No abstract

Optically gated recording and nonvolatile readout in a digital volume holographic data storage system that uses a pair of mutually incoherent light sources during recording and only one for readout were demonstrated recently. This approach used stoichiometric lithium niobate, which 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 time and gating efficiency can be increased compared with previous work. The underlying physical mechanisms of gated recording and the effectiveness of the gating process responsible for this manifold improved performance are discussed, and bipolarons and small polarons are identified as the responsible photorefractive species.

No abstract

We have grown and optically characterized strontium-barium niobate crystals, including both undoped and cerium-doped crystals having two different Sr/Ba ratios (61/39 and 75/25). By measuring the coupling of two optical beams in the crystals, we have determined the following photorefractive properties: the effective density, sign, and spectral response of the dominant charge carrier, the grating formation rate, dark conductivity, and carrier diffusion length. We find that electrons are the dominant photorefractive charge carriers in all of our samples; the typical density of photorefractive charges is ∼1×1016 cm−3 in the undoped samples. The grating formation rate increases with intensity, with a slope of ∼0.3 cm2/(W s) over an intensity range of ∼1–15 W/cm2 in undoped samples. Cerium doping improves both the charge density (increased by a factor of ∼3) and the response rate per unit intensity (∼5 times faster).