PHOTOTHERMAL CHARACTERIZATION OF OPTICAL THIN-FILM COATINGS

Photothermal techniques are widely used in thin film characterizations and are particularly useful in studying laser-induced damage in optic al coatings. The specific applications include measuring weak absorpti on, characterizing thermal conductivity, detecting local defects, and monitoring laser-interaction dynamics and determining laser damage thr esholds as well as thermal impedance at boundaries of multilayers. We take an overview of the principle of photothermal techniques, the vari ous detection methods, and the progress made during the last decade in applying these techniques to optical thin films. The further potentia l and limitations of the techniques will also be discussed, with empha sis on in situ studies of laser interaction with thin films and local defects. (C) 1997 Society of Photo-Optical Instrumentation Engineers.