Dependence of gain and laser power for Cu-II 780.8-nm transition on the diameter of a segmented hollow cathode discharge

The dependence of laser performance and discharge characteristics on the diameter of a segmented hollow cathode discharge for the Cu-II 780.8 nm transition is presented. This transition has a special importance since its upper level is common to potential CW VUV laser transitions (150-170 nm). Laser tubes with internal diameters of 2, 3, 4, and 5 mm were investigated. Decreasing the diameter resulted in an increased gain for a given current (up to 100 %/m in the 2-mm diameter, 5-cm-long tube at 1-A current). The highest output power was obtained from the large-diameter tubes (20 mW from a 5-cm-long, 5-mm-diameter tube at 2-A current, without optimizing the output coupler). This work is a part of a series of investigations aimed at the optimization of the segmented hollow cathode discharge which has already been found to be the most efficient type of discharge for cathode sputtered metal ion lasers