Determination of linear birefringence of a multiple-order wave plate using a phase-sensitive ellipsometer

A phase-sensitive interferometric ellipsometer is setup in order to characterize linearly birefringent parameters (n_o,n_e,m) of a multiple-order wave plate (MWP) precisely where n_o and n _e are refractive indices of ordinary and extraordinary rays respectively while m is the number of the order of interference. In order to avoid multiple reflections in MWP during the phase retardation measurement at oblique incidence, two tilted phase retardations with respect to the oblique incident angle rotated along x-axis and y-axis are measured and then subtracted from each other. In the mean time, the spatial shifting effect of the emerging beams from MWP is reduced too. This results the accuracy of linear birefringence measurement. Finally, a multiple-order quartz wave plate was tested. The experimental results verify that the phase-sensitive interferometric ellipsometer is able to precisely measure linear birefringence and the order number of a MWP. In this measurement, the phase stability of the interferometric ellipsometer was 0.3°/hr. It implies the sensitivity on refractive index measurement at δn∼10^-6 was achieved in the experiment.