Experiment and Analysis of Laser Oscillation and Atomic Processes in Positive-Column He-Cd Discharge

Abstract

The observations of the 4416 Å laser output power and spontaneous emission of several Cd⁺ spectral lines, as well as the measurements of electron temperature and density are carried out on the positive-column He-Cd⁺ laser discharge (3.2mm main bore). Further, the plasma balance equation is extended to a mixture gas in the free fall as well as in the ambipolar diffusion, and then applied to the He-Cd⁺ laser plasma with the consideration of the mean free paths of He and Cd ions in the plasma of the binary mixture. The equation is solved under the typical conditions for lasing, (He pressure of 4 Torr, discharge current of 120 mA and evaporator temperature of 190 to 260°C), in combination with the population densities derived from our previous experiment. The results give the total number density of Cd ions and all the rates for ionization in the plasma. Then, the various rates for the population to the 4416 Å laser lower level are estimated and discussed in relation to the oscillation mechanism of the laser, especially with regard to the population process of the laser lower level.