Optical losses of evaporation-deposited dielectric waveguides

Abstract

The optical attenuation and the refractive indices of evaporation-deposited Al 2O 3, CeO 2, MgO, ZrO 2, CeF 3, LaF 3, NdF 3 and ZnS dielectric films have been measured using the films as optical waveguides. The attenuation resulting from absorption in the planar waveguide and substrate as well as from light scattered in the waveguide and at its interfaces with the substrate and superstrate is not below 10 dB cm -1 and allows a qualitative comparison of the materials conventionally used in interference optics for the deposition of low-loss single layers or multilayers. Owing to their relatively high attenuation, the materials investigated are only suitable for short waveguides where severe demands have to be met with respect to the refractive index. Short optical paths are usually realized by the concentration of optical devices in integrated optics technology. Difficulties are likely to be encountered, however, in experimental integrated optical structures, which are often of large-area design in the interests of simplicity and easy handling.