Excitation mechanism and plasma parameters in pulsed argon-ion lasers

Pulsed argon-ion lasers show several interesting properties at high currents. To understand the inversion mechanism, the plasma parameters, electrical conductivity, electron temperature, and electron density were measured with the double-probe method for the pressure range from 15 to 50 mtorr in a 6-mm-bore tube. When the discharge current increases from 100 to 700 amperes at the optimum pressure for laser oscillation, these parameters increase from 250 to cm^-1, from to K, and to 10¹⁵cm^-3, respectively. At the maximum electron density, the percent of ionization appears to be in excess of 100 percent, as a result of the pinch effect and double ionization. It is certain that this ring discharge is at least ionized very strongly. In a 10-mm-bore tube, only the electron temperature and density were measured. The current dependence of the laser output power at high currents is interpreted with those results. Excitation mechanisms of high-current argon-ion lasers are discussed with experiments and theories for strongly ionized plasmas.