Multi-layered holographic read-only memory and data retrieval method
AssigneeNippon Telegraph and Telephone Corporation
InventorsShougo Yagi, Tadayuki Imai, Michio Ono, Hiroki Yamazaki, Haruki Kozawaguchi
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Abstract
An inexpensive multi-layered holographic read-only memory having a large capacity is provided. In the memory in which single-mode slab waveguides are multi-layered, a periodic scattering center whose period approximately agrees with the period of the guided mode is provided in at least one of a core layer and a clad layer in each waveguide so that a guided wave in the waveguide is diffracted by the periodic scattering center to the outside of the waveguide and a holographic image is generated.
Claims13
A multi-layered holographic read-only memory comprising:
- a multi-layered stack of single-mode thin-film slab waveguides;
- and
- a core layer and a clad layer provided in each slab waveguide, said core layer and clad layer having a periodic scattering center whose period approximately agrees with the period of the guided mode so that a guided wave in the waveguide is diffracted by the periodic scattering center to the outside of the waveguide and a holographic image is generated,
- wherein at least one of the edges of the multi-layered slab waveguide is configured so as to produce a reflecting surface which is slanted by a predetermined angle with respect to the normal direction of the waveguide plane.
A method for retrieving data stored in disc-shaped memory comprising:
- providing a multi-layered holographic read-only memory comprising a multi-layered stack of single-mode thin-film slab waveguides having a core layer and a clad layer provided in each waveguide, said core layer and clad layer having a periodic scattering center whose period approximately agrees with the period of the guided mode so that a guided wave in the waveguide is diffracted by the periodic scattering center to the outside of the waveguide and a holographic image is generated, the multi-layered holographic read-only memory further having a plurality of coupling points for introducing light, wherein at least one of the core layer and the clad layer is made of a UV curable resin and a hologram is recorded by the ultraviolet pattern irradiation, and the recorded hologram functions as the periodic scattering center;
- providing a specific identification pattern for each coupling point at an area of the side face of the disc, the guided wave from the coupling point being transmitted through said area;
- rotating the multi-layered holographic read-only memory;
- and
- detecting the identification pattern so as to establish a synchronous condition with respect to the relevant coupling point.
A multi-layered holographic read-only memory comprising:
- a multi-layered stack of single-mode thin-film slab waveguides;
- and
- a core layer and a clad layer provided in each slab waveguide, said core layer and clad layer having a periodic scattering center whose period approximately agrees with the period of the guided mode so that a guided wave in the waveguide is diffracted by the periodic scattering center to the outside of the waveguide to thereby generate a holographic image,
- wherein a plurality of the multi-layered slab waveguides are arranged to make a disc memory, and the disc memory has a reflecting surface in a central area of the disc memory, so as to guide light introduced into the reflecting surface towards the outer circumference of the disc memory.
Dependencies are inferred from the claim text.