Measurements of material refractive indices using heterodyne interferometry

Abstract

The phase difference between s- and p- polarizations of the reflected light from a test material is measured using heterodyne interferometry. The measured data is substituted into the specially derived equations and the refractive index can be calculated. When an absorbing material is tested, a general heterodyne light source is used and two measurement processes should be performed because of its two unknown parameters to be solved. And only one measurement process is performed with a circularly polarized heterodyne light source for testing a non-absorbing material. Because the phase difference can be measured accurately with heterodyne interferometry, its performance is not affected by surrounding light noise. So, it is very stable and has a high resolution.