Prospects of high power lasers (50 divided by) 100 kW) application in industry and environment protection are presented. The most promising type is gas-dynamic laser (GDL) that is concluded from the given comparative analysis of various types.

Most high power applications either production or defense oriented require good beam quality. A state-of-the-art review shows that current solid state lasers exhibit a clear deficiency as compared to well developed gas lasers. This may be overcome by the new concept of a diode pumped thin disc laser combining the advantages of low optical degradation of the laser medium and good output power scalability. This solid state laser benefits further from the shorter wavelength and better coupling efficiency for a wide range of materials. Yb:YAG is chosen as the preferred laser material because it primarily has a high quantum efficiency, guarantees good energy storage for pulsed operation, and exhibits a broad absorption line at 941 nm for easy and effective pumping with InGaAs diodes. Performance data of the thin disc laser are shown for output powers up tp 350 W CW with optical and slope efficiencies of 49% and 56%, respectively. Scalability of the concept is demonstrated by using a multiple disc design with a zig-zag stable resonator. Beam quality parameter, M², has also been determined for al operation conditions. Best values of M² equals 1.22 have been obtained for 100 W output power at 39% optical efficiency. In addition, passive mode locking and Q-switched operation are demonstrated. Finally, performance in alternative laser active materials (Nd:YAG, Nd:YVO₄, Tm:YAG) is also presented.

The consequences of unstable resonators building main principles are shortly reviewed. The application possibilities of some fairly new resonator schemes suitable for high power lasers are mentioned. The history of application of wave front conjugation for laser techniques are discussed.

An Overview on Chinese National High-tech program on lasers is given. It includes: High power solid state laser program; Advanced Laser program; Laser fusion and other applications of High power lasers.

Ultraviolet excimer lasers are attractive candidates to generate efficiently high brightness soft X-ray sources. Preliminary results on the development of an oscillator- amplifier excimer laser system based on the regenerative amplifier technique are presented. These experiments have been performed in collaboration with the laser company SOPRA in the frame of the EUREKA-EXULT (EU-1182) program.

The high power mobile laser technological complexes with output power 5 kW (MLTC-5) and 50 kW (MLTC-50) have been developed and experimentally tested. Various perspective areas of industrial applications of mobile laser technological complexes are considered. The results of some technological experiments are given.

The theoretical, technical and technological aspects of the high energy and low angular divergence laser beam obtaining by means of Raman's scattering application in the secondary cascade are discussed. Several (2 - 6) unphased, independent, simultaneously working primary cascades were combined into one laser beam having 10 cm diameter and 10¹⁵ - 10¹⁶ W/cm² .sterad brightness at 40% summing efficiency.

A review of recent achievements and new tendencies in the development high energy, high repetition rate excimer lasers will be presented. The paper mainly focuses on the features of KrF, XeCl lasers with different combinations of output energy x pulse repetition frequency, for example: 1 J X 600 Hz (KrF); 3 J X 200 Hz or 10 J X 100 Hz (XeCl), which have been developed as candidates for industrial applications.

An ArF excimer laser has been operated using four different spiker-sustainer excitation circuits. We report on the large differences in the laser output energy caused by nanosecond- scale variations in the preionization timing with each circuit.

The overview of the phase-locking technique is presented. Analysis of the parameters that influence on the phase-locking is given. Admissible range of the deviation of the linear laser diode array, external cavity parameters is estimated. Comparison of the external Talbot cavity configuration with the other ones is held. Attention is paid to both investigation and employment of the laser diode arrays consisting of wide aperture lasers that opens an avenue to high power output radiation in a phase-locked mode. Special consideration is given to the cavity supermodes selection. Our experiments both confirm actual feasibility of 1D and 2D phase-locking of LDA's with specified parameters in the external Talbot (L_c equals Z_T/4) cavity and illustrate theoretical predictions of the system stability and selectivity, so that: (1) phase-locking in 1D configuration allowed diffractional limited lobes width (delta) (Psi) equals 0.5 mrad; (2) tilting of the output mirror provided 'in-phase' supermode selection; (3) phase-locking in 2D configuration of the two LDA's of N equals 8 lasers, separated by 1600 mkm resulted in diffractional lobes full width at half maximum (delta) (Psi) equals 0.5 mrad in slow axis and (delta) (Psi) equals 0.25 mrad in fast axis.

We have tested a high-repetition-rate X-ray diode working in reflection geometry, which uses commercial spark-plugs as plasma cathode. The results show that the spark-plug plasma cathode is a reliable, high-current and long-lifetime electron gun. After more than 10⁶ shots, the dose, uniformity and ionization rate of the emitted X-ray guarantee an effective preionization of XeCl excimer laser discharges. Due to the low cost, the long lifetime and the substantial absence of maintenance, this X-ray diode seems suitable to preionize commercial gas lasers, such as excimer and TEA CO₂ lasers.

The review is devoted to the condition of works on development of powerful lasers pumped by nuclear reactors. Possible schemes of NPL's, LAEL's and concepts of RL's are under consideration. The problems and perspectives of NPL's and RL's are touched upon.

The experimental research results of an laser radiation in excimer lasers and laser systems with output aperture up to 25 X 25 cm² and output laser energy up to 200 J is described. The laser beam divergence 0.01 mrad have been obtained. The problems of the diffraction limited divergence formation of laser beam are discussed.

The status of waveguide lasers is reviewed and new developments on large CO₂ waveguide laser arrays presented. The parallels between gas and diode laser arrays are explored and the transfer of gas laser concepts to new planar waveguide solid-state lasers is discussed.

We describe the behavior of an annular RF-excited CO₂ laser, operated with a Talbot cavity in order to reduce the number of oscillating azimuthal modes. The beam quality is enhanced by means of a phase filter outside the cavity.

High pressure operation of a fast-axial-flow CO₂ laser, with a rectangular cross-section RF slab discharge is demonstrated in both cw and pulsed modes. Spatially resolved measurements of discharge power densities give good agrement with total input powers while calculated values of sheath thickness correspond with visual observations of the gas discharge. Variations in power density and sheath thickness along the gas flow axis are interpreted in terms of pressure gradients and gas flow choking within the discharge.

We developed and experimented a method for obtaining a transverse flow CO₂ laser-TFL- with a matching coefficient (the cross section of the laser beam/the cross section of the electrical discharge) -(eta) _m greater than 0.8 for a Fresnel number of the optical resonator -N_Fless than 2, in which both types of the active medium asymmetries are compensated. This corresponds to a TFL with high efficiency and TEM_00/01 good optical quality laser beam. The main elements for this laser are: gas circulation fluido-dynamical circuit in cylindrical geometry with two opposite electrical discharges; U-type laser resonator with a 90 degree deflection element (pentaprism alike), instead of one corner mirror, which reverse the wavefront of the laser beam in one of the two discharge channels. Also, it was developed a new very stable 90 degree-beam deflection optical element with properties alike pentaprism. This element might be used in optical resonator construction, transport and focusing systems of the laser beam.

The construction of CO₂ laser system generating a train of subnanosecond laser pulses with total train energy up to 5 J is reported. A record level of laser energy was obtained due to utilization of unique 5 X 5 cm² aperture, 6 atm X- ray preionized CO₂ amplifier. The estimations of individual pulses durations in the train are given. The prospective of upgrading of present configuration of laser system towards shortening of laser pulses duration and increasing the pressure of working gas mixture of the amplifier and its efficiency are discussed.

The paper presents the results of a decade studies in the field of phase conjugation and other nonlinear-optical correction techniques application to the wide aperture laser telescopes for the average and high intensity laser beams delivery.

The influence of plasma of the volume discharge on the microstructure of the active surfaces of electrodes and their autoemissive properties in CO₂ laser mixtures at atmospheric pressure is researched. A correlation between a change in a microstructure of the electrode surfaces when the autoelectronic currents are increased is stated. It results in a formation local channels in a cathode area of the volume discharge and a resource limitation of small-sized sealed-off pulse-periodical TEA-CO₂ lasers. Materials the more stable to the influence of plasma of the volume discharge providing for getting of a maximum resource (N greater than 10⁸ of pulses) are determined.

We stabilized a frequency and a power of RF excited CO₂ laser to the centers of the Doppler broadened gain curves using an opto-Hertzian effect generated from the laser itself. The frequency stability is estimated to be better than of 5.1 X 10^-8 and power variation is greatly improved to 2.9%. We suggest that this method can be applied for frequency and power stabilization of other kinds of RF excited laser, for example, Xe and CO laser.

Slab RF-excited pulsed CO₂-laser with the pumping frequency F equals 152 MHz, pulse duration in the range of 20 divided by 50 microsecond(s) , and pulse repetition rate f up to 100 Hz has been investigated. Output power, temporal shape of laser pulses, laser beam divergence were measured at the pumping power up to 400 W/cm³. Pulsed output power was varied in the range of 2 divided by 5 kW. The package of numerical simulation codes of pulse-repetition mode of slab CO₂ laser was created. It is shown that the maximum input power is significantly increased by the change of excitation frequency from 80 up to 150 MHz. The measured and numerical data are compared.

Gasdynamics and aero-optics of supersonic flow after multinozzle banks used in gasdynamic and chemical lasers were investigated. The connection between turbulent characteristics of flow and its optical quality were examined. The gasdynamics characteristics of flow in the resonator cavity were measured by traditional methods, the optical properties were measured by the small-aperture version of focal spot method.

The results are presented of expert evaluations aimed at developing the optimal concept of creation of a compact TEA CO₂ laser with a self-sustained discharge capable of generating the repetitive bursts of ten radiation pulses with 1 kJ-energy in each and the pulse repetition rate of 30 Hz. Particular emphasis is placed on the problems of achieving as small angular divergence and beam wandering as possible.

In conditions of high turbulence, propagation of laser radiation along the horizontal path is characterized by significant decrease of intensity in far zone. Due to different factors, opportunities of adaptive means for atmospheric compensation in this case are rather poor. The possible way for overcoming the turbulence is to elevate the output aperture of the laser optical system over the most perturbed atmospheric layers. As the performed calculations have shown, the elevation up to 15 meters allows us to increase the tolerated turbulence range almost eight-fold.

For optimized laser active media with respect to high efficiency the optical quality, the discharge stability and the small signal gain have to be on a high level at simultaneously high power densities. This goal was achieved by combining a defined swirl flow with helical electrodes and a so-called ignition improver. Besides of the regular gas components CO₂, N₂ and He the gas mixture contains Ar and C₄H₁₀. The benefit of using optimized laser active media was demonstrated with a straight unstable resonator superimposed to two discharge tubes. At an efficiency of 18% and a beam power of 5 kW the laser system produces about the same beam propagation factor as calculated for the undisturbed gain medium. The beam propagation factor was significantly increased by an on-axis reflaxicon mirror system within the external beam path.

A family of the small (100 W) and medium (15 kW) combustion- driven CO₂-Gas-dynamic lasers was developed and tested for new application: teaching and scientific research for laser technology. The laser operated using ordinary fuels (carbon, solid propellant, toluene and air). The midget lasers were tested in both premixing and mixing modes. The medium lasers were optimized for two goal functions: maximum power or minimum divergence.

The possibility of generation of coherent radiation with (lambda) equals 5 - 7 micrometer and 2.5 - 2.8 micrometer in vibrational-rotational transitions of DCl molecules under expansion of N₂-DCl mixture in supersonic nozzles is analyzed. On the basis of numerical modeling energetic and spectral characteristics of gasdynamics and electro-discharge flow lasers are considered.

Applying new techniques such as fast gas-circulation, gas dynamics and RF (or microwave) discharge to high gain gas laser media, i.e., CO₂ and CO and so on, the output power has been extremely enhanced, thereby making their availability wider than ever expected. In particular, a high power CO laser has been extensively expected for machinery, welding, and material processing, because of one-half wavelength of the CO₂ laser which offers various advantages such as beam- focusing efficiency, high absorption coefficient to metallic materials, and convertibility to optical elements. Among various schemes of CO laser, a DC discharged fast-axial flow (FAF) system has been still attracted for the aforementioned purposes due to superiority in beam quality and stability of the discharge. Thus, the authors have developed a prototype of compact DC discharged FAF CO laser system and demonstrated 385 W/m and 165 W/m, respectively, at subroom and room temperature operations. Then, the output power tends to usually decrease with turning on the discharge and to be eventually stable under thermal equilibrium. These transient output-reduction are quite sensitive to the gas temperature which also depends on the gas-flow velocity (upsilon) and the discharge current I_dis in the experiments. In the present paper we shall review our recent works on the DC discharge type FAF CO laser developed, especially focusing on the transient properties of the output power obtained experimentally, in comparison with theoretical analysis. Then, we shall also attempt to improve this transient output-reduction at room-temperature operation by inserting molecular sieve within a gas-circulation path, together with is theoretical interpretation.

Survey of results of experimental investigations of energy and spectral characteristics of open-cycle full-scale mock-up of CW supersonic e-beam sustained CO laser (SSCO-EIL) of 200 kW power and results of numerical investigations of the possibilities of increasing output power, spectral line selection, and Q-switched lasing of SSCO-EIL are presented. The possible influence of properties of SSCO-EIL on efficiency of several laser technologies is considered. It is concluded that unique energy and spectral characteristics of SSCO-EIL open ways to drastic expansion of areas of laser technologies both owing to the increase of efficiency of laser energy utilization, and owing to reduction of the energy cost.

The experimental results of study of sub- and supersonic chemical oxygen-iodine lasers (COIL) based on the jet type singlet oxygen generator are presented. The progress in the high pressure jet type singlet oxygen generators allowed to develop the compact highly efficient COIL. The different types of the mixing schemes were tested in supersonic COIL based on the high pressure jet singlet oxygen generator. The preliminary cooling of the active medium by mixing of oxygen with the cold buffer nitrogen gas results in high efficiency operation of the small scale COIL with subsonic and supersonic gas flow in the laser cavity. In COIL with the fast axial gas flow the chemical efficiency more than 20% was achieved.

Brief history and present status of the industrial COIL (Chemical Oxygen-Iodine Laser) studies in Japan are introduced. Up-to-date experimental results obtained by Tokai University group, including high-power subsonic operation, power stabilization, and theoretical works are presented.

The motion and distribution of a fluid in a rotating disk generator as used in chemical oxygen-iodine lasers for the generation of singlet delta oxygen has been investigated experimentally. A transparent mock-up with 3 disks has been built and glycerine solutions of different concentrations have been used as the liquid. This should simulate the various viscosities that the basic hydrogen peroxide, the actual working fluid in a singlet oxygen generator, can assume. Other important parameters in the investigation with a significant influence on the results were the rotation rate of the disks and the filling level of the liquid bath. Depending on these parameters substantial amounts of liquid are trapped between the disks and reduce the accessible disk area for the actual gas-liquid reaction in the production of oxygen. Simultaneously, the gas flow velocity through the disks can locally increase by a factor of 6.5. A strong vortex has been found in the liquid bath of a batch type generator which limits the exchange of reacted liquid with the bulk. Finally, an estimate of the thickness of the liquid film on the disk surface could be derived.

We report on diagnostic measurements in a small scale supersonic chemical oxygen iodine laser (COIL) with transonic mixing. Using diode laser based diagnostics we measured the O₂(¹(Delta) ) yield and water vapor fraction at the exit of a jet type singlet oxygen generator (JSOG) and the gain in the resonator. In addition the chlorine utilization and gas temperature at the generator exit were measured. For conditions corresponding to the maximum chemical efficiency of the supersonic COIL energized by the JSOG the O₂(¹(Delta) ) yield, water vapor fraction, chlorine utilization and temperature at the generator exit are 0.65, 0.08, 0.92 and 30 C. Small signal gain and temperature at the resonant optical axis are 0.25%/cm and 280 K, respectively. Dependence of the yield on the generator pressure and variation of the temperature along the flow in the diagnostic cell are consistent with rate constant of the O₂(¹(Delta) ) energy pooling reaction of 2.7 X 10^-17 cm³s^-1.

A multikilowatts supersonic chemical oxygen iodine laser has been constructed. An output power of 7.1 kw with chemical efficiency 20.3% has been achieved. The beam quality of (beta) less than 2 were achieved on unstable resonator with beam rotation. The diagnosis of spectral characteristics, dimension small-signal gains and water vapor measurement etc. have been studied.

The gain of COIL is so small (about 0.13%/cm) that scaling up is necessary to achieve high power but considering practical use, reduction of system size is needed. Now, new type of small size COIl using RF discharge dissociation of I₂ is presented. The output power of RFCOIL was obtained two or three times higher power than that of normal COIL and chemical efficiency was 12% at 340 mmol/min chlorine flow rate.

Laser power control of chemical oxygen-iodine laser based on the servomechanism was demonstrated with a Zeeman effect. Response of the feedback system in frequency domain was analyzed and compared to the experimental results. With this feedback system, fluctuation of the laser power was successfully reduced to plus or minus 0.4% in the presence of a disturbance.

The downsizing of Chemical Oxygen-Iodine Laser (COIL) was achieved by applying a turbo blower to a high gas pressure operation of a subsonic COIL. The size of the vacuum system was a factor of 3 smaller than that of the existing one. The laser output power of 290 W with chemical efficiency of 17.1% was obtained at the Cl₂ flow rate of 18.6 mmol/s and the laser cavity pressure of 6 Torr.

This work describes a configuration of an electrochemical apparatus for production chlorine and basic hydrogen peroxide and discusses its use in a continuously operating COIL system consuming only electric power and air.

In a stable resonator configuration, the output power and the power density distribution of a chemical oxygen-iodine laser (COIL) were measured for various outcoupling geometries: Diaphragms with slit apertures of various size were introduced intracavity in front of the outcoupling mirror. The slit was placed at different positions along the flow axis. Furthermore, outcoupling mirrors of various reflectivity were used. For all experimental conditions the measured power density distribution at the outcoupling mirror reveals strong symmetry effects: The beam patterns are always symmetric to the resonator axis. The beam shape and the beam size are defined by the hardware aperture that is nearest to the resonator axis. As a function of the slit width, the laser output power saturates well before the aperture of the resonator is fully opened. Fifty percent of the maximum output power were achieved at a width of 6 mm only. Good agreement is found between the measured data and theoretical calculations, when taking into account the specific flow conditions. The data highlight the significance of deactivation processes and the strong iodine repumping mechanism within the cavity. For standard operating conditions a Rigrod type analysis reveals a small signal gain that is nearly constant throughout the cavity exceeding 1.3% cm^-1. The outcoupling reflectivity for the maximum power output was found at a value of about 94%. These experimental data agree well with a simplified analytic model for gain saturation and power extraction as derived by G. D. Hager et al.

In the supersonic COIL the power output and the laser performance strongly depend on mixing conditions of the gas flows. For the 10 kW COIL of DLR, the effects of the gas mixing on the laser power have been experimentally investigated to work out the relations between maximum laser power and the corresponding optimum mixing conditions. For this purpose, optimally diluted iodine jets have been matched to different molar flow rates of singlet delta oxygen. These energetic considerations have been complemented by the investigation of the power dependence on fluid mechanic aspects.

The processes governing the operation of both the pulsed COIL with a forced homogeneous generation of atomic iodine and the premixed I₂-dissociated continuous-wave laser are identical. It makes it possible to use a pulsed laser with a low chlorine flowrate to simulate the high power CW operation and to predict its performance. The examples of such predictions made for famous CW laser systems 'RADICL' and 'RotoCOIL1' are presented and discussed. Experimental results on application of AOM for generation of a train of microsecond pulses are also presented.

The paper presents the most important efforts in the Chemical Oxygen-Iodine Laser (COIL) research carried on at Russian Federal Nuclear Center VNIIEF and some of their results. In particular, they include experimental data on the laser generation output of subsonic COIL on the water vapor concentration in singlet oxygen, calculated generation values of a supersonic COIL having high singlet oxygen pressure at the nozzle inlet, and experiments with the twisted-aerosol- flow singlet oxygen generator (TASOG) for up to 100 Torr pressures. Requirements are discussed for the supersonic high- pressure COIL components, such as singlet oxygen generator and the system for singlet oxygen mixing with iodine.

A large volume, self-sustained discharge, non-chain reaction, HF/DF laser has been built and tested. It was successfully operated at 12 Hz repetition rate and 20 J per pulse output energy (HF) in accordance with numerical model.

The results of performance theoretical optimization of laser system consisting of a cw chemical HF laser Master Oscillator- Power Amplifier (MOPA) configuration, of a beam-director telescope and of a phase conjugate mirror are presented. The following optimal physical parameters have been found: required active medium length of Power Amplifier, required master oscillator output power, optimal relation between diffraction coefficients of splitting on the diffraction optical element onto the surface of the secondary mirror of laser beam-director telescope to the zero and first orders, required level of the threshold power to ensure phase conjugation by stimulated Brillouin scattering.

Chemical reactions are abundant sources of energy varieties concentrated in their excited products. This experimental fact constitutes the basis of the conception stated by Poolany J. C. in 1961, who offered to use exothermic chemical reactions for population inversion. This conception was implemented by Russian scientists A. N. Oraevsky and V. L. Tal'roze in their works. It was they who formulated the major requirements which chemical reactions must meet for effective lasing.

Overtone supersonic cw HF laser with power density of about 8 kW is developed. Efficiency of the laser relative to emission of the main tone is about 40%. Coefficient of active medium gain measured by the technique of calibrated losses is (5.5 divided by 7.8)(DOT)10^-4 cm^-1. Designed wavelength- discriminating mirrors operated at power density of about 40 kW/cm² (90 kW/cm² in the maximum one-pulse regime). We suggest to use regenerative amplifying principle with application of ring conjugate resonator, having zero effective length, for design of adaptive laser-optical systems based on power lasers with very small gain.

A study was made of a laser based on a chain reaction of fluorine with hydrogen (deuterium) initiated by powerful light sources and operating in the amplifier mode. The conditions for reaching a near 100% energy efficiency of the amplifier at an active mixture length up to approximately 6 meters were determined experimentally. Spectral characteristics of the laser radiation were investigated thoroughly. The tolerable extent of difference between the actuation time of the master generator and amplifier was determined. A possibility was demonstrated to attain a low radiation divergence.

A 400-keV electron beam has been used to initiate HF chemical laser pumped by the nonchain reaction. Quantitative chemical analysis of the F production has been performed by HF aqueous titration for different pressures of SF₆.

Initiation mechanisms of self-sustained volume discharge (SSVD) are analyzed in mixtures of SF₆ with hydro-carbons (deuterocarbons). The possibility is shown to obtain SSVD in a large volume of SF₆ and hydrocarbon (deuterocarbon) mixtures without preionization in the discharge gaps possessing high edge nonuniformity of electric field. The scaling characteristics of nonchain HF (DF) laser are investigated. The highest generation energy has been achieved, namely, 397 J for HF laser and 312 J for DF laser at the electric efficiency 3.8% and 3%, respectively.

Laser action in the optically pumped HF chemical laser using NF₃ molecule as an F atom donor, as well as a bleaching wave regime of pumping HF chemical laser have been observed for the first time. The formation of a bleaching wave running away from the surface discharge, used as a pumping source, at the velocity of approximately 8 km/sec results in very fast (with supersonic velocity) replacement of an active medium in the zone of laser action and provides, thereby, as high as unity quantum efficiency of the laser action. Output energy of 0.4 J in a 3.2 microsecond pulse and specific energy of 3.5 J/l were observed. Also presented are the preliminary results of the first observation of the laser action in HF upon optical pumping of ClF₅/H₂ mixture by radiation from a surface discharge.

The principle of operation of explosively pumped lasers and variants of its construction are described, values of parameters achieved in practice are presented.

The results of research on decrease in angular divergence of radiation of explosively pumped photodissociation lasers (EPPL) with the use of the method of phase conjugation for compensation of active medium optical nonuniformities and distortions of laser beam during its propagation through the atmosphere to an object of influence are presented.

There is a high worldwide interest in middle mass isotopes, particularly in carbon and oxygen isotopes. Over the few last years some industrial installations have been built for producing highly concentrated ¹³C isotope using the method of the low-temperature rectification of CO. However the cost of isotope manufacturing by this method is rather high. One of the ways to increase the output of middle-mass isotopes and to cut its costs is using laser technologies. This report is devoted to the development of the novel laser based technology for ¹³C isotope production.

Pulsed laser ablation has attracted great attention over the past few years as promising technique for depositing thin films. A large variety of successful experimental results were obtained in this field, including the growth of high- temperature superconducting films, ferroelectric films, oxides, semiconductors, diamonds, etc. One of the main advantages of this technology is the simplicity of the experimental set-up. In a common configuration, the laser- generated flux of particles is collected on a planar substrate positioned parallel to the irradiated surface. Several modifications, like simultaneous generation of two plumes from different targets (double ablation), were proposed. Different lasers (e.g. KrF with (lambda) equals 248 nm, Nd-YAG with (lambda) equals 532 nm, etc.) with energy density 2 - 10 J/cm² were used in the ablation experiments both in vacuum and into diluted ambient gas (pressure up to 750 mTorr). Monte Carlo simulation was found to be a successful technique for theoretical investigations of the laser ablation processes. This method has allowed us to investigate the influence of elastic collisions and chemical reactions in the laser ablated plume on the angular characteristics of the flow. The results of the simulation show that elastic collisions give rise to focusing of particles towards the surface normal and to the redirection of the velocities of the more energetic particles in the direction close to the surface normal. The chemical reactions are found to influence the angular distributions in the way opposite to the one of elastic collisions. The reaction heat contributes to the energy of particles and the velocity distributions are affected by reactions. As result of these processes, the angular distributions are broadened from the surface normal. Additional collisions with the particles of the ambient gas were shown to influence the composition and uniformity of thin films. The study of these processes is of a particular interest for the developing of pulsed laser deposition (PLD) technique.

Space debris at low Earth orbits (LEO) in the size range of 1 to 10 cm in diameter poses a severe threat on the International Space Station and other valuable space assets. High-power laser radiation may be the most feasible means to mitigate this problem. Under the irradiation of a high-power laser beam part of the debris material is ablated and provides an impuls to the debris fragment. Proper direction of the impulse vector allows either to deflect the object trajectory to miss the station (defense option) or to reduce the orbital energy of the debris and force it on a trajectory through the upper atmosphere. There the debris burns up instantaneously or after a few revolutions (cleaning option for LEO). A space based deployment of the laser is favored for several reasons: The lack of laser transmission through the atmosphere reduces the total system substantially, laser range and detection requirements are inferior and the laser can be used against an immediate collision threat. Peculiarities of the geometrical situation in the orbital plane are described briefly. Based on a pulsed laser of 100 kW average power, aluminum and carbon as typical materials, and some other assumptions, the capability and limitations with respect to the debris velocity and mass are calculated for both options of the laser utilization.

The operation of laser system based on explosively pumped photodissociation lasers and designed to control the distribution of space debris not observed nowadays is described and the possibility of its breaking using laser radiation effect and its subsequent evaporation in the Earth's atmosphere is discussed.

The problem questions connected with projecting and development of reactor-lasers are considered. Reactor-laser parameters with laser output power from about 100 kW to 1 MW which may be used for applications in the various field of human interest are examined. Some problems which demand auxiliary investigations are considered.

A comprehensive investigation of pulsed CO₂ laser interaction with BK7 disks was carried out. The samples were irradiated with 10 microsecond CO₂ laser pulses to measure laser-induced damage thresholds. Transmission characteristics were observed over a certain time interval. Damage morphology was monitored with scanning force microscopy. Thermal simulations allowed for the interpretation of the laser- induced damage process.

The stratified gradient thermal barrier coating (TBC) on superalloy substrate was obtained by laser cladding. It was no crack and pore, and had good adhesive strength with the substrate. The microstructure of the coating and the interface were analyzed. The effect of microstructure on property and the formation mechanism of the stratified gradient TBC were studied.

This work describes a conceptual design of an industrial chemical oxygen-iodine laser and its applications to dismantlement of nuclear reactors and to aluminum cutting and welding. Choices of specific technologies and system components are made with the aid of a system cost model.

A 1.5 kW high peak power and 140 ns short pulse krypton excimer lamp in VUV spectral region has been developed using a pulsed silent-discharge. In such a high peak power operation, penning ionization was a dominant destructive process as in the same case of a rare gas excimer laser operation.

In the article the results of experimental research of application of lasers for acceleration of material bodies in the air and in vacuum are given. The experimental data about specific pulses of jet feedback, speed and acceleration of flying devices are submitted depending on behaviors conditions of laser influence.

Temperature velocity dependence of the wave of reflection and conduction (WRC) excited by pulse of CO₂ laser in semiconductors ZnS, ZnSe, Ge, was studied by optical methods. Such data are needed for the adequate WRC mechanism development.

Experiments on visible reflection change of High Temperature Superconductors (HTSC) ceramic oxides YBaCuO and NdCeCuO as a result of irradiation by ArF(193 nm) and XeCl(308 nm) excimer lasers were fulfilled for conditions typically below strong ablation threshold. The work was started on the base of a suggestion about inter-molecular structure modification of HT SC materials by means of laser irradiation with the frequency close to or in resonance with vibration or electronic bonds of lattice. Another goal was to find the conditions of the wave of reflection and conduction (WRC) excitation in YBaCuO and NdCeCuO by one of two mentioned excimer lasers. It was detected typically unreversible increase of visible linear- polarized light reflection from ceramics YBaCuO and NdCeCuO in super conducting and semi-conducing phases as a result of irradiation by pulse of ArF- and XeCl excimer lasers. It means that conditions of WRC excitation were not found probably because of ablation influence. It was observed also a cumulative effect of successive laser shots on the relative increase of reflection below threshold for ablation. X-ray micro-analysis showed the appearance of Ce -- or Ba -- reached clusters on the surface of irradiated samples. It gives evidence that reflection increasing could be caused by appearance of mental particles on the surface. The threshold of ablation was evaluated as 0.1 - 0.4 J/cm² for 4 combinations of experimental conditions.

RF excited plasma in a molecular slab laser modifies an impedance of the laser head. We present a simple and practical procedure to correct a laser head impedance changed due to a sheaths capacity. Experimental results for a CO₂ laser are given.

Different aspects of pulse operation of RF excited CO₂ waveguide lasers are presented. The shapes of the output pulses were monitored for the different operation conditions. Peak power, average power and delay time of pulses were measured.

Availability of gasdynamical discontinuity waves (shock and entropic waves) and isentopic waves (depression-type waves or compressive shock waves) is the characteristic singularity of supersonic flows. An interaction of these waves leads to formation of the composite shock-wave configurations. Computation of these shock-wave configurations is reduced to multiple solution of two subproblems -- an interaction of discontinuity waves between themselves and an of discontinuity waves with isentropic waves. Unlike subproblems of first type the suproblems which related to interaction of discontinuities waves with isentropic waves is not enough researched. The reason of this situation is that an interaction between discontinuity waves and is occurred at the some finite field. Thereby approximation calculus for computation of these subproblems is used. In presented investigation analytical solution of these subproblems are offered.

Structure of phase aberration of high-power lasers active media such as gasdynamic, cw chemical, fastflowing electrodischarge lasers as well large-scale pulse and pulse- periodic solid state lasers is connected with repeated design elements. During research is shown, if root mean square of phase distortion (Delta) (psi) _rms more than 0.7 rad, value of frequency of spatial phase distortion will be influenced on divergence of laser radiation.

Classical problem of control flow is a problem of its braking up to subsonic speeds with minimum losses of full pressure. This problem was decided in Russia and in Germany by G. I. Petrov and by K. Oswatich accordingly. In presented investigation it was extended to a case of arbitrary gasdynamical variable f. Solution of problem is based on idea to use in a flow of a system S_n containing n sequentially located shock waves of one direction for achievement of extreme values of variable f behind S_n.

The main regularities of formation of gas flows in laser mixtures of high pressure based on CO₂:N₂:He ((lambda) equals 9,3-10,7 micrometer), N₂:He ((lambda) equals 337 nm) and Xe:He ((lambda) equals 1 - 5 micrometer) with the help of the 'electrical wind' are informed about. Maximum pumping rates of laser mixtures in discharge gaps up to 4 m*s^-1 are obtained. In small-sized sealed-off TEA-CO₂ lasers the pulse repetition rate is increased up to 50 - 70 Hz; in TEA-N₂ and TEA-Xe lasers -- up to 120 - 140 Hz.

The review of the modern state of development of high power CO lasers and the last results of fulfillment of the national programs of creating CO lasers are given. The various methods of discharge excitation and gas flow organization are discussed. The possible industrial applications of CO lasers are considered.

A new simulation code of CO laser has been developed for the recent distributed environment. The partial simulation code is transferred from the server and processed by the clients. The Java language which is independent on computer variation is introduced into the system description.

The numerical investigation of the energy and spectral radiation characteristics of the supersonic e-beam sustained CO laser, operating in the repetitive Q-switched mode, is carried out. All calculations are executed for values of parameters of the e-beam sustained discharge, gas mixture, supersonic channel and optical resonator close to the corresponding values for the experimental CW mock-up of this type laser with output power of 200 kW. In the mode of the resonator quality modulation, the parameters of output radiation depend on frequency of the pulse repetition. For frequency range of 0.7 - 50 kHz the average specific energy per unit of the gas mass is 28% - 96% of the specific energy in CW mode, the peak power exceeds 6400 - 170 times the CW power, the laser pulse length at the half-height is 35 - 60 nanoseconds. The radiation spectrum has some tens lines in the wavelength range of (lambda) equals 4.9 - 9.0 micrometer.

This work describes a new version of a jet singlet oxygen generator using filaments to guide basic hydrogen peroxide jets. The resulting jets are highly stable and resistant to aerodynamic forces.

This paper is a contribution to the current discussion on radiative lifetime, or the Einstein coefficient for spontaneous emission of singlet delta oxygen [O₂(¹(Delta) _g)]. A verification of widely-used the A-coefficient by Badger et al. (2.58 X 10^-4 s^-1) in emission spectroscopy for determination of O₂(¹(Delta) _g) concentration in Chemical Oxygen-Iodine Laser (COIL) was examined. Two independent comparative techniques, the EPR and emission spectroscopy, completed by a proposed mathematical model for calculation of O₂(¹(Delta) _g) concentration from emission measurements, were employed. Singlet oxygen was generated chemically by a conventional way used in COIL. Within the accuracy of the both experimental techniques, the value of the Einstein A-coefficient estimated by this investigation is equal to (2.31 plus or minus 0.51) X 10^-4 s^-1, that is slightly less than the Badger et al. value.

There are two kinds of diagnostics for chemical oxygen-iodine laser (COIL) system, laser device diagnostics and laser beam diagnostics. In this paper, we only discussed systematically the former. We divide them into several diagnostic subsystems such a flow diagnostic, oxygen-iodine flow mixing diagnostic, gain medium diagnostic and resonator diagnostic. In flow diagnostic, we selected some independent and easy-measured physical variables such as temperatures, pressures, flow rates and concentration of compositions to control and measure. From these diagnostics, we can obtain most of knowledge about performance evaluation parameters of COIL device system and subsystems. In oxygen-iodine flow mixing diagnostic, we indicated the mixing status by laser induced fluorescence. In gain medium diagnostic, we showed the spatial distribution of medium's small signal gain by a special device and measured the index of refraction gradients through the flow fields of chemical laser by an interferometer. And in resonator diagnostic, we are concerned about the nonuniformity of medium and the mirror deformation in resonator. During the experiment, the performance of COIL and all these diagnostics should be controlled by a computer, so we can get an immediate and comprehensive information about COIL. From these information, we can understand and then optimize the performance of the laser device.

The experimental results on unstable ring resonator with 90 degree beam rotation for kilowatts class Chemical Oxygen Iodine Lasers (COIL) are reported. The distribution of near field phase and far field intensity were measured. The beam quality of 1.6 plus or minus 0.2 were achieved while COIL average output power was about 5 kw, and most of these results were compared with that using a conventional unstable resonator.

The mechanism of Cl₂ absorption and O₂(¹(Delta) ) generation in JSOG were considered. The concentration of oxygen dissolved in BHP can in 10³ times more than equilibrium oxygen concentration. But it is not enough for spontaneous generation of oxygen bubbles. The 'burying' of oxygen into bulk of BHP occurs during macroscopic renewal of BHP surface. It was found that this effect doesn't result in essential O₂(¹(Delta) ) yield decreasing. Three dimensionless criteria have been derived from one-dimensional model for dynamic scaling of JSOG. The approximate values of these criteria were calculated to achieve 90% Cl₂ utilization and 60% O₂(¹(Delta) ) yield. The measurements of Cl₂ utilization and O₂(¹(Delta) ) yield from JSOG allowed to make more precisely these three criteria. It was found that the rate of chlorine absorption in JSOG is higher than it follows from one-dimension model. It was explained by hydrodynamic renewal of surface of BHP jets. The O₂(¹(Delta) ) yield from JSOG is less than calculated according to one-dimension model. It was explained by additional unknown reactions in reaction zone of JSOG. The dimensionless criteria can be used for the first step of scaling of JSOG. The droplet content at the exit of JSOG with vertical gas outlet is expected to be less than in JSOG with side gas outlet. The Verty-JSOG with initial Cl₂ flux 8 mmole/s/cm² is projected.

The physical properties of basic hydrogen peroxide solutions (BHP) such as viscosity, density, and freezing temperature as well as their variation during laser operation have been experimentally investigated. In these experiments (30 - 50%) commercial hydrogen peroxides have been used, containing stabilizers and an alkali of the following composition: 81.5% KOH and 5.5% K₂CO₃. The use of these substances for generation of singlet oxygen in the COIL has shown their good ability to operate. Consideration has been given to the possibilities of the basic hydrogen peroxide solutions recovery during the industrial COIL operation.

The adoption of ramp nozzle array to a supersonic mixing chemical oxygen-iodine lasers is examined by simulating the mixing and reacting flow fields numerically. Then, the efficiency of the ramps to improve the resulting gain region is studied. The compressible Navier-Stokes equations with a detailed chemical kinetic model are solved by using a full- implicit finite volume method. The numerical results show that streamwise vortices, which are not anticipated in the previous papers, are induced downstream of the base relief region of the ramp nozzle array and accelerate the mixing and reaction significantly. The contact surface between the reactant streams is stretched very rapidly due to the vortices resulting in much higher laser performance.

Conditions allowing a controlled phototriggered operating mode of a 6 cm gap HF/DF laser have been studied. A detailed investigation of the discharge quality and laser performance have been performed through the extensive use of intensified gated CCD camera recordings correlated to the measurements of current and voltage waveforms, and output laser energy.

The HF/DF pulsed chemical lasers, operating on the unchain mixtures SF₆ + H₂ (D₂), have rather low efficiency and relatively small number of lines in a radiation spectrum. The application fluorine-hydrogen (deuterium) mixtures allows to raise many times the specific energy characteristics of the laser and number of lines in a radiation spectrum, that potentially makes such a laser as a universal source of radiation in systems of an ecological and technological monitoring. For the specified applications the generation spectrum on molecules HF-DF covers a wavelength range of 2.6 - 5 micrometer of an absorption spectrum of many atmospheric pollution and technological products. However, for creation the HF/DF repetitively pulsed chemical laser (RPCL) it is necessary to solve a number of scientific and technical problems, therefore till now the mentions of an effective RPCL realization are absent. Highly effective HF/DF-RPCL with active volume 50 cm³ was developed and created. It is initiated by the barrier discharge and operates with the pulse repetition rate up to 50 Hz. In a mode of generation on a molecule HF its characteristics are investigated in detail: a technical efficiency -- up to 10% average power of radiation - - up to 6.5 W, number of the spectrum lines of 23.

Influence of CO₂ impurity within the laser medium on energy and spectral characteristics of the pulsed chemical chain DF-laser has been investigated experimentally. It is shown, that the mechanism of CO₂ influence on the output laser characteristics and their sensitivity to CO₂ concentration depends in a strong degree on lasing conditions. The influence of the CO₂ molecule is determined only by relaxation processes and the sensitivity is minimal when the transition only between the low vibrational levels radiate in wavelength range of 3.6 - 4.2 micrometer due to low resonator quality. With low CO₂ concentration and use of the high quality resonator the DF-laser generates on up to ten vibrational transitions in the wavelength range of 3.6 - 5.0 micrometer, thus the high efficiency of transformation of the reserved chemical energy in lasing is provided. In this case the CO₂ influence on the DF-laser characteristics is defined both the relaxation processes and to greater degree the CO₂ absorption in the range of 4.2 - 4.4 micrometer, and the sensitivity grows almost by the order of magnitude. On the basis of the investigations carried out the requirements to a degree of clearing of a laser medium from technological CO₂ impurity for achievement of high specific energies of HF- and DF-lasers are determined [(CO2) less than 0.4 and 0.005%, correspondingly].

An experimental investigation was made of a self-contained supersonic cw chemical HF laser with a 40 cm X 11 cm three- jet nozzle array and the nozzle-nozzle-nozzle configuration. Such a nozzle array made it possible to form an active medium approximately 12 cm long and of high optical quality. The use of a wide-aperture stable optical cavity resulted in generation of a laser beam of square (11 cm X 11 cm) cross section. A specific output energy of approximately 80 Jg^-1 was reached.

The hydrogen fluoride overtone chemical laser typically operates on approximately 10 to approximately 20 vibrational- rotational lines with wavelengths varying from 1.29 to 1.40 micrometers. Using the combination of the changing mirror reflectivities and the chemical material relaxation, efficient laser on 20P(4)((lambda) equals 1.32 micrometers ) has been demonstrated experimental on HF overtone chemical laser, which both enhance atmospheric transmission and ensure high power extraction efficiency.

A numerical code has been developed to simulate the characteristics of HF chemical laser based on non-chain reaction pumped by a planar sliding discharge radiation. The model considers transport of VUV pump radiation through the nonlinear absorptive active medium containing NF₃/H₂/N₂/Ar gas mixture coupled with chemical and lasing kinetics describing the temporal and spatial evolution of particle species concentration and intracavity lasing photons density. The relative importance of various kinetic processes is evaluated and a 3.2 J/l laser output specific energy is calculated along the laser axis.

An investigation of the optical output for all possible combinations between the capacitances C₁,C₂ in a 'doubling circuit' and in a C-to-C circuit N₂ laser is presented. The results show that, for the doubling circuit, a maximum optical output appears when C₁ equals C₂ for a constant total capacitance. This maximum value increases when the total capacitance increases. This behavior of the optical output is due to the coupling of the two loops which become the best when C₁ equals C₂. For the C-to-C circuit a maximum optical output appears when peaking capacitor obtains a critical value. For low values of the peaking capacitor the optical output follows the rise of the electric pumping pulse. On the other hand, for high values of the peaking capacitor than the critical one, a part of the electric energy arrives at the laser channel after the laser output, while the exploitable electric energy decreases causing reduction of the optical output.

A convection heat removing from the discharge gap and deexcitation of metastabvle states of N₂ onto the plates of the heat-exchanger was used. It is stated that the pumping energy density and the pulse repetition rate area terminated by the local discharges initiated by macroscopic inhomogeneities of the current density of the volume discharge and a repeated breakdown of the gap under the influence of mismatching voltages. Average powers of the laser radiation in molecular nitrogen up to 20 W were obtained.

This paper describes the design of a repetitively pulsed laser with an average output power of up to 50 kW in CO₂-, 15 kW in CO-, and 2 kW in Ar/Xe gas mixtures. Recent experimental results of a laser with 121 discharge volume are reported and extrapolated to a concept which enables the power values mentioned above.

A new excitation system is developed for UV N₂-laser with longitudinal discharge providing laser efficiency of 0.1% and average power of approximately 1 W at 1 kHz prr. High efficiency of unstable resonator using is confirmed for a small aperture laser with high amplification, power density of 10¹² W/sterad is achieved. A multichannel laser system is proposed for output power further improvement.

The influences of gas density depletion on the highly- repetitive, high-pressure, pulsed glow discharge for excitation of excimer laser have been investigated eliminating the other instabilities, such as shock waves, residual ions, discharge products and electrode heating. The gas density depletion is simulated by utilizing a subsonic flow between the curved electrodes. The comparison has been made on the discharge occurred in the presence of the gas density depletion with the second discharge on the double-pulse experiment. We have found that the big gas density non uniformity, (Delta) (rho) /(rho) ₀ approximately 3.6% corresponding to a pulse repetition rate (PRR) of approximately 20 Hz, tends to cause the arc discharge without the shocks, ions, discharge products and electrode heating. On the other hand, the second discharge on the double-pulse experiment becomes arc discharge in much smaller non uniformity ((Delta) (rho) /(rho) ₀ approximately 1.2% corresponding to PRR approximately 3 Hz). The arc discharge in the double-pulse experiment might be driven by the residual ions and/or discharge products other than gas density depletion except for PRR greater than 20 Hz.

An analysis is made of the influence of changes in the density and polarizability of molecules on changes in the refractive index and tendencies of propagating of pulse laser radiation when the molecules in gas absorb or amplify resonant radiation. It has been shown that under absorbing or amplifying radiation in vibrational rotational transitions in the beam channel there may be formed a nonstationary focusing lens.

The dependence of optical quality of active medium of neodymium glass laser on main operation-design parameters is presented. The possibility of increase of laser efficiency by passive correction is shown. The results of optimization of solid-state amplifier for pulse and pulse-periodic operational mode are presented.

In this article are presented new capabilities increase quality for solid state laser beam and new methods compensation thermal distortions and induced thermal birefringence in cylindrical glass and crystal laser rods. Is shown ways of practical implementation these methods for differential conditions of laser operation. Beside that, is shown the advanced feature this group of methods by comparison with classic methods compensation induced birefringence.

Results of theoretical simulation and field tests of a shock wave pumped solid state laser are presented. The laser has demonstrated real capabilities to initiate explosives. Operating without external sources of electrical power, the laser is pumped with the radiation from converging axially symmetric shock waves in argon.

Free-running and Q-switch performance of a flashlamp-pumped Cr:LiSAF laser system have been investigated for repetition rate of 1 - 25 Hz. Laser average powers of 25 W and output pulse energy more 0.1 mJ with 80 ns pulse duration, total laser and slope efficiencies of 5.1% and 3.5%, respectively, have been achieved.

It is informed about development of high-power yttrium aluminate and ruby lasers with the electro-optical negative feedback and controlled duration of quasi-CW pulses with energies up to 50 J/cm². The software was developed on base of results of the theory, taking account of the photorefractive effect in electro-optical elements and the signal integration in the negative feedback loop. This software allows to automate the process of control by general lasers parameters. These lasers are perspective for the using in medical and processing technologies.

Present report gives the results of experimental and numerical investigations of magnetic fields produced by crossed gradients of electron density and temperature in laser plasma. Plasma was formed in vacuum at radiation of HF-laser. The nature of generation of magnetic fields on the other side of the target and outside of laser plasma flame was considered. The numerical investigations of magnetic fields for different laser waves and for dielectric and conductive target was discussed.

This paper is devoted to electrodynamical aspects of laser conditioning of rough dielectric surface. Points of interest are (1) space distribution of scattered radiation near the surface; (2) space distribution of light pressure; (3) laser- induced evolution of surface roughness under action of light pressure. The problems under consideration are of great importance for investigation of surface modification by femtosecond pulses, in particular, formation of periodic ripples. The problems are studied making use of modified finite-difference time-domain technique.

There is presented new approach to dynamical simulation of linear and nonlinear electrodynamical processes coupled with laser-induced heating through temperature-dependent absorption and refraction. That approach is similar to finite-difference time-domain technique. Mathematical model and idea of developed code for the simulation are presented. Among calculation problems there are discussed boundary conditions for transparent boundaries of calculation grid and influence of space resolution. There are considered several applications of the code, in particular investigation of laser-induced modification of dielectric surface by femtosecond pulses, investigation of laser-induced processes in dielectric films with inhomogeneous microstructure. Perspectives of developing of 3D simulation code as well as including of thermomechanical, chemical and other processes into the developed model and code are discussed.

Physical and chemical transformations induced upon metallic materials such as aluminum alloys and steels under KrF excimer laser radiation have been studied in order to improve their mechanical and physical-chemical properties. The laser treatment leads, after laser surface remelting (LSR) process, to important changes in the topography, structure, phases and elements composition resulting in different hardness, wear properties and corrosion resistance. Up to now, the use of excimer lasers for industrial applications remains marginal in spite of the interest related to the short wavelength (better energetic coupling) and the reduced thermal effects in the bulk material. This paper concerns mainly the corrosion resistance improvement of metallic alloys irradiated at 248 nm. Electrochemical tests have revealed a significant change in the corrosion properties mainly due to chemical composition and structural modifications.

The results of the interferometric research of the high power photodissociation iodine laser (HPPIL) are reported. It is shown that there are unstable fluctuations of the HPFIL active mixture density. The influence of the laser active mixture structure on sizes and shapes of the interferometric bands has been investigated.

In this article the results of experimental researches and theoretical evaluations for material treatment by packs of nanosecond laser pulses are described. Are received criterion of choice of optimum modes for different kinds of treatment and requirements to a process equipment are formulated.

On the basis of quantum electrodynamics approach to collision absorption the effective photon-electron absorption cross section is obtained. That allow us to estimate absorption factor and mathematical expectation of absorbed photons number in one act of collision in case of a powerful ultra short pulses.

Gasdynamics of thin films deposition by laser ablation technology has been investigated by the direct simulation Monte Carlo (DSMC) method. Whole spectrum of criterions that determine flow parameters was posed. Basic criterions influence on flow picture and behavior of flux parameters was investigated. High-performance parallel algorithm of DSMC of non-stationary flows has been elaborated for multiprocessors systems. Thin films, laser ablation, gasdynamic processes, direct simulation.

The possibilities of powerful laser application for the body resistance and thermal loading control at supersonic flights are discussed. Different schemes of laser action on the free- stream flow are considered. The effectiveness of the schemes are studied.

Short review of 3-D Laser Synthesis (3D LS) or Rapid Prototyping (RP) is given, including three mali directions such as stereolithography (STL), laminated object manufacturing (LOM) and selective laser sintering (SLS). Comparative advantages and disadvantages of every one of them are discussed. The new direction of 3-D LS is suggested, combining advantages of STL and SLS. This direction based on the creation of 3D models from the resin's powder. The physical processes of the new technique similar with STL- process. In spite of the phase state of the initial material (powder) the mechanism of solidification has many skills of STL with viscous digomer. There are many new possibilities in the process with powder polymerization. One can use not mechanical devices (which are very complex) for powder deposition but electrostatic and so on. Some physical phenomena of powder solidification under the CO₂-laser action are studied, as speed of the process, which is much higher than under the conventional heating and so on. The experimental results of the process investigation are discussed. In particular the chemical analysis of the solidificated model is made which confirm that initial powder under laser treatment gave perfect resin. Main advantages of the new methods are the cheapness of the initial material and good mechanical quality of models, which expands the field of application of models made with described powder.

Provision of safety and drop of ecological risk at salvaging of nuclear submarines (NSM) of Russia Navy Forces represents one of the most actual problems of nowadays. It is necessary to remove from services of Russian Navy Forces 170 - 180 nuclear submarines by 2000. At salvaging of Russian Navy Forces NSM it should be necessary to cut out reactor compartments with more than 150 thousand tons of gross weight and to fragment terminal carcasses of submarines with gross weight of 2 million tons. Taking into account overall dimensions of salvaging objects and Euro-standard requirement on the sizes of carcass fragments, for salvaging of one NSM it is necessary to execute more than 10 km of cuts. Using of conventional methods of gas and plasma cutting of ship constructions and equipment polluted with radioactive oxides and bedding of insulation and paint and varnish materials causes contamination of working zones and environment by a mix of radioactive substances and highly toxic combustion products, nomenclature of which includes up to 50 names. Calculations carried out in the Institute of industrial and Marine Medicine have shown that salvage of just one NSM with using of gas and plasma cutting are accompanied by discharge into an environment of up to 11.5 kg of chromium oxides, up to 22.5 kg of manganese oxides, up to 97 kg of carbon oxides and up to 650 kg of nitrogen oxides. Fragmentation of such equipment by a method of directional explosion or hydraulic jet is problematic because of complexity of treated constructions and necessity to create special protective facilities, which will accumulate a bulk of radioactive and toxic discharges, as a consequence of the explosion and spreaded by shock waves and water deluges. In a number of new technological processes the cutting with using of high-power industrial lasers radiation stands out. As compared with other technological processes, laser cutting has many advantages determined by such unique properties of laser radiation as large power, capability to concentrate power on the small area (up to 10⁸ W/cm²), good spatial and temporal controllability. The laser cutting advantages are the following: (1) high efficiency; (2) capability to cut various materials (metals, alloys, plastics, rubber, ceramics) and their compositions (fiber glass plastics, rubber-plastics, cermets) by one installation; (3) minimum pollution in gas and condensed phases; (4) high degree of technological process automation; (5) remote character of cutting and personnel absence in a processing zone.

A theory for the beam pointing variation of the optical beam from a pulsed XeCl* excimer laser equipped with a positive branch unstable resonator is introduced. The measurements are in good agreement with the calculations.

On the basis of Markov processes theory the equations for variation of universal population number and variation of atoms number of radiating coherency due to external laser radiation are deduced. Derived analytical expressions allow us to estimate relative error of output laser intensity in dependence on input laser intensity.

The dynamics of the lasing of the fast crossflow gas laser with the inhomogeneous steady state pumping in the unstable resonator by means of numerical modeling is investigated. Depending on the system parameters the various dynamical regimes of operation are observed. The detailed investigations of the chaotic lasing features as well as the chaos onset are performed. The possibilities of the control of the laser output characteristics are discussed.

A new integro-differential equation with the only first order derivative describing diffraction of arbitrary transversely nonuniform light beam in the homogeneous transparent medium is obtained. At first, it is introduced for the case of linear media. The ones approximation of the forward propagation is used (so the case of backward propagation is excluded). It is shown that derived equation in the case of light beams with the great diameter transforms to the well-known parabolic equation. The new approach is generalized also for the case of nonlinear media. Thus, the new truncated wave equation describing the diffraction of nonparaxial light beams in the nonlinear media is obtained.

One of the basic problems of the self-sustained high pressure volume discharge gas laser systems, arising at creation, is the energy deposition to the active volume problem. Obviously, that the solution of its is possible by two paths. To energy deposition increase it is possible by the increase of a capacity of high voltage circuit (HVC), or at the expense of rising charging voltage. It is necessary to execute a condition of the reconciliation of HVC and discharge: 2(E/p)_str equals (E/p)_s where (E/p)_str is the effective electric field strength of the discharge gap, (E/p)_s -- is the effective electric field strength of the electric source. Thus, the value of (E/p)_s is established. Also it is necessary to observe a condition of the reconciliation of the HVC and discharge for the internal resistance HVC: (root)L/C equals Z_d where Z_d is impedance of discharge, L -- inductance of HVC, C -- capacity of source impact. The increase of capacity HVC in impact results to increase of energy deposition the expense of increase of current pulse duration, and rising of cathode channels and the contraction of discharge happens. The increase of active mixture pressure results to the increase of ionization process velocity and loss of plasma electrons process velocity. This leads to the reduce of discharge current duration. At the some moment, duration of the discharge becomes comparable to the discharge current time. This processes lead to the afterglow breakdown of the discharge gap and confine energy loading to the discharge. Thus, it is necessary to account to this processes at the building of gas lasers.

The optimum excitation conditions for pulsed CO₂ laser oscillation excited by microwaves are investigated to achieve oscillation with a short pulse width at a high repetition rate. The excitation conditions are optimized as follows; (1) by evaluating the decay time of excited N₂ molecule population density to optimize the gas mixture, and (2) by evaluating the discharge stability and the laser output waveform to optimize the magnetron drive conditions. We have developed a new coaxial fast gas flow pulsed CO₂ laser oscillator excited by microwaves, which produces pulses output with a rise time of less than 5 microsecond(s) ec rise-time and a 1/e- fall time of 30 microsecond(s) ec at a maximum repetition rate of 5 kHz. It is also possible to modulate the output power and the pulse waveform at high speed. The oscillator is currently being tested for application to a laser drilling system for printed wired boards.

The non-stationary structure of the flow in the cathode region are calculation. Its influence on the normal current density, size of the cathode voltage and concentration of N₂ in the N₂:He mixture is investigated. The results of the calculation of the current density in the cathode stain will be satisfactorily coordinated with experimental data.

Studies on some laser interactions to fluid materials are presented. Firstly, pulsed-laser-induced cavitation bubble in liquid nitrogen is investigated by YAG laser irradiation. High speed schlieren photographs by Imacon-790 are taken to observe the laser-induced bubble dynamics. Bubble and solid wall interactions are also investigated. Based on the results obtained, a novel laser surface processing technology using the pulse-laser-induced cavitation bubbles is secondly proposed. Furthermore, discussing by the fundamental results of the experiment of laser-gas molecular absorption, the possibility of decomposition of environmental gases by CW CO₂ laser irradiation is also studied.