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

In this paper we present experimental measurements of elasto-optic con stants on a number of silicate glasses having a refractive index rangi ng from about 1.5 to 2.0. Values of the elasto-optic constants, obtain ed from longitudinal and transverse Brillouin peak intensities, are al most independent of the glass composition and show a quite regular beh avior versus the refractive index. We also introduce a microscopic the ory for evaluating elasto-optic constants in disordered isotropic soli ds composed of units carrying a spherical polarizability. This theoret ical model predicts that the elasto-optic constants are only determine d by the refractive index of the system under consideration. A compari son is made between experimental findings and theoretical predictions of this simplified model: the discrepancies found are discussed.