Influence of the pre-pulse plasma electron density on the performance of elemental copper vapour lasers

A detailed computer model for the kinetics in an elemental copper vapour laser (Cu-Ne-H₂) has been used to investigate the importance of the pre-pulse electron density on the performance and lasing characteristics of such a device. The results show that the laser output power and operating efficiency are increased by 65% and 100%, respectively, at a pulse repetition frequency of 17 kHz, if the pre-pulse electron density is reduced by a factor of 5-10. Modelling of the plasma kinetics during the afterglow period suggests that such a reduction is brought about when trace quantities (∼ 0.3%) of HCl are introduced into the plasma to increase the electron density decay rates via dissociative attachment reactions. The predicted improvements in laser performance which occur as a result of a reduced pre-pulse electron density are consistent with the observed operating characteristics of Kinetically Enhanced copper vapour lasers which use HCl-H₂-Ne buffer gas mixtures.