The results of studies on the formation of a volume discharge in an electric-discharge XeCl laser with a maximum specific pumping power of 4.7 MW/cm<sup>3</sup> are presented. It is shown that with a half-cycle duration of discharge current of 20 ns, the radiation pulse duration on the base is 100 ns. A good agreement between the experimental and numerical results obtained with the XeCl laser was demonstrated. Plasma-chemical processes occurring in a volume discharge at a maximum electron concentration in the plasma of ~ 7×10<sup>15</sup> cm<sup>-3</sup> are considered.
Results of experimental studies of the chemical HF laser with a non-chain reaction are presented. The possibility of the total laser efficiency of 5 % is shown when a traditional C-to-C pumping circuit with the charging voltage of 20-24 kV is used. It is experimentally shown that the specific radiation output energy of 21 J/l is reached at the specific pump energy of 350 J/l in SF<sub>6</sub>/H<sub>2 </sub>= 14/1 mixture at the total pressure of 0.27 bar.
The results of the formation and amplification of positive chirped 0.1 ns laser pulse at a central wavelength of 470 nm in the laser system THL-100 are presented. It is shown that a front-end allows forming a radiation pulse with a Gaussian intensity profile and the energy up to 7 mJ. At amplification in XeF(C-A) amplifier of the pulse with 2-5 mJ energy a saturated mode is realized and 3.2 J output laser beam energy is reached.
The paper presents the results of studying the possibility of remote detection of explosive vapors in the atmosphere on the basis of the LIDAR principle with the use of the laser fragmentation/laser-induced fluorescence approach. A project of the mobile automated scanning high-performance UV LIDAR for remote detection of explosives is presented. Experimental data on the detection of vapors of trinitrotoluene (TNT) and mixture of hexogen (RDX) and TNT (Composition B) at a distance of 13 m are obtained. The sensitivity of the LIDAR detector of explosive vapors is estimated. For TNT vapors, the sensitivity limit of the LIDAR detector is estimated as 1×10<sup>-12</sup> g/cm<sup>3</sup> at the probability of detection of P= 97%.
The development of effective discharge pulse-repetition KrF laser is informed. Research the possibility of forming in this laser long laser pulse with input pump energy for a few half periods of the discharge current are presented. In the repetitively pulsed regime (up to 100 Hz) laser provides laser pulses with energy of 1 J and duration of 60 ns at the base. The maximum total efficiency of the laser is 3%. The results of studies on the formation in this laser of narrowband radiation with a wide spectral band tuning are reported. The possibility of forming a radiation pulse with a linewidth 2 pm, energy 0.15 J and spectral tuning region 247.5-249.6 nm are demonstrated.
Evolution of spatial and energy characteristics start pulse with energy of 0.8 mJ in duration of 2 ps in the XeF(С-A) amplifier of THL-100 laser system have been studied experimentally and by numerical simulation. Laser radiation energy E = 2 J was obtained experimentally. In that work we present the 3D-model amplification of conically diverging laser beams, that takes into account the spatial inhomogeneity of the pump, and the geometry of THL-100 laser system amplifier. Description and the test results of the model are submitted. At the start pulse energy 0.8 mJ, the calculated radiation energy at the XeF(С-A) output reaches 2.4 J. Simulation results shows that, maximal intensity of the laser radiation in this mode reaches P = 60 GW/cm<sup>2</sup>. The evolution of the energy and space-time structure of the laser beam in the amplifier was investigated. It is shown that in the ideal case (excluding the processes of nonlinear interaction of laser beam with an active medium), at the start pulse energy of 5 mJ, the energy of the laser radiation at the output of the amplifier is increased to E<sub>out</sub> = 3.8 J. In this mode, the maximal radiation intensity reaches a value of I = 148 GW/cm<sup>2</sup>.
Results of 2D simulation of a KrF laser are presented. In the model, inhomogeneities of distributions of the electric field and plasma particle concentration are considered. It is demonstrated, that the laser energy depends not only on the value of the total pump power, but also from its spatial distribution. The shape of the electrodes is a major determinant of the spatial distribution of pumping power in the active medium. For electrodes with small radii of curvature, the pumping power in the center of the discharge may be too high. This leads to the suppression of radiation in the center of the discharge and the limitation of the laser energy.
The possibility of remote detection of traces of high energetic materials using laser fragmentation/laser-induced fluorescence (LF/LIF) method is studied. Experimental data on the remote visualization of traces of trinitrotoluene, hexogen, composition B, octogen, and tetryl obtained at a distance of 5 m with a scanning lidar detector of traces of high energetic materials are presented.
The study results of a high-quality radiation formation in the UV and IR spectral ranges for using in lidar systems to detect the vapors of nitric oxide and complex molecules, including data radicals, are discussed. The influence of the existing cavity losses on the radiation formation in the dispersion cavity is studied.The development of KrF laser with a broad spectral band adjustment of 247.5-249.5 nm and high energy are presented about. The possibility of pulse formation with duration of 30 ns in CO<sub>2</sub> laser is shown.
Detailed model study of THz generation by CO<sub>2</sub> laser down-conversion in pure and solid solution crystals GaSe<sub>1-x</sub>S<sub>x</sub> is carried out for the first time. Both forward and backward collinear interactions of common (eo-e, oe-e, oe-o, oo-e, ee-o) and original (ee-e, oo-o) types are considered. Possibility of realization, phase matching angles and figure of merits are estimated for line mixing within 9 μm and 10 μm emission bands, as well between them. Dispersion properties of o- and e-wave refractive indices and absorption coefficients for GaSe, GaS and GaSe<sub>1-x</sub>S<sub>x</sub> crystals were preliminary measured by THz-TDS, approximated in the equation form and then used in the study. Estimated results are presented in the form of 3-D figures that are suitable for rapid analyses of DFG parameters. The most efficient type of interaction is eo-o type. Optimally doped (x = 0.09-0.13) GaSe<sub>1-x</sub>S<sub>x</sub> crystals are from 4 to 5 times more efficient at limit pump intensity than not doped GaSe crystals.
Results of experimental measurements and numerical simulations of the N<sub>2</sub> and XeF<sub>2</sub> gas pressure effects on the gain characteristics are presented in the paper. It is experimentally and theoretically is shown that maximum total gain (5-6)×10<sup>4</sup> achieved at a pump energy E = 240 J, 0.2 Torr XeF<sub>2</sub> and 0.5 atm N<sub>2 </sub>pressure. Increasing and decreasing of N<sub>2</sub> pressure leads to decrease of the gain. The possibility of the XeF(C-A) amplifier operation in a generator mode is discussed and the theoretical study results of generation are presented. It is shown that an annular laser radiation with energy up to 8.5 J can be obtained. The study results of the influence on the laser energy of N<sub>2</sub> and XeF<sub>2</sub> pressure and reflectance coefficient of output mirror are presented.
This paper presents the results of the research of possibility of remote detection of explosive traces using laser fragmentation/laser-induced fluorescence (LF/LIF) approach. Experimental data on the detection of traces of cyclonite in fingerprints at a distance of 4 m are presented.
The design and characterization of a THL-100 multi-terawatt hybrid laser system based on a Start-480M titaniumsapphire
starting complex and photochemical XeF(C-A) amplifier with a 25-cm aperture are described. The first
experiments results are presented. A laser beam peak power of 14 TW at 475 nm wavelength has been attained.
Development of KrF laser system for lidar designed for detection of the compound molecules containing a nitric
oxide is presented. The system consists of the master oscillator and the amplifier operating at pulse repetition rate up to
100 Hz. Laser radiation having energy up to 0.2 J and bandwidth of 2 pm is smoothly tuned in a spectral range of 247.6-249.5 nm.
Terawatt hybrid (solid state/gas) laser (THL-100) system on the basis of Ti:sapphire starting complex (50 fs, 5 mJ)
and photochemical XeF(C-A) amplifier with the aperture of 24 cm is presented. Laser system is built at Institute of High
Current Electronics SD RAS, Tomsk, Russia. The design and peculiarities of optical pumping of XeF(C-A) amplifier,
methods of pump power measuring, gain distribution across the active volume are discussed. The results of numerical
modeling of the output parameters simulation are presented and one compared with first experimental results.
Terawatt hybrid laser (THL-100) system on the basis of Ti:sapphire starting complex and final amplifier with
gaseous optically driven active media on XeF(C-A) molecules is presented. Laser system is built at Institute of High
Current Electronics SB RAS, Tomsk, Russia. It consists of Ti:sapphire starting complex and photochemical XeF(C-A)
amplifier. The active media of amplifier pumped by VUV radiation has 24 cm aperture and 110 cm length. The results
of numerical modeling of the output parameters and first experimental results are presented in this paper.
In the present paper the perspectives using of excimer media for formation of a short high power laser radiation pulses are discussed. Research results of Gas Laser Laboratory of IHCE SD RAS, Tomsk, Russia in this area are shown.
In present paper the results of an experimental research of a qualitative radiation formation with pulse duration of 3.5 and 0.15 nanoseconds in one discharge block of XeCl laser with pump pulse duration of 35 ns at use resonator with SBS mirror are presented.
Results of experimental and theoretical investigations of discharge XeCl laser with 35 ns (FWHM) radiation pulse
duration are presented. Laser generates the laser pulse energy of O.6 J with 2% total electric efficiency and 100 Hz pulse
repetition rate. 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 3.5%.
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%.
Influence of the discharge burning conditions on output radiation parameters and overall performance of a discharge pumped XeCl laser with pump pulse duration of 20 ns is experimentally investigated. It is shown that a 3.9 J/l•atm maximal specific output laser energy from the active medium is realized in the discharge consisting of the
strongly pronounced macro heterogeneities. Laser efficiency of a 2.7 % is reached at discharge current density of a 1.2-1.4 kA/cm<sup>2</sup>.
Results of experimental and theoretical investigations of pump discharge and generation of XeCl laser with 0.21 J laser energy, 2.7% electric efficiency nad 20 ns (FWHM) pulse duration are presented. The influence of step ionization, dissociative attachment and recombination processes on an active volume spatial uniformity and radiation parameters is shown.
A 250 J/210 ns four-stage XeCl laser system named Photons 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.
A four-stage XeCl laser system named Photons has been developed for studying laser interaction with materials. The Photons are outlined and preliminary results characterizing the system are given. The master oscillator Photon-1 can provide “seed” light with laser energy of about 40mJ, pulse duration of about 250ns and good beam quality of nearly diffraction-limited divergence angle and narrow line width less than 1 cm<sup>-1</sup> for whole system. The output energy of laser system of 251J has been obtained by four-stage amplification. The synchronization among five lasers is realized by the combination of low voltage timer, high voltage synchronic generators and compensated cables. The demonstration shows Photons good operation with low jitter of less than ±20ns.
Experimental results of long-pulse generation in X-ray preionized XeCl lasers with a 9 x 7 cm<sup>2</sup> and 5.4 x 3 cm<sup>2</sup> apertures are described. Lasers operate at Ne-Xe-HCl mixture with pressure up to 4 atm. Paper-oil pulse forming lines and rail-gap switch for discharge pump was used. An 2 - 10 J output with optical pulse duration of 250 - 300 ns (FWHM) have been extracted. Problems and peculiarities of long laser pulse formation are discussed.
Experimental results of long-pulse generation in X-ray preionized XeCl lasers with the 9x7 cm<sup>2</sup> and 5.4x3 cm<sup>2</sup> apertures are described. The lasers operate in the Ne-Xe-HCl mixture with the pressure up to 4 atm. Paper-oil pulse forming lines and a rail-gap switch for the discharge pumping were used. A 3.5 and 10 J output with the optical pulse duration of 250-300 ns (FWHM) has been extracted.
This paper reports on experimental results and simulation of XeCl-laser with short laser pulse duration. Experimental investigation was aimed at obtaining of maximal lasing power and efficiency. The processes taking place in plasma and in resonator were simulated. Temporal evolutions of plasma particle density as well as simulation rates of processes of ionization, recombination, attachment and formation of XeCl molecules in excited states were obtained. Simulation dependencies have been analyzed; mechanisms of initial parameter effect on lasing power have been established.
An X-ray preionized XeCl laser with a large aperture (9x7 cm) is described. Laser operates at Ne-Xe-HCl mixture with pressure up to 4 atm. Paper-oil pulse forming lines and rail-gap switch for discharge pump was used. 10 J output with optical pulse duration up to 300 ns (FWHM) have been extracted from active volume 5.4 l with an electric efficiency 1.2%.
Formation of high quality laser beam and the reasons of wave front distortion in electric discharge XeCl laser had been investigated. The influence of macro and micro-inhomogeneities in active volume on radiation divergence is discussed. Possibility of amplification of diffraction limited laser beam practically without distortion is shown.
Formation of a diffraction limited divergence and obtaining a high contrast of radiation in electric-discharge XeCl laser system due to SBS are investigated. Possibility of a correction of laser beam wave-front distortion on an astigmatic and a spherical aberrations and on a refractive coefficient non-uniformity in optics elements and atmosphere is shown. Correction of laser beam wave-front having the 20- fold distortion of diffraction limited angle using phase- conjugate Brillouin mirror allowed to obtain the initial angle of 2 X 10<SUP>-5</SUP> rad divergence of laser beam. Use the threshold conditions of Brillouin scattering allowed to increase the XeCl laser radiation contrast from P<SUB>gen</SUB>/P<SUB>noise</SUB> approximately 4 up to P<SUB>gen</SUB>/P<SUB>noise</SUB> equals 10<SUP>6</SUP> - 10<SUP>7</SUP>.
Development of a long-pulse master oscillator with pulse duration of 300 ns (FWHM) is reported. The oscillator is made on the base of a long-pulse spark preionized XeCl-laser pumped by a self-sustained discharge using a double- discharge circuit. The pre-pulse is formed by a generator with an inductive energy storage and a semiconductor opening switch. The laser produces up to 1,5 J in pulse with total duration up to 450 ns.
Influence of active medium non-uniformity of 300 ns pulse pump electric discharge XeCl laser on divergence of amplified radiation has been investigated. It was shown that in case of 100 - 200 kW/cm<SUP>3</SUP> pump power the laser active media allows to amplify the diffraction limited laser beam practically without distortion. In case of 400 - 500 kW/cm<SUP>3</SUP> pump power after 120 ns of discharge burning the micro- and macro-inhomogeneities appeared. These inhomogeneities increased the amplified radiation divergence. It was established that basic reason of a divergence degeneration was inhomogenity of gain profile in active medium. In our case amplification increased when the macro-inhomogeneities developed and the absorption increased when the micro- inhomogeneities developed in local regions of active medium.
High power XeCl laser system and experimental results of diffraction limited laser beam amplification are described. Beyond the preamplifier, the 5 cm X 6 cm laser beam contained 50% of the radiation energy in the diffraction core. At the output from the system an irradiation brightness of 2 X 10<SUP>14</SUP> W/cm<SUP>-2</SUP>cr<SUP>-1</SUP> was obtained. Minimum divergence near 0.05 mrad of output beam was restricted to turbulence of air and optics elements. A numerical model of the amplification of the radiation, taking onto account the influence of the amplified spontaneous emission, was developed.
The experimental research results of an laser radiation in excimer lasers and laser systems with output aperture up to 25 X 25 cm<SUP>2</SUP> and output laser energy up to 200 J is described. The laser beam divergence 0.01 mrad have been obtained. The problems of the diffraction limited divergence formation of laser beam are discussed.
The review of the papers devoted the research of excimer lasers with SBS medium is presented. The possibilities of using SBS for phase-conjugation, pulse compression, formation of narrow-band and highly directed radiation are discussed.