Ion-assisted codeposition of CaF_2-rich CaF_2–TiO_2 composites as infrared-transmitting films

The influence of the TiO(2) concentration (<or=10 at. %) on the structural and the optical properties of CaF(2)-rich CaF(2)-TiO(2) composite films fabricated by reactive ion-assisted codeposition are investigated. The composition-dependent properties are found to be similar to those reported for composite films with higher TiO(2) concentrations. The surface roughness of CaF(2) films and their adhesion to a glass substrate are greatly improved by the addition of a small amount of TiO(2). These composite films are quite suitable for IR coatings as a transparent, low-refractive-index material at wavelengths of <10 microm. Two examples, a Fabry-Perot filter and a mid-IR dichroic filter, of applications that use CaF(2)-TiO(2) with 10-at. % TiO(2) and Ge as low- and high-refractive-index coating materials, respectively, are presented.