Optical distortion due to gas-dynamic motion in a photolytically pumped cylindrical laser cavity

Abstract

We give a general solution for the growth of refractive disturbances caused by gas-dynamic motion accompanying diffuse photolytic pumping of a cylindrically symmetric laser medium. Results are derived in sufficient generality to reveal scaling with all important system parameters except bleaching of the pump transition. A simple bounding relation is derived which ensures the preservation of near-diffraction-limited laser beam quality. The results apply to any cylindrical gas laser pumped by an external diffusely illuminating light source. The amount of optical disturbance is characterized by the pump-band optical depth or extinction and the thermal energy release per pump-band absorption event. Specific details are given for the photodissociation atomic iodine laser; the usefulness of buffer gases to increase the heat capacity of the active medium is quantified.