Abstract

In the optical thin film field, the fluoride coatings have been widely used for many years, particularly for IR applications. More recently, owing to the increasing demand of optical components for UV-lasers, these materials are also the object of an intense investigation for their use, for example, in UV multilayer minors [1,2]. Among the different dielectric materials available, the fluorides exhibit, indeed, the wider optical gap. Most of the time, the deposition of fluoride films is achieved by conventionnal evaporation. Nevertheless, such a process two main limitations which are i) a mechanical instability of the film for a thickness higher than 1-2 μm, ii) a natural trend of the films to generate optical scattering, in particular in the shorter wavelengths spectral range. For two years, in the framework of the MEGAJOULE project and the achievement of 351 nm - centered UV mirrors, the LETI-CMO laboratory has been investigating a new way to deposit fluoride coatings by using the ion beam sputtering technics (IBS) [3]. This paper aims at focusing on the main characteristics of these IBS fluoride coatings and at evaluating the future prospects of this technology in relation with its extension to deep UV applications.

© 1998 Optical Society of America