Thermal lensing: a practical a

摘要

Abstract: In this paper, an attempt is made to estimate the degree of focussing that results from thermal deformation of solid laser windows without solving the heat equation. Steady state conditions were assumed for spherical, parabolic, and gaussian thermal deformation. Calculations are performed for germanium, potassium-chloride, and zinc-selenide assuming CW power absorption of the window at the infrared wavelength of 10.6 microns. Formulas for the time dependant focal length and temperature rise of the window are developed using the thin lens equation. These formulas are expressed in terms of the density, window dimensions, specific heat, incident power, coefficient of thermal expansion, absorption coefficient, refractive index, refractive index temperature gradient, and laser beam spot size.!8