Optical waveguide, holographic medium, holographic storage and retrieval method and system

摘要

A holographic medium comprising an optical waveguide including at least one core layer positioned between portions having a lower refractive index; a diffraction grating layer formed at a boundary between the core layer and the above portions or in the core layer; and a storage layer outside the optical waveguide. An optical waveguide having the above structure in which the diffraction efficiency of the diffraction grating layer has a specific distribution is useful. In multiple-angle storage, a reference beam is emitted from an end face of a core layer or from the upper or lower side of the medium and a photodetector may be used, so as to control the incident angle. The reference beam and/or the optical waveguide is moved so that the reference beam couples only with a specific diffraction grating layer. The object beam may be focused onto a small target area of the storage layer.