Acoustic Plasma Effects in the Diffusion-Cooled Working Medium of an Electric-Discharge CO2 CW Laser*

We have studied the effect of shallow modulation of the discharge current on the burning regime and the plasma parameters of a diffusion-cooled glow discharge in CO2/N2/He laser gas mixtures. We have established that modulation of the discharge current leads to excitation in the discharge of pulsations in the acoustic pressure, the electric current, and the intensity of the generated laser radiation, with the frequency of standing acoustic waves arising in the discharge tube and also with the frequencies of the current modulation, its harmonics, and combinations of all these frequencies with the frequency of the current pulsations in the power supply. We have shown that when self-sustaining resonant oscillations in the discharge current are excited or when the current is modulated, the IR luminescence intensity from the upper laser level of the CO2 molecule and the power of the radiation generated by the laser vary because of plasma heating in the positive column of the discharge, due to its contraction in the acoustic wave field initiated by the current pulsations.