Optical quality of the active media of high-power cw chemical lasers

The influence of inhomogeneities of the refractive indices of the active media of high-power cw chemical (CWC) hydrogen fluoride lasers on the quality of the output beam is discussed. The spatial compensation of the small-scale periodic inhomogeneities of the active media of CWC lasers for a certain geometry of the nozzle array is examined and the conditions for manifestation of this effect are indicated. Specific CWC-laser nozzle array schemes, designed taking into account such compensation, are presented. The large-scale inhomogeneities, associated with the chemical processes in the active medium and with the downstream pressure rise and having in the main the form of an optical wedge, are estimated. The contributions of the resonant and nonresonant components to the refractive index of the active medium are examined. It is shown that, in the operation of a laser in the amplification regime, the resonant component of the refractive index exceeds appreciably the nonresonant component and this actually makes the main contribution to the distortions of the wavefront of the CWC laser output radiation.