This PDF file contains the front matter associated with SPIE Proceedings Volume 8677, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Continuing experiments with Electric Oxygen-Iodine Laser (EOIL) technology have significantly increased laser power output by increasing the product of gain and gain-length, g₀L. Increasing the system size by a factor of 3 resulted in a 5-fold increase in laser output on the 1315-nm transition of atomic iodine. The peak output power observed was 538 W.

Recent research on high-pressure hybrid radiofrequency/arc (RF/DC) generator of singlet oxygen for DOIL is presented. A stable hybrid RF/DC discharge with a diffusive arc root near the anode side was demonstrated experimentally under well defined conditions. A minimization of anode erosion and a non-equilibrium state of the arc plasma were achieved in this way. The RF discharge is used for the ignition of the DC arc and its sustainment. The hybrid discharge can be characterized as an RF sustained (i.e. non-self sustained in the pure DC mode) DC arc between a conventional glowing tungsten cone cathode and a cooled aluminum cylindrical anode with a diffusive arc mode. The diffusive mode of the arc is assisted by a plasma anode formed inside the aluminum anode channel due to the radiofrequency. The generation of singlet oxygen was achieved by a laterally symmetric injection of neutral oxygen in a mixture of O₂+He+NO into the Ar+He plasma jet of the hybrid RF/DC plasmatron. An overview of basic characteristics and CFD modeling of some key gas flow phenomena are presented. The research is directed to experimental investigation and theoretical modeling of the hybrid plasma. In the case of its successful completion it will be used for pumping a discharge oxygen-iodine laser.

A supersonic all gas-phase iodine laser driven by NF₃/D₂/DCl/CF₃I combustion has been experimentally studied. the gain signals of I(²P_3/2,F=4)← I(²P_1/2,F=3) at 1315.246nm and I(²P_3/2,F=3)← I(²P_1/2,F=3) at 1315.222nm were observed with an intensity of 3x10^-5cm^-1 and 1x10^-5cm^-1 respectively. The small signal gain of I(²P_3/2,F=4)← I(²P_1/2,F=3) at different location relative to HN₃ injector along the flow direction also was obtained. The experimental results indicate that the AGIL driven by NF₃/D₂/DCl/CF₃I combustion is feasible.

A simplified two-level generation model predicts that power extraction from an cw oxygen-iodine laser (OIL) with stable resonator depends on three similarity criteria. Criterion τ_d is the ratio of the residence time of active medium in the resonator to the O₂(¹Δ) reduction time at the infinitely large intraresonator intensity. Criterion Π is small-signal gain to the threshold ratio. Criterion Λ is the relaxation to excitation rate ratio for the electronically excited iodine atoms I(²P_1/2). Effective power extraction from a cw OIL is achieved when the values of the similarity criteria are located in the intervals: τ_d=5-8, Π=3-8 and Λ≤0.01.

A scalable high pressure centrifugal spray generator of singlet oxygen for chemical oxygen-iodine laser (COIL) was developed. This generator uses nitrogen as chlorine diluting gas. Different spray nozzles were tested which could be assembled together and so enable a high chlorine flow rates for a high-power COIL. The designed generator can produce singlet oxygen, O₂(¹Δg), with reasonable chlorine utilization and O₂(¹Δg) yield even at very high generator pressures, which cannot be attained by other O₂(¹Δg) generators. This high-pressure operation is beneficial for a pressure recovery system of the laser. Another advantage of this generator is a very high BHP utilization. The problem of heating of exit gas was solved by introducing additional nitrogen between the separator rotor and stator.

A review of the methods for generation of iodine for oxygen-iodine lasers (OIL) is presented. The chemical and physical methods for production of both atomic (AI) and molecular (MI) iodine have been searched in order to improve the efficiency and/or technology of OILs. These trials were motivated by the estimations that a substantial part of singlet oxygen (SO) could be saved with these methods and the onset of the laser active medium will be accelerated. Vapour of MI can be generated by the evaporation of solid or pressurized liquid I₂, or synthesized in situ by the reaction of Cl₂ with either HI or CuI₂. The chemical methods of generation of AI are based on the substitution of I atom in a molecule of HI or ICl by another halogen atom produced usually chemically. The discharge methods include the dissociation of various iodine compounds (organic iodides, I₂, HI) in the RF, MW, DC-pulsed or DC-vortex stabilized discharge. Combined methods use discharge dissociation of molecules (H₂, F₂) to gain atoms which subsequently react to replace AI from the iodine compound. The chemical methods were quite successful in producing AI (up to the 100% yield), but the enhancement of the laser performance was not reported. The discharge methods had been subsequently improving and are today able to produce up to 0.4 mmol/s of AI at the RF power of 500 W. A substantial enhancement of the discharge- OIL performance (up to 40%) was reported. In the case of Chemical-OIL, the enhancement was reported only under the conditions of a low I₂/O₂ ratio, where the “standard” I₂ dissociation by SO is slow. The small-signal gain up to 0.3 %/cm was achieved on the supersonic COIL using the HI dissociated in the RF discharge. Due to the complicated kinetics of the RI-I-I₂-SO system and a strong coupling with the gas flow and mixing, the theoretical description of the problem is difficult. It, however, seems that we can expect the major improvement of the OIL performance for those systems, where the SO yield is rather low (DOIL) or for the high-pressure COIL, where the quenching processes are important and the shortage of the distance needed for the preparation of active media is essential.

Usage of an external iodine atom generator can improve energy efficiency of the oxygen-iodine laser (OIL) and expand its range of operation parameters. However, a noticeable part of iodine atoms may recombine or undergo chemical bonding during transportation from the generator to the injection point. Experimental results reported in this paper showed that uncoated aluminum surfaces readily bounded iodine atoms, while nickel, stainless steel, Teflon or Plexiglas did not. Estimations based on experimental results had shown that the upper bound of probability of surface iodine atom recombination for materials Teflon, Plexiglas, nickel or stainless steel is γ_rec ≤ 10^-5.

The output energy stability of discharged-pumped pulsed HF laser in repetition rate mode is studied experimentally, and the optimal operating conditions are obtained. The experimental results show that the output energy decreases quickly with the increase of repetition rate, and increasing gas flow rate is beneficial to improve the discharge stability and the output energy stability as well. By optimizing the operating conditions, the laser can operate stably at the repetition rate of 50 Hz, with the stable output energy of about 260 mJ, and the average power is about 13 W.

Usage of iodine atoms instead of molecules in oxygen-iodine laser permits to expand its range of operation parameters and improve the weight per power ratio. Results of experiments and modeling of plasma chemistry processes resulting in CH₃I dissociation in a planar 40 MHz discharge are presented, showing that addition of oxygen or water into Ar:He:CH₃I mixtures can lead to a noticeable increase in CH₃I dissociation rate and inhibit iodine recombination during transport.

A fluorescence image detection system that can visualize the COIL hot mixing flow field by taking images of the fluorescence of active I₂ with a high speed camera was set up. Based on the captured flow field image, O₂(a¹Δ)/I₂ mixing quality was evaluated quantitively by an exclusive image processing program. With this method, the hot supersonic mixing flow field in COIL which uses parallel stream supersonic mixing nozzles with a set of trip tabs was investigated. Meanwhile the effectiveness of the trip tabs was demonstrated.

Laser-plasma chemistry has become a rapidly rising field in science and technology. Current interest in the process called laser-induced dielectric breakdown, while the phenomenon is called a laser spark, is mainly motivated by a rapidly growing area of their applications in the study of chemical reactions and their utilization in chemical analysis. A systematic study of chemical reactions initiated by laser sparks is based on finding simple reproducible conditions for the formation of small biomolecules, the preparation of well-defined fine particles, laser ignition of fuel mixtures, and so on. Research on LIDB-initiated chemical reactions has been triggered again recently by the advent of nanotechnologies. The systematic part of this contribution describes the laser-plasma-chemical behaviour of simple inorganic gases and their mixtures, and metallic and organic vapours. The strongest motivation for the studying laser-spark chemistry comes from the planetary sciences, where laser sparks have been used as a laboratory model of high-energy-density phenomena (e.g., cometary impact, lightning) in planetary atmospheres. This contribution is primarily focused on the laser-plasma chemistry of homogeneous gases, but chemical consequences of LIDB in liquids (laser cavitation) and on liquid-solid and gas-solid interfaces are also briefly reviewed. Particular processes responsible for the chemical action of a laser spark are identified and discussed.

Laser-assisted bending allows the bending of brittle materials by laser-heating the work-piece. We present a new development based on macro-channel cooled diode-lasers, initially developed for pumping of disc lasers. The new solution is more robust and reliable and will show the life-time necessary for an industrial application. The optical concept, however, shows problems with the uniformity of the intensity distribution.

Here we present recent progress from the new CLF Adaptive Optics program including a new development laboratory and tests of a high damage threshold dielectric deformable mirror. The recently refurbished laboratory has versatile optical layout, multi wavelength, large beam diameter and large propagation distance (~10 m) for testing deformable mirrors up to 150 mm diameter, as well as manufacturing capabilities.

Different sorts of carbon monoxide laser systems such as a compact slab RF discharge overtone CO laser (λ~3.0-4.0 μm) with output power up to ~2.0 W, a master oscillator - power amplifier fundamental band CO laser facility emitting nanosecond pulses with peak power up to ~0.4 MW in the spectral range of ~5.0-7.5 μm, an efficient (~25%) second harmonic emitter based on the latter system, and difference frequency generation (4.3-4.9 μm) under nonlinear mixing of fundamental, second harmonic and sum frequency CO laser spectral lines are discussed.

We present an overview of recent progress in ultrahigh-peak-power CO₂ laser systems and discuss a roadmap for further development.

Among the most important UV lasers are the excimer and the nitrogen. A nitrogen gas laser is widely used in various fields. We considered some ideas for a nitrogen laser built in more easily by using of triboluminescence. In this study, we discussed development and discussion of convenient nitrogen laser. We considered utilization of triboluminescence for control of discharge and the system of electric generator using triboluminescence in the longitudinally excited nitrogen laser.

In order to contribute toward the development of a highly-repetitive TEA-CO₂ laser, small-signal gains are measured for a double-pulse operation of a laser medium in a supersonic flow at a Mach number of 2. It is found that the time interval of the double-pulse operation should be longer than 60 μs in order to have the gain of the subsequent pulse comparable to that of the preceding one. It is also found that the gain is enhanced with a low-temperature laser medium owing to the concentration of excited CO₂ molecules in the state of a specific rotational quantum number. The results suggest the possibility that the output power of a TEA-CO₂ laser device can be increased by utilizing the supersonic flow.

The exciplex pumped alkali laser (XPAL) system has been demonstrated in several different mixtures of alkali and rare gas. A simple theoretical analysis of continuous-wave XPAL systems is presented along with more detailed pulsed calculations using the BLAZE model. The model predicts that an optical-to-optical efficiency in the range of 40-50% can be achieved for XPAL with a requirement of relatively high pump intensities.

The thermal effect produced by quantum defect is an important factor that affects the performance of DPAL. We report on 3D simulation results of temperature distribution inside the alkali gain medium. The results show a high and non-uniform temperature rise under CW pumped condition, and the current models that assume uniform alkali density distribution needs to be modified. A convective cooling scheme should be applied for high power DPALs.

We have developed a three dimensional computer model of the combined guiding mechanism for the transverse mode formation in the end-pumped laser resonator. The finite difference beam propagation method is used to solve the nonlinear Schrodinger-type wave equation in the gain medium with combined guiding mechanism, i. e. the thermal induced refractive index guiding effect as well as the gain guiding effect. After establishing the pump absorption model of end-pumped YAG/Nd:YAG/YAG laser resonator, the temperature distribution in the gain medium is obtained by the numerical solving of the heat diffusion equation. The combined guiding effect is observed in the end-pumped Nd:YAG laser resonator; numerical results show that combined guiding mechanism dominates the transverse mode formation in high power end-pumped laser resonator.

In the present paper the scaling laws for the oxygen-assisted laser cutting of low-carbon steel of 5-25 mm is studied experimentally. No dross and minimal roughness of the cut surface were chosen as criteria of quality. The paper also studies the possibility to describe the cutting process by the similarity method and as ratios between dimensionless variables. Normalized power W/ktT, normalized velocity V_cb/a (Peclet number) and kerf width have special optimum numb. Formulas were obtained to determine the optimum values of the laser power and cutting speed for the given sheet thickness. The energy balance of the oxygen-assisted laser cutting is studied experimentally at these optimum parameters. The absorbed laser energy, heat conduction losses and cut width were measured experimentally, and then the energy of exothermic reaction of oxidation was found from the balance equation. To define the integral coefficient of absorption, the laser power was measured on the cutting channel exit during the cutting. The heat conduction losses were measured by the calorimetric method. It has been established that the absorbed laser energy, oxidation energy, thermal losses and melting enthalpy related to a sheet thickness unit, do not depend on the sheet thickness at the cutting with the minimal roughness. The results enable to determine the fraction of the oxidized iron in the melt and thermal efficiency at the cutting with the minimal roughness. The share of the oxidation reaction energy is 50-60% in the total contributed energy.

In this work we investigate the dynamic effects occurring during laser cutting of sheet metal. In particular, we focus on the ejection of droplets of molten material on the lower side of the workpiece and the impact of surface tension of the molten material on this process. We also point out how this influences the formation of striations on the cut kerf and other quality defects.

Nickel-base alloys, such as Hastelloy X and René 80, are among the most common ones for aerospace applications, due to their mechanical strength at high temperatures and oxidation resistance properties, although processing for missile and space vehicle applications requires extensive fusion and resistance welding for fastening. Laser welding using a Yb:YAG disk laser in continuous mode emission is investigated in this paper for overlap joining of Hastelloy X plates on René 80 samples resulting from waste turbine blades. An explorative study is carried out in order to find an appropriate processing window as well as discussing bead features and common issues. Special fixtures for clamping have been specifically developed and tested. A 3-factors study with power, welding speed and focus position as governing parameters has been arranged; 2 levels have been chosen for each factor. Geometric features, defects and indications are discussed referring to the parameters main effects.

Laser assisted joining of aluminum and steel causes the formation of intermetallic compounds. Especially compounds with high aluminum content should be avoided due to their high brittleness. Excellent experimental results where joining and cooling temperatures have been optimised are presented. A FE software package has been used to simulate temperature development during laser assisted joining of dissimilar materials.

Novel devices can be produced by means of femto-second laser processing. A new function of the optical fiber sensors has successfully achieved by a femto-second laser to detect directional bending which has been impossible for conventional fiber sensors. The proposed sensor has an internal structure which is consisted of micro-voids array configured along the optical fiber axis in a non-axially asymmetric configuration. The bending direction can be detected sensitively with the sensor to intensity changes of light through the fiber core because of the non-axial form of produced voids array. A laser processing system has been constructed to accomplish the fine control of laser beam for precisely creating micro structures in a very thin optical fiber core region with a monitoring camera by which the micro structures made can be viewed. Optimum irradiation conditions were set so as to fabricate sensor elements with different sensing lengths. Based on the directional detection principle proposed in this work, various sensor performances has been obtained in terms of the possibility and repeatability for directional bending detection by observing transmitted light intensity through the optical fiber core.

Unsteady heat transfer with simultaneous melting and crystallization at laser cladding process with coaxial metal powder injection is investigated numerically. Numerical modeling determined that the main parameters that govern melt pool dynamics and system maximum temperature are mass feed rate, laser power and scanning speed. Also it is determined that taking in to account the kinetics of phase change results in melt pool boundary and melting temperature mismatch. Dimensions of melted zone and cladding height are compared with experimental data.

It was performed a Time of Flight (TOF) study for the plume produced by laser ablation of cooper by 355 nm, 23 ns duration laser pulses, in vacuum. The plume sensor was made of a piezoelectric PVDF film associated with a pair of electrodes. By varying the electrodes polarization we evaluated the fraction of neutral atoms, which ranged from 8 to 30 % of the plume. By adjusting a TOF function to the PVDF electric signal we obtained the center of mass velocity and the translational temperature. It was observed that product v_CM × T_z remains constant with the electrodes potential and that the accelerating potential to which the plume is submitted has practical limits.

We present a recently patented apparatus which consists of an extreme ultraviolet radiation source writing invisible patterns on thin tags of alkali halides. The tags patterned using this method are almost impossible to counterfeit, and offer a much better protection against fakes than available anti-counterfeiting techniques. We will discuss if this novel technology is ready for industrial production of anti-counterfeiting tags.

The surface stress effects on the Rayleigh wave propargation characteristics in elastic solids with a distribution of laser induced atomic point defects are studied. The frequency equations for waves are obtained and analized. It is found that the Rayleigh waves are generally dispersive; and in the case of low frequency with residual surface tension, a critical wave length exists, below which the propagation of Rayleigh waves is not possible. This critical wave length depends on both the residual stress and the defect distribution.

DPSSLs are the leading technology for several high energy pulsed applications needing a simple and tough design along with a high “wall-plug” efficiency. Among others, interesting applications include space-born instrumentation, laser x-ray or electron generation, or inertial fusion ignition. Recently we adopted the large area zig-zag ceramic slab scheme as baseline for the amplifier of a Diode Pumped Solid State ns-pulsed MOPA laser system for space applications. Our experience shows that ASE and Parasitic Oscillations are the enemies to face adopting this format. ASE clamped gain measurements and possible countermeasures are reviewed in this paper.

Eye safe laser radiation at 1.6 μm is realized by a resonantly pumped Er:YAG laser operating in cw- and q-switched mode employing high brightness laser diode modules. These modules provide high power and narrow bandwidth emission at 1.5 μm from a 100 μm fibers providing high pump efficiency.

Power, special and temporal characteristics of high–performance advanced LD–pumped solid–state laser systems emitting in the spectral ranges of 1064, 1535 and 1570 (fundamental modes) as well as 266, 355 and 532 nm (fourth, third and second harmonics) are discussed. The ways for further improvement of those laser systems are proposed. In addition, the problem of optimization of the pump unit based on the powerful laser diode arrays (LDAs) is analyzed. The effect of the LDA internal optical loss on the amplified spontaneous emission flux value developed within the LDA active layer is considered in detail.

The design and characterization of a THL-100 multi-terawatt hybrid laser system based on a Start-480M titaniumsapphire starting complex and photochemical XeF(C-A) amplifier with a 25-cm aperture are described. The first experiments results are presented. A laser beam peak power of 14 TW at 475 nm wavelength has been attained.

The joule-range high-beam-quality Nd³⁺:YAG laser oscillation in the multiloop self-pumped phase-conjugate cavity without an output coupling mirror at four-wave mixing of intracavity beams directly in the 110-mm long Nd³⁺:YAG rod with 12.6 kW diode side-pumping is developed and studied. The oscillation efficiency of up to 18 % and average power of up to 22 W were achieved in the optimized geometry of the laser cavity at the 13.9 kW pumping with repetition rate of up to 20 Hz and pulse duration of up to 475 μs. The laser generated a single high-intensive 200-ns giant laser pulse (or series of such pulses with microsecond period at increased pumping) oscillated at self-Q-switch on gain gratings with relatively narrow linewidth of about 2 GHz followed by low-intensive free-running wideband lasing. We also realized a passive Q-switch by the F₂^-:LiF and Cr⁴⁺:YAG crystals with oscillation of pulse trains and also 30-ns single-pulse oscillation with an individual pulse energy of up to 60 mJ and peak power of up to 4 MW at narrowed laser spectra down to 1.7 GHz.

In the last ten years we have been working on the design, construction and testing of several diode pumped solid state lasers with various formats, all based on a thin slab ceramic active medium. We adopted different cooling and pumping schemes. A novel configuration with passive cooling, edge-pumping and edge zig-zagged internal propagation has recently shown a high conversion efficiency (43% optical conversion and 60% slope) at a 230 W CW extraction level.

In this paper phase explosion in aluminum targets induced by Nd:YAG pulsed laser beam is studied. The phase explosion occurs in ablation process when the Nd:YAG laser beam (single pulse) is focused on the surface of target in ambient air. The phase explosion was investigated by monitoring the transmission of a cw laser probe beam through the ablating region. Two different aluminum targets were used in this study; a thin film aluminum on a quartz substrate, and a thick aluminum foil. The results show that the probe beam transmission through the ablated region is enhanced significantly when the laser fluence is enough for the phase explosion to be occurred.

We have observed the optical amplification of femtosecond VUV seed pulses at 126 nm by using an optical-fieldinduced ionization (OFI) Ar₂* amplifier. The maximum amplification ratio of 2.57 was observed. This corresponded to the maximum one-pass gain value of 0.94, which was consistent with that observed in previous experiments. We measured the spatial distribution of the gain region in the OFI Ar plasma by probing the 126 nm VUV seed pulses. The gain region of 220 μm (FWHM) was evaluated after 20 ns of the plasma production, which indicated the average plasma expansion temperature of 1.2 eV. An Ar⁺ density contour measured by using laser interferometry showed consistency with the spatial distribution of the plasma gain region.

]HF chemical laser with MOPA configuration is a good solution to achieve high output power with high reliability. Kinetic models for HF amplifier are important for prediction and optimization of the performance of MOPA chemical lasers. In this paper, a simplified model for HF chemical laser amplifier is presented. The main processes which are included in the model are: (a) chemical pumping of HF (v=2) and HF (v=1), (b) stimulated transitions and spontaneous emission. (c) relaxation of vibration excited HF molecule by H₂,N₂ and HF. Some assumptions are taken in this model: (a) the density of H₂, N₂, HF, translational temperature and velocity of gas mixture are averaged across the laser cross section, (b) only two vibration-rotational transitions (2P6, 1P7) occurs in the amplifier, (c) gas temperature does not change during the lasing process in the amplifier. Based on these assumptions, a set of three-level rate equations is formulated and then solved by an iterative technique. Comparison is made with recent experimentally obtained data from a low power discharge-driven CW HF laser with MOPA configuration. It is shown that experimental results are consistent with the calculation from the simplified model.

Design optimization of several distribution flow pipeline levels in nozzle blade is important for uniformization of reaction flow field and the cooling of primary nozzle blade by the secondary nozzle flow. Characteristics of the secondary nozzle with three distribution flow pipeline level transport structure were studied based on three-dimensional fluid dynamics method. Flow field uniformity of every distribution flow pipeline levels were calculated under the 1st level inlet pressure of 3, 5, 8 atm. The existing designed area ratio of inlet and outlet of the 1st distribution flow pipeline level is rational, and the flow uniformity of it meets the request of system. But the area ratio of the 2nd and 3rd levels needs to be optimized.

Production of iodine atoms due to dissociation of iodides CF₃I, CH₃I, C₂F₅I, and C₂H₅I in a self sustained pulsed discharge has been investigated. The efficiency of iodide dissociation as well as a yield of excited iodine atoms has been measured for different experimental conditions.

An investigation of exciplex pumped alkali laser (XPAL) has been conducted. A 4-cm gain cell containing Cs as an active medium is pumped by a tunable Ti: sapphire pulse laser. Laser oscillation is observed in both five-level and four-level systems. Small signal gain and saturation intensity of the active medium is measured by both probe laser amplification and oscillation experiment with varied output coupling. A one-dimensional numerical simulation is developed and the result of calculations is compared with the experiments. The pulse shape and oscillation threshed agree reasonably while calculated optical-optical conversion efficiency is underestimated.

A short pulse XeCl laser system is being developed for plasma physics and material science study. Partial spatial incoherence seed with short pulse is amplified by MOPA chain including three discharge pumped amplifiers and two electron beam pumped amplifiers for one beam. Final laser output of 5~10J in energy with pulse width of around 10ns has been achieved, which lays a good foundation for full scale construction.

A review of the physical properties and range of practical applications of layered (quasy two-dimensional (2-D)) GaSe-type (gallium selenide) semiconductors is given in the present article with emphasizes on GaSe. First data on the NLO properties of ε-GaSe (hereinafter GaSe) has been reported in 1972 by the Azerbaijanian (Institute of Physics Azerbaijan National Academy of Sciences, Baku, Azerbaijan) and Russian (Lebedev Institute of Physics USSR Academy of Sciences, Moscow, Russia) teams. GaSe has been recognized by the world scientific community as a crystal with an outstanding NLO properties which may be characterize shortly as follows: high optical birefringence Δn ~ 0.3 at 700 nm; wide optical transparency range of 0.65 nm - 18 μm with low absorption coefficient in this range ( α ≤0.3 cm^-1); one of the highest second-order NLO coefficient (d₂₂ ≈ 86 ± 17 pm/V); high power optical damage threshold; possibility to perform frequency conversion under phase-matching conditions in the near- to mid-IR and THz- range of spectra, etc. Occurrence of different polytypes (ε, γ, β, δ), in the bulk grown crystal highly increases the interest to study the physical properties of GaSe and leads to formation of a domain structure. The latter is discussed also in the present article as studied by confocal microscopy 2D imaging experiments. Some results on the optical and NLO properties of nanoparticles of this class of materials are considered also. Present article, does not pretend to be one reflecting all existing papers on above mentioned subjects.

The new method to estimate the erosion threshold of various material surfaces with high power pulsed electron beam was extended to the surface erosions with various pulsed laser lights. We are interested in the erosions of candidate materials to be useful under very severe eovironmental conditions with various laser lights, including ArF and Nd:YAG laser lights.

We demonstrate a simple pulsed laser design with a potentially high efficiency for high harmonics generation. The basic idea is to generate pulsed laser operation with a resonantly oscillating piezo-electric crystal made of LiTaO₃ or LiNbO₃, i.e. Q-switching with a Single Crystal Photo-Elastic Modulators (SCPEM). The pulsed mode operation shows 30 (internal SHG) to 50 (external SHG) times higher green power than the cw-mode operation with a maximum green output of 290mW.

Frequency conversion of a single longitudinal mode Nd:YAG laser operating at 1.064 μm is realized by an external third order Stokes barium nitrate Raman laser providing narrowband radiation at 1.599 μm wavelength which coincides with a CO₂ absorption line. Transmission measurements employing a multi-pass absorption cell yield good agreement with theoretical simulations of the CO₂ absorption characteristics.

Since the emergence of laser and henceforth laser remote sensing in the 1960's, lidar (light detecting and ranging) technology has became a significant tool for the detection of various phenomena like wind direction and intensity, atmospheric temperature, urban and rural topography, forest fires, ocean planktonic development, and detection of various constituants such as tropospheric aerosols, stratospheric ozone, trace chemicals and etc. In 2009, a homemade multiwavelength Raman aerosol lidar (named MRC K09) was designed, developed and installed in the Scientific and Technological Research Council of Turkey (TUBITAK) Marmara Research Center (MRC), and since 21 February 2011, it has been accepted to EARLINET (European Aerosol Research Lidar Network). Since 2009, aerosol spatio-temporal distribution and microphysical properties have been investigated in the extremely industrialized vicinity [1,2]. MRC K09 lidar uses a Quantel Brilliant B Nd:YAG laser (1064 nm) with the second and third optical harmonics at 532 and 355 nm, and a homemade Newtonian 40 cm aperture 120 cm focal length telescope. It has 7 channel spectrum analyzer detecting: parallel and perpendicular polarizations at 355 nm, elastic signals at 532 and 1064 nm, Raman signal of molecular nitrogen at 387 nm and Raman signal of water vapor at 408 nm (excited with 355 laser line), and Raman signal for molecular nitrogen at 608 nm (excited with 532 nm laser line). In Spring 2010, preliminary applications for the determination of forest tree species and of forest health in the Black Sea Area using an aeroborne lidar in collaboration with Bartin University, Bartin, Turkey have been made. In early 2011, a fluorescence module utilizing a Princeton Instruments PI-MAX3 1024x256 resolution CCD camera with a Princeton Instruments Acton SP 2500 0.500 m Imaging Triple Grating Monochromator/Spectograph was connected to the MRC K09 lidar system, and the first remote measurements of chlorophyll from different types of trees were made. Figure 1 demonstrates the results of these measurements, which must be considered as preliminary and in the future, the measurements can be carried out by the lidar mounted on an aircraft to cover large spatial areas. One of the most important reasons for biodiversity loss, habitat loss and fragmentation can be monitored in large areas by aeroborne lidars and therefore the extent of the situation can be accessed precisely, faster and more efficiently. This paper aims to give a brief overview to show the possibility of detecting the detailed situations of the habitats on terrain surfaces using lidar technology by summarizing the successful examples which have been realized thus far in different types of ecosystems like savannas, forest and grasslands.

Aerosols affect the radiation budget of the Earth by scattering and absorbing the incoming solar radiation, and by acting as cloud condensation nuclei (CCN) to form clouds and/or change their properties. Because of their high spatio-temporal variability and remote nature, investigations of aerosols physical properties have been rather limited until the last few decades. Lately, multiwavelength Raman lidars became an important tool for the measurements of aerosol physical parameters. Such lidars allow to get three aerosol backscattering and two extinction coefficients (so called 3β+2α) and from these optical data the particle microphysical parameters such as number, surface area and volume concentrations, effective radius, particle size distribution, particle and volume polarizations and complex refractive index can be retrieved through inversion with regularization, principle component analysis and linear estimation techniques. During 2009-2011, using a homemade multiwavelength Raman lidar with a Quantel BrilliantB Nd:YAG laser generating also the 2nd and the 3rd optical harmonics, the spatial and temporal distribution of aerosols and their microphysical properties have been measured and evaluated in various seasons, meteorological conditions and with different horizontal measurement angles. Reliability of our results have been confirmed with the synergistic measurements done with lidars located in Greece, the EUFAR aircraft (European Facility for Airborne Research, FAAM-Bae146 aircraft), ACEMED campaign (Evaluation of CALIPSO’s (Cloud-aerosol Lidar and Infrared Pathfinder Satellite Observation) aerosol classificatiomn scheme over Eastern Mediterranean) and GOSAT (Global Greenhouse Gas Observation by Satellite project). In early 2012, the addition of the scanning module mounted on the top of the telescope, allowed to obtain information about the aerosol distribution within fixed and regular time intervals in a given time frame and from various measurement angles, and thus it made possible to cover a large spatial area and to evaluate the changes in the aerosol microphysical properties in space and time. It uses Newport ESP301 Motion Controller allowing to make measurements in 340° azimuthal and ± 15° vertical scanning angles by a 300 x 600 mm plane mirror. In this paper, the description of the new multiwavelength aerosol lidar scanning system installed in the Scientific and Technological Research Council of Turkey (TUBITAK) Marmara Research Center (MRC), KA09 Laser and Lidar Laboratory is explained, and the first results obtained from the data acquired during Spring and Summer 2012 are presented by integrating the results with a geographical map of Gebze Area.

Damage threshold of non-linear GaSe crystals under IR fs (Ti:Sapphiere 800 nm laser and 1.1-2.9μm OPG) and ns (2. 79 Er³⁺:YSGG and 10.6μm CO₂ laser) pulse pumping is studded in details. Local micro defects and field induced effects (GaSe dissociation, multiphoton absorptions and transient transparency origin effects) are identified as responsible for damage threshold in this case. Local (including nano scaled) defects and thermal effects are identified as reason of damage threshold under ns pulse pumping.

A strip Volume Bragg Grating (VBG) locked 64 emitter diode laser array’s center wavelength shift of each emitter according to VBG’s local temperature is experimentally studied, which is consistent well with thermal imaging temperature distribution, Finite element analysis (FEA) is then used to study strip and large area VBG’s temperature gradients, we find even with minute heat deposition, due to PTR glass’s low heat conductivity, tens degrees temperature gradient could easily be built, we suggest it may be partially respond for stack’s poor spectra narrowing performance compared to single laser diode and diode array. Finally, some measures are further suggested to alleviate the effect.

Surface discharge Radiation Source has been used as optical pumping source of XeF(C-A) gaseous laser. In previous works, discharge deposition power, transition efficiency and UV radiation intensity of surface discharge Radiation Source were mostly concerned, but the jitter of repetitively pulsed surface discharge was little studied. An optical pumping source by segmented surface discharge on Al₂O₃ ceramic substrate is developed to design stable XeF(C-A) laser with pulse repetitive mode. Distorted electric field near the surfaces of the ceramic substrate is calculated based on equivalent chain circuit model under conditions of charging voltage from 0 to 26.8kV, thickness of the substrate from 1mm to 3mm, and trigger pulse voltage from 47kV to 63kV. Analysis about trigger characteristics of pumping source is carried out, and influence of these conditions on discharge jitter is discussed. And discharge jitter is investigated in detail under different conditions. The experimental results show that discharge jitter decreases with increasing charging voltage and trigger pulse voltage, as well as decreasing thickness of ceramic substrate, and the pulse repetition rate has little influence on the discharge jitter in the range of 1Hz to 30Hz. These experimental results are coincident with numerical simulation results. Normally, the discharge jitter can be less than 30ns. Research results indicate that the optical pumping source has good time stability of repetitive pulse discharge.

The present work focuses on the use of Selective Laser Melting (SLM) technique for manufacturing of near-net-shape aircraft component prototypes with Ti-6Al-4V titanium alloy, which has already successfully employed for the production of turbine blades since it combines mechanical properties with excellent wear resistance. The main characteristic of SLM is layer manufacturing which allows to obtain complex shaped elements using three dimensional computer aided design data, with the addition of particular features like channels or cavities which can not been easily obtained with traditional technologies. The other key aspect in comparison with investment casting is shorter post-processing. The feasibility of manufacturing turbine blades with mentioned process using a laser sintered machine EOSINT M 270 (Titanium version) is analysed. The first experimental phase has dealt with the definition of processing parameters which would guarantee laser sintered part maximum density. Preliminary specimens have been manufactured to define any material-dependent scaling value to control dimensional shrinkage. Afterwards a prototype of a turbine blade has been produced using optimal process parameter set. The element positioning and support definition are discussed as they influence the overall job time and the need of post processing operations. Further analyses have been carried out to check the whole structure of the prototype using X-rays and Fluorescent Penetrant Inspection, aiming to point out possible imperfections; no defects have been detected. Furthermore, laser sintered part dimensional inspection has been successively performed via coordinate measuring machine. Eventually, the microstructure of the prototype has been examined.

We have designed some holographic gold gratings in 700-1100nm wavelength range for stretching and compressing pulse in CPA technology. These gratings optimized by Gsolver software based on rigorous coupled-wave analysis (RCWA) for TM polarized light in the 1st order (littrow mount) and have super Gaussian profiles. We also shown dependency of diffraction efficiency (DE) to depth and duty cycle of super Gaussian gold gratings in 1064nm.

In this paper we have investigated three wave interaction analytically for stimulated Raman back-scattering in resonance and non-resonance conditions in an under dense plasma. We have solved equations by similarity transformations and have found self similar solutions. It has been shown that by increasing time, maximum of amplified pulse increase constantly while the duration decrease inversely. Effects of initial seed pulse’s amplitude and detuning parameter have been investigated.

The simulation for high power application has been executed. The simulation has done not by the local computer but in the “cloud” computing environment. Now, the authors apply the cloud computing environment to the high power simulation. The details will be presented in the conference.

Population densities for the excited levels of hydrogen-like ions in an optically thin plasma have been calculated in order to investigate the appropriate conditions for the generation of population inversion by recombination and subsequent development of gain in laser systems. To achieve this goal, collisional-radiative model in a range of electron temperature of 4000Z² - 256000Z^{2 0}K and electron density of 10⁸ Z⁷ - 10¹⁸ Z⁷ cm^-3 is used. In addition, the inversion threshold temperature is introduced and used in characteristic graphs which helps to identify the inversion conditions.

In this paper formation of nano- ripples on the surface of a polyethersulfone film upon non polarized KrF laser irradiation at fluences below the ablation threshold and micro ripples upon XeCl laser irradiation are reported. The effect of number of pulses and the repetition rate on the formation, periodicity and orientation of the ripples and the possible mechanisms of the formation are discussed.

Efficient Nitrogen diluted HF/DF laser with cryogenic adsorption provides a possible way to realize compact and relative high power mid-infrared laser system. Driven by only one dc-discharge tube, 117 Watt laser power, total e-o efficiency of 6.6% in HF case, and that stands four to five-fold increase had been achieved with Nitrogen dilute by careful designed supersonic nozzle array gain generator. Spectra, gain distribution, and chemiluminescence are further investigated to explain the enhancing mechanism.

In this paper propagation of beams from positive branch confocal unstable resonator through turbulent atmosphere is investigated numerically. It was assumed that the resonator has one variable reflecting mirror in one end and an ordinary uniform reflecting mirror in the other end. Using Huygens-Fresnel integral and iteration method, the dominant transverse mode of the resonator in near field was calculated. Then by using extended Huygens integral, the propagation of fully coherent output beam of the resonator through turbulent atmosphere was evaluated. The effects of resonator characteristics and the atmospheric turbulence parameter as well as propagation distance on the propagated beam were investigated.

In this paper, we present experimental results of an investigation in silicon surface morphology induced by nanosecond laser pulses in distilled water. The silicon surface was initially rough at micro-scale and irradiated by nanosecond regime laser at different pulse numbers and fluences. Under the conditions of the experiment, nano-structure cluster morphology was formed on the surface of silicon after exposed to the laser beam. The effective diameter and surface density of clusters were estimated from the SEM images of irradiated silicon. Optical reflectivity of silicon surface was also measured by a probe beam. The reflectivity results present an estimation of the clusters height. The results show that the number of nanoclusters depends effectively on laser fluence and pulse numbers. Moreover, the nanoclusters height is influenced by pulse numbers.

This paper presents the results of experimental investigation of thermal lens effect. The thermal lens effect was induced by Ar ion laser in liquid ethanol, as an absorbing medium. Using a simple model, the focal length of the thermal lens medium was determined by evaluating the experimental results.

This paper presents the results of numerically studying for the enhancement of the soft continuum x-ray yield emitted from porous metal targets irradiated by sub-nanosecond high power pulsed laser beam when considering the effect of plasma opacity. In the calculations, the main emission mechanisms were assumed to be the free–bound and free–free (bremsstrahlung) transitions at water windows wavelengths ranges 2.3-4.4 nm and also wavelength ranges 12.6-14.6 nm which is useful for lithography applications. The free-free, and bound–free transitions were also considered for calculating the opacity. The results show that the opacity may significantly influence the x-ray yield detected by an observer outside the target.

A novel optical fiber sensor has been developed for gaseous material detection by means of a femto-second laser which has ultrashort pulse and ultrahigh peak power. This sensor has attractive sensor potion consisted of drilling holes array which is machined on the glass optical fiber. Additionally, the sensor potion is coated with thin gold film. This work expects that an interaction could be induced between transmitted light through fiber core and a bottom of the drilled holes which reaches the fiber core. The interaction could induce near-field optical phenomenon excited by transmitted light through the fiber core. This scheme could make it possible to detect gaseous-material phase substances around the optical fiber. In this study, we found that localized surface plasmon (LSP) was excited by the transmitted light through the fiber core. This paper shows experiment to obtain optimum irradiation conditions and investigation for sensor principle for the development of a novel fiber sensor.