RECORDING AND READING OF VOLUME HOLOGRAMS IN DIFFRACTION-LIMITED SYSTEMS.

The use of thick layers for recording purposes in holographic memory devices makes it possible to increase the diffraction efficiency and the memory capacity. A simple approximation is used to analyze the recording and reading of individual volume holograms with the aid of a diffraction-limited aperture. Some features not found in thin-film holograms are revealed by this analysis. For example, the average diffraction efficiency of thin-film holograms is inversely proportional to the size w//k of the spot formed by the reconstructing (read) beam. The corresponding dependence for thick-film (volume) holograms has a maximum but in the range of small values of w//k a direct proportionality is observed. In the plane of incidence the dimensions of spots formed by the signal and reconstructing beams are equal. At right-angles to this plane the spot size is less for the reconstructing beam, i. e. , the distribution is asymmetric.