Dynamic grating filtering in photorefractive crystals by using vibration

We propose a simple theory to analyze the effect of application of a high frequency vibration signal to a photorefractive crystal on the dynamic index grating. The theory shows that the grating visibility is zero when the vibration amplitude is an integral multiple of the grating space. By using this principle, we can apply a vibration signal to a crystal and construct a low-pass filter on the index grating in spatial domain.