SEDL / STP / STP1028-EB / STP18591S

An Investigation of Laser Processing of Silica Surfaces

Weber, AJ
Air Force Weapons Laboratory Kirtland Air Force Base, New Mexico

Stewart, AF
Air Force Weapons Laboratory Kirtland Air Force Base, New Mexico

Exarhos, GJ
Air Force Weapons Laboratory Kirtland Air Force Base, New Mexico

Stowell, WK
Air Force Weapons Laboratory Kirtland Air Force Base, New Mexico

Pages: 8    Published: Jan 1988

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Abstract

An initial set of experiments has been conducted to determine the practicality of laser processing of optical substrates. In contrast to earlier work, a high average power CO² laser was used to flood load the entire surface of each test sample. Fused silica substrates were laser polished on both surfaces at power densities ranging from 150 to 350 W/cm². During each test sequence sample surface temperatures were recorded using a thermal imaging system.

Extensive pre- and post-test characterization revealed that surface roughness and scattering of bare silica surfaces were reduced while internal stress increased. Laser damage thresholds were found to increase only for certain conditions. Changes in the microstructure were observed. These preliminary experiments have demonstrated that laser processing can dramatically improve the optical properties of fused silica substrates. Optimization of processing parameters will be the subject of future work.