PHOTOREFRACTIVE MATERIALS FOR NONVOLATILE VOLUME HOLOGRAPHIC DATA-STORAGE

Optically gated recording and nonvolatile readout in a digital volume holographic data storage system that uses-a pair of mutually incoheren t light sources during recording and only one for readout were demonst rated recently. This approach used stoichiometric lithium niobate, whi ch after post-growth processing gave rise to an at least two orders of magnitude improvement in sensitivity over the best materials reported previously. it is also shown that by adding certain dopants (iron and manganese) to near-stoichiometric lithium niobate, the dark storage t ime and gating efficiency can be increased compared with previous work . The underlying physical mechanisms of gated recording and the effect iveness of the gating process responsible for this manifold improved p erformance are discussed, and bipolarons and small polarons are identi fied as the responsible photorefractive species.