The influence of the TiO<sub>2</sub> concentration (≦10 at. %) on the structural and the optical properties of CaF<sub>2</sub>-rich CaF<sub>2</sub>–TiO<sub>2</sub> 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<sub>2</sub> concentrations. The surface roughness of CaF<sub>2</sub> films and their adhesion to a glass substrate are greatly improved by the addition of a small amount of TiO<sub>2</sub>. These composite films are quite suitable for IR coatings as a transparent, low-refractive-index material at wavelengths of <10 μm. Two examples, a Fabry–Perot filter and a mid-IR dichroic filter, of applications that use CaF<sub>2</sub>–TiO<sub>2</sub> with 10-at. % TiO<sub>2</sub> and Ge as low- and high-refractive-index coating materials, respectively, are presented.
© 1999 Optical Society of America
Rung-Ywan Tsai, Sen-Chrong Shiau, Doris Lin, Fang Chuan Ho, and Mu-Yi Hua, "Ion-Assisted Codeposition of CaF2-Rich CaF2-TiO2 Composites as infrared-Transmitting Films," Appl. Opt. 38, 5452-5457 (1999)