EXPERIMENTAL AND THEORETICAL INVESTIGATIONS OF A XECL PHOTOTRIGGERED LASER

Detailed experimental and theoretical studies of a phototriggered XeCl excimer laser have been performed through the development and the experimental validation of a zero-dimensional model, which self-consistently coupled the solution of the Boltzmann equation, the kinetic equations of heavy particles, the electrical circuit and the photon equations. A detailed description of the XeCl molecule and of the associated kinetics has been taken into account, together with the effect of the gas temperature growth on the stimulated emission cross section. The model predictions have been compared with the experimental results obtained from a complete set of time-resolved electrical and optical diagnostics including emission and laser absorption spectroscopy on various xenon and neon states. A specific output energy of 7.6 J I-1 and an efficiency of 3.5% are reported, which indicates the effectiveness of the phototriggered discharges to produce high-performance excimer lasers. Simple rules allowing the calculation of the required voltage for best efficiency or maximum output laser energy are given. It is shown that these optimum voltages can be estimated from a solution of a steady state Boltzmann equation requiring only knowledge of the gas mixture composition. At low capacitance values, some discrepancies between the model predictions and the experiments appear whenever the initial voltage is higher than the voltage corresponding to the maximum output energy. The spectroscopic investigation of the discharge has pointed out that these discrepancies can be ascribed to the onset of an instability, which cannot be predicted in the frame of a zero-dimensional model.