Three-dimensional optical memory with a photorefractive crystal
Appl. Opt., Vol. 34, No. 20, pp. 4105-4110 (1995).
Y. Kawata, H. Ueki, Y. Hashimoto, and S. Kawata

Abstract
We propose a three-dimensional optical memory using a photorefractive crystal, in which refractile dot data are directly (not interferometrically) recorded. To record a single dot of data, laser beam is focused with an objective lens on a point in the crystal. A refractive-index at the data point changes due to the photorefractive effect of crystal. The crystal is three-dimensionally translated while the objective lens for data writing is stationary; laser-beam intensity is modulated according to the data with a beam shutter. The recorded data in memory are read out with a phase-contrast microscope objective lens. We demonstrate the experimental results of three-dimensional recording and reading with a LiNbO3 crystal. The distribution of refractive index formed by a focused beam is analyzed through the charge-transport model.