Continuous-Chemical-Laser Cavity Studies

Abstract

The extent of the lasing medium along the jet axis in a continuous chemical laser is variable under changes in the jet temperature, pressure, velocity, reactant concentration, etc. The laser cavity must be readily tunable to accommodate the changes in lasing length in order to maintain maximum multimode laser power operation in a high-Fresnel-number cavity under variation in the jet parameters. In addition, as an aid in understanding laser performance, it is desirable to have the means to determine the multimode laser intensity distribution in the lasing region for various conditions in the jet. Techniques are presented to determine the optimum optic axis position for maximum multimode power operation, and to measure the intensity distribution along the jet and extent of the lasing medium. A flat and spherical mirror tuned during laser operation determine peak laser power position and the lasing length of the jet (typically 1. 6 in. in N2 flows). Axial local power surveys are made with this same cavity array coupled with a movable aperture which limits lasing to a small fraction of the total lasing region. A visual display of lasing length and the power distribution pattern along the jet, both axial and off-axis, is obtained by coupling power out of one of a pair of optical flats into a lucite block.