Recording and reading of volume holograms in diffractionlimited 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.