Abstract

A Gaussian beam travelling through an absorbing medium may exhibit some special ring patterns arising from the thermal self-deforcusing effect^(1)–(3) In this paper an expression for the beam divergence was obtained from an optical ray equation and a thermal conductivity equation as follows: The first term is a nonlinear divergence angle, which depends on the incident laser power Po, the absorption coefficient ∝, the thermal conductivity coefficient K, temperature-refractive index coefficient dn/dT, and beam radius w. The second term is an initial divergence angle according to the curvature radius of Gaussian beam at the front end medium R.

© 1985 Optical Society of America