Polarized common path optical heterodyne interferometer for measuring the elliptical birefringence of a quartz wave plate

A novel method based on a polarized optical heterodyne interferometer with a common path feature was proposed and set up. This interferometer was used to measure the phase difference δ_f of the fast wave of the elliptical polarized eigenstate in the directions of the P and S waves in an elliptical birefringence wave plate. The values of δ_f are calculated on the basis of the phase difference and the ratio of the amplitude of input polarized light with the accuracy up to 10^-3 . The measurement results provide evidence of the existence of elliptical birefringence in both λ/4 and λ/2 quartz wave plates.