Abstract

Volume holographic data storage offers many potential advantages over conventional magnetic mass storage including high parallelism, fast access, and high storage capacity. The high capacity of volume holography is partially attributable to the Bragg selectivity of thick media. For angularly multiplexed uniform gratings in media of finite thickness the Bragg diffraction efficiency has a well known sinc²(ϑ) dependence vs. dephasing (i.e., dephasing ϑ ∝ Δθ reconstruction angle for angular multiplexing). When a desired hologram is read out at a particular reconstruction angle, holograms stored at other angles will also be reconstructed, albeit with much lower efficiency. The superposition of the undesired reconstructions is known as crosstalk and this phenomenon has been investigated by several authors^1,2. Such crosstalk will result in noise on the data detected from the desired hologram and can be diminished by reducing the density of the angular multiplexing². Thus, crosstalk forms an upper bound on volume holographic memory density and capacity in the limit of small fixed noise sources. In this paper, we will consider the storage capacity limit imposed by crosstalk for a grating that is uniform throughout the finite medium and compare this with the limit obtained when the grating is apodized to reduce crosstalk. We will also show experimental verification of the apodization effect.

© 1996 Optical Society of America