Visible and Infrared Laser-Induced Damage to Transparent Materials
Semiannual technical rept. 1 Jan-30 Jun 1973
RAYTHEON CO WALTHAM MA RESEARCH DIV
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By using Q-switched and mode-locked NdYAG lasers, the authors have measured the dependence of intrinsic damage fields on both lattice disorder and laser pulse duration and have interpreted the results in terms of avalanche breakdown. It was found that severe lattice disorder such as present in fused silica measurably increases the intrinsic damage intensity. The breakdown field was also found to increase when the pulse duration was reduced below about 1 ns. Damage from inclusions was observed in various dielectric coatings. It was found that inclusions having diameters approximately 3.5 micrometers were responsible for damage from Q-switched pulses and that inclusions with diameters less than approximately 0.4 micrometers were responsible for threshold damage from 20 ps mode-locked pulses. An operating CO2 TEA laser has been assembled for use as a source for damage measurements. Future cavity refinements are needed to restrict lasing to a TEM00 mode with peak powers in excess of about 150 KW.
- Lasers and Masers