Temperature,Stress and Optical Phase Difference for a Window Transmitting a CW Laser Beam.

摘要

A crystal of CVD zinc selenide was placed in the steady 2kW beam of a 10.6micrometer laser. The beam was approximately gaussian with 1/e radius of 0.24cm. Fifty frame per second motion pictures were taken of the time dependent optical distortion as observed with He-Ne light and a Mach-Zehnder interferometer. Thirty-one circular fringes originated in 10seconds. A theoretical solution is derived for the heating rate,rate of development of thermoelastic stress and rate of change of optical path as a function of time,radius,and surface cooling rate. The expressions are obtained in closed form for a gaussian laser beam and presented in non-dimensional form. The theory is then compared with the experiment. For the first five seconds of heating,there is good agreement. In the next four seconds,the heating rate is higher than calculated and the discussion contains some possible explanations. (Author)