High-density nonvolatile volume holographic disk storage

The batch-thermal fixing scheme was combined into holographic disk storage, for the first time to our knowledge, yielding to a track-division thermal fixing scheme (TDTF), in order to increase the storage density and overcome the volatility of the holographic memories. As a specific batch-thermal fixing scheme, the concept of TDTF scheme was described in this paper. Three principal holographic time-constants of a photorefractive crystal for TDTF scheme were measured, based on which an appropriate exposure-time sequence was calculated and applied to record multiple holograms. The disk mount has been designed and finely manufactured, consequently, the reposition accuracy of the crystal disk can meet the requirement after the crystal experienced off-line thermal fixing. 5000 images, each contains 768 X 768 pixels, divided into 4 tracks, have been stored in a disk-shaped 0.03wt% Fe doped LiNbO3 crystal using TDTF scheme. The samples of retrieved holograms showed approximately equal diffraction efficiency and good fidelity. The Experiment resulted in a high areal density of 50 bits/mum(2) and volume density of 10 Gbits/cm.