Acoustical wave effects on the beam quality of a high energy CO electric discharge laser

A high efficiency CO, e(-)-beam sustained electric discharge laser has been operated at 500 J/pulse with near diffraction limited beam quality. The high Fresnel number cavity configuration employs a confocal unstable resonator with a geometric magnification of approximately 2.5. In spite of the high quantum efficiency of the CO laser, significant fractions of the pumping energy are absorbed in the gas as bulk heating giving rise to acoustic waves that refract portions of the light from the beam axis. The strength of the density waves have been measured using interferometric techniques and correlate well with the observed refraction of the laser light.