Optimum laser energy and the interpulse afterglow in a Cu/CuCl double pulse laser

Optimum laser pulse energy for a copper/copper chloride double pulse laser is shown to be a function of processes occurring during the interpulse afterglow. The dependence of optimum laser energy on buffer gas pressure is explained with the experimental electron density measurements and afterglow model results. It is shown that as the electron temperature relaxes from its initially high value during the afterglow, the CuCl is depleted and the copper is largely ionized. At high buffer gas pressure, electron temperatures are lower than optimum. Laser pulse energy is limited since the resulting small CuCl dissociation rate provides few ground state copper atoms. It is reported that the afterglow model was unable to reproduce the local minimum in laser pulse energy seen experimentally at intermediate buffer gas pressure. It is concluded that this indicates that processes besides those considered may be important during the afterglow in determining optimum laser energy.