Photothermal techniques are widely used in thin film characterizations and are particularly useful in studying laser-induced damage in optical coatings. The specific applications include measuring weak absorption, characterizing thermal conductivity, detecting local defects, and monitoring laser-interaction dynamics and determining laser damage thresholds as well as thermal impedance at boundaries of multilayers. We take an overview of the principle of photothermal techniques, the various detection methods, and the progress made during the last decade in applying these techniques to optical thin films. The further potential and limitations of the techniques will also be discussed, with emphasis on in situ studies of laser interaction with thin films and local defects. © 1997 Society of Photo-Optical Instrumentation Engineers.
Key words: optical thin films; laser damage; optical absorption; thermal conductivity; localized defects; photothermal technique; nondestructive evaluation; overview.