Dependence of the amount of stored information and its input and access rate on storage medium characteristics in volume holographic memories

摘要

The times of information input and access during the processes of a hologram recording and reconstruction basically depend on the amount of information stored in a medium. This dependence is different for different media. Besides dependence on each other, these values depend on the medium characteristics such as sensitivity dynamic range (DR) and medium indices defining the hologram diffraction efficiency (DE). Amount of the stored information, access and input times - important parameters for holographic memory devices (HMD) - are of different importance for different problems solving. Usually the total information amount and data access rate are of the biggest importance. In this case it is necessary to provide wide DR of a medium, multiplexing possibility, and recording of phase holograms which have bigger DE. For large amount of information fast input it is necessary to provide high holographic sensitivity. Its threshold value is defined by the value reciprocal to input energy enough to produce DE providing the information unit reconstruction. For DE providing transmission of N information units the energy must be increased in more than N times. Such recording media as lithium niobate and some photopolymeres have the characteristics which allow to provide very high information capacity, acceptable access rate but insufficient holographic sensitivity which allows to input large data amount only at expense of parallelism. The medium characteristics variations allow to provide the optimal relationship of the parameters.