Electro-optic coefficients measurement based on a multiple-reflection Mach–Zehnder interferometer

Multiple reflection (MR) effects in flat optical crystals can cause significant errors in electro-optic coefficient (EOC) measurements. We present a Mach–Zehnder interferometer method that incorporates MR modeling and suppresses its influence by selecting specific incidence angles ( Θ = 2mπ and Θ = (2m+1)π ). Numerical simulations with congruent lithium niobate show that angular deviations below 0.1°limit EOC errors to <2.5%. Experiments using a He–Ne laser achieve <1% variance in γ13 and γ33, confirming theoretical predictions. The approach also enables frequency-resolved EOC characterization, offering a simple, high-precision solution for MR suppression in optical metrology.