Measurements of material refractive index with a circular heterodyne interferometer

Abstract

When a light coming from a circularly polarized heterodyne light source incidents on an optical material, a phase difference between s- and p- polarization components of the reflected light occurs. This phase difference can be measured accurately with the heterodyne interterometry. The measured data are substituted into the special equations derived from Fresnel equations, the refractive index can be estimated. This method bears both merits of a common-path interferometer and a heterodyne interferometer. The refractive indices of three optical glasses and two birefringent crystals were measured to show the validity of this method.