The discharge conditions of the multi-atmospheric e-beam sustained Ar-Xe laser are investigated. It is observed that the quasi-stationary period of a laser pulse depends on the e-beam current, the discharge power deposition and the gas density. The laser efficiency can be as high as 8%. The pulse energy with optimum efficiency depends strongly on the gas density. The best results are obtained for 4 bar with an input power of 8 MW/l. The pulse duration with corresponding output energies are 12 microsecond(s) with 10 J/l and 16 microsecond(s) with 16 J/l for e-beam currents of 0.4 and 0.9 A/cm² respectively. An analysis of the quasi-steady state conditions that include the effects of electron collision mixing and atomic quenching is presented. The effects of output power saturation by the fractional ionization and atomic collisions are in agreement with the observations. The analysis clarifies the optimum performance conditions.

The present report describes gas lasers pumped by generators with inductive energy storage and semiconducting opening switch. It is shown that these generators significantly improves output parameters of different gas lasers. Longitudinal small-scale N₂ laser and CO₂ and non- chain HF transverse discharge lasers are developed using this pumping technique. Efficiencies of CO₂ and HF lasers up to 17% and 5,5%, respectively, were demonstrated. Advantages of generators with inductive energy storage are discussed.

Recent progress in high power IR gas laser research at DLR is reviewed. Emphasis is given to repetitively pulsed high average power CO₂ laser, pulsed CO-overtone, pulsed Ar- Xe, and diffusion cooled CO₂ waveguide laser. Performance improvement of a chemical oxygen iodine laser is also reported. Finally, examples of advanced applications including environmental related technologies are discussed.

Frequency selected Q-switched e-beam controlled-discharge CO-laser has been researched and developed for surface heat treatment of polymeric materials (poly(ethyleneterephthalate) and nylon) having strong absorption bands near wavelength of approximately 6 micrometers . The laser generates pulses (including short ones with duration (tau) _0.1 approximately 1 - 10 microsecond(s) ) having different spectral content within 4.9 - 6.5 micrometers spectral range. Different geometry and methods of irradiation were used to process samples with the laser radiation of different temporal, spectral and energy density characteristics. Different types of microstructure were formed on the surfaces of the sample. Experimental conditions corresponding to each type of microstructure were defined. Visual (macro) changes of polymeric material properties (if any) and their correlation with formed microstructures were analyzed.

An average laser output power as high as 5 kW has been produced from a TEA CO₂ laser pumped with a new solid state exciter. The exciter providing a 100 J transfer energy consisted of a high voltage pulse generator and a two stage magnetic pulse compressor. A sophisticated discharge head was equipped with the corona preionization with acoustic dampers. A maximum average laser power of 4.6 kW was attained at a repetition rate of 550 Hz with an overall efficiency as high as 10.5%. A maximum repetition rate achieved was 1.1 kHz, at which the corresponding laser output was 3.4 kW. New TEA CO₂ laser applications to material processing include organic material ablation, semiconductor material ablation, ceramic ablations and aluminum conductor line writing on aluminum nitride ceramic.

The repetitively-pulsed electron beam pumped excimer laser has been demonstrated to be capable of delivering high average power in the ultraviolet region of the spectrum. The results of recent experiments and comprehensive numerical modeling are presented. The experimental data were obtained from an electron beam pumped XeF laser with a decentered unstable resonator and a flowing gain medium. This device produced a pulse energy of 40 to 50 J at a pulse repetition frequency of 100 Hz. The numerical modeling was focused on providing detailed understanding of observed pulse shapes. These simulations involved two separated models: a detailed XeF kinetics code and an optical extraction code which is based on a novel stable resonator formulation. This integrated model was used to analyze and interpret the results of several recent experiments.

The review of the papers devoted the research of excimer lasers with SBS medium is presented. The possibilities of using SBS for phase-conjugation, pulse compression, formation of narrow-band and highly directed radiation are discussed.

High average power phototriggered XeCl lasers have been built. The conditions for high repetition rate operation have been studied. An average power of 1200 W for XeCl and 460 W for DF has been obtained. Intrinsic efficiencies were close or higher than 5%.

The peculiarities of output radiation formation in electroionization CO₂-lasers with smooth tuning of frequency are experimentally investigated. The possibility of the output radiation formation using system master oscillator-amplifier in one excited volume is considered. Operation of tuned CO₂-laser in pulse-repetitive mode is tested.

To improve the beam quality of industrial solid state and excimer lasers, self-pumped phase conjugating mirrors based on stimulated Brillouin scattering (SBS) were applied in different oscillator and master oscillator power amplifier systems. Pulsed Nd-lasers for industrial applications with up to 500 W average output power at 1 micron wavelength and high beam quality were realized. Due to phase conjugation the beam diameter and divergence do not depend on the average output power. In the ultraviolet range, a commercial XeCl laser from Lambda Physik was equipped with an SBS- mirror resulting in a self starting oscillator with phase conjugation at a wavelength of 308 nm. The beam profile could be converted from rectangular to near gaussian and the brightness could be improved. As an alternative to widely used SBS-materials like liquids and gases we developed a new kinds of self-pumped SBS-mirror based on multimode quartz fibers. These exhibit lower SBS thresholds and therefore continuously pumped Q-switched laser systems with SBS-mirror can be realized.

Three-electrode XeCl laser, based on the use of a double discharge and regime of preliminary electron multiplication, was investigated. Utilization of this method of discharge formation allowed significantly to decrease operating voltage at the main storage capacitor, obtain full matching of the pumping source with a load, and increase laser efficiency up to 3.7%.

The results of the experimental investigations of the discharge in Ne/SF₆/CH₄ and Ne/SF₆ mixtures are presented. It has been found, that the discharge has a tendency to expand over the total electrode area. The discharge current shape remains aperiodic at the different initial conditions. The experiments have detected an interesting effect. The discharge current changes the polarity at the remaining positive discharge voltage. The possible explanation of this fact is given. The stages of the development of the inhomogeneities in Ne/SF₆ mixtures are described. The influence of the total pressure of the mixture has been studied.

The pumping discharge of XeCl laser was modeled, taking into account the main kinetic processes. The inhomogeneity was set on the cathode, both as local enhanced density of the initial electrons, and as a metal hemisphere. It is shown, that the plasma channel with high conductivity is formed from the initial inhomogeneity in the discharge.

A spatially 1D model including a parallel resistor description of the discharge plasma is used to study the effect of an inhomogeneous preionization on the characteristics of discharge-pumped XeCl* laser. The special pumping technique of this laser discharge is base don the additional use of a stabilizing low-current preliminary discharge. The model takes into account the time-dependent electron Boltzmann equation including electron-electron interaction for the determination of the electron kinetics, an extensive reaction kinetics involving various heavy particles and photons, and the relevant electrical circuit equations. The study has shown that density perturbations of preionization electrons lead to the inhomogeneity of the discharge plasma and the laser output. Furthermore, the impact of a low-current preliminary discharge for the discharge operation is discussed.

The development of high-efficient and scaleable CO₂- lasers is important both for technology and for large-scale laser systems engineering. Our paper reports about original method of active medium excitation with no limits for its volume. Efficiency of the laser constructed on the basis of this method reached 22% and specific power output -1 W/cm³. Pulse regime is proved to be more efficient for active medium excitation then continuous one. Pulsed radiation is also more suitable for material processing.

A review of the investigations of the main processes determining the attainable pulse repetition rate of elemental metal vapor pulsed gas discharge self-terminating lasers, such as copper vapor laser, gold vapor laser, lead vapor laser, is given. Kinetic processes during an excitation pulse and interpulse period are considered as well as experiments with lasers operating at high repetition rate.

The paper reports up to day progress in investigations and developments of ion metal vapor lasers, excited by three of the most effective processes in gas discharge plasma, namely, by collisions of metal atoms with electrons, by the collisional-radiative recombination of doubly-charged metal ions and by heavy-body collisions of the metal atoms with buffer gas ions or metastables. The main attention given to the latter type of excitation in the plasma of pulsed hollow cathode discharge and the output characteristics are presented and discussed. The output characteristics of the hollow cathode discharge ion laser with combine active media (He-Kr-Hg mixture) emitted on (lambda) 469,4 nm Kr+ and (lambda) 615 nm Hg+ lines are presented.

Results obtained from comparative analysis of the pulse repetition rate performance of Cu- and CuBr-vapor lasers operated at high pump pulse repetitions (approximately 100 kHz) are reported. For a CuBr laser with a 8 mm diameter discharge tube the laser pulse repetition rate as high as 270 kHz was realized.

For the first time, the cataphoretic input of metal vapor into active media of the pulsed He-Cd⁺ and He- Sr⁺ lasers is proposed and experimentally realized. For small-size cataphoretic recombination He-Sr⁺ laser with discharge channel of 3 mm i.d. and active length of 26 cm, rather high values of the average output power (510 mW) and record values of specific average output power (277 mW/cm³) as well as gain coefficient (0.15 cm^-1) were achieved.

As has been found gas-phase chemical reactions with participation of excited atoms of Ca and Sr maintain metastable states relaxation velocities of this atoms sufficient to obtain continuous generation mode on transitions ¹P₁ - ¹D₂.

Using the isoelectron superposition method we showed that the density of autoionizing states of elements with d- and f-equivalent electrons may be from 1 to 10 states per 1 cm^-1 of energy. For such elements a conception of an `autoionization continuum' may be introduced. The characteristic times of the resonant capture of electrons are comparable, in this case, with the radiation times ((tau) approximately 10^-8 s), therefore, the autoionization processes and the capture of the resonant electrons result in inversion in the ions spectra, as well as, in spectra of Beitler's states. The experimental results on selective autoionization and selective interaction between the ions excited states and the autoionization continuum are presented.

The paper presents the results of the investigation of space-power structure of laser radiation characterized by high amplification factors of active medium and short pulse duration. The experimental-theoretical method are proposed, which indicate that the copper vapor laser radiation is the superposition of several components, and enable one to determine the number of these components as well as the divergence and power of each component. The potentialities of the above methods are given when determining the output copper vapor laser radiation characteristics.

Processes of collisional energy transfer as the population inversion creating mechanism in metal vapors under gas discharge condition are considered. Results of experimental investigation of the gas discharge thulium vapor lasers are adduced.

The basic rules of the approach to study of the mechanism of photobreak of chemical bonds in complex molecules of linear and cyclic structure by methods of quantum chemistry are stated. Photolysis of disulfides, chlornaphthalenes, diphenyloxazones, thrinitrotoluene, coumarine is investigated by offered method. Mechanisms of primary photoreactions are revealed. Electronic excited states are established, in which there is the break of chemical bond, and opportunity them occupation.

Lasing properties of two dyes in polymeric matrix radiating in blue-green region of the spectrum pumped by a XeCl laser are studied. The lasing efficiency and photostability of the solid state active media are compared with corresponding characteristics of the same liquid active media.

Fluorescence characteristics of 2-(4-pyridyl)-5phenyloxazole (4PyPO) and trans-stilbene has been studied under high power XeCl laser excitation. Anomal fluorescence phenomenon has been found. Gain and losses were measured in 4PyPO active media in range of excitation rate from 10²³ to 10²⁶ phot/cm²s. Dynamics of losses in laser pulses in coumarine substituted was studied under XeCl laser pumping.

The spectral-energy characteristics and the spatial-angular distribution (SAD) of the radiation from a pulse-periodic flashlamp-pumped dye laser with a polarizing interference filter (PIF) was studied experimentally. The laser radiation SADs were measured for alcohol, aqueous and combined solutions. We showed that aqueous solutions, in particular, that of the coumarin 120 inclusion complex with (beta) - cyclodextrin provide a high directivity, a rather uniform distribution of the radiation across the beam, and a comparatively high laser efficiency for both the nonselective cavity and for those with the PIF. This is why these solutions may be used for the pulse-periodic operating modes. Relatively small radiation divergence is obtained for the small dye concentrations only when an alcohol or combined solutions is used, and the achieved laser efficiency is not high though. A system with the polarizing interference filters had been examined demonstrating a smooth tuning of the laser wavelength over the whole visible range (the laser dye had been changed).

Theoretical and experimental results of studies on the fluorosubstituted derivatives of coumarines are presented. The emission properties have been investigated under XeCl*- laser excitation ((lambda) equals 308 nm). The quantum chemical algorithms and programs are based on the semiempirical method with intermediate neglect of differential overlapping involving particular spectroscopic parametrization. The intermolecular donor-acceptor interactions have been researched using molecular electrostatic potential method. It is shown that the fluorination leads to longer lasting lifetime (E_1/2) both due to high strength of CF-bond and to absence of the absorption of the final photoproducts in the lasing region. The introducing of F atoms at the photochemically active positions to the molecules reduces the rate of formation of the secondary photodecomposition products. The radiative and nonradiative relaxation constants of the excitation energy are calculated.

Amplification of stimulated Raman scattering radiation of ethanol in a polydispersion of microdroplets of ethanol solution of Rhodamine C is obtained experimentally when irradiating the droplets with laser pulses of 0.532 micrometers wavelength.

Wavepackets formed from the ns and (n-2)d states of Rb and K (n equals 8 for K, 11 and 12 for Rb) have been observed by four wave mixing in pump-probe experiments. The temporal behavior of the wavepacket is observed by monitoring the coherent ultraviolet radiation generated near the alkali mp ²P yields ²S_1/2 resonance transitions (7 (3) of the medium, thus rendering the wavepacket detectable.

A new idea of the holography process realization is developed. The method opens a way to the direct recording of information simultaneously on the spatial and temporal (spectral) characteristics of the field of light using the femtosecond pulses. The analysis of 1D- and 2D-cases under the conditions of an infinitely short (delta-shaped) pulse illumination is performed. The process of the hologram recording is similar to that in the conventional holography. The reference delta-wave interferes with the wave scattered by an object. No stationary interference pattern is formed, but the trace of the two-wave crossing point or line is recorded inside the photosensitive medium. The illumination of the hologram formed in such a process by the reference wave reconstructs the object wave, and vice versa. New property of the capability for the precise recording and reconstruction of the scatterer color is predicted. The time-encoding system for the holography is proposed, which facilitates the hologram recording and enables the femtosecond pulse amplification. Some fundamental problems of the ultrashort pulse diffraction are also considered.

The possibilities of use of a photoresonant plasma induced by gas-discharge pulsed lamps or an open discharge, as active medium of lasers, are discussed. The both pumping regimes producing maximum electron density and maximum nonequilibrium distribution on energy levels are considered. Results of experiments are presented. The properties of such laser active medium were studied.

The process of laser isotope separation of Yb have been studied with numerical simulation and experimentally. Installation which is capable to produce highly enriched ¹⁶⁸Yb in industrial scales was created. Contents of ¹⁶⁸Yb in laser produced plasma was reached 80 - 95%, in the deposited on the ion collector material--up to 62%, in washing liquid--up to 32%. The rate of the enriched ytterbium production was 3 - 6 mg/hour.

Optical microlithography is continuing to play a key role in the fabrication of feature sizes in the 0.25 - 0.1 micrometers regime as the semiconductor industry enters manufacturing of the gigabit chip generation. Several important advances in technologies are needed to achieve this goal. These include the use of excimer lasers and optical resolution enhancement schemes, which will be addressed in this work.

Design, development, and application of novel all-solid- state spectroscopic gas sensors is reported. These compact instruments employ mid-infrared difference-frequency generation in a nonlinear optical medium pumped by room- temperature semiconductor lasers, and are capable of real- time selective measurement of trace gases in ambient air with better than 1 ppb precision (part per billion, by mole fraction).

The schemes of use of two various methods in a problem of restoration of altitude structures of concentration of gases from results of satellite sounding of atmosphere are submitted. Computing experiment on both methods on an example ozone is spent. Results having acceptable accuracy are received. Lacks of both methods are specified.

The destruction of alkali-halides crystals (alkali-halides) under action of CW-laser irradiation has thermomechanical character, therefore the mechanical properties of materials define their laser firmness and durability in many respects. It is known, that the crystals strength connected to process of dislocations movement, which delay at the expense of creation of admixture or own defects by alloyage, reception of a firm solution of replacement, or by deformation strengthening of monocrystals is possible.

Provided is the experimental study of the laser melting, treatment and oxidation of metals and alloys (steel, copper, brass, titanium and others) in a real time by the laser brightness amplifier on the basis of a copper laser. The image processing of obtained results has been carried out by computer. Worked out is the technique of measuring of the oxide layer growth by registration of movement of the interference minima (maxima) in reflective ability for radiation of the copper laser reflected from the inhomogeneous distribution of oxide over the cross section of the interaction zone. The results are compared with introduced theoretical models.

Back scattered vibrational Raman lidar equation computer simulation for hydrogen molecules and its heavy isotopes with cuprum vapor and excimer lasers have been made to choose optimal lidar system for studied molecules monitoring in atmosphere. Background stray sunlight power were calculated to determine the minimum molecules concentration at ranging distance up to 6 km.

The absorption of laser radiation along various atmospheric paths have been estimated basing on the data on the spectral composition of HF, DF, and iodine lasers radiation and on the atmospheric molecular absorption coefficient. Applications of these lasers to atmospheric transmission problems require the information on the attenuation characteristics of the atmosphere at each of the lasing frequencies.

Low-energy laser irradiation (LELI) is known to modulate some parameters of immune system and free radical and antioxidant reactions in organism. LELI have been shown to enhance the efficacy of chemo- and radiotherapy in experimental models of tumor growth. The aim of our work was to study the ability of copper steam laser irradiation to modulate the antitumor effect of 5-fluorouracil (5-FU) and antioxidant enzyme activities in blood and tumor tissue of mice with transplanted Lewis lung carcinoma. The data obtained show that the copper steam laser irradiation is able to increase the efficacy of treatment with 5-FU. Laser irradiation increase the SOD activity in plasma and in contrary, decreases it in tumor tissue. Laser irradiation effect on the activity of antioxidant enzymes may be considered as one of the mechanisms mediating its ability to increase the efficacy of cytostatic therapy.

Molecular and aerosol scattering of laser radiation, propagating in the atmosphere, makes it possible to visualize it in space. This phenomenon can be used for navigation in the navy, air force and astronautics. The laser radiation scattering is known to be used in the visual laser beam systems. The scattered laser radiations is small as compared with direct laser radiation and safe for sight. The method being developed uses the scattering effect and enables one to create the instrumental laser beam systems for pilotage alone fairways and approach canals in coastal waters and seaports.

Excimer formation in dense gas targets is studied using a 10 to 20 keV electron beam for the excitation of rare gases. A SiN_x ceramic foil, only 300 nm thick but strong and completely vacuum tight is used as an entrance window. The electrons loose only 4 to 6% of their energy in this foil. The low electron energy allows a table top setup without high voltage or x-ray radiation hazards. First applications of the system for excimer physics research and the development of novel vacuum ultraviolet light sources are described.

Excilamps with different tube geometry pumped by continuous glow and barrier discharges are described. It was shown that the efficiency of barrier discharge excilamps pumped by sinusoidal pulses with duration of several tens microseconds can be sufficiently improved. The range of UV wavelength emitted by glow discharge excilamps was extended. Intense radiation of KrBr*, XeBr*, I₂* and IBr* molecules was obtained in rare gas - CH₃Br (I₂) mixtures pumped by glow discharge KrCl* excilamp ((lambda) approximately 222 nm) with output power up to 200 W was developed. UV power of 500 W from three KrCl* excilamps operating in parallel was demonstrated. Efficiency of exciplex molecule luminescence in the positive column of glow discharge was found to be as high as approximately 30%.

Efficient energy transfer between neon excimer molecules and hydrogen has been found. A small, high gap density light source has been developed, emitting entirely on the hydrogen 2p-1s transition at 121.567 nm (Lyman-(alpha) ). Light output densities of 10 W/cm² are obtained. Electron beam energy conversion efficiencies of approximately equals 10% have been measured.

The result are presented on experimental study of VUV spectra of double and triple mixtures of argon, krypton and xenon in dc and barrier discharges. Region of 120 - 200 nm was studied that corresponds to the transitions between dimer lowest excited states and the weakly bound ground states 1_u, 0⁺_u yields 0⁺_g. The pressure in capillary dc discharge was 100 - 1000 hPa and discharge current was 20 - 50 mA. The experiment with 10, 20 and 40 cm tubes corresponded a gain 0.1 cm^-1 at (lambda) approximately 147 nm.

Single crystals (beta) -BaB₂O₄ (BBO) are new perspective nonlinear-optical material used for development of laser sources tunable in wide spectral range from near IR to UV. It is well known that BBO single crystals cannot be grown from their own melt because of formation of (alpha) - phase of BaB₂O₄ at melting point of 1095 degree(s)C. Therefore the solution-melt (flux) technique is used for growth of low-temperature (beta) -BaB₂O₄ phase (temperature of (alpha) yields (beta) phase transition is 925 degree(s)C). This method is applied still quite seldom because of high labor-consuming. BBO single crystals were grown by top-seeded solution growth technique with high temperature gradient with simultaneous decrease of temperature. The main difficulties of the growth of BBO single crystals are related to high viscosity, tendency to stratifying and vitreous formation, incongruent evaporation of solution-melt, and possibility of simultaneous co- crystallization both (alpha) - and (beta) -phases from the supercooled solution-melt. Any of them result in formation of various growth defects with concentrations depended on peculiarities of technological conditions.

Infrared tunability of parametric superluminescence is studied in ZnGeP₂. Q-switched and actively mode-locked Er³⁺:YSGG laser (2.79 micrometers ) is used to investigate the temperature tunability. Angular tunable wavelength gap near degeneracy in type II phase matching is partially covered by crystal temperature rise thereby eliminating beam walk-off/displacement unavoidable in angular tuning. The result is explained by changes in crystal phonon absorption, birefringence and refractive indices with rise in temperature.

This paper describes detailed analysis of optical and dielectric properties of ZnGeP₂ crystals in middle IR and FIR spectral ranges, and also first experimental results on 1 W level 102 - 110 micrometers emission generation by means of difference frequency generation of CO₂ laser line pairs. It is shown that MW level is achievable now, and AgIn_0.35Ga_0.65Se₂ crystal can be used for efficient generation of FIR emission.