Ultrasonic monitoring of laser damage in fused silica

The growth of a laser induced, surface damage site in a fused silica window was monitored by the ultrasonic pulse-echo technique. The laser damage was grown using 15 ns pulses of 1.053 mum wavelength light at a fluence of similar to 25 J/cm(2). The ultrasonic signal amplitude exhibited variations with the damage size which are attributable to the changing subsurface morphology of the damage site. The sensitivity to subsurface morphology makes the ultrasonic methodology a promising tool for monitoring laser damage in fused silica optics. This type of diagnostic capability may facilitate the safe deployment of large, high powered laser systems used in high energy and fusion research facilities. (C) 2001 American Institute of Physics.