A holographic storage optical system includes a storage medium, a recording unit, an imaging unit and a servo unit. The recording unit comprises a movable Fourier lens, by which the positions and irradiation angles of a signal light spot and a reference light spot are adjusted. The servo unit comprises a calibration lens for adjusting the positions of a servo light spot in the horizontal and vertical directions so that the servo light spot is located at an optimal position relative to signal light beam and reference light beam. The beam calibrating method comprises (1) before recording a data hologram, burning a calibration hologram at a calibration holographic positioning mark on an optical track of a storage medium; (2) before reproducing the data hologram, using the calibration hologram to optimize the signal-to-noise ratio of the hologram reproduced by adjusting the calibration lens and the Fourier lens.

A holographic storage optical system includes a storage medium, a recording unit, an imaging unit and a servo unit. The recording unit comprises a movable Fourier lens, by which the positions and irradiation angles of a signal light spot and a reference light spot are adjusted. The servo unit comprises a calibration lens for adjusting the positions of a servo light spot in the horizontal and vertical directions so that the servo light spot is located at an optimal position relative to signal light beam and reference light beam. The beam calibrating method comprises (1) before recording a data hologram, burning a calibration hologram at a calibration holographic positioning mark on an optical track of a storage medium; (2) before reproducing the data hologram, using the calibration hologram to optimize the signal-to-noise ratio of the hologram reproduced by adjusting the calibration lens and the Fourier lens.

A multi-channel multiplexing method for a disc storage medium includes: S1) recording holograms at holographic positioning marks of the storage medium by a reference light beam and a signal light beam, S2) rotating the storage medium in a circumferential direction and repeatedly performing step S1 until the holograms have been recorded at all the holographic positioning marks on optical tracks, S3) translating the storage medium to switch an optical head to another optical track, S4) repeating steps S1-S3 until recording of one cross channel is completed, S5) changing a relative angle of the center of the storage medium with respect to the optical head, and repeating steps S1-S4 to complete recording of another cross channel, S6) repeating steps S1-S5 until recording of all cross channels is completed, and S7) reproducing the holograms at any channel or recording position of the storage medium by using the same beam of reference light.

A multi-channel multiplexing method for a disc storage medium includes: S1) recording holograms at holographic positioning marks of the storage medium by a reference light beam and a signal light beam, S2) rotating the storage medium in a circumferential direction and repeatedly performing step S1 until the holograms have been recorded at all the holographic positioning marks on optical tracks, S3) translating the storage medium to switch an optical head to another optical track, S4) repeating steps S1-S3 until recording of one cross channel is completed, S5) changing a relative angle of the center of the storage medium with respect to the optical head, and repeating steps S1-S4 to complete recording of another cross channel, S6) repeating steps S1-S5 until recording of all cross channels is completed, and S7) reproducing the holograms at any channel or recording position of the storage medium by using the same beam of reference light.

A method of performing a write operation in a holographic data storage system, in which schedule schedules at least one write operation across multiple non-contiguous write intervals, the write operation pertaining to a set of data to be stored in a region of a holographic recording medium. In each of the non-contiguous write intervals, the region of the holographic recording medium is exposed to an interference pattern caused by interference between a reference beam and an input beam carrying the set of data. The multiple non-contiguous write intervals have a total aggregate duration of sufficient length to cause a persistent state change in the exposed region, such that the set of data is recoverable from that region by the end of a final write interval of the multiple non-contiguous write intervals.

A method of performing a write operation in a holographic data storage system, in which schedule schedules at least one write operation across multiple non-contiguous write intervals, the write operation pertaining to a set of data to be stored in a region of a holographic recording medium. In each of the non-contiguous write intervals, the region of the holographic recording medium is exposed to an interference pattern caused by interference between a reference beam and an input beam carrying the set of data. The multiple non-contiguous write intervals have a total aggregate duration of sufficient length to cause a persistent state change in the exposed region, such that the set of data is recoverable from that region by the end of a final write interval of the multiple non-contiguous write intervals.

In an optical data transfer system, a beam modulator is configured to embed a set of data in an input beam. A multimode optical waveguide network has an in-coupling region for receiving the input beam. The multimode optical waveguide network is configured to guide the input beam to an out-coupling region of the multimode optical waveguide network. A spatial coherent detector is configured to measure a phase and an amplitude of an output optical field at multiple locations. The output optical field is at least partially defined by the input beam and thus exhibiting distortion effects caused by the passage of the beam through the multimode waveguide network. Signal processing is applied to an output of the spatial coherent detector, in order to compensate for the distortion effects, and thereby recover, from the output of the spatial coherent detector, the set of data embedded in the input beam.

In an optical data transfer system, a beam modulator is configured to embed a set of data in an input beam. A multimode optical waveguide network has an in-coupling region for receiving the input beam. The multimode optical waveguide network is configured to guide the input beam to an out-coupling region of the multimode optical waveguide network. A spatial coherent detector is configured to measure a phase and an amplitude of an output optical field at multiple locations. The output optical field is at least partially defined by the input beam and thus exhibiting distortion effects caused by the passage of the beam through the multimode waveguide network. Signal processing is applied to an output of the spatial coherent detector, in order to compensate for the distortion effects, and thereby recover, from the output of the spatial coherent detector, the set of data embedded in the input beam.

A polarization volume grating (PVG) includes a bulk, birefringent medium characterized by a plurality of helical structures with helix axes and a periodicity Λ.sub.y and an anisotropic alignment material having a rotatable optical axis, disposed on a top or bottom surface of the medium. The PVG is characterized in that the optical axis of the alignment material has a continuously rotated optical axis orientation in a plane of the material surface and a periodicity Λ.sub.x, wherein the helix axes are normal to the optical axes in the alignment material surface, further wherein the birefringent medium is characterized by a plurality of controllably slanted refractive index planes having a slant angle φ=±arctan (Λ.sub.y/Λ.sub.x) and a Bragg period Λ.sub.B. Fabrication methods are disclosed.

A polarization volume grating (PVG) includes a bulk, birefringent medium characterized by a plurality of helical structures with helix axes and a periodicity Λ.sub.y and an anisotropic alignment material having a rotatable optical axis, disposed on a top or bottom surface of the medium. The PVG is characterized in that the optical axis of the alignment material has a continuously rotated optical axis orientation in a plane of the material surface and a periodicity Λ.sub.x, wherein the helix axes are normal to the optical axes in the alignment material surface, further wherein the birefringent medium is characterized by a plurality of controllably slanted refractive index planes having a slant angle φ=±arctan (Λ.sub.y/Λ.sub.x) and a Bragg period Λ.sub.B. Fabrication methods are disclosed.