Measurements of the ordinary and extraordinary refractive indexes of synthetic sapphire are reported. Direct independent measurements of the birefringence are given. Temperature and piezo-optical coefficients of birefringence are given and combined with published data and calculations of W. L. Bragg to yield order of magnitude values for the thermal coefficient of expansion and Young’s modulus.
MYRON A. JEPPESEN, "Some Optical, Thermo-Optical, and Piezo-Optical Properties of Synthetic Sapphire," J. Opt. Soc. Am. 48, 629-632 (1958)