Modified Michelson interferometer for probing refractive index of birefringent crystal CSBN50

Based on the modified Michelson interferometer and phase analysis method, a high-accuracy method for probing the refractive index (RI) of transparent medium is proposed. The validated test was performed on a birefringent crystal CSBN50 with the estimated accuracy being up to 10−4. The ordinary and extraordinary refractive indices of CSBN50 at 632.8 nm are determined as n0=2.32853±0.00016 and ne=2.27664±0.00016, respectively.