Image-degradation in a two-wave mixing spatial-light modulator

Abstract

Optical real-time image processing by spatial light modulators (SLM’s) that utilize photorefractive crystals has attracted much attention /1/. The two-wave mixing SLM is based on the selective spatial erasure of the uniform phase volume hologram created by the two plane coherent beams using an incoherent image bearing beam Iinc(r→) resulting in an additional spatial modulation of the refractive index distribution I1(r→) (commonly with a greater spatial period then the grating period of the hologram). The parameters of these Bragg-type SLM’s are strongly determined by the diffraction properties of the nonuniform volume gratings and are analyzed here by means of the two-wave mixing coupled-wave formalism in it’s two-dimensional description /2/.