LASER MODULATED SCATTERING AS A NONDESTRUCTIVE EVALUATION TOOL FOR DEFECT INSPECTION IN OPTICAL-MATERIALS FOR HIGH-POWER LASER APPLICATIONS

Laser modulated scattering (LMS) is introduced as a tool for defect in spection and characterization of optical materials for high power lase r applications. LMS is a scatter sensitive version of the well-known p hotothermal microscopy techniques. Because only the defects of a super polished optic generate a scattering signal, the technique is essentia lly a method for dark-field photothermal microscopy. Experimental resu lts show that the technique (1) measures the local absorption properti es of defects, contamination, and laser damage sites; (2) when used in conjunction with DC scattering, can differentiate between absorbing a nd non-absorbing defects; and (3) detects thermal transport inhomogene ities. (C)1998 Optical Society of America