Wavefront Distortions Caused by Thermally Induced Mirror Deformations.
ROME AIR DEVELOPMENT CENTER GRIFFISS AFB N Y
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Mirror distortions can seriously hamper coherent signal detection, employed in laser radar, especially in high power applications. These distortions reduce signal sensitivity by reducing the heterodyne efficiency of coherent optical detection due to the induced wavefront phase mismatch between signal and the optical local oscillator. This study analyzes thermally induced mirror distortions which occur when the mirror face is heated by intense, Gaussian distributed laser radiation. These distortions are derived by considering the body strains brought about by the longitudinal and radial temperature gradients generated within the mirror. Conditions affecting reduced mirror distortions are then determined by examining the effects of base cooling on the radial temperature variation throughout the thickness of the mirror. These results are applied to the metals invar, brass, aluminum, copper and silver in an effort to determine the metal and cooling conditions which will provide minimum distortions over a wide range of kilowatt laser power levels and power distributions. Author
- Infrared Detection and Detectors