ELASTO-OPTIC CONSTANTS IN SILICATE-GLASSES - EXPERIMENT AND THEORY

In this paper we present experimental measurements of elasto-optic constants on a number of silicate glasses having a refractive index ranging from about 1.5 to 2.0. Values of the elasto-optic constants, obtained from longitudinal and transverse Brillouin peak intensities, are almost independent of the glass composition and show a quite regular behavior versus the refractive index. We also introduce a microscopic theory for evaluating elasto-optic constants in disordered isotropic solids composed of units carrying a spherical polarizability. This theoretical model predicts that the elasto-optic constants are only determined by the refractive index of the system under consideration. A comparison is made between experimental findings and theoretical predictions of this simplified model: the discrepancies found are discussed.