Pulsed HF/DF Laser Damage in Window Materials.
NAVAL WEAPONS CENTER CHINA LAKE CALIF
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Laser damage thresholds are reported for several alkali-halides, alkaline earth fluorides, ZnSe, As2S3, sapphire, spinel and quartz at HF 2.7 micrometers and DF 3.8 micrometers wavelengths. A low pressure, transversely excited, double discharge laser and two different focal length lenses were used. A gaussian spatial beam distribution was obtained by spatially filtering out high order modes in the far field of an unstable resonator cavity. Sapphire was found to have the highest bulk damage threshold of the materials tested, 100 GWsq.cm at 2.7 micrometers peak intensity on axis. The damage threshold was found to vary as the inverse of the spot diameter. The measurements also show that all of the materials evaluated in this effort are surface damage limited when exposed to pulsed HF or DF laser radiation. Evidence concerning the roles of material manufacture, surface finishing and laser irradiation conditioning in the damage process are presented.
- Lasers and Masers