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Photoelastic coefficient measurement method of optical glasses based on Mach–Zehnder interferometer

Abstract. A method based on Mach–Zehnder interferometer and stress optical coefficients theory was proposed for measuring the photoelastic coefficients of optical glasses. The corresponding apparatus is built to measure the photoelastic coefficients of fused silica and As2S3 glasses, with p12  =  0.27 and 0.26 at 632.8 nm, respectively. The validity and accuracy of the present technique were tested on the samples of fused silica and As2S3 glass, with the relative error not exceeding 10% compared to that in previous studies and the causes of errors were analyzed. The photoelastic coefficients of tellurite glasses with component 75TeO2-20ZnO-5Na2O were measured, with p11  =  0.23 and p12  =  0.22. The acousto-optic (AO) figure of merit M2 of the three types of glass was calculated and the role of photoelastic coefficient in the equation was discussed, providing an effective technique for investigating the AO interaction in a glass.