Linear writing of waveguides in bulk photorefractive crystals through a two-step polarization sequence

We demonstrate a technique that allows the optical imprinting of waveguides in the bulk of photorefractive crystals without resorting to nonlinear beam dynamics, self-focusing, or solitons, making use of the beam reshaping properties of the pattern deposited by the intensity distribution of a diffracting Gaussian beam. The procedure is made possible using a polarization-resolved scheme that, in distinction to previously reported methods based on temperature cycles, can be implemented in ferroelectrics both in the polar and in the centrosymmetric phase.