This paper reports the recent progress in our research on defect characterization of optical thin films. The technique itself, based on photothermal microscopy through optical beam deflection, has been reported earlier by several groups including ourselves. The work here focuses on the differentiation between optical and thermal defects by photothermal imaging at different frequencies. We first present a brief introduction of the principle and the experimental method, and then the data of samples with artificially introduced surface and subsurface structures. The results demonstrate that the technique is capable of depth-profiling for absorption defects as well as of differentiating between optical and thermal imperfections. Finally, as typical examples of the applications of the technique, the results of various practical optical coatings are presented, including TiO_{2$, ZrO(subscript 2}, SiO₂, and ZnS single layers as well as TiO₂/SiO₂ AR and HR coatings. The effects of undercoats to AR and overcoats to HR are also investigated and compared with the damage experiments.

Date Published: 29 July 1992
PDF: 11 pages
Proc. SPIE 1624, Laser-Induced Damage in Optical Materials: 1991, (29 July 1992); doi: 10.1117/12.60116

Published in SPIE Proceedings Vol. 1624:
Laser-Induced Damage in Optical Materials: 1991
Harold E. Bennett; Lloyd L. Chase; Arthur H. Guenther; Brian Emerson Newnam; M. J. Soileau, Editor(s)