FRONT AND BACK ILLUMINATION OF COATED SUBSTRATES FOR IN-DEPTH LOCALIZATION OF ABSORPTION

We experimentally demonstrate that part of the absorptance of coated m ulticomponent glass substrates results from a photoinduced absorptance of the substrate during the evaporation process. This increase in the glass substrate absorptance is due to a solarization process by UV ra diation, which is produced in the coating plant when electrons emitted by the electron gun interact with the material to be evaporated. Thus , we can experimentally show the dependence of the multicomponent glas s substrate absorptance on the evaporation time. An original method of front and back illumination of samples is presented that enables the separation of each part of the in-depth absorptance using photothermal measurements: bulk and interface absorption of the thin film and subs trate photoinduced absorption. This new method overcomes the difficult ies presented by other measurement techniques and caused by the depend ence of substrate and interface absorptances on the evaporation time. Absorption losses in different single-layer films are balanced. (C) 19 97 Society of Photo-Optical Instrumentation Engineers.