Transparent Non-Linear Optical Composites Based on Glass and Ferroelectric KNbSi2O7

Abstract

Transparent glass composites containing nonlinear optical (NLO) and luminescent crystals are of significant interest for the optical materials science in spite of a lot of difficulties to synthesize high-quality NLO composites: refractive index and density matching of glass matrix and crystal, controlled chemical interaction between them, absence of crystal aggregation, cords, bubbles, etc. Low density and refractive index, high second harmonic generation (SHG) activity, rather a high melting point allow to refer KNbSi2O7 ferroelectric to a promising candidate for using in the NLO glass composite technology. Manifestation of NLO properties of crystals in glass composites is established to depend drastically on glass matrix composition. During re-melting lead containing glasses react chemically with KNbSi2O7 forming pyrochlore Pb2Nb2O7 which is dissolved gradually up to nano-scaled state exhibiting moderate SHG efficiency by analogy with nanostructured glasses because of space modulation of polarizability originated from nano-sized inhomogeneities enriched with Pb and Nb. Using of TeO2-based glasses permits to match refractive indexes of glass matrix and crystal, reduce glass melting temperature and fabricate transparent composites containing micron and sub-micron crystals with high second harmonic generation activity.