Nikolai G. Ivanov

The development of a long-pulse excimer laser system

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.

Peculiarities of an e-beam-pumped nonchain hf laser

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.

High-power XeCl laser system MELS-4k with a 25X25-cm output aperture

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 1014 W/cm-2cr-1 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.

Evolution of spatial and energy characteristics conically divergent beams in the XeF(С-A) amplifier

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/cm2. 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 Eout = 3.8 J. In this mode, the maximal radiation intensity reaches a value of I = 148 GW/cm2.

Wide-aperture discharge-pumped XeCl laser triggered by x-ray and e-beam

Output radiation performances of XeCl laser with 10x10x80 cm3 active medium dimensions depending on pumping circuit parameters, intensity and uniformity of preionization have been researched. It was shown that radiation pulse duration and accordingly discharge uniformity depend first of all from preionization homogeneity and not from its intensity.

Experimental study on a long-pulse excimer laser system

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-1 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.

Discharge-pumped XeCl laser triggered by e-beam

Output radiation performances of XeCl laser having 5.5 1 active medium volume depending on electric circuit parameters, intensity and uniformity of preionization are researched. The maximum output radiation energy of 7 J and pulse duration of 160 ns were obtained only in the presence of modulation of discharge current. It is shown that first of all laser efficiency depend on preionization homogeneity and not from its intensity. The largest laser output realized only in case the small percentage of Xe in gas mixture (≤0.25%).

Stimulated rotational and vibrational Raman conversion of high-quality XeCl laser beam in hydrogen

An experomental study of stimulated Raman conversion of high-coherent XeCl laser radiation in H2 has been carried out. About 50 vibrational-rotational components were realized with a circularly polarized laser beam pump. High spatial and temporal coherence of conversed radiation was obtained. Quantum efficiency of conversion in first vibrational Stokes was achieved 95%.

Using SBS for improvement of output beam divergence in excimer laser systems

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 10-5 rad divergence of laser beam. Use the threshold conditions of Brillouin scattering allowed to increase the XeCl laser radiation contrast from Pgen/Pnoise approximately 4 up to Pgen/Pnoise equals 106 - 107.

High-quality beam formation in wide-aperture excimer lasers and laser systems

The experimental research results of an laser radiation in excimer lasers and laser systems with output aperture up to 25 X 25 cm2 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.