Laser Damage Measurements at CO2 and DF Wavelengths.
NAVAL WEAPONS CENTER CHINA LAKE CALIF
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Preliminary results from laser damage tests conducted with CO2 and DF lasers on samples mounted in a newly constructed ultrahigh vacuum sample chamber are reported. The lasers operate single mode and the pulse lengths are 100 nsec for CO2 and about 500 nsec for DF. A precise method of focusing which permits accurate determination of power densities is described. Incorporated in the test chamber are a scanning electron imager, an optical microscope, a profiling Auger system and a charged particle collector for in situ analysis. Analytical results are presented and implications for physical damage processes are discussed. Measurements in nitrogen on aluminum samples indicate that the threshold for N2 breakdown is reduced some 20 times in the vicinity of the aluminum surface. Laser supported gas plasma waves are formed which shield the surface, and no physical damage occurs for single 100 nsec pulses even at power levels of 10 GWsq cm. However, in vacuum damage does occur at about the expected power levels.
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