High-fidelity modelling of Cs-Ar and Cs-Xe exciplex pumped alkali lasers with temperature-dependent energy pooling and ionization reactions

Abstract

Parametric measurements of pulsed output energy from the four-level exciplex pumped alkali laser (XPAL) for Cs-Ar, Cs-Kr, and Cs-Xe as a function of input pump energy and temperature show a strong dependence on temperature. All three Cs-rare gas mixtures show a D 2 line laser performance increase with temperature towards a peak efficiency, followed by a decrease as temperature is increased beyond a peak performance point temperature. Prior simulations of Cs-Ar XPAL measurements indicated that energy pooling from the 6 2 P 3/2 state of Cs was significant at higher temperature and it was hypothesized that the addition of temperature-dependent reaction rates may be important. This paper presents new BLAZE Multiphysics TM simulations using temperature-dependent energy pooling reaction rates baselined to available experimental rate data. Also included are photoionization and Penning ionization reactions. These new calculations for Cs-Ar and Cs-Xe (Cs-Kr not yet simulated) show that the inclusion of temperature-dependent energy pooling rates and the subsequent onset of significant ionization can explain the rise and fall of XPAL performance with temperature with reasonable accuracy. Further, while Cs-Xe has a much stronger absorption characteristic than Cs-Ar, simulations show that the energy well present in the Cs-Xe B 2 Σ + 1/2 state increases the fraction of the Cs-Xe B-state relative to the Cs-Ar B-state, thereby resulting in energy output levels of Cs-Xe similar to that of Cs-Ar.