The US Air Force Airborne Laser (ABL) is a major weapon system development by the United States Air Force to provide an airborne, multi-megawatt laser system with a state-of-the-art atmospheric compensation system to destroy enemy theater ballistic missiles at long ranges. This system will provide both deterrence and defense against the use of such weapons during regional conflicts. This paper provides an overview of the ABL weapon system including: the notional operational concept, the development approach and schedule, the overall aircraft configuration, the technologies being incorporated in the ABL, and the risk reduction approach being utilized to ensure program success.

The dissociation of I2 by O2(a1Æ) is a critical process for the chemical oxygen iodine laser. Despite many years of study the dissociation mechanism is not properly understood. Currently accepted models assume that vibrationally excited I2 is the immediate precursor to atomic I. However, studies of I2 vibrational relaxation kinetics cast doubt on this assignment. New measurements of quenching rate constants for I2(A') indicate that electronically excited I2 is a more likely precursor. A revised kinetic model for the dissociation process is proposed, based on the active participation of electronically excited I2. Vibrationally excited I2 remains an important species in this model as the I2 must be vibrationally excited before the electronically excited states can be accessed. A preliminary rate constant package for the new model is presented.

The US Air Force Research Laboratory has actively pursued the development of the Chemical Oxygen-Iodine Laser (COIL) since its invention in 19771. The power scaling potential of the COIL was verified in the late 1980's on the RotoCOlL device, which was later decommissioned. A smaller COIL teststand (ReCOIL) was then upgraded with a rotating-disk oxygen generator and a variable-height slit nozzle to become the principal testbed for continued COIL development. The modified device was named the Research assessment evice Iodine chemical Laser (RADICL). RADICL has supported several major test campaigns during the past 9 years, many of which have been published. These include 2-D gain maps2, iodine dissociation studies3, magnetic gainswitching demonstrations4, mode-locking5, metal cutting/fiber delivery demonstrations, and more recently measurements of water concentration and oxygen yield . Areview of the major results of these test programs and previously unpublished data are presented.

We report on a detailed experimental study of the gain and temperature in the cavity of a supersonic chemical oxygen-iodine laser operating without primary buffer gas and on preliminary power measurements in this laser. In particular, a study is carried out to find optimal values of the flow parameters corresponding to the maximum gain. The measurements are performed for slit nozzles with different numbers and positions of iodine injection holes. Using a diode laser based diagnostic, the gain and temperature in the cavity are studied. Maximum gain of 0.73%/cm is obtained at chlorine and secondary nitrogen flow rates of 15 mmole/s and 7 mmole/s, respectively, for a slit nozzle with transonic injection of iodine. Preliminary power measurements are performed. For slit nozzle with iodine injection in the diverging part ofthe nozzle output power of 287 W with chemical efficiency of 21% was measured at 15.1 mmole/s of Cl2 with no primary buffer gas. This is the highest reported chemical efficiency of a supersonic COIL operating without primary buffer gas.

A study of chemical oxygen-iodine laser (COIL) for the use of decommissioning and dismantlement of nuclear facilities is conducted. A scaled-down model was developed as a prototype. Laser duct and optical cavity were designed so that it can be operated in both supersonic mode and high-pressure subsonic mode for the comparative study. A 1.34kW output with chemical efficiency of 24.6% was obtained in the supersonic mode. In the high-pressure subsonic mode, output power was 1 .12kW with chemical efficiency of 20.6%. A subsonic operation at 12Torr was demonstrated for the first time. A preliminary experiment of thick steel cutting was demonstrated by the developed system. The obtained data was in good agreement with published data.

A multi-kilowatt supersonic chemical oxygen iodine laser (COIL) has been constructed. Two types of jet singlet oxygen generator (SOG) such as tube-array and plate have been tested. An output power of 8.8KW with chemical efficiency of 2 1 .4% was obtained at the chlorine flow rate of 45Ommole/s. The influence of BHP (basic hydrogen peroxide) temperature on the output power of COIL has been studied. And the absolute concentration of O2(1Æ) in the jet SOG was measured using the Piston-source method.

An RF plasma jet generator of singlet delta oxygen has been developed for use in an oxygen-iodine laser. The plasma jet was produced in an Al cylindrical nozzle, having the inner diameter of 3 mm and the length of 8 mm. The discharge was done in the gas mixture O2:N2:NO=200:20:10 sccm and then it was chilled reactively by the mixture Ar:NO2=200:10 sccm, which was injected into the plasma jet at the nozzle exit. The RF frequency was 99.9 MHz and the RF power was 200 W. The O2(?1Æg) relative yield of 32 % was achieved at the pressure of 0.43 Torr. The current device DSOG-3 was tested in a discharge oxygen-iodine laser (DOlL). The reaction scheme of DOlL is the same as in COIL, except of the generator of singlet delta oxygen. The pressure inside the laser was 0.6-0.9 Torr and the mixtures O2:NO=200: 100 sccm and Ar:NO=2100: 100 sccm were used. The iodine flow rate was 0.3 mmol/min. Both types axial and transverse subsonic flow lasers were examined. The latter had better performance. The CW output power was 3 nW at the laser wavelength of 13 15 nm, when the yield of O2(?1Æg) was 25%. The RF DOlL has been demonstrated experimentally.

CW laser action has been demonstrated on the electronic I* (2P1/2) ? I (2P3/2) transition of atomic iodine at 1 .3 15 ?m from the NC! (a1Æ) + I (2P 3/2) energy transfer reaction. The stimulated emission was generated in a transverse subsonic flow device when hydrogen azide, HN3, was injected into a flow of iodine and chlorine atoms. The measured laser output power was 180 mW.

Advanced chemical iodine laser technology will logically include novel all gas phase generation techniques for an iodine energy donor and the injection of atomic rather than molecular iodine. Candidate methods are discussed for the creation of an all gas phase energy donor as well as for injecting atomic iodine. This research will lead directly to designs that will be fabricated and tested extensively with detailed diagnostics to evaluate the chosen design's performance attributes. Preliminary analysis and modeling of the ElectriCOlL system concept is presented. ElectriCOIL will reduce weight and simplify both military and commercial chemical iodine laser systems. Potential cost and weight savings are also envisioned as the massive quantities of liquid chemicals will be completely eliminated from the device operation.

In the 10-kW chemical oxygen-iodine laser (COIL) of DLR, the small signal gain and the laser output power were measured for identical gas flow conditions. The comparison of both results is used to elaborate the expressiveness of small signal gain for COIL laser design. For these investigations the temporal and spatial dependencies of small signal gain and laser power are measured along the flow axis of the cavity. The measurement of small signal gain is perlonned by a commercial diagnostic system of PSI with a software package upgraded by the Air Force Research Lab of Kirtland, U.S.A. 1,2,3,4 The laser power is extracted in a stable resonator configuration. In case of spatially resolved investigations, slit apertures of 6 mm width in flow direction are integrated in the cavity.

A mathematical model of oxygen-iodine laser is described. A numerical analysis of three alternatives of mixing is performed.

The results of experimental and numerical-theoreticalsupersonic COIL study carried out at RFNC-VNIIEF in 1998-2000 are performed. The novel data concern our research into the twisted-flow SOG (TA SOG) performance. The experimental investigations of gas-dynamic and energy performance, chemical efficiency, and optical quality are reported and discussed for the supersonic COIL with the parallel-flow system of gaseous iodine and singlet oxygen mixing. Application of TASOG together with the parallel-flow mixing system was shown to allow high values of COIL operation. The peculiarities of numerical-theoretical model developed at RFNC-VNIIEF are discussed.

The numerical calculations of the gain and dissociation degree of molecular iodine in a supersonic COIL channel are reported for supersonic mixing of flows and 0.2-, 0.3-, 0.4- mm- height critical sections of nozzles profiled for Mach number 2.5 to 4.0.

An analytical model is developed for calculating the iodine dissociation fraction F and the number N of O2(1Æ)molecules lost in the region of iodine dissociation per I2 molecule in slit nozzles. The model is applied to results obtained for different mixing schemes.

In this paper, we mainly describe the structure of an unstable resonator with 90-deg beam rotation(UR9O) outputting annular beam for a chemical oxygen iodine laser(COIL) and the geometry mode of the beam. A beam quality of 3.2 times diffraction limit was achieved in the experiment while the COIL average output power was approximately 4kw in the case ofmagnification of 1.69, as well as the property ofthe annular beam was analyzed.

In the cavity of the supersonic COIL of DLR, the time dependence and the spatial dependence of small signal gain (ssg) and intra-cavity temperature (ict) are investigated for a broad range ofoperating conditions. The ssg is measured by a commercial diagnostic system of PSI with a software package upgraded by the Air Force Research Lab ofKirtland, U.S.A.1,2,3,4,5 The line-shape ofthe COIL gain profile is scanned in frequency by a diode laser of narrow linewidth operating in the region of the COIL transition frequency. The ict is derived from the frill bandwidth at halfmaximum ofthe inscribed Gaussian profile. The experiments are performed for different combinations of secondary gas flow at unchanged primary baseline conditions. The results are interpreted with regard to the ssg and the temperature distribution for optimized COIL operation.

A frequency conversion technique applied to iodine laser beams is described in detail for the ISKRA-4 and PERUN as representatives of wide and narrow aperture systems. The conversion efficiency was measured and predicted theoretically for both the 2nd and 3rd harmonics. The performance of conventionally grown conversion DKDP crystals is compared with that grown by the accelerated and the directional method. Examples are given of physical target experiments using the converted beams.

This work describes a conceptual design of a chemical oxygen-iodine laser (COIL) where diluent gas is continuously recirculated in a closed cycle. Scaling laws, component design, and expected performance are discussed.

The most important part of chemical oxygen-iodine laser (COIL) is the singlet oxygen generator (SOG) that produces pumping energy source of the laser system. A new prototype high pressure SOG, which has possibility to overcome the problems existing several types of SOG have, was developed. This SOG, we call multi-guideplate SOG, is based on jet-type one. The jets of basic hydrogen peroxide (BHP) are spread and fixed on the surfaces of some guide plates auached to the nozzle plate. In this study, it was shown that multi-guide plate-SOG could produce higher O2 (1Æ) pressure and make the jet flow stabler than jet-type SOG in the high flow rate of the gas stream.

New type mist singlet oxygen generator (Mist-SOG) for the chemical oxygen-iodine laser (COIL) has been developed. This SOG is devoted to make the liquid recirculation unnecessary with the complete reaction through a single pass of basic hydrogen peroxide (BHP). 75% of Cl2 utilization and 76% of O2(1Æ) yield were obtained with Cl2 molar flow rate of 3.0 mmol/s. H2O2 utilization in the BHP was achieved as high as 12.3%. This value is about 24 times larger than that obtained by the liquid-jet SOG.

We suggest pre-dissociation iodine molecule utilizing RF-discharge (Radio Frequency discharge) dissociation of I2 for chemical oxygen iodine laser (COIL). The object of the study is to make clear that RF discharge is effective on our experiment. We focus chemical reaction of COIL itself, and especially consider a scheme of dissociation of I2 So following chemical reaction is a process of dissociate iodine molecule into iodine atom by O2(1Æ). I2+ nO2(1 Æ) ? 2I + n O2(3? ) n=4~6 This chemical reaction indicates that to dissociate iodine molecule into iodine atom needs a lot of O2(1Æ ). In our experiments we could prove that RF was effective in this term. Approximately 60% of iodine molecular, which is dissociated by RF discharge, is carried to laser cavity. It is estimated that the other 40% of iodine atom is recombination in our COIL system. As the results, we can obtain higher power, higher gain by using RF discharge dissociation than normal COIL.

Throat-mixing systems for the supersonic flow chemical oxygen-iodine laser (SCOIL) are proposed and assessed in the present study. Three-dimensional, numerical simulation solving compressible gas dynamics together with chemical kinetics has been made for investigating the characteristics of the mixing condition and chemical reactions. The compressible Navier-Stokes equations and a chemical kinetic model encompassing 21 chemical reactions and 10 chemical species are solved by means of full-implicit finite difference method. Two types of nozzles, a Laval nozzle and cylinder nozzle are adopted. The results show satisfactorily high values of the small signal gain coefficient (SSG). The SSG value increases along the flow in the nozzle in relatively short distance of x, reaches to the maximum at the position of 25 ~ 47 mm distant from the throat, and decreases slightly downstream the flow. The proposed throat-mixing system shows higher efficiency than the supersonic parallel-mixing system. The Laval nozzle is found to give the peak SSG value of 40 % higher than that of the parallel-mixing system. It is also noted that the cylinder nozzle has superior ability than the parallel-mixing system, in spite of its exceedingly simple structure.

A purely chemical method was suggested for generation of atomic iodine from gaseous reactants for the use in a COIL. In this method, fluorine or chlorine atoms are produced and subsequently react with hydrogen iodide forming atomic iodine. Both reaction systems were modeled for different reaction conditions. A yield of atomic iodine up to 80 % was achieved in the optimum case for the system leading via chlorine.

A COIL (Chemical Oxygen-Iodine Laser) of 2.2 kW output power has been developed in Korea. The effects of stability and uniformity of the BHP(Basic Hydrogen Peroxide) jet columns on the operation of the COIL are reported. In this paper, the uniform jet speed distribution ofjet SOG (JSOG) in a supersonic COIL is achieved by using the centrifugal pump. And the vane plate in front of BHP jet plate is installed to suppress the turbulent BHP flow generated by the centrifugal pump. The stability and uniformity of BHP jet columns are increased by installing the vane plates. Substantially, the chemical efficiency is increased up to 21 .7 %.

A chemical method of atomic iodine generation with a potential application in chemical oxygen-iodine laser (COIL) was investigated experimentally. The process consists in a fast reaction of gaseous hydrogen iodide with chlorine atoms produced in reaction of gaseous chlorine dioxide with nitrogen oxide. In conditions characteristic for a subsonic mixing region of COIL, atomic iodine was produced with a yield of 20-50 %. This is in a fair agreement with results ofmathematical modeling ofthis complex reaction system.

An experimental study of energy performances and chemical efficiency of supersonic COIL with twisted aerosol SOG and the parallel-flow system was made. An experimental supersonic COIL setup is present.

This work examines the prospects of generating gas-phase O2(1Æ) from thermal decomposition of (C6H5O)3PO3 for use in the oxygen-iodine laser. The process promises major advantages over the traditional production of O2(1Æ) from the reaction of C12 with basic hydrogen peroxide, namely (1) producing O2(1Æ) from a single liquid fuel (as opposed to reacting liquid fuel and oxidant gas), (2) fuel with a long storage life, (3) up to four times lower heat release which greatly reduces needs for refrigeration, and (4) simple hardware.

A new strategy for pulse oscillation of chemical oxygenÑiodine laser based on a combination of a porous pipe SOG with an instantaneous atomic iodine generation, has been developed to seek the potential of COIL as an amplifier of the nuclear fusion driver. This new scheme allows one to produce a large aperture high pressure laser medium, which is favorable to the laser amplifier, while maintaining a minimum degradation of stored energy by water vapor. The experimental apparatus consists of the porous pipe SOG, an iodine donor (CH3I) injector, a flash lamp for the iodine dissociation, and an optical resonator. Operational characteristics of the apparatus including dependence of output energy on an iodine concentration was studied. As the result, the maximum output energy of 800mJ was obtained. It was also found that the CH3I was dissociated through unidentified chemical reaction associated with the O2(1Æ).

A series of experiments were done on COIL with a pipe-array jet-typeO2(1Æ) generator. The investigation emphasized on the performance, parameters and relative techniques of the generator. A chemical efficiency of 20.6% was obtained.

The PALS project is based on iodine photodissociation system ASTERIX transferred from the Max-Planck-Institute fŸr Quantenoptik, Garching, Germany, to a dedicated experimental hall built at the Institute of Plasma Physics of Academy of Sciences of the Czech Republic. A novel feature of the system is a newly designed twin interaction chamber comprising several technical innovations. As a user facility the system was inaugurated in June 2000 and starting from October it will serve the users coming under the EU 5thFP "Transnational access" scheme. A brief description of planned upgrades of the original system is given. These include (1) implementation of adaptive optics, (2) replacement of the iodine master oscillator by a more flexible solid state oscillator based on fiber optics, and (3) a fs extension of the laser output using the OPCPA method.

The roles that rotational nonequilibrium, mixing and the optical resonator play in determining the power speciral perfonnance ofthe cw HF laser are reviewed. Experiments and analyses that led to an understanding of these elements ate summarized. The factors that influence the overtone perfomiance of the HF laser are reviewed. The line selected pthbrmance is related to multiline perfmnance.

The results of experimental and theoretical investigations on a pulsed, chemical e-beam pumped, non-chain HF laser with a 25 I active volume are submitted. It is shown that there are conditions of anomalous behavior of the output radiation which could be explained by the existence of a space-charge effect in the plasma.

Energy, temporal and spectral characteristics of HF-laser pumped by non-chain chemical reaction initiated by radially converging e-beam, planar e-beam and non-self-sustained discharge have been investigated. The major channels of vibrationally excited HF molecules formation have been analysed. It has been confirmed that the high efficiency (~ 10 %) of non-chain HF laser can be reached only by simultaneous atomic and molecular fluorine formation under the action of e-beam and molecular fluorine participation in the inversion releasing process. It is shown that the laser pulse has a complex spectral-temporal structure caused by consecutive generation of the P-lines P2?P1?P3?P4?P5?P6 and overlapping of the rotary lines of the same oscillatory band and separate oscillatory lines during a pulse of radiation. With e-beam pumping of a 30 1 active volume laser, the output energy as high as 115 J and efficiency with respect to e-beam energy deposited into gas mixture up to 8 % were demonstrated. The optimal gas mixture SF6 : H2 =8 : 1 under pressure of 0.45 atm has been obtained. At pressure 1 .1 atm and non-uniform output distribution, total laser energy and efficiency with respect to e-beam energy deposited into gas were found to be up to 200 J and 1 1 %, respectively. Use of e-beam initiated low pressure pulsed discharge for excitation HF molecules leads to increase of radiation energy in 2.8 times. Also investigations on zeolite-based different absorbents influence on energy stability of HF-laser are presented and radiation energy decay after 103 shoots not more than 15-20 % is gained.

The cascade scheme "master generator Ñ amplifier" of the photoinitiated pulsed chain chemical HF/DF-laser is investigated by numerical modelling and in experiment. The possibility to control the duration and spectrum of the laser pulse is shown, the efficiency of amplifier can exceed the efficiency of the equivalent generator.

Results of the investigation of the discharge parameters, active medium homogeneity and stability, and laser performance are reported for a 2.5x2.5x50 cm3 HF phototriggered laser working either in chain and non-chain mode. Using a Ne/F2/H2/O2=93/5/1.5/0.5 mixture, a specific output laser energy of 9 J/l was obtained with an electrical efficiency of 38%. Compared to the performance ofnon-chain reaction HF lasers, these data correspond to an increase ofthe efficiency by a factor of 8. However, due to the development of discharge instabilities the output laser energy is not higher than that obtained with the non-chain laser mixtures.

The study of DF laser generating average power 25 to 30 W at 1,200 Hz repetition rate is reported. Acoustic perturbation effect on the stability and homogeneity of discharges produced in the laser active medium and thus on output laser power is demonstrated.

This paper provides information about the basic technology of high power diode lasers and their applications in a tutorial way. Each step from the milli-watt laser light generation in the pn-transition to the multi-kilo-watt laser system is explained. Typical applications of high power diode lasers, some of them already in industrial manufacturing, are described.

We are developing high average power diode pumped solid state laser DPSSL for laser fusion power plant, for space propulsion and for various applications in industry. The common features or requirements ofour High Average-power Laser for Nuclear-fusion Application (HALNA) are large pulse energy with relatively low repetition of few tens Hz, good beam quality oforder of diffraction limit and high efficiency more than 10%. We constructed HALNA 10 (10J X 10Hz) and tested the performance to clarify the scalability to higher power system. We have obtained in a preliminary experiment a 8.5J output energy at 0.5Hz with bean quality of2 times diffraction limited far-field pattern. We are also trying to extend the laser technology of high peak power with low repetition to that of high averge power laser with high repetition or CW operation. The progress of power laser technology is now opening new fields of applications in science and industry. The flexibility and variety ofperformance are needed.

All-solid-state laser sources are required for numerous applications in industry and science. Scaling of average output power while preserving a diffraction limited beam quality results in high brightness operation. However, conventional laser systems suffer from thermally induced phase distortions in the active medium, which considerably reduce their beam quality. Advanced pumping geometry, diode pumping, as well as active media with high quantum efficiency can reduce the thermal load. But the remaining phase distortions result in a reduction of beam quality. Optical phase conjugate mirrors are suitable to compensate for phase distortions in master oscillator power amplifier systems (MOPA). Stimulated Brillouin scattering in conventional, commercially available silica fibers facilitates reliable and stable phase conjugation. These all-solid state devices reveal an energy reflectivity of almost 90% and require low financial efforts. Moreover, the SBS threshold is determined by the appropriate fiber core diameter. Therefore fiber phase conjugators can be applied in continuously pumped, repetitively q-switched laser systems which usually exhibit smaller peak power in comparison with pulsed pumped systems. A four-pass amplifier arrangement with birefringence compensation was developed. Nearly diffraction limited output with 32 W average power has been achieved at 10 kHz repetition rate. Power scaling up to 100 W seems to be possible.

Copper vapour lasers are high repetition rate, pulsed devices with output at 511nm (green) and 578nm (yellow). In recent years, diagnostic studies have led to advances in power, efficiency and output beam quality. Originally developed for industrial scale isotope enrichment processes, new applications for these lasers include high-speed imaging, velocimetry and micro-machining of hard materials. By frequency doubling the 51 mm green output, output powers of order 1W at 255nm in the UV can be obtained. This radiation is ideal for the manufacture of Fiber Bragg Gratings Ñ essential components for modern optical telecommunications. Kinetic enhancement of the excitation mechanisms of the laser provides not only increases in output power of compact copper lasers but also dramatic improvements in laser brightness.

We are presently developing nonlinear spectroscopic techniques for measuring the spatio-temporal density behaviour of H and halogen atoms species to investigate the action of these species in halogen enhanced copper lasers. In this paper, we report time resolved measurements of ground-state H atom density in a Cu HyBrID laser obtained using two-photon allowed laser induced fluorescence. Ultraviolet probe radiation (205nm) was focussed through an end window to excite the n=3 level and the resultant Balmer fluorescence detected via a side window. The results indicate that the H atom density is depleted to less than half its prepulse value during the excitation pulse and then recovers almost fully during the first 20 microseconds of the interpulse period. By interrupting the discharge, we also have used the technique to investigate the H reassociation rate at the tube wall. The results suggest the technique, which may also be adapted to obtain halogen densities and gas temperature measurements, is a promising diagnostic for investigating halogen enhanced Cu laser vapor plasmas.

For 8 years, Copper Vapour Lasers (CVLs) driven by solid state power supplies have been experimented and used in French SILVA program development in co-operation with industrial partners. We presend high performances and reliability obtained and applications to other laser systems.

In the paper, we present new results of CuBr-laser study in a regular pulse mode with a high PRF and in a mode of modified double pumping pulses with PRF = 30 kHz. It has been shown a stable PRF over 500 kHz can be obtained.

A 50 W CuBr laser is reported. Characteristics of the major laser parameters are presented: output power, laser pulse repetition frequency, and laser beam quality. The laser has been designed for precision material processing in industry.

In ns-putsed longitudinal discharge-excited He-Cu and He-CuBr vapor ion lasers oscillation in the IR spectral range has been obthined. UV laser operation has been obtained only in Ne-CuBr vapor ion laser. An average output power of 210 mW has been measured on the laser line 248.6 nm and a 270 mW on multiline - 248.6, 252.9, 260.0 and 270.3 nm.

We report laser characteristics of a gold ion laser radiating on the lines 282.3nm, 284.7nm, 289.3nm and 291.8nm A longitudinal nanosecond discharge has been used for excitation. Quasi-cw lasing was obtained with 33%/m small-signal gain and 110 mW average output power for the strongest line 282.3nm This average output power corresponds to the record peak power of 1.7W. The investigated laser offers promising prospect for various scientific and technological applications.

The performance of a small-scale KE-CVL operating at a pulse repetition rate of 50kHz has been investigated by comparing modelling results and experimental data to understand the underlying plasma kinetics issues for pulse repetition rate scaling. Comparison between initial modelling predictions and experimental results relating to the laser output power and the population densities of the metastable lower laser levels (Cu* 4s2 2D3/2,5/2 ) suggests that there is an additional de-excitation mechanism for the metastables in the KE-CVL. The most likely de-excitation mechanism involves vibrationally-excited H2(v) molecules Cu*2D+H2(v) => CuH+H. A rate-coefficient of 2x10-16m3s1 is obtained by comparing modelling results with experimental data relating to the laser output power and the time-evolution of the axial 2D3/2 metastable population density.

The pulse parameters of a Cu-HyBrID laser were measured in a large range of discharge conditions. It was shown that the laser efficiency is determined by an adequate pre-pulse electron density. Almost constant laser average power and efficiency can be obtained in very different pulse repetition rates provided other discharge parameters were adjusted in order to maintain the optimal pre-pulse electron density. We observed that the pulse width depends mainly on the HBr concentration while the pulse energy is mainly dependent on the absolute HBr pressure and repetition rate.

A survey of experimental and theoretical results on physics of a CO laser operating on first-overtone (FO) vibrational transitions V+2?V is presented. A special attention is paid to quite new results recently obtained at the Lebedev Physics Institute (Russia), TRINITI (Russia) and Air Force Research Lab (USA). Efficient multiwavelength pulsed FO CO lasing with output efficiency up to 1 1% and specific output energy up to 50 J/l Amagat is observed within the spectral range of 2.5-4.1 ?m corresponding to the vibrational transitions V+2?V from 6?4 up to 37?35. Single-line frequency tunable FO CO lasing on the wavelengths from ~2.7 up to 4.2 ?m with the maximum output efficiency up to ~1% is also observed. Multiline and single-line lasing on 430 ro-vibrational lines is obtained. Theoretical calculations based on the experimental data predict that multiline FO CO laser efficiency can be enhanced up to 20%. The effect of "spectrum alternation", i.e. an alternation of strong and weak vibrational bands, in pulsed FO CO laser spectrum, which is determined by two sets of cascade transitions, is experimentally observed for the first time. An influence of nitrogen on spectral characteristics of a single-line FO CO laser operating on very high vibrational transitions up to 38?36, which is related to quasy-resonance overlapping of the transition with 0?1 transition of nitrogen molecule, is discussed. High efficiency and high specific output energy places the FO CO laser amongst other high-power lasers such as CO2 laser, fimdamental band CO laser and HF(DF) laser.

Experimental results on a pulsed e-beam sustained discharge CO laser are reported. The gas was cooled down to a temperature of 5¡ C, the active volume was 1.5 1. Optimizing gas composition, gas pressure, and output mirror reflectivity, pulse energies up to 8 J corresponding to a specffic value of 16 J / lbar could be demonstrated. The spectrum of the laser radiation was analyzed, lines between 2.8 and 3.3 ?m were found. In burst mode operation, up to 100 pulses at pulse frequencies up to 30 Hz have been achieved, resulting in an average laser power of 60 W.

Studies of vibration-vibration exchange in CO molecules excited up to vibration quantum numbers v=20 are performed both theoretically and expethnentally. New kinetic model taking into account muhi-quantum VV exchange in temperature range T=100Ö300K is described for the first time. Description of the experimental methodology allowing for studies of effects of relaxation of the vibrational distribution after a sudden disturbance is given. The disturbance of the vibrational distribution is produced by Q-switched short pulse of single line radiation in fundamental band The relaxation is studied by measuiing laser pulse energy of the second pulse initiated by resonator Q-switching produced with variable time delay relative to the first pulse. A set of kinetic rate constants accepted in the model for various gas temperatures, vibration level numbers and number of exehanged vibration quanta from 1 to 4 is presented. Good agreement between experiniental data and results of the advanced theory is the first direct evidence in support of multi-quantum exchange model.

The vibrational distribution function (VDF) of CO molecules in the mixture with helium decreases rapidly for vibrational levels higher than 1 1 . The VDF plateau may be significantly increased by addition of nitrogen or Xe. There is a strong correlation between VDF and concentrations of plasma-chemical products in the mixture.

The laser gas of a 700 W CO laser is excited by microwaves and cooled down to room temperature. A mass spectrometer controls the supply of O2 and CO and the adsorption of CO2 in zeolithe traps

A mathematical model for gas discharge CO lasers includes vibrational kinetics of CO and N2 molecular species as well as the equation for electron energy distribution and gas dynamic equations. The effective method for numerical simulation of powerful CO lasers is proposed.

Computer simulation codes for first-overtone CO laser have been developed. The codes are designed to be executed in distributed computing environment. Performance characteristics have been analyzed and compared with those of fundamental- band CO laser.

Sealed-off slab CO2 lasers excited by a dielectric barrier discharge are studied. The laser output power is measured at excitation frequencies between 0.4 and 0.6 MHz; discharge gaps are in the range 1.6 Ñ 6.0 mm. Due to the scaling laws of radio frequency excitation no laser activity should be possible for the laser under investigation. The use of high-frequency excitation (0.4 - 0.6 MHz) combined with a dielectric barrier discharge gives the possibility of creating a homogeneous and stable CO2 laser gas discharge with high laser activity. The excitation efficiency of the all-solid-state generator reaches 90%.

The peak power and gain available from the RF excited planar waveguide CO2 laser has been enhanced for pulses in the 10 to 100 ?s range at pulse repetition rates up to 4 kHz. The specific peak power output for unit electrode area has been enhanced to a value of240 kW.m-2 . Relative to cw, the small signal gain coefficient has been pulse enhanced by a factor of 7 to 2.5 m-1

For a kW annular diffusion-cooled laser, we tested the possibility of using the electrodes directly as waveguide wall. We considered dielectric and metallic spacers. Electric field distribution calculations and preliminary experimental results are presented.

A 7-pass, master oscillator and power amplifier CO2 laser system is reported using planar waveguide structures. An acoustooptic modulator between oscillator and amplifier is shown to introduce thermal lens effects that modify the mode-matching. Amplification ofpulse bursts at 50 kHz in cw gain is presented, and gain saturation and recovery effects are demonstrated to pulses at a modulation rate up to ~55O kHz.

The paper presents the results of measuring of the small-signal gain in the active medium of the high-power pulserepetitive RF-excited slab C02-laser. The measurements were carried out for the pumping pulse durations in the range 20.50 Ls and pulse repetition rates 100.500 Hz. The maximal specific energy, delivered to the active medium, was 430 W/cm3. In the experiment were measured the average output power of radiation, pulse energy and power and the output beam divergence.

A small signal gain was detected using a CO2 laser during microwave-enhanced combustion of methane-air mixture in a quartz combustor suggesting perturbation of the Boltzmann distribution of molecular energy levels. A maximum value of g = 0.69 %cm-1 was obtained when the combustion zone was irradiated by microwaves at 1000W sustaining the possibility of utilizing the system for laser applications.

Time-resolved gas dissociation inside diffusion-cooled RF excited CO2 lasers was measured with NIR laser absorption spectroscopy and UV-VIS emission spectroscopy. Roto-vibrational temperatures were derived directly in the discharge region. Effects of gas additives on the plasma processes were studied.

The results of the use of two types of adaptive mirrors to generate quasi Q-switch pulses of the CO2 laser radiation are presented. The excess ofthe output power in peak above the average level in CW regime was more then 2.5 times. The power of the lasers that were used in the experiments was in the range of 1 Ñ 3 kW CW. Also, the design of the different types of the active conectors used in the experiments is discussed.

Using selective layered, and combined metallic-dielectric electrodes, the higher order mode selectivity of the slab waveguide resonator can be improved, reducing the sensitivity of the beam quality on small variations of the electrode gap by high power CO2 lasers.

A multikilohertz operation of a transversely excited atmospheric CO2 laser driven by an all-solid-state exciter has been demonstrated. The exciter consists of a long life time high-voltage pulse generator employing a transistor equipment working along the principle of fourier synthesis. High voltage pulses with a maximum voltage of 50 kV, 2 ?s pulse duration, and a maximum pulse repetition rate of 17 kHz ignite the laser gas discharge. The electrodes have to be insulated by a dielectricum like glass, which homogenizes the laser gas discharge so that no preionization is necessary. A small device of this multikilohertz TEA CO2 laser reaches an average laser power of 140 W and a laser efficiency of 1 1 % at a pulse repetition rate of 17 kHz.

Results concerning the polarization state measurements of the beam emitted by an industrial cw CO2 transverse-flow laser workin at 1.2kW are reported in the paper. A measurement procedure with a rotating analyser and a quarter-phase retarder, designed for a CO2 laser radiation is applied . The measurements prove that the optical beam transport system modifies the polarization ofthe laser radiation by increasing its ellipticity. The investigations of the temporal stability of the polarization show that polarization state ofthe investigated laser fluctuates considerably versus time.

A compact and efficient multi-joule TEA CO2 laser using the modified overshoot mode (MOM) magnetic-spiker sustainer (MSS) excitation technique is described, giving an enhanced laser performance at a significantly reduced spiker switching energy (typically ~5% of total input energy) necessary for producing a stable discharge. A laser output energy of 7.1J was obtained with an overall efficiency of ~13.5%. The implementation of this technique in a dual module 10J TEA CO2 laser is also successfully obtained, demonstrating the scalability of this technology to high pulse energy ( ³10J) systems.

Investigation of the effect of dissociation products on the discharge stability and laser performance of TE/TEA CO2 lasers using magnetic-spiker sustainer excitation technology is presented. The tolerance of the discharge to O2/CO concentration is determined, giving improved results to that found in conventional systems. Both solid state and gaseous catalyst are also investigated for extending operational lifetime of the laser gas mixture.

We stabilized an optical power of RE excited slab CO2 laser on the pick of the Doppler broadened gain curves using an optogalvanic effect generated from the laser itself. The power stability is greatly improved to 2.9 %. We suggest that this method can be applied for frequency and power stabilization of other kinds of RF excited laser, for example, Xe and Co laser.

A computer model for injection seeding of a high pressure CO2 laser is presented. A rate equation model is used to predict single longitudinal mode (SLM) operation through injection of a cw seed into the resonator cavity. The coupled non-linear differential equations are solved using a Runge-Kutta method. Predictions for the minimum injection power required to produce SLM pulses are made. Detuning off resonance and the effect of the output coupler reflectivity and small signal gain on SLM operation is also considered. Conditions for stable SLM operation through injection of a cw seed are suggested. Single mode operation, even in the detuned case, can be attained due to the homogeneous broadening of the gain, and the rapid growth of the pulse under high gain conditions.

For the grounding of the program of the wide-aperture several THz bandwidth CO2 laser amplifier creation it was initiated the experimental investigation of a HF laser radiation transformation in a multiatmospheric C02/He medium. The C02/3He mixture (46x50x63 mm3, 4 atm) was pumped by the 1P8 spectral line of the pulsed chemical HF laser (85 J, 1 ps). Transverse pumping geometry was used. Up to the power density of 2.7 MW/cm2 an absorption saturation was not observed. At the deposited energy of 58 J and output coupling of 20% it was obtained CO2 laser pulse of 2.7 J (quantum efficiency was about 1 8.6%). The estimated small-signal gain was of 0.05 cm1

CO2 laser system generating the train of ~200 ps pulses with total energy up to 5 J was put in operation in General Physics Institute of Russian Academy of Sciences (IOFRAN) recently. Initial ~100 ps 10.6 ?m laser pulse with energy 10 ?J was regeneratively amplified in 5 x 5 x 5 cm3 discharge volume X-ray preionized TB-CO2 discharge unit developed and manufactured in D.V.Efremov Scientific Research Institute of Electrophysical Apparatus (NIJEFA) in cooperation with JOFRAN. The results on upgrade of this unit towards obtaining 10 atm volume self-sustained discharge in C02:N2:He mixtures with reasonably high percentage of molecular gases are reported. Owing to this upgrade free running mode laser radiation energy B1 (when the unit was equipped with unstable telescopic resonator) at 6 atm was increased up to 22.2 J, which corresponds to specific energy extraction 5.4 J/l/atm and efficiency 4.5%. The estimated value of B1 from such a laser at 10 atm is 15 J. It corresponds to peak power of regeneratively amplified 2 ps 10 ?m pulse formed in master oscillator of laser system Ñ1.5 TW. Prospective of further upgrade of laser system using new 10 x 10 x 100 cm3 discharge volume 10 atm TE-C02 discharge unit which is under construction now in NIIEFA in the network of ISTC Project #1072 is discussed.

Excimer lasers are now being used in the manufacturing ofultra-large scale integrated devices that require feature widths ofless than O.25?m. The excimer laser for microlithography, since its introduction in 1987 has evolved from a laboratory instrument to a manufacturing tool. We will trace the history of the excimer laser in this industry and explain why it is and remains the total solution for the present and for many years in the future.

For new industrial applications, mini excimer lasers with a wavelength of 157 nm were developed. The main goal was to extend the component lifetime. The laser tube is designed in metal-ceramic technology. An erosion-free corona preionization is installed. The pulsed-power module contains a solid state switch with additional compression stages to generate the high current rise at the electrodes of the laser tube. All of the modules in the laser system are designed for long lifetime. At 157 nm the mini excimer laser reaches a maximum single-pulse energy of 2 mJ up to a repetition rate of 1000 Hz. An overview of the results of long-term testing of these stateÑofÑtheÑart mini excimer lasers at 157 nm will be given.

We have realized a stable self-sustained discharge of high-pressure rare gases (Ar and Kr) using a compact discharge device. The glow discharge was obtained up to 10 atm of pure Kr. The vacuum ultraviolet emission intensity centered at 148 nm abruptly increased when the charging voltage exceeded a certain value. This "threshold" behavior indicates the onset of the stimulated emission at the wavelength. In addition to this threshold behavior, a considerable spectral narrowing was observed when the charging voltage exceeded the threshold value. The deconvoluted spectral width was 0.5 nm (FWFIM), which was much narrower than that of 4 nm (FWHM) at the charging voltage below the threshold. This significant spectral narrowing also strongly indicates the onset of the stimulated emission at 148 nm.

For some specific application areas like (V)UV lithography or special processing of certain materials with high average power (V)UV lasers excimer lasers have to be developed further. In this contribution we will summarise the recent progress of our VUV excimer laser programme on the ArF and F2 laser. Key point in our research programme is the production of long laser pulses in the order of 100 ns (FWHM). An existing laser chamber was modified and optimised for the ArF laser research programme. Different excitation circuits have been tested. For long pulse operation the laser is operated in the ferrite switched resonant overshoot mode using 18 cm2 of ferrite in the switch for a discharge volume of approximately 60 x 0,7 x 1,2 cm3. Long optical pulses of up to 116 ns have been obtained with a lean gas mixture and a very low self-inductance of the electrical circuit of the packing capacitors. For the F2 laser a new discharge chamber and a new X-ray preionisation source was designed. With this set-up it was possible to produce a F2 laser with a large optical cross-section of 1,5 x 2,4 cm2 operating at an intrinsic efficiency of 0,1%. With a different electrical circuit the system produced long optical output pulses of 70 ns (FWHM) in a gas mixture of helium and 3 mbar F2 at a total gas pressure of 2 bar.

Recent progress in excirner laser technology developed at TRINITI is reported. The key of the technologT is a combination of simple reliable UV preionizer based on creeping discharge on surface of a sapphire plate and the compact highly efficient gas flow system. This technology allows to develop very compact, high power, high repetition rate models of excimer lasers capable to deliver stabilized average power up to 500W (XeC1, KrF), 250W (ArF) and realise pulse repetition rate of more then 5 kHz..

Two key engineering issues in the development of a KrF laser driver for Inertial Fusion Energy are high transmitting and long life e-beam window and optical laser windows. We have performed experiments with e-beam-pumped KrF laser installation GARPUN on the transport of relativistic e-beams through Al-Be and Ti foils and compared them with Monte Carlo numerical calculations. It was shown that both 50-?m thick Al-Be foils and 20-?m thick Ti foils had equal transmittance of about 75% for ~3OO keV, 50 A/cm2, 100 ns e-beams. However in both cases the observed transmission was lower than calculated one. In contrast to Ti foil, whose surface was strongly etched by fluorine, no surface modification or fatal damages were observed for Al-Be foil after ~1000 laser shots and protracted fluorine exposure. It was shown that applied magnetic field of ~1kG significantly reduced electron scattering both across and along laser cell at typical pumping conditions with 1 .5-atm pressure working gas. Without magnetic field irradiation of optical windows by scattered electrons resulteu in additional transient and residual induced absorption of laser radiation. The analysis of different optical materials for KrF laser windows and coatings has also been done.

An efficient electric-discharge XeCl laser is developed, which is pumped by a self-sustained discharge with a pre-pulse formed by a generator with an inductive energy storage and a semiconductor opening switch on a basis of SOS diodes. An output energy up to 800 mJ, total pulse length up to 450ns, and a total laser efficiency of 2.2% were attained using a spark UV preionization.

High contrast nanosecond pulse trains are produced by an oscillatorÑamplifier XeCl laser system incorporating polarizing optics. The device is simple and flexible allowing to deliver nanosecond pulse trains up to 17 mJ and with adjustable characteristics mainly concerning the number ofpulses (2 to 6 pulses) and the individual pulse peak power (0.2Ñ2.3 MW).

The floating particles produced by the excitation discharge for TEA gas laser have been visualized by the pulsed-laser reflection method. The double-pulse discharge experiments have also been carried out to study the effects of the floating particles on the discharge instabilities. Two kinds of gas mixture are used to simulate KrF excimer laser; F2/Kr/He/Ne (gas A) and Kr/He/Ne (gas B). The particles with diameter of the order of 100 jtm are observed in the discharge region. In both gas mixture, the number density ofthe particles increases to ~ 3 particle/cm3 at 200 ms after the discharge, and then decreases to ~ 1 particle/cm3 at 500 ms. On the other hand, the double-pulse discharge characteristics are very different between gases A and B. In the gas A, the second discharge tends to be an arc when the pulse interval decreases to 300 ms. However, the arc does not occur in the gas B. It is deduced that the floating particles of the order of 100 ?m in diameter do not strongly affect the discharge instabilities.

For discharge pumped F2 lasers, the uniformity of the laser medium is important for the laser quality. So that, we developed a one-dimensional simulation code to investigate the effect of the inhomogeneity of the initial electron density. Only a few percent initial fluctuations affected the main-discharge electron number density largely.

Highly efficient Nd:YAG ceramic laser at 1064 nm was demonstrated. Using 1 W LD end-pumping scheme, with 883 mW pumping, 499 mW 1064 nm CW laser output has been obtained corresponding to an optical to optical efficiency of 56.5%. High power CW Nd:YAG ceramic rod laser was also demonstrated for the first time. The maximum output power of 3 1 W with 1 8.8% slope efficiency was obtained at 1064 nm. The potential of Nd:YAG ceramic laser was also discussed.

The nonlinear Kerr refractive index n2 was determined in several crystal hosts, suitable for Ce3+ doping to obtain tunable laser emission in the UV (LiBaF3, LiLuF4, LiCAF, SrA1F5) and in the KMgF3, suitable for Yb2+ doping, a potential laser material in blue region. These parameters were measured by means of Z-scan measurements at 1064 nm and 532 nm, using picosecond laser pulses. The materials under test didn't exhibit two photon absorption effects, within the experimental sensitivity limits. The characterization of these new optical materials is important in view of the development of high peak power laser oscillators and amplifiers.

The observed absorption and emission spectra ofYb:YLF at low temperature show that energy extraction efficiency is improved drastically with the reduced saturation fluence of 9 J/cm2 and the expanded spectral width of 38 nm. Yb:glass also shows a similar temperature dependence of the spectral characteristics to that of Yb:YLF.

Results of consideration of nonlinear dynamics and switching regimes in a solid state laser with a saturable absorber, which take into account spectral properties of both an active medium and saturable absorber with different resonant frequencies, give us multi-stability of their steady states and coexistence of two regular regimes with sequences of nanosecond sinusoidal pulses or picosecond high intensity pulses both with constant in time intensity regime in dependence on the beginning conditions. Switching regimes between coexisting steady states are demonstrated. Another model is proposed for consideration of the polarization of light in a isotropic cavity with crystal active medium and saturable absorber. Steady states both with two directions of linear polarization as result of self induced anisotropy effects are described.

The influence of electromagnetic fields on a DC discharge in a C02:N2:He mixture is studied by means of a Monte Carlo simulation. The HF fields polarised in parallel and perpendicular directions to DC are considered.

The theoretical investigation and numerical simulation of phase conjugation (PC) at stimulated Brillouin scattering (SBS) with feedback is carried out. A case of long pulse PC is considered. At this condition both running and standing phase gratings which responsible for the positive feedback are taken to account. The threshold of PC wave generation and PC reflectivity are calculated. The numerical solution for temporal behavior of PC intensity is obtained.

Considered is recent progress in development AMT GDL Ña high power ~100 kW CW) C02 highly mobile industrial laser of wide application. Substantiated are general composition scheme of AMT GDL and choice of prototype engine for power unit of AMT GDL.

Some important applications of High Power Gas Flow and Chemical Lasers (HPGCL) are aimed to ground level operations. HPGCL are understood here as open cycle machines. It means that after the laser cavity their exhaust gases run out to the ambient atmosphere. Exhaust gas products after resonator cavity cannot be evacuated directly to atmosphere. The atmosphere pressure on the sea level exceeds the cavity pressure by 1 0 Ñ20 times for CO2 gasdynamic lasers (GDL) and by 150 Ñ200 times for chemical oxygen-iodine lasers (COIL).

The method of estimation of Cn2 of laser mixture turbulent flow is proposed based on experimental dependencies of amplitude of gas pulsation on spatial pulsation scale. The connection between degree of nonequilibrium and C,2 magnitude is shown. The boundaries of inertial and viscosity ranges are determined. The estimation of Cn2 is within (3 .. . 14). 10 15 cm2/3 as dependence of gas- discharge current.

Advanced chemical iodine laser technology will logically include novel all gas phase generation techniques for an iodine energy donor and the injection of atomic rather than molecular iodine. Candidate methods are discussed for the creation of an all gas phase energy donor as well as for injecting atomic iodine. This research will lead directly to designs that will be fabricated and tested extensively with detailed diagnostics to evaluate the chosen design's performance attributes. Preliminary analysis and modeling of the ElectriCOlL system concept is presented. ElectriCOIL will reduce weight and simplify both military and commercial chemical iodine laser systems. Potential cost and weight savings are also envisioned as the massive quantities of liquid chemicals will be completely eliminated from the device operation.

In activity the device of the high-power electrodigit laser with optical system and the problem of pressure losses upon gas motion along a closed circuit containing channels in which heat is supplied to and removed from the gas is studied. The object where the pressure losses are studied is a CO2 laser with a crossflow.

The general view of PRS is shown in the paper [1] of the present book. The PRS is known gasdynamic device consisting from the next main elements: supersonic diffuser and supersonic ejector. Traditionally it is utilized for providing of supersonic wind tunnels exhaust.

The influence of shock waves on the excitation discharge for TEA gas laser have been investigated eliminating the other factors which may affect the discharge instabilities, such as gas density depletion, discharge products, residual ions and electrode heating. A shock wave of 1.2 in Mach number is produced by a shock tube with gas mixture of helium and argon in order to simulate the ArF excimer laser. The schlieren photographs of shock wave and direct images of light emifted from the discharge are recorded simultaneously by a high-speed image-converter camera. It is found that, if the shock wave does not reach to the discharge region, glow discharge occurs only in front of the shock wave. Even if the shock wave passes through the middle of discharge region, the glow discharge occurs only in front of the shock wave. However, an arc-like filament through the shock front is also produced. If the shock wave passes through the discharge region, the weak glow discharge can be produced again, however, a surface discharge is also produced between the main electrode and the pre-ionization electrode. It becomes clear that the discharge instabilities depend on the location of shock wave in the discharge region.

A lineselective C02-laser with a 'Variable Reflectivity Grating' (VRG) instead of a 'Variable Reflectivity Mirror' (VRM) was realised. The binary grating has a constant grating-period and -depth and a modulated width of the grating-bars. Stable and unstable resonator designs were investigated.

Properties of laser cavity composed of two plane segmented mirrors placed at half-Talbot distance are considered theoretically in application to gas laser with annular active medium. Discrimination of in-phase mode against other supermodes is demonstrated. For saturable gain model, a critical small gain is found for which the in-phase mode become unstable.

Enhanced birefringence compensation together with dynamic thermal focus correction was demonstrated in a high-power, high-pulse-energy oscillator based on two flashlamp-pumped, 1x10cm Nd:YAG rods. Birefringence compensation was achieved by 90¡ polarization rotation with either a quartz rotator between the rods or with a Faraday Rotator between forward and backward resonator passes. An Imaging Variable Radius Mirror ÑIVRM composed of discrete optics was used as the resonator rear mirror. Imaging was required to re-image the rod principal plane onto itself so as to minimize the birefringence compensation's bifocal tensing sensitivity. Dynamic control of the IVRM radius of curvature was required to compensate thermal focusing variations. Integration into a Reentrant configuration, enabled average output power of 114W @ 20Hz with 3% overall efficiency in a polarized beam. Pulse energy dropped by only 3% compared to "cold" operation.

By analysing the advantages and disadvantages of the unstable resonator with phase-unifying output coupler, An improved unstable resonator is designed. The numerical simulation results indicate, that the fat-field intensity focusing of the improved resonator is better than the conventional resonator.

As a result of experiments and numerical simulation of phase conjugation (PC) in the SBS-mirror with an ordered raster of small lenses, its optimal configuration is determined that has unique properties as compared with the current SBS-mirrors. In current SBS-mirrors in the focused beams the high PC quality takes place at high reflection coefficients only that is often unachievable. The presented SBS-mirror fixedly yields the PC quality that is near to an ideal at any level of SBS saturation, i.e. any reflection coefficient. The simulation results are in good agreement with the experimental data obtained for pulsed Nd laser radiation with using a super-clean SBS-cell and multi-level raster ofsmall Fresnel lenses.

Phase conjugation of CO2 and iodine laser radiation in SBS cell placed into resonator of this same laser has been demonstrated experimentally. The first experimental results on simulating of operation of iodine-oxygen laser with SBS- mirror with the help of photolytic iodine laser are presented. The possibilities of creation of COIL with phase conjugation are discussed.

Each mode inside a rectangular slab-waveguide laser consists of four quasi plane waves propagating at small angles to its axis and inducing specific grating ofthe refractive index in the slab medium. Multimode operation of such laser is a superposition of single modes. Each mode can be spatially separated into two high quality lobes with M2 parameter near l . When geometry ofthe slab is controlled, high stability of a mode pattern can be obtained. This effect is particularly strong when extra single mode selection (for example Talbot filtering) is applied. The experimental evidences were performed on a RF excited CO2 slab-waveguide laser.

The spatial and temporal characteristics of the laser beam extracted from the industrial high power cw CO2 laser are investigated experimentally and analysed. The beam properties are compared for two optical stable cavity configurations characterised by the different values of the Fresnel number. It is found that the beam shape fluctuations, observed for both cavities, are mainly due to the mechanical vibrations of the laser construction. The cavity of the lower Fresnel number emits the beam ofbetter quality and provides better focussing condition in the processing zone.

An unstable double-pass resonator of the hybrid, confocal type has been designed for outcoupling the radiation of a 10 kW chemical oxygen-iodine laser (COIL) with optimum beam quality. The single pass gain length is 20 cm and the measured small signal gain is 1.1 m-1. The near and far field mode distributions have been calculated by solving the Kirchhoff-Fresnel integral for optimum mirror alignment as well as for a misaligned resonator. A particular problem is the provision of glass mirrors with large radii of curvature for the preferred resonator of the positive branch. These radii are a consequence of the low total round trip gain of smaller COILs. The problem has been solved by using one-element adaptive minors. A second problem has been identified in the high sensitivity in angular adjustment of the resonator mirrors.

We discuss the system of laser energy delivery to a remote object using joint action of high-sensitive phase conjugation mirror and of dynamic hologram in optically addressed liquid crystal spatial light modulators. This scheme (the scheme of "frozen" phase conjugation) makes it possible to use the advantages of phase conjugation application in laser systems, whose radiation can be hardly subjected to standard methods of phase conjugation.

The French Commission for Atomic Energy is currently involved in a project which consists of the construction of a 2 MJ/500TW (351-nm) pulsed Nd:glass laser and which will be devoted to Inertial Confmement Fusion (ICF) research in France. With 240 laser beams and almost 10,000 m2 in coated area required, the proposed megajoule-class laser will be the largest laser system ever built in the world. Room temperature and atmospheric pressure deposited coatings such as sol-gel for antireflective (AR) applications and silicone for environmental protective coatings, with high optical and laser-included damage performance, can be applied at a low cost compared to conventional vacuum deposition processes. Today, we are using such a technology to AR-coat prototypes of lenses, windows, blast-shields, debris-shields, flashlamps and harmonic converters required by our proposed megajoule-class laser. This technology has also been selected for the preparation of multilayer highly reflective (HR) coatings for use as cavity-end deformable mirrors in the laser system. Due to their suitability to ensure appropriate deposited optical thickness, room-temperature deposition techniques such as dip-, spin- or laminar-flow-coating have been optimized for such laser coating production.

Results of consideration for bimodal laser regime in aerosol micro particle under the action of the second harmonic of a Nd-doped power glass laser as a pumping source for the mixture of an active substance and a saturable absorber as micro impurity in a spherical micro particle are proposed. Bimodal radiation in aerosol microparticle as spherical cavity is considered. Interactions of modes in presence of impurity as absorber both and enlargement and inhibition effects are described to enlarge sensitivity to impurity.

The general propagation equation of flattened Gaussian beams passing through a paraxial optical ABCD system, where the amplifying and absorbing media with a linear gain and absorption are included, is derived and the applications are illustrated with numerical examples. Keywords: Flattened Gaussian beam(FGB), general propagation equation, ABCD system, linear gain and absorption.

A high-power Raman fiber laser (RFL) with maximum output power of 4.11 W/1239 nm and 2.24 W/1484 nm is obtained using a continuous wave (CW) 8.4 W/1064 nm Yb-doped double-clad fiber laser (DCFL) as a pump, phosphorous-doped fiber (PDF) and cascaded cavities made with fiber Bragg Gratings (FBG). RFL performance for the 300, 700 and 1150 m PDF lengths and output mirror reflectance was experimentally investigated by observing maximum output power, slope efficiency, threshold power, and full-width at half maximum at both the first and second Stokes wavelength.

A theoretical and experimental study investigated beam perturbations on propagation through a MOPA chain, including both optical and medium influences. Analytical models are presented to explain the influence of thermal aberrations on the beam, and these effects are related directly to the change in M2 (quality factor) of the beam.

In high power applications of multimode optical fibers such as high power beam delivery and optical phase conjugation, the estimation of critical power of stimulated Brillouin scattering is important. Nevertheless, the estimations have taken no account of mode dispersion effect to date. In this paper we show that the critical power in a multimode fiber depends on the numerical aperture (NA) of fiber, i.e. mode dispersion, and fmd out the analytical solution taking account ofthe effect. The critical power increases as the fiber NA increases.

Experimental results of investigation in plexiglas support previously published our groups data of JR laser and e-beam excitation in solids of solitonic Wave of Change in Reflection and Conduction (WCRC). Method of single IR detector WCRC registration was applied in addition to JR thermovision method used before (there were used also -5other different methods). Results of slow WCRC components investigations showed that solitonic heat transfer play additional role to usual diffusive heat transfer. This role could be important at some conditions. As the control, the measured in this work WCRC component velocity ~ 0.26 cm/s does not depend from sample thickness which was equal 1.5 and 2.0 mm. Analysis of records treatment by help of (x-t) diagram permit to show many features of studied solitonic excitations lived in the solid sample during many minutes. Irradiation of the front surface by single laser pulse produced WCRC components; in experimental conditions of this work one can see pair components of the same velocity which were born as on front as on rear sample surface. They moved in different directions and reflects from sample surfaces many times with small energy losses. This work was sponsored by RFBR (Russia), project 97-02-17954-a) and 00-02-17249 a).

Lasers have reached a relevant importance as production means, and are integrated in the manufacturing cycles of the most diversified industrial sectors, ranging from micromachining to heavy industry. This memory gives a short account of the state ofthe art of laser application in industrial production.

This paper describes the implementation and numerical evaluation of a transient three-dimensional computer simulation of the CO2 laser cutting process. Utilising Crank-Nicolsen-Finite-Difference equations for the solution of the Fourier heat transfer equation with Newtonian convection, the temperature distribution is predicted. For high accuracy the mesh is of non-equidistant nature, following a Weibull Distribution for the grid spacing. A parallel computation solver will be used, based on Aztec (a parallel iterative library for solving linear systems -www.sandia.gov), to calculate the nodal temperatures using a cluster of two HP J5000 workstations. Included in the solution is the behaviour of the material during phase change, whilst the open structure of the developed software allows incorporation of effects such as surface oxidation, radiation and limited convective flow. The main area of interest is the cutting capability with respect to varying material thickness (e.g. tailored blanks), cutting speed, power of the laser, laser mode, focal spot diameter and material properties, as well as the effect of these parameters on the quality of the cut. Further developments will also be outlined in this paper.

The purpose of this work is to study and model the formation of voluminal defects in laser spot weld on tantalum. Formation of these defects has been studied by radiography X-flash and modelled with FLUENT software.

Laser texturing was performed on the sliding surface of silicon carbide sealing rings, in order to investigate the surface modification in relationships with the laser processing parameters and the tribological performances of the mechanical face seals. As no graphs or data sheets were found in literature on the surface absorption (or reflection) properties of the SiC versus the laser wavelengths, it was necessary to execute a series of screening tests using different laser sources, wavelengths (0.532 ?m, 0.810 ?m. 1.06 ?m and 10.6 ?m) and modes (Normal and Q Ñ Switch) to verify the surface absorption properties of the SiC seal faces. So far, only the pulsed CO2 laser irradiation was proved to be efficient in producing regular shaped holes. Hole size and microstructural modification were related to laser power, pulse duration and spot size. Under selected processing conditions, seal faces were regularly textured producing microholes (80 to 100 ?n diameter) at a distance of about 200 ?m (center to center of the holes). Tribological performances of these mechanical seals under specific proof tests evidenced the increase of the fluid film stiffness and seal life and the reduction of friction coefficient and torque values.

The paper summarizes drilling results obtained in the pulse regime from milliseconds to several hundred femtoseconds. A new drilling procedure for unprecedented accuracy and a model explaining experimental results will be presented.

In this paper we summarise the results of the annealing of a-Si films done at ENEA Frascati by the XeC1 laser facility Hercules and the preliminary results of the characterisation work done on the first Italian industrial high-energy excimer laser, named Hercules L. Some information will be also given on a novel process to obtain homogeneous, large grain poly-Si and on a new homogeniser with zoom.

In this paper, we report the fabrication of a neodymium-doped Gd3Ga5O12 (Nd:GGG) film and neodymium, chromiumcodoped Gd3Ga5O12 (Nd,Cr:GGG) film to realize a self Q-switched laser grown upon Y3A15O12 (YAG) substrate by pulsed laser deposition (PLD) method. Consequently, epitaxial films have been grown.

Shadowgraphic and interferometric analysis of vapor/plasma plumes generated by pulses of a ns-Nd:YAG laser display a distinctive morphology for each of three different processing wavelengths (1064 nm, 532 nm, and 355 nm). Analytical models of shock wave expansion can be applied to determine the total energy stored within the plumes. Electron density distribution measurements reveal the regions of absorption and, using a simple model of inverse bremsstrahlung and photoionization, allow us to estimate absorption coefficients.

The interaction of picosecond pulsed laser radiation with BK7 glass has been investigated. Focusing laser pulses with 40 picosecond pulse duration in BK7 glass leads to plasma and crack formation by evaporation and induced stress. The plasma dynamics is measured by pump and probe techniques using the speckle method with a time resolution of 50 Ps and a spatial resolution of 1 ?m. Plasma transmission and refractive index changes are measured during and after irradiation on a picosecond time-scale. The plasma emission is investigated on the time scale of 10 ps -500 ns by high-speed photography and by time-resolved spectroscopy. The morphology of the cracks is evaluated using Nomarski microscopy.

Chemical and mechanical modifications are expected to be the two major types of side effects in the UV laser ablationbased processing of strongly absorbing molecular substrates. For the systematic characterization of these effects, studies on model polymeric systems are presented. As far as photochemical effects are concerned, UV ablation is shown to promote chemical pathways over the ones observed in the sub-ablative regime. However, the extent of these effects can be limited by an optimal etching depth vs. effective optical penetration depth in substrates of high absorptivity. Concerning mechanical effects, UV ablation is similarly shown to result in structural defects that are not observed in the irradiation at low energy fluence values. In practice, these may be limited by the inhomogeneous and stratified structure of the substrates encountered in real-life applications. The applicability of the results to the implementations of UV laser ablation is exemplified using the procedures that have been defined in laser restoration of painted artworks as a study case. Besides their implications for laser material processing implementations, the present results indicate that UV ablation introduces new physical and chemical paradigms that are of scientific importance in their own right.

The achievement of high quality cleaning of encrusted stone and metals manufacts by optimised laser ablation processes was demonstrated for several deterioration typologies. Here we present some representative cases were intermediate pulse duration Nd:YAG lasers we developed allowed to achieve specific restoration goals.

Laser-assisted generating by the blown powder process is investigated, both, experimentally and theoretically, with respect to layer cross section, grain growth, mechanical testing, track remelting and wall surface roughness compared to postremelting.

Recent research results concerning lasers and the laser ablation of solid and liquid targets are described briefly. The main laser for experiments was KrF laser pumped by an electron beam. The model calculations were performed for the high reprate F2 lasers in mind. An infrared laser and X-ray were taken into account for the model calculations of a space re-entry program and the wall material ablation of an inertial confmement fusion implosion.

In this paper we report measurements (0.3 < ?(?m) < 2) of the diffuse reflectivity and absorptivity of TNT obtained from different manufacturing processes (cast or compressed) and HMX. Particular emphasis is placed on the Nd:YAG laser (? = 1.064 ?m). It has been found that the diffuse reflectivity of TNT increases from about 50%for the cast material to 97% for the compressed one; furthermore, liquid TNT (T >81 ¡C) appears to be quite transparent. The laser beam volume absorption has been computed according to the Kubelka-Munk (KM) semi-empirical model including our own measurements. This diffusion model has been incorporated into a 2D numerical code of heat conduction of reactive materials in order to predict thermal ignition. Numerical applications of this model are in agreement with the concept of "critical laser intensity", providing material phase changes are taken into account. Otherwise, the same numerical model has been used in order to optimize the dopant (CB) concentration in HMX to enhance its thermal ignition. It has been shown that a very low CB concentration (< 1 %) has a dramatic effect on the optical properties of doped HMX.

The Chemical Oxygen-Iodine Laser (COIL) has been studied for several industrial applications. Recent demonstrations have shown that lasers can be highly effective for size-reduction cutting of radioactivelycontaminated structures.

We present results of computer simulations of the launch through the atmosphere of a cone-shaped flyer which demonstrate that laser ablation rockets, using a 1MW ground-based laser, can lift 6kg payloads into low earth orbit. We discuss optimization of delivered mass, mass ratio and energy cost.

There have been various processing methods such as marking, masking, and rapid prototyping system have been typically known as an attractive application ofhigh power laser based on single stroke drawing. We have proposed a segmented pixel drawing (SPD) method which creates a surface by laser in a segmented pixel-base, in which various surface effects can be given such as fluent, opaque, and rugged tones. This can be referred to as a digital way of display. Experiments of SPD method were performed on acrylic surfaces by the pixel processing base with a pixel size of 2mmx2mm. The pixel patterns in this study were variously demonstrated by means of the varied density of the dot-matrix. From the degree of transparency of produce SPD pixels, visual effects of surfaces were analyzed to evaluate gray-scaled tones of produced pixels. The proposed method based SPD would offer a new possibility to realize more sophisticated sculpture on acrylic surfaces supported by visual effects using image information. In addition to the SPD, coloring on acrylic surfaces has been successfully made using the CO2 laser. This coloring process was performed based on a heat effect due to CO2 laser irradiation on acrylic materials, the surface of which was exposed with a dye-containing liquid sheet flow.

This paper reports the results obtained by using a measuring system concerned automatically residual stress by Hole- Drilling Strain Gage Method, in depth, on thin stainless steel sandwich structural panels all laser welded. Different corrugated cores, core geometries (usually trapezoidal ones), face thickness, welding parameters and methodologies (spot or continuous ones) have been carried out.

Ablation of cubic-boron nitride (c-BN) and hexagonal-boron nitride (h-BN) ceramics irradiated with Ti:sapphire laser (110fs) and Nd:YAG laser (100ps) pulses is studied. The relationship between ablation rate and laser fluence for the Nd:YAG laser shows a semi-logarithmic formula for c-BN and h-BN, and also the ablation rate of h-BN by Ti:sapphire laser is observed similar to that by the Nd:YAG laser, except that of c-BN. It is found that there are two different regimes of ablation rate for c-BN as same as metals by Ti:sapphire laser ablation. In addition, it is found from XPS analysis and SEM observation that the area ablated with Ti:sapphire laser shows the BN surface unchanged and has no evidence of melting. These results are different from the ablated surface with the Nd:YAG laser. In short, the microscopic processing of BN ceramics using femtosecond Ti:sapphire laser shows little heat effect and keeps the chemical composition of the ablated surface unchanged.

The interaction of a high power (infrared) laser beam with samples of rock encountered in hard-rock metal mining operations was experimentally investigated. These tests were intended to explore the feasibility of using high power lasers to improve the speed, performance, accuracy, and safety of rock cutting and drilling in mining operations. The current results were compared to similar tests, performed with the same laser, of materials typically encountered in gas and oil well drilling.

The influence of high power CO2 laser beam parameters on the process of the laser elevating of cavitation resistance of steels was investigated. The samples of structural carbon steel and corrosion resistant chromium steel were melted superficially with the laser beam and subsequently subjected to the cavitation loading. It was discovered, that the power distribution in the cross section of the laser beam was of the great importance for the elevating of the cavitation resistance of the steel surface subjected to the multipath scan processing. The dependence of the erosion resistance of the tested materials on the frequency of the laser pulses as well as on the power of the beam was also discussed.

In this paper the possibility of applying the new-generation high-power CuBr laser in precision micromachining is presented. Several industrial applications of the presented CuBr laser set-up are shown.

A controllable, homogeneous stream of metal powder particles is remelted by a focused, coaxial CO2 laser beam at the outlet of a multi-stream nozzle and applied for production of the protective coatings and volumetric structures for prototyping. For the stellite SF6 layers the optical, chemical, and metallographic tests show the fine-grained and chemically homogeneous structures with only a minor presence ofthe Cr/C precipitates and local micro-defects.

Visualization of thermal surfaces has been used in various fields. In this study, thermal monitoring of acrylic surfaces has been performed which were processed by a segmented pixel drawing (SPD) method using a slab-RF excited CO2 laser. The SPD method has been newly developed to make an artistic sculpture. In this method, it is possible to obtain various effects on processed surfaces by controlling processing parameters. This method demands uniform processing shapes in a pixel and reproducibility of results. The purposes of this study are to evaluate the processing results and to investigate the causes of unfavorable processing shapes by capturing thermal phenomena. Thermal distribution on laser processed surfaces obtained by this study can be useful to correct some important data for acrylic laser sculptures. The causes of unfavorable processing can be improved so as to obtain uniform processing shapes.

The employment of laser systems for completely automated welding processes needs an analysis of physical mechanisms by means of mathematical models to correlate the characteristic quality indexes of welding to working parameters. In this paper we describe the application of neural networks method in order to correlate, for different kinds of stainless steel, the melting area and the welding efficiency to working parameters, leaving out of account the knowledge of the chemical and thermo-physical properties of working materials. The results are quite satisfactory even if a direct search of the optimal process conditions is not possible.

The purpose of this work is to understand keyhole formation observed during pulse Nd:YAG laser welding. We determine the power deposit law during laser pulse. We present a calculation of the energy deposit law by Fresnel reflections. The aim is to calculate the ray trajectory in keyhole to deduce the local absorption. A previous study allows to observe keyhole formation using flash X-ray radiography, and determine evolution of keyhole geometry. These results are compared with a previous experimental determination of the interaction efficiency.

Recently, much attention has been focused upon generation of ionized particles from solid target by coulomb explosion using high intensity and ultrashort pulse laser since the high intensity electric field can easily ionize to the maximum charge of the element. This paper reports the generation of molecular carbon ions and decrease of multiple charged ions in case of irradiation of low power nanosecond laser pulse prior to femtosecond laser pulse. The changes in the ion current waveform have been analysed by time of flight measurement with 76.4cm of drift section. This observed waveform was interpreted using energy conservation law.

Experimental investigations of the effects of laser irradiation on the response (sensitivity) of HgCdZnTe photoconductors (p type) working at ambient temperature have been performed. In-band (band III) irradiation of these devices has been carried out with two collinear CO2 laser beams: a CW probe laser (beam diameter ? = 60 ?m) modulated by an acousto-optical modulator at a frequency of 500 kHz with a low energy output level giving the reference signal of the tested detector, and a second pulsed laser (named pump laser with ? = 300 ?m) used as the irradiation source. The pulse characteristics are a maximum energy of 200 mJ and a pulse duration of 2.5 ?s. These two CO2 lasers are part of an JR detector test bench design for experimental studies in JR band II (3-5 ?m) and band III (8-12 ?m) but only the experiments in band III are described herein. The irradiation densities range from 20 ?J/cm2 to 6.6 J/cm2. Both reversible effects, when the morphological damage threshold is not reached, and irreversible ones above this threshold have been observed. Moreover, it has been shown that irradiation produces a dramatic sensitivity decrease due to alloy concentration redistribution and thus causes a modification of the initial gap energy.

The influence of the X-rays preionization on the performance of a 312 cm3 active volume phototriggered HF laser has been studied for Ne/SF6/C2H6 and SF6/C2H6 mixtures at a fixed SF6 partial pressure (78 mbars). Parameters are the Xrays dose (0.1 -10 mR), the pumping current pulse duration (60-155 ns), the electric charge deposited in the medium (< 3 mC), and the ethane partial pressure (< 10 mbars). It is shown that, without ethane in the mixture, arcs develop close to the discharge peak current as soon as the pumping pulse duration exceeds 100 ns at a fixed deposited charge value, in the whole range of X-rays dose values studied. An efficient discharge stabilisation effect can be obtained by addition of ethane, even without X-rays preionization and with a pumping pulse duration value as high as 155 ns. Nevertheless a low ethane concentration in the mixture is required in order to optimise the laser performance. In such conditions an arc free discharge, and correlatively high output laser energy and efficiency values, can be obtained only with use of the preionization. Optimum laser performance can be achieved with a low X-rays dose.