Dynamics of composite grating in photorefractive SBN:60

Abstract

Dynamic photorefractive memories that store image information multiplexed in a photorefractive volume are promising for parallel information processing and computing due to their large storage capacity, fast access, and read/write/erase capability1. Incoherent erasure process can be used for updating these dynamic memories, but this process is much slower than the writing process. In contrast, selective erasure process2 based on superimposed recording of a π-phase-shifted image onto the old image is reported to be much faster than the incoherent erasure3. Arbitrary phase shift has also been investigated for optical interconnects4, assuming a grating with maximum refractive index modulation at the beginning of the selective erasure process. For dynamic photorefractive memory application it is important to understand the dynamics of the selective erasure process for multiplexed images, where each of them is characterized by a much smaller refractive index modulation. Dynamic photorefractive memory that uses π-phase-shifted selective erasure process has recently been implemented, demonstrating fast erasure capability5. In this manuscript, we analyze and confirm experimentally the dynamics of the erasure process. For simplicity and generality we assume two gratings with an arbitrary phase shift between them to be a composite grating, one being the old grating and another the new grating.