Design features and problems in development of autonomous mobile DF laser systems of various power, with exhaust of laser gas flow to the atmosphere, are considered. Various versions of such laser systems design are discussed. The ways and means to reduce the mass and size of the main laser subsystems are analyzed, which allows DF laser with high output power up to ∼300 kW to be installed on various vehicles, like trailer trucks, ships, and so on.

In this paper we report on studies of a continuous wave laser at 1315 nm on the I(²P_1/2) → I(²P_3/2) transition of atomic iodine where the O₂(a¹▵) used to pump the iodine was produced by a radio frequency excited electric discharge. The electric discharge was sustained in He/0₂ gas mixtures upstream of a supersonic cavity which is employed to lower the temperature of the continuous gas flow and shift the equilibrium of atomic iodine in favor of the I(²P_1/2) state. The results of experimental studies for several different flow conditions and mirror sets are presented. The highest laser output power obtained in these experiments was 510 mW in a stable cavity composed of two 99.993% reflective mirrors. Blaze II laser model was used to model typical ElectricOIL conditions in the post-discharge region through the laser cavity. Overall the Blaze II simulation model appears to be predicting many of the observed qualitative trends that have been measured and the quantitative comparisons to data are reasonable.

The CW and HRR facilities developed at the Prospective Research Department of TRINITI and their application for various laser - matter interactions are discussed. The high power lasers are as follows: the CW self - sustained discharge CO₂ lasers LT-1 (output power up to 5 kW) and PM-1 (output power up to 85 kw); the e-beam sustained discharge HRR CO₂ lasers: with traditional gas mixture composition at atmospheric pressure in the discharge chamber (output power up to 100 kw) and with gas mixture of atmospheric air and 5% C0₂ at reduced pressure (output power up to 30 kw); the e-beam sustained discharge cryogenic CO lasers: with a subsonic gas flow CW laser (average power ~85 kw) and with supersonic flow of the active mixture quasi-CW laser (specific output energy up to 40 Jg^-1 and efficiency ~14%). These laser facilities are used for studies on interaction of laser radiation with different materials, metals, rocks, etc.

A 300 J/210 ns XeCl laser system has been developed. Five lasers in MOPA chains characterized by different pumping techniques are described. Also, the main experimental results of the Photons are given.

Formation of nanosecond discharges in air under atmospheric pressure at different voltage pulse polarities and various discharge gap geometry has been investigated. It has been shown that in a wide range of experimental conditions at high voltage nanosecond pulses used, electrode construction or voltage pulse polarity have no essential effect on volume character of a discharge. With negative voltage pulses applied to a potential electrode, no matter what construction it has, X-ray radiation is being recorded both from anode surface and volume. Under a voltage pulse of positive polarity, X-ray radiation is recorded with the lower intensity. It has been shown that with subnanosecond voltage pulse rise time and a discharge of diffusion character, X-ray radiation is observed fiom a brightly glowing corona discharge area. The mean energies and velocities of fast electrons in nitrogen have been calculated. It was shown that head-on collisions establish the fact that the mean velocity of a group of fast electrons is permanent. These head-on collisions of electrons lead to emission of X-ray radiation from a volume.

We report on a detailed gain measurements and analysis of the extremely efficient supersonic chemical oxygen-iodine laser (COIL) recently developed in our laboratory (Appl. Phys. Lett., 85, 5851 (2004)). The power and spatial distributions of the gain and temperature across the flow were measured for different supersonic nozzles with both staggered and non-staggered iodine injection holes, different injection locations along the flow and nozzle throat-heights. 40.0% efficiency was measured for 1 s at the early stage of operation, followed by a sustained 35.5% chemical efficiency for 20 s. By carefully studying and optimizing the operation of the chemical generator, 0.73 yield of singlet oxygen was obtained for conditions corresponding to the highest efficiency.

An alternative method of atomic iodine production for a Chemical Oxygen-Iodine Laser (COIL) was studied. The proposed all-gas process include reaction of chlorine dioxide (C1O₂) with nitrogen oxide (NO) followed by subsequent reaction of atomic chlorine with hydrogen iodide (HI). In difference to our previous experiments, atomic iodine was produced separately from the primary flow. The generated atomic iodine was injected through two rows of sonic orifices into the supersonic part of the converging-diverging nozzle, 2 mm downstream the nozzle throat. A penetration of atomic iodine to the primary flow was substantially improved by introducing additional nitrogen downstream the iodine injector. This led to an increasing I number density and static temperature. Inversed order of reactants injection (HI-NO instead of NO-HI) substantially increased the production efficiency. Some results were explained by 2-D modelling. Number density of atomic iodine up to 1.6 × 10¹⁵ cm^-3 was attained in laser cavity with nearly 100% efficiency.

Radio frequency discharge CO overtone lasing with output power of 50 W was demonstrated with supersonic cooling system. The lasing was observed on 9→7, 10→4 and 11→9 vibrational transitions at around 2.7 μm wavelength. Fundamental band lasing was observed within 4.9 - 5.7 μm spectral range. Output power of 2.1 kW with efficiency of 21% was obtained in fundamental band. Modeling experiments on electron-beam sustained discharge overtone CO laser demonstrated that the time interval needed to populate high vibrational levels by W pumping is considerably more than transit time from the supersonic nozzle to laser resonator axis in the RF facility. Possibilities of supersonic overtone CO laser design improvement, for instance, gas pre-cooling and excitation in supersonic cavity were discussed.

Experiments were performed at 100-J-class GARPUN KrF laser installation on optimization of e-beam pumping and amplification of 20-ns pulses in e-beam-pumped amplifiers with gain volumes of 10 × 10 × 100 cm³ and 16 × 18 × 100 cm³. Amplified spontaneous emission (ASE) was measured in the near field close to the output window and in the far field along the amplifier axis. Suppression of transverse ASE by amplification of a laser signal was also investigated. The experimental data were compared with numerical simulations of e-beam transport using Monte Carlo code and 3-D numerical simulations of large-aperture single-pass and double-pass KrF laser amplifiers. Finally, the verified numerical codes were applied for optimization studies of large-scale KrF amplifiers with output energy up to 10 kJ being developed for Inertial Fusion Energy application.

A high-pressure CO₂ laser with a discharge initiated by a subnanosecond electron beam formed in the laser operating medium under pressure 5 atm. Radiation energy of 40 mJ in active volume of ~ 4 cm³ at radiation duration of 20 ns has been obtained. Laser operation at pulse repetition rate (p.r.r.) of up to 5 Hz has been demonstrated. Specific energy input of ~0,07 J/cm^3.atm have been realized in laser operating gas mixture CO₂:N₂:He = 1:1:6 under pressure of 5 atm on the course of a pulsed non-sustained discharge with pre-ionization.

The consideration of the solid state laser with the electro-optical regenerative negative feedback is carried out in this work. The mode-locking regime is shown experimentally in this laser with the envelope duration about 1.5 ms. Possibilities of the technological and medical laser-plasma applications of such laser are shown too.

The dependence of resistance of a discharge on time is discussed in this work. The linearized effective ionization coefficient near breakdown voltage is introduced. It is shown, that the time of a discharge formation depends only on the square under a curve of a dimensionless overvoltage on a discharge gap, instead of from its curve shape.

Calculation of wave-front phase distortions caused by small-scale periodical optical inhomogeneities of active medium and by thermal deformations of mirrors and windows in large-scale cw DF laser is performed. The ways of reducing aberrations influence are offered. It shows a possibility to reach the angle divergence of the output laser beam close to diffraction limit.

The burning voltages of a self-sustained volume discharge (SSVD) in SF₆ and SF₆-C₂H₆ mixtures subjected to a 10.6 μm pulse CO₂ laser irradiation are measured on varying the laser fluences and delays between the laser and voltage applications over a wide range. These voltages are found to considerably increase as the specific absorbed laser radiation energy increases. The observed effect is treated in terms of enhanced electron attachment due to the capturing of electrons by vibrationally excited molecules of SF₆. Also given are the results of measuring the burning voltages in a non-irradiated confined SSVD in the same mixtures versus the specific electric energy deposited. Most plausible scenarios of vibrational relaxation in SF6 are qualitatively discussed and, on this basis, some inferences about the peculiarities of electron attachment to vibrationally excited molecules of SF₆ are drawn. At lowest values of the specific absorbed laser radiation energy, realized in the present experiments, no significant impact on the discharge voltage was observed. Together with data on the burning voltages in a non-irradiated SSVD this fact has allowed some conclusions about the role of electron attachment to the discharge-produced vibrationally excited molecules of SF₆. In particular the results obtained appear to give no evidence for the electron impact vibrational excitation of SF₆ is capable of considerably affecting the operating characteristics of current electric discharge non-chain chemical HF lasers using SF₆ and SF₆-based mixtures.

Results of experimental and theoretical investigations of discharge XeCl laser with 30 ns (FWHM) radiation pulse duration are presented. Laser generates the laser energy of 0.35 J with 2.2% total electric efficiency. Calculated laser radiation parameters and discharge parameters have a good agreement with experimental results. Influence of basic plasma-chemical processes in discharge on laser output and efficiency is shown. Maximal laser efficiency relatively pumping power was 3.7%.

Numerical simulations of self-pulsing oscillations in fast-flow laser fitted with unstable generator and multipass amplifier were performed. Possibility of the control of the depth of power modulation was shown. A number of governing parameters can be used to vary the regime of lasing in the system. Modulation of output power depending on the pumping rate was observed experimentally in fast-flow CO₂ laser.

The results of numerical simulation for fast-axial-flow gas discharge CO₂ lasers are presented. Quasi-one-dimensional consideration of the processes for powefil CO₂ lasers with conic discharge tubes shows that laser operation may be more effective in the case of tubes which are narrowed down fiom anode to cathode provided that gas flow is directed towards the cathode. On the contrary, when tube is narrowed down from cathode to anode, no any advantage in the laser operation may be received. The calculated quantities are in satisfactory agreement with the available experimental data.

Characteristics of CO₂ laser with 27.1 MHz transverse RF discharge in quartz tubes were significantly improved by distributed gold catalyst. Parameters of catalytic layer were optimized for RF discharge conditions to avoid RF-current shunting while maintaining good catalytic properties. Output power 0.77 W/cm and maximum efficiency 18.5% were demonstrated in prototype laser.

An all-solid-state, diode-pumped Nd:YLF laser system that produces fiducial timing signals at three wavelengths (fundamental, second, and fourth harmonics) has been developed and tested. It will be used as a primary timing reference for the OMEGA facility diagnostics. Performance results of the new OMEGA fiducial laser are reported here.

The enhancement of optical inhomogeneities of active medium of high-power fast-axial flow CO₂ laser is coupled with increasing of the isobaric fluctuations of temperature and density in turbulent flow due to nonuniform heat-releasing.

Spectral, energy and temporal parameters of a pulsed discharge in xenon are studied. It is shown that the use of unidirectional current pulse instead of oscillating one improves radiation power in the range 200-350 nm, while duration of the radiation pulse at half-maximum decreases. The use of SOS-diodes in the pulse generator allows obtaining the maximal radiant intensity 64 kW/sr in the range 200-350 nm and the pulse duration of ~2 μs FWHM.

Fluorine-resistant coatings for fused silica windows of high-energy KrF lasers with damage thresholds as high as 20 J/cm² have been developed using two comparative deposition techniques: ion-assisted e-beam evaporation and magnetron ion sputtering. They were evaluated by means of atomic-force microscopy, Fourier spectroscopy, and laser-damage testing in large irradiated spots ~ 1 cm at powerful GARPUN KrF laser.

Laser aided direct metalimaterial deposition (DMD) process builds metallic parts layer-by-layer directly from the CAD representation. In general, the process uses powdered metaUmaterials fed into a melt pool, creating fully dense parts. Success of this technology in the die and tool industry depends on the parts quality to be achieved. To obtain designed geometric dimensions and material properties, delicate control of the parameters such as laser power, spot diameter, traverse speed and powder mass flow rate is critical. In this paper, the dimensional and material characteristics of directed deposited H13 tool steel by CO₂ laser are investigated for the DMD process with a feedback height control system. The relationships between DMD process variables and the product characteristics are analyzed using statistical techniques. The performance of the DMD process is examined with the material characteristics of hardness, porosity, microstructure, and composition.

Indigenous development of high power CO₂ laser technology and industrial application of lasers represent two important mandates of the laser program, being pursued at Centre for Advanced Technology (CAT), India. The present paper describes some of the important laser material processing studies, involving cladding and dissimilar welding, performed in authors' laboratory. The first case study describes how low heat input characteristics of laser cladding process has been successfully exploited for suppressing dilution in "Colmonoy6" (a nickel-base hardfacing alloy) deposits on austenitic stainless steel components. Crack free hardfaced deposits were obtained by controlling heating and cooling rates associated with laser treatment. The results show significant advantage over Colmonoy 6 deposits made by GTAW, where a 2.5 mm thick region of dilution (with reduced hardness) develops next to substrateiclad interface. The next work involves laser-assisted deposition of graded "Stellite6" (a Co-base hardfacing alloy) with smooth transition in chemical composition and hardness for enhanced resistance against cracking, esp. under thermal cycling conditions. The following two case studies demonstrate significant improvement in corrosion properties of type 304L stainless steel by laser surface alloying, achieved through cladding route. The following case study demonstrates engineering of fusion zone microstructure of end plug dissimilar weld (between alloy D9 and type 3 16M stainless steel) by controlled preferential displacement of focused laser beam, which, in-turn, enhanced its resistance against solidification cracking. Crater appearing at the termination point of laser weld is also eliminated by ramping of laser power towards the end of laser welding. The last case study involves engineering of fusion zone microstructure of dissimilar laser weld between type 304 austenitic stainless steel and stabilized 17%Cr ferritic stainless steel by controlling welding parameters.

We optimized the TEA CO₂ laser operation and selective dissociation process of Freon22 with the laser for efficient enrichment of C-13 isotope. We maximized the yield of C-13 isotope by irradiating Freon-22 towards red edge of its absorption spectrum and utilized laser energy efficiently employing a novel Linear Multi-Pass Cavity (LMPC) for irradiation at constant laser fluence. We produced C-13 at 1 5mghr rate with 240mJ laser energy at 100Hz repetition frequency, which corresponds to a one of the highest reported production efficiency factor of about 1.7×10^-7g/J.

Results of experimental research and qualitative modeling of the process of channeled penetration of high-power (0.3 - 3.5 kW) CW-CO₂ laser beam into water are presented. Experiments were made on: laser power threshold for channel formation; channel development phase (10^-3-10^-1s); quasi-stationary phase. The experiments revealed that the depth and mean diameter of the channel fluctuate at fiequencies in the range of 1-10² s^-1. The channel depth is 3-6 cm at laser power of up to 3 kW, depending upon the conditions for heat exchange in the water vessel. The conclusion is made, based on a qualitative hydrodynamic model, that geometrical and dynamical parameters of the channel (its depth, mean diameter, the velocity of the depth increasing) depend upon the intensity of turbulent heat transfer from the channel liquid walls into the bulk of the liquid. Simultaneously, the noticeable role play the evaporative losses of laser energy inside the free space of the channel, filled with evaporating microdroplets, torn-off from liquid walls of the channel by the process of capillary-evaporative instability. The principal point of the physical model consists in the assumption that energy and momentum balances of the channel can be attributed to radial transfer of vapor condensation enthalpy into liquid walls and to the equilibrium of dynamic pressure of vapor radial flow impinging the walls with the sum of hydrostatic and Laplacian pressures of the liquid.

Self-focusing and filamentation of nearly-Gaussian femtosecond laser pulses propagating in photosensitive silicate glass was investigated. The filamentation was visualized by the precipitation of NaF nano-crystallites along the beam pass after post-exposure treatment of photosensitive glass, which provides a direct proof that ionization of silicate matrix takes place along the filament propagation lines. Theoretical model of the multi-filamentation based on the propagation of a Gaussian beam with elliptical transverse intensity profile modulated by a spatial noise in a medium with multi-photon absorption is proposed. Self-action of the femtosecond Gaussian-Bessel pulses in borosilicate glass was observed at high fluence. This model reproduces qualitatively the dotted damage lines observed after the beam propagation in borosilicate glass.

We describe an application of laser cleaning of metallic wheels with a Q-switched Nd:YAG laser. The beam is divided in four parts injected into fibers, sent on an automated machine for stripping the protective varnish on metal sheets, parts of large electrical motors, before soldering of cylindrical spacers via an electrical discharge.

The process of laser ablation of fused and crystal silica and natural silicates induced by pulsed CO₂ laser irradiation (total pulse duration of 35 μs, laser pulse rise time of 0.1 μs, pulse energy of 10 J) has been studied. By action of focused laser radiation at the surface of samples the appearance of erosion plume at the irradiated surface take place. For study of ablation regimes the frame image of laser induced plume by use of high speed photography method with 2 microsecond expose of each frame have been made. It has been observed the formation of two different type of laser plume during laser pulse action. First type plume represents a long narrow plume with the onset close to start of laser pulse. The maximal length of this plume is about of 20 millimeter. The second type of plume represents a conical plume with the onset, which is late from laser pulse start for a few microsecond. The first type plume expands in to laser beam direction. The second type plume expands normal to the surface. The velocity of laser plume particles by means of measurements of moment transferred into samples during laser pulse action has been measured. It has been obtained, that value of this velocity varies in region of (l÷3)10³ m/s in dependence of laser fluency value. The appearance of first time plume have a threshold which equal to 0.30 kJ/cm² whereas the appearance of second type plume have not a such threshold and may take place at low laser fluency. We believe, that the first type plume connects with the selective ablation of Si_mO_n complexes whereas second type plume connects with the thermal heating caused by dissipation of laser energy in to system of low frequency acoustics phonons.

We have developed high power transverse flow (TF) CW CO₂ lasers up to 15kW, a high repetition rate TEA CO₂ laser of 500Hz, 500W average power and a RF excited fast axial flow CO₂ laser at the Centre for Advanced Technology and have carried out various material processing applications with these lasers. We observed very little variation of discharge voltage with electrode gap in TF CO₂ lasers. With optimally modulated laser beam we obtained better results in laser piercing and cutting of titanium and resolidification of 3 16L stainless steel weld-metal for improving intergranular corrosion resistance. We carried out microstructure and phase analysis of laser bent 304 stainless steel sheet and optimum process zones were obtained. We carried out laser cladding of 316L stainless steel and Al-alloy substrates with Mo, WC, and Cr₂C₃ powder to improve their wear characteristics. We developed a laser rapid manufacturing facility and fabricated components of various geometries with minimum surface roughness of 5-7 microns Ra and surface waviness of 45 microns between overlapped layers using Colmonoy-6, 3 16L stainless steel and Inconel powders. Cutting of thick concrete blocks by repeated laser glazing followed by mechanical scrubbing process and drilling holes on a vertical concrete with laser beam incident at an optimum angle allowing molten material to flow out under gravity were also done. Some of these studies are briefly presented here.

A novel approach to control the combustion processes by laser-induced excitation of vibrational or electronic states of target molecules is investigated. Target molecules are supposed to use to enhance the chain reactions in the gaseous combustible mixtures. The computations based on the extended physical-chemical model involving chemical processes with vibrationally and electronically excited molecules show that laser-induced excitation of O₂ molecules to the a¹Δ_g and b¹Σ_g⁺ electronic states makes it possible to reduce considerably the ignition threshold in CH₄(H₂)/O₂ (air) mixtures and to intensify the conversion of CH₄ to H₂ during oxidation of hel-rich CH₄/air mixtures. A simultaneous excitation of O₂ molecules to the electronic and vibration states enhances these processes additionally.

A physical and mathematical model of non-stationary laser remote welding for line lap welds and its numerical approximation are presented. The model takes into account the variation of the beam incidence angle and the focus position. The calculated results correspond very well to the experimental data obtained by means of a CO₂-laser and a Nd-YAG laser.

The refractive index of paper was determined by measuring the propagation delay of photons in optically cleared paper boards. The determination was based on the assumption that photon propagation delay achieves minimum value as the paper is optimally cleared. The measured paper sheets was made from elemental chlorine-free market pulp, i.e. fully bleached, unbeaten, softwood kraft pulp. Nine different clearing agents with a refraction index between 1.329 and 1.741 were eLuperimented with. According to the streakmem measurements, the refractive index of the test paper was 1.557.

The experimental AVLIS setup showed good results for Nd-150 enrichment. The original method of experimental data processing allows determining the internal parameters of separation cell and the further optimization.

The laser optoacoustic method is applied for nondestructive evaluation of residual stresses in metals. Theoretical background establishes the acoustoelasticity relationships between applied biaxial stresses and deviations of the longitudinal wave velocity in solids. The experimental technique bases on laser thermoptical excitation of nanosecond ultrasonic pulses on the surface of samples under study and their backward mode piezodetection with a high temporal resolution. The samples, produced from stainless steel, had thickness from 1.67 mm to 8.87 mm. Welds are made up by means of electronic beam overheating of the samples with different intensities of the beam. Plane distributions of relative longitudinal wave velocity deviations, produced by stresses, were obtained.

It is shown that the presence of surface contaminant layer exerts influence upon the parameters of ionic bunches from laser plasma formed under interaction of superintense femtosecond laser pulses with solid targets. The usage of pulsed laser pre-cleaning of the targets leads not only to reducing Contaminant ions but also to emerging of additional high-energy component in spectra of bulk ions. We showed that one can control the parameters of ionic bunches from plasma such as maximum and mean ions charge, maximum energy of bulk substance ions by adjusting of the preceding time of the cleaning laser pulse. Thus, using the silicon target and pulses of moderate intensity (2⋅10¹⁶ W/cm²) it is possible to produce the ionic bunches with maximum ions energy of about 400 keV and with a charge state of up to +12.

In the present work the properties of laser-induced MW discharge was investigated experimentally. For these purpose both Slieren and interferometry techniques has been developed. Laser spark is created by impulse Ruby laser (6943 A, 0.22 J pulse energy and 25 ns-pulse duration) in focal point of short-focus lens (12 mm). This point is placed in the vicinity of the main maximum of MW-field in the focal area of parabolic mirror. The X-range impulse MW generator with output power 180 kW and pulse duration 1,2 μs via radiating system illuminates the focal area. Digital synchronous Schlieren system is used for visualisation of shock wave structures, exciting by laser spark and initiated MW discharge. The temporal evolution of optical density fields for breakdown plasma and thermal well, arising on this place are studied using the high-sensitive intro-chamber Fabry-Perot interferometer. Investigation area of supersonic flow is placed between the interferometer mirrors, which is installed inside the test chamber. In this case the chamber windows are not included in the optical path of the interferometer and it sensitivity for intro-cavity phase objects becomes very high. Intro-chamber plane interferometer Fabry-Perot has fineness about 14, light orifice diameter 86 mm and distance between mirrors 650 mm. Interferometer operates with single - frequency, stabilising (σλ/λ≤10^-10)He-Ne laser with output power 1 mW . The interference picture is analysing by the high-sensitive gated (exposition time 1-500 μs) CCD camera.

Laser microhole drilling using radially and tangentially polarized Q-switched laser radiation has been analyzed comparatively. Tangential polarization exhibited a significantly higher drilling speed compared to radial polarization. Light attenuation through interaction with the walls of a microhole was found to be weaker in the case of tangential polarization than in the case of radial polarization, thus leading to the assumption that the observed higher drilling rates utilizing tangential polarization are due to more energy being deposited at the bottom of a microhole. The required radiation has been generated using a Q-switched Nd:YAG laser resonator in a configuration that exploits thermally induced birefringence to render the laser resonator stable only for radial polarization.

For two different pulse shapes, Gaussian and piecewise, the electron acceleration by a circularly polarized laser pulse is considered. First, with a piecewise shape similar to Gaussian, it is shown that the acceleration results for different pulse shapes coincide well, especially for strong self-generated magnetic field in the acceleration direction. Then the effect of extending the rising part or falling part of piecewise pulse shape on electron acceleration is examined. For falling part, no new result is obtained but spreading the rising part reduces the electron energy gain.

A research on the laser cut formation by means of a physico-mathematical model and software is presented. The processes of energy absorption, chemical reactions, and vaporization in the film under the supersonic gas flow forces, accounting for the compression shocks along the front, are analyzed.

The seam formation in laser beam welding of fillet weld is considered. The aim of modelling is to predict the position, shape and size of the weld cross section dependent on the applied process parameters and the material properties of the workpiece. The numerical simulation is based on solving the equation of conservation of energy by the finite difference method within a continuous simulation domain. The zones of the simulation domain are different in respect of the thermodynamical material properties and the velocities of matter motion. The position of the inner and outer interfaces between the zones results from the numerical solution of the equilibrium equation of the interface forces. The mass balance is set up inclusive of the filler wire, the thermal expansion of the base and filler metal and the gap width between the jointed parts. The effect of the wire feed rate on the formation of laser beam welded butt with the displacement of edges inclusive tailored blanks and fillet welds in steel and aluminium alloys is verified by experimental results.

Due to the demands of the market to increase efficiencies and power densities of gas engines, existing ignition schemes are gradually reaching their limits. These limitations initially triggered the development of laser ignition as an effective alternative, first only for gas engines and now for a much wider range of internal combustion engines revealing a number of immediate advantages like no electrode erosion or flame kernel quenching. Furthermore and most noteworthy, already the very first engine tests about 5 years ago had resulted in a drastic reduction of NO_x emissions. Within this broad range investigation, laser plasmas were generated by ns Nd-laser pulses and characterized by emission and Schlieren diagnostic methods. High-pressure chamber experiments with lean hydrogen-methane-air mixtures were successfully performed and allowed the determination of essential parameters like minimum pulse energies at different ignition pressures and temperatures as well as at variable fuel air compositions. Multipoint ignition was studied for different ignition point locations. In this way, relevant parameters were acquired allowing to estimate future laser ignition systems. Finally, a prototype diode-pumped passively Q-switched Nd:YAG laser was tested successfully at a gasoline engine allowing to monitor the essential operation characteristics. It is expected that laser ignition involving such novel solid-state lasers will allow much lower maintenance efforts.