Laser induced damage in fused silica contaminated by Al film

Fused silica substrates were artificially contaminated to estimate the resistance against laser damage. Uniform thin contamination films (about 8 nm thick) were deposited on the substrates by Al sputtering. The laser induced damage threshold (LIDT) was tested at 355 nm with a 6.8 ns Nd:YAG laser in the air. Thermal absorption, thickness of the films and surface morphologies of fused silica before and after contamination were investigated by Stanford photo-thermal solutions, ellipsometer and optical microscope, respectively. The damage sites located on the clear fused silica, and on the input and output surface of the contaminated fused silica have been irradiated respectively with 355 nm pulsed laser. Photographs of the growth of the damaged sites have been taken by the microscope on line,