Measurement of the principal refractive indices of thin films deposited at oblique incidence

Abstract

Shadowing causes form birefringence in optical thin films that are deposited at oblique incidence. For light incident in the plane containing the direction of deposition and the substrate normal, the TE and TM polarizations in the film are decoupled, and field transfer can be described using 2×2 matrices. The three principal indices of birefringent films are deduced from measurements made on narrow-band interference filters. In one example refractive indices of 2.688, 2.429, and 2.452 were computed for TiO2 deposited at 27° to the substrate normal. Both TiO2 and ZrO2 behave as positive biaxial media.