Development of a photorefractive grating via temporally modulated photoconductivity and a correlated ac bias

A process is described which utilizes an alternating electric bias field to develop a photorefractive grating. The bias field is applied synchronously with an optically modulated photoconductivity. The key to the technique is correlation between the applied ac bias and the time varying intensity field. This differs from previous work in which an uncorrelated ac bias was applied to enhance photorefraction. A theoretical development of this process is presented along with the experimental confirmation of this effect. The ac bias utilized in the experiment consists of an electric field produced by a bulk acoustic wave (via piezoelectricity). This is applied in the presence of a modulated optical field to produce the photorefractive grating. Over 30 dB of dynamic range of the grating deflected signal is observed by this approach.