Microgratings for optical data storage

Summary form only given.The limitations of the storage capacity of conventional optical disks may be overcome by recording the digital data holographically as microscopic reflection gratings. The data is stored bit-wise in a thin photosensitive layer coated on optical disk substrate. The pitland structure is replaced by volume gratings seated in a sub-micrometer range, which vary locally the reflectivity of the disk. For writing, a laser beam is focused within the storage layer and then reflected from the reflecting unit on the other side of the disk. The interference intensity pattern of the incident and reflected write beam induces a corresponding spatial modulation of the refractive index in a photosensitive storage medium. To retrieve the stored data, the information is reconstructed by reflection of the read beam at the induced grating.