The influence of the TiO2 concentration (≦10 at. %) on the structural and the optical properties of CaF2-rich CaF2–TiO2 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 TiO2 concentrations. The surface roughness of CaF2 films and their adhesion to a glass substrate are greatly improved by the addition of a small amount of TiO2. 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 CaF2–TiO2 with 10-at. % TiO2 and Ge as low- and high-refractive-index coating materials, respectively, are presented.
© 1999 Optical Society of America
Original Manuscript: March 16, 1999
Revised Manuscript: June 7, 1999
Published: September 1, 1999
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)