Subsurface damage identification in optically transparent materials using a nondestructive method

Total internal reflection microscopy has been applied to image subsurface damage sites in conventionally polished fused-silica flats. This technique can differentiate between surface and subsurface features by changing the illuminating polarization. The method is nondestructive, and no surface preparation is required other than a thorough cleaning of the surface. The intensity distributions in the illuminated region of interest are discussed. The technique has been used successfully as an optical fabrication in-process diagnostic.