophthalmologic microsurgery because of its specific wavelength of 1064 nm, which has the property to penetrate the transparent medium of the eye. We design a specific ophthalmic system, containing a Q-switch Nd:YAG laser, an optical stereomicroscope and an aiming system. This laser-stereomicroscope system is used for eye examination and for microsurgical proceedings like posterior capsulotomy and pupilar membranectomy. We had to design an optical scheme of the laser to settle the radiation route. In order to cover the medical domain of the energies, we calibrate eleven attenuation filters using ratiometric method. For a correct position of the place where the laser pulse strikes, we used an original system consisting of two red laser diodes mounted on each side of the binocular One of the advantages of this laser system is taht the output energies can be varied widely (0.8-15 mJ), making a great numbers of applications in clinical ophthalmology possible.
An ophthalmic surgical instrument is presented. It contains a specific Q-switch YAG:Nd laser, an optical stereomicroscope, two red output laser diodes and a digital system for optical processing of the microscope images. As Q-switch, a Cr4+:YAG crystal is used. It works in monopulse or double pulse regime. Four red spots mark the optical object plane. The laser beam is sent in the central part, between four spots and is focused at 150 microns behind the optical plane to reduce the risk of pitting the lens when performing posterior capsulotomies. In order to obtain eleven different energy levels in the (2÷10)mJ domain, eleven attenuators are used. The laser ophthalmic system must fulfill many precautions. The energy level, the pulse length and the used attenuators must have such values to eliminate every undesired effect in the medical applications. This instrument has an important application in posterior capsulotomies and posterior membranectomies.
The realization of a portable laser rangefinder, capable to measure ranges up to 1,200 m, raises particularly difficult problems related to the selection of an appropriate laser diode, having a sufficient optical power, but also the generation of very short rangefinding pulses, with very steep fronts. The authors used as emitter a high power pulsed laser diode CVD 193 from Laser Diode Inc. and build up for it a driving stage made up of a signal formatter that takes over the pulse sent by a microcontroller (that controls the whole rangefinder) and a switch based on a power high frequency MOSFET transistor 501N16A from DEI.
The realization of a portable laser rangefinder, capable to measure ranges up to 1,200 m, raises some difficult problems. The first one is that a good temporal resolution is required to get a good ranging resolution and that means that both the transmitter and the receiver must be rapid. The other problem is that at measurements of range larger than 1,000 m the level of the reflected pulse current in the phodiode is of the order of the dark current, which has to be compensated, as well as the temperature offset of the photodiode (in order to keep the calibration). A novel solution was adopted to solve these problems: the AC coupling (it doesn’t matter any more the dark current nor the temperature offset) and the use of wide band amplifiers, with a very low noise.
A portable laser rangefinder, capable to measure ranges up to 1,200 m, implies the measurement of time intervals ranging between some tens of ns and some tens of μs with an accuracy of less than 1 ns. Taking into account that laser pulse rate is low (1...10 kHz) our solution was the time expansion in few stages followed by a classical time interval measurement. We actually expanded the time range 100 ns ÷ 10 μs into the range 25 μs ÷ 2.5 ms and the new time interval is measured using a 5 MHz quartz driven clock. The measurement accuracy is then 0.42 ns.
The optical fiber video transmission system enables up to 2 km video link for standard video color signal (1 Vp-p/75(Omega) ). The system consists of the following parts : a video camera, an optical transmitter, an optical cable, an optical receiver and a TV monitor. The optical transmitter is build around a laser diode module, controlled through two feedback loops : one stabilizes the laser diode operating temperature while the other stabilizes the laser diode optical power, in order to lock the laser output settings in any operating conditions. The transmitter contains also a modulating stage, enabling the direct internal modulation of the laser diode. The optical receiver consists of a PIN-FET photodiode amplifier module and a bipolar output stage, for impedance matching with the TV monitor. The system operates at a wavelength of 1300 nm, using multi-mode optical fibre.
A fiber optics explosion primer is proposed to remove the major drawback of the electrical cable links by transmiting of the ignition primer signals through an optical fiber cable, insensitive to the electromagnetic induction generated by the atmospheric electric discharges. The primer consists of a transmitter, an optical cable and a receiver. The system has some features that assures a completely safety operation. The first feature is the signal encoding and the microcontroller supervision. Both transmitter and receiver are microcontroller assisted and all comands for the receiver operation and priming are coded and password-protected. The other feature is the absence of the power source (battery) on the receiver, preventing from accidental priming. The receiver power supply is replaced by a capacitor that is charged by the energy of the light beam coming through the optical cable to a PiN photodiode operating in photovoltaic regime. The primer operates in two steps. In the first step the capacitor is charged and all devices of the receiver are powered, while in the second step all the optical signals coming through the fiber are considered as commands. Wrong or unauthorized (nonmatching passwords) commands reset the receiver and cut off the power supply by discharging the capacitor.
The coded IR proximity detector is able to generate an electrical signal when the distance between the detector and a certain object becomes shorter than a preset value. The detector may be used as an automotive indicator and control. The detector consists of four parts : a controller, a transmitter, a receiver and the optical system, used both for transmission and reception. The transmitter contains a high-power laser diode driven by a recurrent sequence of position coded pulses. The receiver consists of a PIN photodiode amplifier module, a decoder and an output stage. The outgoing beam is separated from the incident (reflected) beam using a beam-splitter. A CMOS microcontroller comands the generation of the coded pulses, the reception and the decoding of the received pulses. The device features a very low power consumption due both to the pulsed regime and to the use of CMOS technology of the controller. A personalization through code for each detector is possible due to the use of the microcontroller, avoiding unauthorized or parasite commands from other similar devices in the neighborhood. The device’s detection range is 10-15 m, enabling its use in military and robotics applications.
An optical fiber multiplexed image transmission system can be used in dangerous and low accessible environments, such as in nuclear or high explosion risk environments because the optical fiber cable is insensitive to the electromagnetic disturbances and, when an appropriate optical fiber is used, it withstands the gamma radiation. The system has the capability to simultaneously transmit, by using the video signals switch, the image from four CCD cameras placed in the dangerous environment to a remote surveillance center, at 2 km distance.
We report Q-switching of a Nd:YAG laser with a phase-conjugating mirror based on external stimulated Brillouin scattering in carbon disulfide using a linear resonator. Q-switching is provided by a nonlinear LiF:F2- crystal before the stimulated Brillouin scattering takes place. Employing proper mode selectors pulses with 6 mJ minimum energy and duration of 20 ns were generated, the beam divergence being 1.5 the diffraction limit. A new theoretical model of the Q-switching regime has been proposed and good agreement between experimental and theoretical data has been obtained.
The influence of some factors that affect the diode pumped solid state lasers (DPSSL) efficiency is analyzed. By using simple phenomenological models few simple and efficient criteria fora n optimal design of such DPSSL in an end-pumping configuration were derived. Some numerical results for a Nd:YAG laser are discussed.
This paper presents a new fiber optic transmission system which is developed to operate at a data rate up to 34 Mb/s. The entire system operates at 1300 nm and may be used with single or multimode fiber optic cable.
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