NOVEL ASPECTS OF THE OPTOGALVANIC EFFECT IN THE CO2-LASER MEDIUM

Dynamic properties of the optogalvanic signal in the CO2 laser medium are investigated as functions of the modulation frequency of the incident laser beam and the gas pressure. It is determined that a positive optogalvanle effect occurs in the gain medium when the gas pressure is sufficiently low, while a negative optogalvanic effect occurs at higher gas pressures. The mechanism of the signal inversion is explained by the competition between the collisional relaxation process and the spontaneous emission from the upper laser level. © 1990 The Japan Society of Applied Physics.