Beam shaping and effective guiding in the bulk of photorefractive crystals through linear beam dynamics

The authors demonstrate a technique to optically imprint through linear beam propagation an index pattern in the bulk of a photorefractive crystal capable of beam reshaping and waveguiding. The procedure is based on the separation into two distinct phases of the photosensitive and refractive response, so that light is in all cases undergoing only linear propagation. When saturation in the response becomes dominant, the scheme is able to achieve both one-dimensional and two-dimensional waveguiding. The result allows the straightforward writing of multiwaveguide circuits, where traditional schemes based on spatial solitons are in practice burdened by nonlinearity.