Abstract

Nanometer-size arsenic clusters in a GaAs matrix have large capacities to trap photocarriers and to store charge. The material is prepared by low-temperature-growth (LTG) of molecular beam epitaxy (MBE) GaAs. We demonstrate that the thin films can be used as a high-density optical storage medium. The material exhibits an unexpected large electro-optic effect at room temperature for photon energies close to the bandgap. This effect is attributed to quantum effects of the mesoscopic clusters. Charge storage and electro-optic properties combine to produce a low-laser-power high-density holographic storage medium. The ultra-fast lifetimes of the photogenerated carriers produce excellent spatial resolution during the writing of holographic space-charge gratings. Fringe spacings as small as 6000 Å can be supported in this material, yielding two-dimensional optical data density greater than 10⁸ bits/cm². The saturation intensity is 10 mW/cm² with a device storage time of 2 ms. With additional processing, fringe spacings as small as 2000 Å should be possible, with storage times approaching minutes.

© 1992 Optical Society of America