SUBSTRATE EFFECTS ON ABSORPTION OF COATED SURFACES

Photothermal deflection is used for mapping the absorption of bare and coated surfaces. The same area is mapped before and after coating and also after annealing. The great importance of the substrate with resp ect to the total losses of the coated component is emphasized. First t he influence of surface contamination of the bare substrate on the tot al absorption of the coated substrate is studied for BK7 and fused-sil ica substrates. Then the mean value of the coated-substrate absorptanc e is shown to be strongly dependent on the type of substrate. Experime ntal results show that this effect is associated with a localization o f the absorption at the near surface of the substrate and at the inter faces of the film. (C) 1996 Optical Society of America