Investigation of optical inhomogeneity of the active medium in a CO2 laser with hf excitation

An investigation was made of the optical inhomogeneity of the active medium in a fast-flow closed-cycle CO₂ laser with a transverse hf capacitative discharge and a 5-liter active volume. A lateral-shear interferometer employing a pulse-periodic copper bromide vapor laser was used in the measurements. Optical inhomogeneity of the wedge type in the flow direction and of the positive lens type in the transverse direction was found to be present at the start of the discharge, and there was a 2-mm-thick layer at the electrodes. The inhomogeneity was considerably smoothed out toward the end of the discharge zone along the flow direction. The gain and gas temperature distributions in the active medium were measured in the discharge current direction. The results obtained prove that the active medium homogeneity in a laser with an hf capacitative discharge is higher than that when a self-sustained discharge is pumped by a dc current.