Experimental results obtained from a 500 Hz, 750 W average output power XeCl laser are presented. The dynamical behavior of the pulse energy and optical investigations of the discharge volume pointed out the limits of the present design. There are strong indications that acoustic perturbations currently prevent the efficient operation of the module at repetition rates higher than 500 Hz. To pass the 1 kW level, further improvements must be made. Increasing the discharge efficiency from 1.1% to date will reduce the creation of shock waves. An aerodynamically designed flow loop will help to shift the ratio of fan power to excitation power (currently 40 kW and 66 kW, respectively) to more reasonable values. The additional use of pulse compression techniques will simplify the choice of adequate high-voltage switching elements.

The Siemens excimer laser is designed for industrial scale production processes. Its unique features are liquid dielectric capacitors, side-wise x-ray preionization, efficient cross flow gas circulation and an all metal/ceramic discharge head. All parts are integrated inside a hermetically sealed pressure vessel.

Within the Eureka EU213 excimer laser program, the Laser Technology Centre at Culham is developing high average power excimer lasers operating at pulse repetition frequencies (PRFs) of greater than 1 kHz. This paper reviews recent high PRF results obtained on the testbed CHIRP I laser in the areas of preionization and pulse power. PRF limiting mechanisms observed in preliminary multikilohertz laser operation are described.

An experimental parametric study of a small volume x-ray preionized XeCl laser which uses the double discharge (spiker-sustainer) principle and a new fast ferrite magnetic switch is presented. This high-efficiency discharge excitation system, with a Ne/Xe/HCI mixture at relatively low pressure (P equals 2.5 atm.), in a 50 cm3 active volume (25(DOT)2(DOT)1 cm3), has made possible an efficiency of 3.2% in energy and 4% in power at maximum with up to 140 mJ of extracted optical energy in a 130 ns (FWHM) laser pulse in switch mode. The authors discuss laser characteristics dependence with magnetic switch and electrical circuit parameters, for switch mode. Future studies of the present advanced excitation system for conditions of very high PRF, in the frame of Eureka EU205 Eurolaser program, are presented. The experimental part of these planned studies will be made with LUX very high PRF high average power IMFM test-bed

Increasing the interest in high-power coherent UV light sources, the ENEA Frascati Centre is developing 1 kW average power XeCl laser systems. In order to analyze the physical behavior of these sources, net gain measurements spatially and temporally resolved have been done on a large-volume prototype and compared with the results of a numerical 2-D simulation code.

A complete model of a long-pulse x-ray preionized self-sustained discharge XeCl excimer laser has been established for the case of excitation by an advanced electrical circuit associating a double discharge (spiker/sustainer) and a fast low-loss ferrite magnetic switch with pulsed reset. This model allows simulation of the potential working conditions of the IMFM high average power, very high repetition rate LUX test-bed. The model, which considers Ne as buffer gas and HCl as halogen donor, includes a rate equation for species with the most recent available rate constant values, circuit equations with time-dependent ferrite inductance and plasma impedance and rate equation for laser emission taking into account absorbtions. Modeling takes into account time delay between spiker and sustainer, low value of sustainer field and dynamics of magnetic switch. The model has been validated with a long- pulse x-ray preionized XeCl laser, with double discharge and magnetic switching, developed at IMFM, which has already obtained over 3% efficiency and 140 mJ extracted energy in 150 ns (FWHM) from a 50 cm3 active volume at 2.5 atm. pressure. Numerical results are in good agreement (within 30%) with IMFM experimental results. A parametric study of the XeCl laser with double discharge and fast magnetic switch is presented as well as a comparison with both experiments and numerical results of excitation by a C-L-C classical circuit for the same geometric and gas conditions and the same input energy.

The first part of the paper represents theoretical investigations on the propagation and reflection of shock waves and the corresponding density perturbations which have been performed using a two-dimensional unsteady finite-difference method. The influence of electrode or mirror mounting design on the reflection of shock waves and the resulting density distribution is shown. It was found that in modifying the design, the local distribution of pressure and density in the laser gas can be influenced, but that the decay rate of the perturbations is not affected. The effect of using helium instead of neon as a major gas component is also briefly discussed. The second part describes the experimental setup to generate and investigate shock waves. In a special piston-driven shock channel of rectangular cross-section, remarkably good shock waves have been produced with regard to both the rise time and the evenness of the shock front. Interferometric observations of density variations (Delta) (rho) /(rho) as low as the order of 10-4 are possible. Some results of attenuating shock waves with a simple muffler design are presented.

The construction and some characteristics of XeCl excimer lasers with active volumes of 0.4 cm3 and 1 cm3, and output energies of 50 (mu) J and 1.6 mJ, respectively, are described. In both cases, preionization by discharge on the ceramic surfaces of peaking capacitors is used in excitation schemes. In the case of the second laser, 'electric wind' is used in gas circulation which allows it to work with pulse rates up to 100 Hz.

This paper reports the behavior of an XeCl laser having two independent preionizers which generate UV radiation into the discharge region in the perpendicular and parallel direction to the electrode surfaces. Output energy and other parameters have been measured using a single preionizer and both preionizers, changing the power supply polarity and varying the delay time between the preionization and the main discharge. When the preionization system generated photons only in the direction perpendicular to the electrode surfaces and a negative power supply was used, a high discharge current and a high-output laser energy were obtained. Besides, diffusion coefficient of the photo-preionized electrons played an important role in the laser behavior, particularly when a consistent delay time between the onset time of the preionization and the main discharge was present.

Nonequilibrium vibrational kinetics of HCl in Ne-Xe-HCl has been investigated using different models. The results show that an accurate description of this kinetics can be achieved by introducing seven vibrational levels in the Ne-Xe-HCl codes.

An x-ray preionized excimer laser is described. For this laser, the special sealed metal- ceramic x-ray preionizer with cold cathode was constructed. The cathode was made from carbon felt and had 4 X 80 cm2 area. The discharge volume was 70 X 4 X 3 cm3 and on XeCl one provided the energy up to 2J in a pulse. In the same discharge chamber, the different types of preionizers (spark discharges, UV laser radiation) were investigated. It was shown that the output energy depends on the electron density uniformity rather than the electron concentration.

Excimer laser excitation with resonant microwave structures was obtained both for XeCl* and KrF*. The discharge tube containing the laser gas is placed inside one or several coupled microwave resonators. Depending on the microwave structure, laser pulse energies up to the mJ range were achieved with XeCl*.

Microwave pumped rare-gas halide mixtures feature excimer laser emission without preionization. The performance of a XeCl excimer laser is investigated with an optimized waveguide coupling geometry. Parameters such as the microwave power, duration of the microwave pulse, and the rise time of the microwave pulse from 25 ns to 220 ns were varied. The pulsed microwave L-band transmitter had a power of up to 10 MW, an adjustable pulse duration (500 ns to 6000 ns), and a pulse repetition frequency up to 400 Hz. The coupling geometry consisted of a double ridge waveguide. The discharge tube was a quartz capillary placed between the ridges. Two tubes were used. One had an outer and inner diameter of 10.3 mm and 2.6 mm, the other 8 mm and 5.8 mm, respectively. The total active length was 438 mm. A study of a microwave power of 2.5 MW deposited into the discharge yielded at low repetition frequencies a non-homogeneous deposition. With a new resonant coupling geometry, a XeCl laser energy of up to 1.8 mJ in a 16 ns long pulse was achieved.

The short wavelength and high power of excimer lasers have made them attractive candidates as exposure sources for photolithography. Unfortunately, direct application of excimer lasers for microelectronic steppers is restricted by certain negative properties of the excimer laser radiation. This means that for the successful stepper's operation the radiation properties should be optimized. In this work the authors present the results of the optimization of the excimer laser characteristics for a deep-UV stepper.

Waveform conjugation of narrowband KrF lasers with linewidth 0.02 cm-1 and divergence 10-4 rad was investigated. By means of Brillouin scattering in SF6 gas, the 12 ns duration pump pulse was compressed up to 1.5 ns with energy efficiency about 80% and the laser beam divergence retention. The waveform conjugation under thermal Raleigh scattering in hexane, heptane and hot water was also investigated. The maximum efficiency in hexane was about 10% and scattered pulse duration 2.5 ns. Waveform conjugation in a wide region of liquid absorption coefficients was also observed.

The work described in this paper forms part of the Eureka EU213 HiPulse excimer laser project to build an excimer laser with an average power greater than 1 kW, and a pulse repetition rate up to 5 kHz. Because of the very large volume of gas needed in such a laser, and the rising costs of rare gases such as xenon, a sophisticated gas processor system is needed which is capable of recycling the rare gas component of the gas mix indefinitely. If the laser head needs to be opened up for some reason, the laser gas needs to be pumped out and stored in a suitable vessel. When the laser is running, a variety of contaminants are generated by various chemical reactions going on inside the laser head; the exact contaminants depend on the materials from which the head is made. As part of the design of a laser gas processor, the authors are investigating the changes in gas constituents as the laser is running, using a quadruple mass spectrometer connected to a computer. The mass spectrometer samples the laser gas through a special capillary and porous plug arrangement which maintains the necessary pressure difference between the laser gas at 2-5 bar and the analyzer head at microbar pressure levels.

The experimental results of high-repetition-rate pseudospark switch testing are reported, with particular interest in applications like high-repetition- rate, high-average power excimer lasers and pulsed TEA CO2 lasers. Typical test parameters are hold-off voltage of about 20 kV, peak currents around 15 kA, and pulse durations of less than 100 ns, discharge conditions that are typical for high average power excimer lasers. These were realized in a low inductive discharge circuit using discrete ceramic capacitors of up to 10 nF total capacitance and an impedance of about 1 (Omega) . The resulting peak currents were about 19 kA in the short-circuited, ringing discharge. A special feature of the switch is being capable to withstand severe current reversal, high rates of current rise of about 5*1011 A/s and peak currents above 20 kA. Some 107 shots have been performed with a sealed-off metal-ceramic pseudospark switch with integrated hydrogen reservoir without degradation of the switch performance. In this setup, repetition rates of up to 1.8 kHz were achieved. The switch-triggering behavior and measurements of the switch resistance in dependence of the peak current are reported.

At Laser-Laboratorium Gouttingen, damage and durability tests are performed on excimer laser optics. Within the automated experimental set-up, image processing techniques are applied for both spatial laser beam profiling in the target plane and real-time damage recognition. Along with a description of experimental details, results of damage threshold measurements at 248 nm and 193 nm are presented which demonstrate a strong relationship between absorption of laser radiation on defect sites and the subsequent damaging process. In addition, the influence of surface quality as well as laser pulse length on damage thresholds of fused silica substrates has been investigated.

The electrical discharges which exist in a gas-pulsed laser (ignition system and laser tube) constitute an additional problem to the study of the whole laser system. This is due to their time-dependent behavior during the discharge. An electrical discharge can be symbolized as time-dependent resistance and inductance in the laser electric circuit. The analysis of the circuit is impossible if the resistance and inductance functions in relation to time are not known. This work illustrates a very easy way of finding the resistance and inductance functions in relation to time. This can be achieved by measuring only the waveform of the voltage across the capacitors of the system. By combining this waveform with the differential equation of the system performance, the evolution of the resistance and the inductance in relation to time can be determined. The quantities which can be calculated after that, in relation to time, are the oscillatory frequencies, the damping constants as well as the impedances of the discharges.

Excimer laser irradiation of polymers can be used to generate a modification of the surface morphology at the irradiated regions. The normally smooth surface of synthetic fibers can be modified by this technique to a regular, roll-like structure, which is of great effect to general properties of the fiber, e.g. adhesion of particles and coating, wetting properties, and optical appearance. A systematic study of the properties of the laser-induced surface structure as a function of experimental conditions is reported for varying types of polymer including high- performance fibers like aramides. The experimental data support a synergetic understanding of the effect, where laser-induced temperature fields and intrinsic stress fields are understood as cooperative driving forces of the effect. Examples of practical, textile applications of this effect for modification of macroscopic properties of fabrics and nonwovens are discussed. In laboratory scale UV-laser irradiation was used to change the optical appearance of fabrics and to improve dust filtration properties. The adhesion of pigment dyes and particles on poly(ethylene terephthalate) fibers could be improved to a degree similar to natural fibers like cotton.

The use of excimer lasers for patterning flexible materials such as polyethylene/non-woven in sheets is reported. This technique is compared with two widely used non-laser techniques -- rotary dies and water jet. Excimer laser processing parameters, e.g., laser wavelength, power density, etc., will be discussed in relation to the final cut quality.

The paper describes investigations concerning the enhancement of adhesive bonding strength between polypropylen (PP) and adhesive on a resinous basis by UV-laser-induced photochemical reactions. Possible mechanisms of the laser-activated processes are discussed. A preliminary result of the experimental examinations is the bonding strength enhancement of more than 5 X under certain conditions.

Effective temperatures of laser ablation of certain polymers are extracted from experimental dependences of ablation depths on laser fluences. Dependence of these temperatures on laser pulse durations is established. Comparison with the known thermodestruction data shows that the effective temperature corresponds to transient thermodestruction proceeding by the statistically most probable way.

A 2 J/20 Hz XeCl (308 nm) excimer laser with a flat intensity distribution is used for processing Al2O3, Si3N4, SiC and AlN ceramics and short glass fiber reinforced polymers. In order to get reproducible results, an excimer laser material processing system is built up, including a variable optical system, diagnostics, and a high-precision xy- translation stage. With this system, modifications of the surfaces at low-energy densities and the production of submillimeter structures at higher energy densities are investigated. Monitoring of important process and beam parameters with a diagnostic system is essential to get reproducible results. A CCD-camera system is used to measure the uniformity of the intensity distribution of the laser beam. The aim of the investigations is to find some correlation between beam and processing quality. Due to the low penetration depth of the laser beam into the material and rapid evaporation, only thin layers below the workpiece surface are affected, and the extension of the heat-affected zones remains extremely small. The treatment of larger areas of the materials at lower energy densities results in modifications of the surface topography. Uniform and reproducible changes of ceramics surfaces are obtained with optimized process parameters. Various mask geometries are imaged onto the surface of the material by a projection technique to produce submillimeter structures. The sharpness of the image on the workpiece surface proves to be an important parameter for producing reproducible and small structures. Larger areas are machined with the help of the xy-table. The processing quality is characterized using profilometry and scanning electron microscopy.

Excimer lasers have been employed for large area surface treatment of bulk ceramics and/or ceramic coatings on a metallic surface. These applications are aimed at the improvement of surface morphology (e.g., grain size, roughness, porosity, etc.) and properties (e.g., hardness, corrosion resistance, conductivity etc.). The influence of KrF laser processing parameters on Al2O3 ceramic samples and/or coatings are discussed in relation to the above- mentioned surface characteristics.

The formation of nitride surface layers on titanium plates (0.14 mm and 3 mm thick) by multipulse (100 to 500) XeCl excimer laser ((lambda) equals 308 nm) irradiation in N2 and NH3 atmospheres (1100 mbar) at a laser fluence of approximately 1 J/cm2 and repetition rate of 50 Hz, with careful experimental precautions against oxygen contamination, is studied. After irradiation, the samples were examined by scanning and transmission electron microscopy, analyzed by Rutherford backscattering and nuclear reaction techniques and by x- ray diffraction spectroscopy. All the experimental results point to the formation of pure titanium nitride layers without any detectable oxide phase

A theoretical model of surface polishing of materials evaporating by light from solid phase is proposed. On the basis of the model, an explanation is given for the experimentally observed phenomenon of diamond films surface polishing as a result of their graphitization and vaporization from solid phase under the action of multipulse radiation of an excimer XeCl laser. The proposed model of surface polishing by light can also be applied for the case of thermochemical etching by radiation where the rate of etching also has Arrhenius dependence on surface temperature. This new technique has promising possibilities in the processing of hard and superhard materials.

Thin films of Y1Ba2Cu3O7-x were deposited via pulsed laser ablation onto MgO and YSZ (Yttria-Stabilized Zirconia) substrates. The use of an IR Nd:YAG laser leads to nonstoichiometric deposition. The best quality superconducting films were deposited by means of UV excimer laser ablation ((lambda) equals 308 nm). These films were strongly orientated with c-axis perpendicular to (100) substrate. The film quality was found to be strongly dependent on substrate temperature, oxygen pressure, sample cooling rate and laser fluence. The deposition process was characterized by the time-resolved spectroscopic measurements of the emission from YO molecules.

The possibility of using a KrF excimer laser to remove indium-tin-oxide (ITO) and tin-oxide (TO) films from glass substrates is investigated. Etching with the excimer laser is compared with etching with a CO2 laser and a Nd:YAG laser. Patterns of removed film are made on the glass substrates using a mask imaging technique. The removal of the ITO and the TO is considered to be complete when the resistance across the removed tracks is greater than 20 M(Omega) . The length of the track is 1 cm and the width is 25 micrometers . Different substrates are tested. The fluence is varied. The results are characterized using a scanning electron microscope, by resistance measurements and by ablation depth measurements. The results are discussed.

In advanced contact materials one aim in processing is the reduction or even substitution of precious metals. However, newly developed materials have to exhibit excellent corrosion resistance and good electrical conductivity as well as mechanical stability, especially if abrasive wear loaded contacts are concerned. One strategy is the total substitution of precious metals by non-noble metals such as copper and its conventional alloys. Such materials, however, suffer from their poor mechanical properties. Chromium would be a candidate for an unusual alloying element that may help to overcome these weaknesses, but unfortunately Cr does not mix with Cu by standard metallurgy. For low current contacts a surface layer of a mixed material might be sufficient, and powder metallurgical routes are therefore inefficient and hence inadequate. The excimer laser is an excellent tool to produce the required thin films by surface alloying. This is possible due to its short wavelength and short pulse duration. The present investigations were carried out in order to understand the phenomenon of laser surface alloying using excimer laser irradiation. To achieve technical relevance, the system Cu/Cr was chosen. The irradiations were monitored using difference reflectometry, to check whether alloying occurred at all and to what degree. Structural details of the produced layers were investigated using a diffractometer with glazing incidence. To obtain quantitative information about depth and stoichiometry of the alloyed layer, sputtering AES was applied.

ArF excimer laser deposition of tin and tin-oxide films on Si was obtained dissociating tetramethyltin Sn(CH3)4(TMT) and TMT/N2O mixtures. Information on the gas phase photoproducts was achieved by spontaneous emission spectroscopy. Electronically excited CH and Sn fragments were detected and their formation and decay mechanisms investigated through spectral and temporal analysis of the fluorescence signal. The effect of buffer gases on the emission characteristics was also studied.

The investigation of UV laser chemistry of dimethylcadmium (DMCd), both adsorbed in UHV on n-type Si(100) with native oxide and in low pressure gas, has been carried out using KrCl and XeCl excimer lasers. The kinetics of the DMCd chemisorption and spontaneous decomposition on silicon as well as the photoprocesses in chemisorbed, physisorbed, and gaseous species induced by the absorption of UV laser radiation by molecules and substrate surface have been studied using mass spectrometry. As the coefficients of the absorption of silicon at the wavelengths of KrCl (222 nm) and XeCl (308 nm) lasers are alike but DMCd only resonantly absorbs the radiation of the KrCl laser, the mechanisms of the action of these lasers on the adlayer are quite different. The KrCl laser induced an efficient DMCd fragmentation and also photoionization of desorbed species, while the photoexcitation of silicon by XeCl laser pulses resulted in desorption of neutral species and some decomposition of the initial molecules. The comparison of DMCd excitation at these wavelengths allows selection of resonance-enhanced effects and determination of the composition of the adlayer as well as the mechanisms of the photoprocesses.

This paper presents a novel application of UV laser radiation: fabrication of soft or apodized apertures (AA)I-3 with transmission profiles decreasing smoothly from the center to the edges for high-power single-pulse visible and near-IR lasers. Such units are used both outside and inside the cavity for beam shaping, for avoiding hard-edge Fresnel diffraction ripples in laser amplifiers, for increasing the second harmonic conversion efficiency, and for the brightness enhancement of master oscillators in single-mode lasing.

The interaction of UV radiation with organic tissue, and dangers and problems arising from medical applications of excimer lasers are discussed. These topics deal not only with beam guidance, but also with questions concerning carcinogenity and mutagenity resulting from UV radiation. Examples of several applications are given.

For the transmission of high-power excimer laser radiation in the kilowatt range, a flexible bundle of tapered quartz fibers is presented. Thirty fibers with a tapered coupling section are assembled in a bundle, which is tested with an excimer laser providing 2 J pulse energy at repetition rates of up to 20 pulses per second. The bundle showed good transmission qualities at 308 nm wavelength with an output power of 0.5 J/pulse. Catastrophic damage of fibers or other bundle elements did not occur during irradiation. The transmitted energy remained constant over the energy range tested with short irradiation times and low frequencies and is sufficient for material processing. At present, the transmission efficiency of the bundle is about 25%.

An excimer-laser-based Lidar fluorosensor, designed for operation from a mobile station, has been assembled at the ENEA Centre in Frascati, and laboratory measurements on different samples have been performed both with spectral and time resolution. A low divergence, high- power XeCl laser has been used for excitation of typical chemical and biological materials polluting water surfaces. Results were obtained on thin films of oils most frequently found in the Mediterranean sea. A rough correlation has been found connecting the average oil density with both the overall visible fluorescence yield as well as the time decay constants.

A simple laboratory set-up for cutting the round transplants of the cornea is described. An excimer ArF laser served as the ablating 193 nm radiation source. The results of the first experiments to produce some cylindrical and segmental transplants are presented.

Radiative characteristics of laser-plasma XUV sources are reviewed. The dependence of the main plasma parameters on the heating laser wavelength is discussed, as well as the use of application-specific excimer lasers to generate XUV radiation. A comparison is given with other XUV sources, such as electron storage rings. Examples of the application of normal- incidence multilayer XUV optics, e.g., to collimate the laser-plasma radiation or for projection lithography, are given.

The Rutherford Appleton Laboratory Repetitive Laser-Plasma X-ray Source has been scaled to repetition rates of up to 100 Hz. An average power of 40 mW/sr has been measured from mylar tape targets in the spectral region 0.28 < h(upsilon) < 0.53 keV (the `water window') with approximately 30% of the emission in the hydrogen-like carbon ion L(alpha) (h(upsilon) equals 368 eV) line. A scanning transmission x-ray microscope (STXM) was used for the first time with a laser-plasma source to generate test images. The source was also run with Cu and Fe targets to generate h(upsilon) approximately equals 1 keV x-rays in atmospheric pressure helium, yielding at 30 Hz an average power of approximately 9 mW/sr. Proximity x-ray microlithography images in 1.2 micrometers thick photoresist have accurately reproduced features of approximately 0.3 micrometers.

The measurement of photoionization cross-sections of free ions or refractory atoms is difficult as a suitable absorbing column must be produced and backlighted by a bright synchronized XUV-continuum emitting source. In the dual laser plasma (DLP) technique both the absorbing and backlighting plasmas are produced by the interaction of high-power laser beams with suitable solid targets. The authors describe some recent results obtained with the DLP technique. With a single-laser system and photographic detection, inner-shell excitations from both ground and excited states in Al and Si species up to the fourth stage of ionization have been recorded. New and unexpected results were obtained for La3+. By using a photoelectric-based multichannel detector and a synchronized multilaser system, the versatility and reliability of the DLP technique is greatly improved. Time-resolved spectra have been obtained for atomic Cr and Mn and their ions at photon energies between 40 and 70 eV where the dominant absorption mechanism is excitation of the 3p subshell. An intercomparison is made between results obtained with the DLP method and corresponding results recorded with alternative techniques. Preliminary results for atomic tungsten and platinum are shown.

The spectrum of a laser-produced plasma in the XUV-VUV region consists typically of many strong emission lines together with varying degrees of continuum, the latter being due primarily to recombination. In plasmas produced by a Q-switched ruby laser (approximately 1 J output in approximately 25 ns) on a range of high Z targets, in particular the rare earth metals, it was found that the spectrum, over a wide wavelength region, consisted of smooth continuum with apparently no individual lines. The spectrum of samarium, for example, consisted of continuum from approximately 200 to 4 nm with no evidence of lines (except occasional impurity lines, due usually to oxygen). For ytterbium a similar clean continuum extended from 60 to 4 nm (the limit of the authors observations). The dominant stages of ionization in the plasmas are A10+ to A15+, and the observed absence of lines can be explained by a consideration of the electron configurations in these stages. The continua are very useful for experiments such as absorption spectroscopy and other applications in the XUV-VUV region and offer an alternative to the synchrotron when polarized radiation is not required. The sources are simple to mount and operate, are reproducible, intense, and insensitive to ambient pressure. Because of their pulsed mode of operation they are particularly suitable for time-resolved studies. Several applications of the sources are described and some possible future developments are suggested, including the use of excimer lasers.

Results related to the emission of radiation by the argon dimer in the 128 nm region are presented. The excited dimers are produced by a supersonic expansion of a fast discharge excited plasma.

A description is given and the results are reported of the first photoionization-recombination laser using atomic xenon excited by thermal ionizing radiation from a plasma. The pump source was a multichannel plasmadynamic in magnetoplasma compressors, which was ignited in the active medium of the laser. When the composition of the working mixture was optimal (Xe:Ar equals 1:250) and the total pressure was 1 atm, the output energy was approximately 0.5 in the form of pulses of approximately 10 microsecond(s) duration, and maximum specific output energy represented by laser radiation was 1-2 J/l. The unsaturated gain was 27 m. A kinetic laser scheme was proposed and analyzed. It allowed for the processes of photoionization, ion conversion, dissociative recombination, interaction of excited states with electron and buffer gases, etc. An important role played by heating of the active medium during pumping was demonstrated; it explained the observed characteristics of the spatial and temporal structure of the lasing process, particularly bleaching of large volumes of the active medium. The potential output energy of the laser was considered, and specific constructions were proposed to attain a lasing efficiency amounting to a few percent.

Basic regimes of the KrF-laser-assisted patterning of a-C:H and of W-alloyed a-C/Si/O:H diamond-like films (DLF) of dielectrical and metal-like varieties are studied. Laser-induced processes of the film graphitization and ablation under the multipulsed irradiation are considered. The submicron resolution of the film structurization is shown to be possible by using the ablative projection UV laser lithography.

A time-resolved x-ray absorption spectroscopy apparatus on a laboratory scale is being prepared which utilizes a laser plasma as an x-ray source. One of the major aims imposed on this apparatus is to observe x-ray absorption or reflection spectra of various materials in an energy region from 100 eV up to 3 keV. For this purpose, two sets of optical systems are provided, i.e., a toroidal mirror and grazing incidence flat-field grating for the lower-energy region (100-1000 eV), and a toroidal mirror and curved KAP crystal for the higher-energy region (1-3 keV). Detection of x-rays is performed with MCPs for both energy regions. Preliminary experiments on the generation of x-rays have revealed that the intensity of x-rays in the energy region below 300 eV is as high as 10(16) photons/pulse in 2(pi) steradian.

The paper presents the construction and basic characteristics of an excimer-dye laser system designed for diagnosis and therapy of cancer using the HpD method. The laser generates 405 nm or 630 nm lines. The basic characteristics of the laser system are presented.

Laser based x-ray sources at h(upsilon) approximately equals 0.9 - 1.2 keV (Fe to Cu L-shell) developed for applications are studied from the point of view of x-ray emission spectra. X-ray spectra obtained with different laser intensities and wavelengths using Nd and KrF lasers are described. Results are qualitatively compared with the predictions of simple analytical models for plasma temperature Te and average ionization Z*. When using KrF lasers it is possible to introduce a He atmosphere in the interaction chamber to reduce the debris problem. X-ray spectra at different He pressures were recorded and x-ray L-shell emission of Fe and Cu were shown to be largely independent of the pressure.

A wide-aperture, x-ray preionized discharge pumped XeCl laser is described. The laser head is included in a gas circulation loop. The x-ray generator is made of a secondary emission electron gun. The x-ray pulse duration is 400 ns (FWHM). The laser energy (EL) and the average power are given as a function of various parameters: charging voltage (Vc), buffer gas pressure (PL), total capacitance (CT), the interelectrode distance (d), and the repetition rate. The laser discharge is driven by a classical LC-inversion circuit. The stored energy (ES) in the capacitor bank is CTxVc2/2 and the efficiency is defined by EL/ES. Up to a repetition rate of 50 Hz, the laser energy per pulse remains almost constant, with low fluctuations. The best efficiency, for different pressures, is obtained for the same Vc/PLxd value. The optimal buffer gas pressure decreases with an increase of the total capacitance. More than 4.5 J per pulse, single shot, have been extracted from a 40 X 5.8 X 4 cm3 discharge (efficiency equals 1%). At a lower laser energy level (2.5 J), the maximum efficiency reaches 2.5%. An average output power of 175 W has been obtained. With this device, good preliminary results on Kr/F2/Ne mixture are given.

High-power operation of excimer lasers was investigated using UV-preionization schemes based on a dielectric surface creeping discharge. The design and operation of the high average power excimer laser systems are described. A large-aperture (10 X 7 cm2) XeCl laser with UV preionization can produce 10 J per pulse at a repetition rate of up to 100 Hz. When the aperture was decreased, the XeCl laser operated at repetition rates of up to 500 Hz and could produce average output power of more than 600 W.

An original multistage excimer XeCl laser system with the ultra-narrow spectral bandwidth and high brightness of radiation is described. Experimental results of stimulated scattering of UV ((lambda) equals 308 nm) radiation are reported.

Along with the excimer lasers, the pulsed argon lamps with MgF2 windows can be used for photodestruction of organic compounds. The lamps were used in our experiments for photocleaning of the optical materials surfaces and photoetching of the submicron PMMA films. The irradiation was carried out in air, the test samples being placed 10 - 100umapart from the light source window surface. The following specific features were observed: high degree of molecular oxygen dissociation in the microgap, pulsed heating of air and pressure rise in the microgap causing ejection of the photodestruction products, and pulsed radiation heating of the organic compound which can result in the diffusion flux grow of the volatile fragments of the irradiated test sample. The kinetics of accumulation of the double C=C bonds was measured by the change in transmission of the submicron PMMA films at A = 200 nm. The photomodification results in a considerable decrease of the film substance ejection. The pulsed VUV irradiation is shown to be a simple and efficient technique for photocleaning of the surface layers of the optical materials removing hydrocarbon compounds.

Deposition of thin (200 $ANS) metal films onto various substrates (glass, fused quartz, sapphire) is reported. The process is initiated with a cw Ar+ laser beam ((lambda) equals 514 nm) irradiating a solution of FeAcetyleAcetonate (FeAcAc) through a transparent substrate. Two types of deposit morphology are observed: either thin films or thick porous structures. The transition from one type to the other has the character of instability, being characterized by a threshold laser power.

The free-electron laser (FEL) amplification mechanism is discussed in this paper, including the influence of the electron beam quality (energy spread, emittance, stability) on the FEL performance. Considerations regarding the choice of the electron accelerator are presented and some characteristic properties of the laser radiation are discussed. An overview of FEL-facilities for the infrared spectral region, which are being designed and built worldwide, is given.

OptiComp has focused on a digital optical logic family in order to capitalize on the inherent benefits of optical computing, which include (1) high FAN-IN and FAN-OUT, (2) low power consumption, (3) high noise margin, (4) high algorithmic efficiency using 'smart' interconnects, and (5) free-space leverage of gate interconnect bandwidth product. Other well-known secondary advantages of optical logic include zero capacitive loading of signals at a detector, zero cross-talk between signals, zero signal dispersion, and minimal clock skew (a few picoseconds or less in an imaging system). The primary focus of this paper is to demonstrate how each of the five advantages can be used to leverage other logic family performance such as GaAs; the secondary attributes are discussed only in the context of introducing the DOC III architecture.