Low energy electron beams with particle energies of typically 10 to 20 keV are used for pumping gas lasers. Extremely thin (300 nm) ceramic (SiN_x) membranes are used as entrance foils for the electron beam. Laser gas pressure up to several atmospheres is possible using this technique if the dimension of one side of the foil is restricted to about 1 mm. Energy loss of the electrons in the foil is less than 10%. The short range of the low energy electrons in the laser medium leads to a high specific power deposition. In transverse geometry the beam pumped volume is cylindrical with typically 1 to 3 mm diameter. This is well matched with the diameter of optical modes in stable optical cavities. The new pumping method is demonstrated using the 1.73 micrometers 5d[3/2]₁-6p[5/2]₂ XeI laser line in Ar-Xe laser gas mixtures at pressures between 130 and 650 mbar. Laser effect was observed for Xe concentrations between 0.1 and 1%. A low threshold pumping power of 5.5 W and a maximum output power of 6 mW at 13 W pumping power were measured. Scaling to higher power and shorter wavelength laser systems is discussed.

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 in accordance with numerical model.

Output characteristics of a pulsed e-beam controlled discharge laser operating at the first-overtone (FO) transitions ((Delta) V equals 2) of CO molecule have been studied both experimentally and theoretically. Various sets of dielectric mirrors with high reflectivity in the range of the overtone spectrum have been used for the laser resonator. Multiwavelength lasing has been obtained in the wide spectral range of 2.5 - 4.1 micrometers on vibrational transitions from 6 yields 4 up to 37 yields 35. Maximum output efficiency 11%, the highest of eve laser, has been experimentally obtained for the broad band multiline FO CO laser. Maximum specific output energy (SOE) is 50 J/I Amagat. FO CO lasing was observed within an initial gas temperature interval of 100 - 220 K. Spectral characteristics of the overtone laser operating on a selected set of vibrational bands have been analyzed theoretically. Theoretical calculations based on the experimental data predict that multiline FO CO laser efficiency can be increased up to 20%. The experiments with pulsed FO CO laser using diffraction grating as a frequency selective element demonstrated a feasibility of a development of frequency tunable single line pulsed FO CO laser. Tunable FO CO lasing on wavelengths from 2.7 up to 4.2 micrometers corresponding to vibrational transitions from 13 yields 11 up to 38 yields 36 was obtained. The maximum SOE came up to 2.8 J/I Amagat, single line output efficiency being up to 0.6%.

The paper studies a self-sustained volume discharge without preionization-self-initiated volume discharge (SIVD)--to excite non-chain HF lasers on SF₆-C₂H₆ mixtures. Once initiated by a local discharge gap breakdown, SIVD is found to propagate then over the whole gap normally to the applied electric field through successively starting diffuse overlapping channels at a voltage close to the quasi- stationary value. With forming new channels, the current through those previously originated decreases. The volume occupied by SIVD tends to expand with increasing the energy released within the discharge plasma, whereas a discharge bounded by a dielectric surface shows a simultaneous increase both in burning voltage and current. All these features combined allow a concept to be put forward of the existence of certain restriction mechanisms depending on the specific energy released and not permitting the total deposited energy to pass through a single channel. It is suggested that SF₆ dissociation by electron impact and the electron attachment to vibrationally excited SF₆ molecules are just those mechanisms. Simple analytical models have been developed allowing these mechanisms to be qualitatively described.

Results of experimental and theoretical investigations of a homogeneous discharge in SF₆ gas have been presented. Experiments with use of electrodes made of Al have clarified that even by small current densities (below 20 A/cm²) and pulse durations (50 ns) the cathode surface is covered by a number of hot spots, which influence discharge homogeneity and stability. The hot spot density of about 10 cm^-2 is found to be necessary for ignition of a homogeneous discharge. In order to achieve desirable hot spot density special kinds of cathodes with predefined hot spot number have been designed. These cathodes have provided high discharge homogeneity and stability.

This paper shows experimental and theoretical results obtained with an oscillator-amplifier XeCl laser system of short duration (3 ns) and high energy. This laser system is based on a four pass amplification scheme with off-axis incidence to the active medium to minimize the formation of the Amplified Spontaneous Emission in the amplifier. In this configuration, pulses of approximately 10.2 mJ energy and of 3.8 ns duration have been obtained with a high contrast. These results are discussed and compared to numerical ones issued from a numerical code describing the amplification of the oscillator beam in the active medium.

High-energy electron beams have been used to produce HF chemical lasers operating either on the chain reaction with high specific energy (100 J/I) or on the nonchain reaction with lower specific energy (10 J/I). This initiation is usually performed by injection of an electron beam along the optical cavity axis or perpendicular to this axis.

The ability of middle pressure room temperature combined discharge pumped CO-laser development is investigated in this paper. The active media optimal parameters (pressure, specific energy input, E/p relation for different mixtures) are obtained. The efficiency approximately equals 14% is calculated at this optimal parameters for mixture CO:He equals 1:3. The influence of the N₂ and Xe addition also is investigated.

A critical overview of the results of electron density measurements in copper vapor lasers is presented. There are considerable contradictions between the results of measurements made by different methods especially between the results concerning temporal behavior of electron density between excitation pulses. Possible reasons of these contradictions are discussed. The method of electron density measurement based on atomic hydrogen Balmer lines broadening is considered in greater detail. Possible nature of the Balmer lines emission under the conditions of copper vapor laser operation and processes of the lines broadening are discussed.

We have developed and tested a technique for controlling copper-vapor laser output parameters by superimposing a secondary repetitively pulsed discharge on a primary discharge with a controlled time delay. As the time delay is varied from tens of microseconds to several microseconds, the output energy and average power can be varied from 0 to 100%. A lasing management mechanism based on prescribed variations in the microcharacteristics of the discharge plasma is discussed.

Systematic overview is presented of the design and output parameters of the small scale (1 + (430.5 nm), He-Ca⁺ (373.7 nm) gas- discharge recombination lasers. Such compact lasers are usually characterized by reliability, durability, ease of handling; they demonstrate elevated pulse repetition frequencies f, better quality of laser radiation, and high specific output powers.

Developed and studied is a pulsed Ti:Sapphire laser with new active medium parameters. For the first time, short (3 - 5 mm) Ti³⁺:Al₂O₃ crystals with relatively high Ti³⁺ ion concentrations (0.18 - 0.22%) have been employed. The developed laser has comparatively high generation power and very simple reliable construction design. The best-achieved differential efficiency of the Ti:Sapphire laser amounted to 30.4%. Considered are the advantages of the proposed laser pumped with a Cu-vapor laser as applied to two-photon photodynamic therapy.

The influence of HBr admixture on the electron energy distribution function in discharges in mixtures of neon and copper vapor was studied. The Boltzman kinetic equation was solved by a numeric method with some approximations. It is shown that admixture of HBr can lead to significant deformations of the electron energy distribution function. Rates of excitation of Cu resonance and metastable levels were also determined using the calculated electron energy distribution functions. It was confirmed that the changes of electron energy distribution functions caused by the HBr admixture can improve conditions for population inversion formation on transitions from resonance to metastable levels of Cu atom.

Investigations were performed of spatial-angular characteristics of radiation from flashlamp-pumped dye lasers in different temperature conditions of active elements. It was found that the laser beam divergence depends on the parameters of the active element and cooling conditions. A prerequisite for ensuring a high directionality of radiation from these lasers operating in the repetitively pulsed regime was shown to be temperature stabilization of the active element and coolant.

We describe the results of investigations into spectral and temporal characteristics of powerful radiation from flash lamps operating in the microsecond pulse mode. In these conditions a number of factors are shown to play an essential role, among which are electric pulse parameters, thermal inertia of the discharge gap, and spectral transmission region of the lamp shell.

Fluorescence of solutions of rhodamine 6G in the form of single drops of millimeter sizes excited by the intense IR and visible laser radiation (with duration of laser pulses of approximately 10 ns and wavelengths of 1064 and 532 nm) is experimentally investigated. It is found that the power thresholds of fluorescence excitation for drops comprising the dissolved dye are by an order of magnitude less than for a cell with dissolved dye. The dichromatic drop fluorescence has been revealed, which is manifested through the occurrence of two maxima in the fluorescence spectrum of drops comprising dissolved rhodamine 6G. The first maximum coincides with that of the dye fluorescence spectrum, while the second maximum is shifted by approximately 1000 cm^-1 and is on the slope of the fluorescence line profile. It is shown that the duration of drop fluorescence does not exceed the duration of the exciting pulse.

Many kinetic and spectroscopic studies were performed on alkali rare gas ionic excimer. The main results obtained during these investigations are presented. We observed fluorescence spectra from diatomic and triatomic molecules. Vacuum ultraviolet fluorescence emissions from alkali rare gas ionic excimer molecules were studied in detail by low- energy electron beam excitation. Measurements were performed as a function of gas composition, gas pressure and deposited energy in order to investigate the kinetic mechanisms of these molecules. The rate constants of the formation and competitive reactions were determined from the observed fluorescence signal decay.

A description is given of detailed nonstationary multiwave kinetic model of a laser, based on Xe atom transitions with (lambda) equals 1.73, 2.03, 2.65, 2.63, 3.37 and 3.51 micrometers in He-Ar-Xe mixture pumped by a hard ionizer. The proposed kinetic model is tested against the results of experiments on e-beam and nuclear pumping of a Xe-laser containing pure Xe, binary and ternary mixtures. Numerical simulation showed that the processes of three-body recombination of Xe⁺ ions (He-Xe mixture), dissociative recombination of Xe₂⁺ ions (pure Xe), dissociative recombination of ArXe⁺ ions and excitation by the electrons from Xe(6s') states play the main role in the pumping of upper active levels.

The problem of delta-shaped pulse of light diffraction from the aperture in the plane screen is formulated and solved in general form for the plane wave. Two examples are considered: diffraction from the slit and from the circular aperture. The analytical solution is given for the illuminated zone of the space behind the aperture and for the shadow. The temporal response is shown to consist of the direct wave and that scattered from the aperture edges. At large distances from the screen the Fourier transform of the solution coincide with well-known results for the plane monochrome wave.

The qualitative interpretation is given to the observed temporal anomalies in the emission spectrum of the Sun. The hypothesis of population inversion existence is verified using modeling of processes in Solar photosphere. The quasi resonant charge exchange of doubly ionized Helium on Hydrogen atoms is considered for the most probable mechanism to form the population inversion. A set of HeII lines is given together with corresponding relative amplification coefficients that can explain the results of observations.

The application of excimer laser ablation process to the decontamination of radioactive surfaces is discussed. This technology is very attractive because it allows to efficiently remove the contaminated particles without secondary waste production. To demonstrate the capability of such technology to efficiently decontaminate large area, we studied and developed a prototype which include a XeCl laser, an optical fiber delivery system and an ablated particles collection cell. The main physical processes taking place during UV laser ablation will be explained. The influence of laser wavelength, pulse duration and absorption coefficient of material will be discussed. Special studies have been performed to understand the processes which limit the transmission of high average power excimer laser through optical fiber, and to determine the laser conditions to optimize the value of this transmission. An in-situ spectroscopic analysis of laser ablation plasma allows the real time control of the decontamination. The results obtained for painting or metallic oxides removal from stainless steel surfaces will be presented.

Detailed analysis of electric voltage distribution and electric currents in adaptive liquid crystal (LC) based lenses is presented. Approximation of constant LC layer impedance is shown to be useful for physical insight. More generally, a computer simulation is developed, taking into account the voltage dependencies of the LC capacitance and conductance. Computer simulated phase shift distributions are in good agreement with experimental profiles produced via Zigo interferometer measurements. Also addressed is the influence of the lens's electrical parameters on its dynamics.

Reported are the results of development, prototyping and investigation of a powerful laser system based on a frequency-stabilized dye jet laser pumped with a copper vapor laser. Short- and long-term frequency instability of the system is approximately +/- 50 MHz at output power 4.5 W in the 610 - 620 nm spectrum range. In case two amplification stages are used, the overall efficiency of the system is higher than 15%. It can be further bettered by raising the pump power of the output stage. The region of smooth output frequency tuning of the stabilized master oscillator is as wide as 8 GHz, while maintaining the scanning rate of up to 1 GHz/sec. The system allows pumping of the master oscillator as well as amplifiers with either open beam of a copper laser or by way of fiber delivery. When pumping the master oscillator through a fiber, for the first time we focused the radiation at the exit of the fiber by means of a modified Fraunhofer objective lens. This type of optical system creates the focal spot twice as small as the fiber diameter while maintaining minimum spherical aberrations.

Results of treatment and prophylaxis of complications in children with malignant and benign tumors subjected to chemotherapy, radiotherapy, combined therapy, and surgery are presented. The efficiency of treating the patients with external irradiation by a low-intensity pulsed copper vapor laser is estimated. The immediate and long-term results of treating 252 children are analyzed.

The proposed new interfacial spectroscopic method allows to measure the fluorescence emission spectra of the two tryptophans of the Bovine Serum Albumin (BSA) during its adsorption at the air/water and egg-lecithin (egg-PC)/water interfaces, using an UV excimer laser. Surface fluorescence spectroscopy shows changes in the spectroscopic properties of adsorbed BSA, spread BSA and mixed egg-PC/BSA films. These results are related to the surface pressure measurements which characterize the different BSA surface organizations.

The paper describes the results of investigations carried out the Institute of Atmospheric Optics SB RAS on the laser radiation propagation on the paths of various geometry for different geographical regions depending on the synoptic factors as applied to the laser navigation systems (LNS). The considered results form the basis for the development of new methods of guidance of vehicles nearby to a place of arrival. LNS designed on the basis of these methods enable one to execute visual and instrumental guidance with a necessary for practice accuracy of position fixing.

The fluorescence of dense rare gas targets has been produced and analyzed using X-ray flash, e-beam and ion beam as excitation techniques. For the first time to our knowledge an extended database of argon and krypton molecular UV emissions, i.e. the Molecular Ion Continua, has been obtained with a very good agreement between spectra whatever the pumping technics is used. The estimation of potential surface for both singly and doubly charged argon trimers and the consideration of previous ab initio calculation for the argon dimer enables us to confirm some former hypothesis but also to suggest new pathways likely to be at the origin of the population of the upper states radiating in the Molecular Ion Continua.

Time correlated optical emission spectra of argon, krypton and xenon in the wavelength range from 110 to 450 nm, and 0 to 6000 ns time interval, recorded at the Munich Tandem accelerator using heavy ion beam excitation with 2 ns beam pulses, were measured in order to clarify the origin of the so called third rare gas excimer continua. Experiments were performed at xenon and krypton pressures between 50 and 250 mbar, and argon pressures between 230 and 1500 mbar. All spectra clearly show different distinct peaks, emerging at different time delays after excitation. These spectral maxima are interpreted as arising from excimer emissions by separate radiating species, formed by gas kinetic processes. While the spectral shape of the components, forming the third continuum radiation in the heavy rare gases krypton and xenon turned out to be of complicate structure, in the case of argon all wavelength spectra could be reproduced by fitting a limited number of Gaussian functions with fixed center wavelengths and fixed widths to the data. Hereby, six distinct maxima, appearing at four different times after the excitation pulse, could be identified.

The studies on third continua in rare gases carried out over the last decade are considered. The comprehensive analysis of the available experimental data confirms our earlier interpretation of the nature of third continua. When dense rare gases (at a pressure on the order of and higher than one atmosphere) are excited with a hard ionizer (electron or ion beams or short-wavelength photons), the dominant contribution to the emission of third continua comes from transitions of singly charged dimer ions from the first electronically excited bound states to repulsive states correlated with the ground electronic states of ions and atoms.

In this paper an electronic ballast for pulsed operation of dielectric barrier discharges (DBD) is presented. The converter is designed as a transformer coupled square wave power source optimized for capacitive loads like DBD. The special features are the bipolar trapezoid waveform with variable slew rate (dU/dt), duty cycle, frequency and amplitude of the output voltage, which is balanced to ground. The power stage is designed in zero voltage switching technology. The ballast is primarily designed to investigate the discharge characteristics of DBD in dependence on the waveform parameters. A simple electrical DBD model is presented, which allows to predict the external DBD voltage and the discharge power in dependence of slew rate and duty cycle. The paper is closed with some experimental results of pulse XeCl*-excimer lamps.

We have measured the efficiency and spatial characteristics of output radiation as a function of fill pressure for a Xe excimer lamp employing a short voltage pulse (approximately 100 ns) excitation circuit, and compared the results with those obtained using conventional AC (ie. sinusoidal voltage waveform). When using pulsed excitation, VUV output is obtained from a homogeneous discharge at efficiencies which increase linearly with Xe pressure in the range 50 - 750 torr up to 3.2X the maximum efficiency obtained when using AC. When using AC excitation, the efficiency saturates with increasing pressure > 350 torr for which pressures the discharge appearance is altered from a diffuse discharge to one which is comprised of stochastic or stationary filaments. We have also recorded discharge spectra which highlight the different character of the homogeneous and filamented types of discharges. It is deduced that the enhanced efficiency arises due to the capability of pulsed excitation to produce a homogeneous (glow-like) discharge at higher pressure, which brings about more optimal electron density and temperature conditions for exclusively exciting Xe metastables than possible using AC. We attribute the homogenizing effect of short-pulsed excitation to the rapid rate at which the applied E-field increases to the necessary value for homogeneous discharge breakdown to proceed at a faster rate than the formation of filaments.

The results of experimental study of Ne emission in the wavelength range of 200 - 600 nm under excitation by electric discharge and short-duration e-beam are presented. It was found that temporary behavior of the emission intensity distinguished in different spectral regions. The nature of the radiation in the ranges of 120 - 300 nm and of 300 - 500 nm was suggested due to transitions of molecular ions and those from Rydberg states Ne₂^R, respectively.

The results of experiments on measurement of broadband UV radiation efficiency in Xe and Kr pumped by nanosecond e- beam are presented. The values of efficiency of the 3-rd continuum in Kr and Xe, calculated on the basis of experimental data, do not exceed 0.25% in gas pressure range 0.25 - 2.5 atm. It indicates that the main part of energy of a band is radiated by single-ionized molecular ions Rg_n^+* (where n equals 2.3). The influence of ions of a type Rg_n⁺⁺ is more pronounced at lower pressure p < 0.5 atm, where the efficiency of broadband radiation in Kr increases.

This paper reviews the basic discharge physics and procedures that have been used to pulse excite gas lasers. A variety of different discharge schemes have been implemented over the past thirty years to volumetrically excite high pressure discharges with cross sections ranging from 102 iO cm2 and lengths of 102 lO3cm. The associated energy outputs derived from these systems range, in the case of C02 lasers, from lO — 106 J/pulse. The techniques use transverse excitation and have been successfully applied to a wide variety of gases and mixture with lasing outputs extending from the vacuum ultraviolet to the long-wave infrared. The various schemes have been adapted to provide effective discharge excitations lasting from iO —iO seconds. The short excitations have been applied to miniature and traveling wave preionization stabilized discharges and the long pulses to large cross section high energy devices. The paper will focus exclusively on discharge excitation and stability issues and relevant discharge related kinetics. It will not specifically address issues relating to laser extraction, repetitively pulsed operation and the associated problems of thermal control, flow management and acoustics dumping. The review provides a somewhat parochial perspective in that it reflects my own personal contributions to this field and my direct association with lasers covering this size distribution and associated energy range. The parochialism is reflected mainly in the representative devices I have selected for the paper. The paper is presented in six parts. This introduction is followed by a brief review of the relevant discharge physics of high pressure discharges. The next three sections separately address and provide specific properties and examples of each category. The paper concludes with a brief summary.

In the present report the results of study of kinetic and electrophysical questions connected with the development of pulse-periodic sources of luminescent and coherent VUV- radiation on dimers of inert gases with e-beam pumping of active media are presented. With using of the received results technical proposals on the creation of coherent VUV- source on superluminescence os excimers, capable to work with average power of radiation of not less 5 W at pulse- repetition rate of up to 10 Hz have been elaborated.