Two-wave mixing gain in Bi_12SiO_20 with applied alternating electric fields: self-diffraction and optical activity effects

Abstract

An experimental and theoretical analysis of the two-wave mixing gain in Bi12SiO20 with alternating electric fields applied is presented. The electromagnetic portion of the photorefractive theory is extended by including both optical activity and self-diffraction effects. This is significant for thick crystals of the sillenite family. This theory simplifies to the well-known Kukhtarev result when there is no optical activity. An expression for the electric space-charge field based on the band transport model of conduction is tested against experimental data and found to leave some discrepancy. An ac conductivity experiment is used to resolve the discrepancy and shows that the hopping model of charge transport is more appropriate than the band transport theory.