Volume holographic memory apparatus having a reference beam and a signal beam with opposite intensity distributions

摘要

A volume holographic memory-based optical information-recording/reproducing apparatus is capable of enhancing density of spatial multiple recording. A recording medium is mounted in the apparatus for recording a three-dimensional optical interference pattern formed by at least two coherent light beams as spatial changes in refractive index of the recording medium. A signal beam optical system supplies a coherent signal beam to the recording medium through a Fourier transform lens. A reference beam optical system supplies a coherent reference beam to the recording medium. The reference beam is caused to intersect with the signal beam within the recording medium and an angle of intersection between the reference beam and the signal beam is changed. Diffracted light of the reference beam diffracted from the recording medium is detected. Spatial beam modulating means is arranged in the optical path of the reference beam optical system for limiting light intensity of the reference beam in a manner such that a cross section of the reference beam in the recording medium has a light intensity distribution opposite to a light intensity distribution of the signal beam in the recording medium.