High-power ArXe laser

Abstract

The discharge conditions of the multiatinospheric e-beam sustained Ar-Xe laser are investigated. It is observed that the quasi-stationary period of a laser pulse depends on the e-beain current, the discharge power deposition and the gas density. The laser efficiency can be as high as 8%. The pulse energy with optimum efficiency depends strongly on the gas density. The best results are obtained for 4 bar with an input power of 8 MW/i. The pulse duration with corresponding output energies are 12 ts with 10 J/l and 16 s with 16 J/I for e-beam currents of 0.4 and 0.9 A/cm2 respectively. An analysis of the quasi-steady state conditions that include the effects of electron collision mixing and atomic quenching is presented. The effects of output power saturation by the fractional ionisation and atomic collisions are in agreement with the observations. The analysis clarifies the optimum performance conditions. INTRODUCTIONThe research interest in the Ar-Xe laser has been strengthened considerably because this high power laser has an efficiency up to 8 per cent. produces pulse energies above IOJ/liter and power densities of several MW/liter'8. Also the continuous 910 with RF excitation in waveguide structures produces output power densities of about 0.5W/cm3. It is essential for this laser that three-body-collisions are quite frequent so that high gas densities are required. Molecular ions like Ar and ArXe and subsequent volume recoinbination of these ions with electrons will then occur. In this process the system works as a four level system that uses the inetastable state as the ground state in the excitation scheme. Discharge electrons ionize these metastable atoms. In three-body-collisions molecular ions are fonned followed by volume recombination and the decay of the excited Xe-states to the upper laser level. After the laser transition the lower level finally decays to the inetastable state. In this way it closes a cycle that contains a high quantum efficiency.Although this scheme looks relatively simple the kinetic chain is complicated by the competition processes of quenching and excitation by the electrons and atoms. The production process, with the molecular ion formation and dissociative recoinbination. for instance, depends on the gas temperature, so that the gas heating has a strong influence on th output pulse or output power. For pulsed operation of an e-beam sustained system with constant input power we observed that the maximum obtainable output power depends strongly on the gas density and that only for a limited period the output power of the pulse is constant. An analytic model has been used to analyse the quasi-stationary behaviour. It is found that the increasing gas temperature during the pulse effects the apparent saturation of the radiation production. The pulse duration as a functions of input power density and gas density will be presented together with the analysis ofthe process.

Influence of water vapour impurities on the atomic Xe laser

“…It is one of the most promising NPLs in the IR region for high-power applications [4]. This laser has a high efficiency (maximum 8%) [5][6][7] and a low threshold [1,8]. It is a potentially high-energy (up to 50 kJ) NPL with pulse lengths of ∼10 ms [9].…”

“…Laser oscillation is observed for gas mixtures of Xe with other inert gases (He, Ar, Kr). Many experiments have been performed on the 1.73 µm line of Xe using an Ar(99.5%)-Xe(0.5%) gas mixture with total pressures ranging from 0.5 to 4 atm [1][2][3][4][5][6][7][8][9][10][11].…”