title: Infrared absorption signature on laser-damaged optical thin films.
abstract: Optical coating degradation under laser irradiation can take several forms. Perhaps the most common that is not due to particulates is thermal breakdown, caused by heating of the coating to a catastrophic failure induced by local melting, delamination, evaporation, or some other change. We demonstrate that micromachined dielectric membranes show strong differences in their hydroxyl signatures as measured by Fourier-transform IR spectroscopy. The changes correspond to regions of high fluence (3200 J/cm2) from a Nd:YAG laser. It is found that the absorption peaks associated with OH decrease after laser treatment, indicating a reduction in the number of film hydroxyl groups.
authors.affiliation: Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Sangho S
authors.initials: SS
authors.lastname: Kim
authors.forename: Nicholas T
authors.initials: NT
authors.lastname: Gabriel
authors.forename: Wing S
authors.initials: WS
authors.lastname: Chan
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Talghader