Abstract: A holographic medium is formed of an optical waveguide including at least one core layer positioned between at least one portion of a material having a lower refractive index, a diffraction grating layer formed at a boundary between the core layer and the material of lower refractive index or in the core layer, and a storage layer outside the optical waveguide. Upon storing information in the storage layer a reference beam and an object are input into the optical waveguide and in retrieving stored information the reference beam is emitted to an end face of the core layer and transmitted through the core layer to be transformed into a diffracted beam in a diffraction grating layer that is emitted outside the core layer and transmitted through the storage layer, where the object beam is retrieved as a retrieved beam.

Abstract: 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.