Anomalously Fast Response of Photorefractive Lithium Tantalate and Niobate

Abstract

It is well known that in photorefractive lithium tantalate and niobate, photoinduced light scattering (PHILS) and holographic-type parametric scattering (HTPS) [1] are possible. In PHILS light is scattered by a set of random holographic gratings, and HTPS is scattering by a subset of these gratings satisfying the four-wave phase matching condition. The characteristic time of recording such gratings is defined by the Maxwell time τm ~ε/4πσ (here ε is the dielectric function and σ the electric conductivity of the crystal), which can vary in LiNbO3 and LiTaO3 from some minutes to many hours depending on the pump intensity.