Phase-controlled photorefractive running holograms

We report on the use of phase modulation in two-wave mixing with negative feedback to record stabilized photorefractive running holograms with arbitrarily fixed phase shift between the transmitted and the diffracted beams behind the crystal. By adequately choosing this phase one can select the running hologram speed and associated properties like diffraction efficiency. This technique is an alternative to the classical frequency detuning one with the advantage that the recording is at the same time actively stabilized referring to the own hologram being recorded. We describe the setup, analyse its behavior and report experimental results for a Bi12TiO20 crystal. (C) 1997 Elsevier Science B.V.