Comparison of He-Cd+white-light laser oscillations in longitudinal and transverse hollow-cathode tubes

The results of a direct comparison of laser oscillations in two different hollow-cathode discharges, i.e., longitudinal and transverse, used for exciting the blue (441.6 nm), green (533.7 nm and 537.8 nm), and red (636.0 nm) lines of the Cd+-ion in an He-Cd mixture are presented. The design of the discharge tube, which allows a direct comparison of the laser properties of both discharges in the same hollow-cathode segments and laser cavity is shown. The results showed the superiority of the longitudinal hollow-cathode discharge in generating the blue, green, and red lines simultaneously. The transverse hollow-cathode discharge more efficiently generates the green lines if the other laser lines are absent. This suggests the application of the longitudinal hollow-cathode discharge for white-light He-Cd+ lasers.