Compact architecture for holographic systems

• US 5,959,747 A
• Filed: 09/11/1996
• Issued: 09/28/1999
• Est. Priority Date: 09/11/1996
• Status: Expired due to Fees

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Barbastathis, George, Psaltis, Demetri, Drolet, Jean-Jacques P.
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Schuberg, Darren E.
• Application Number:
  US08/712,170
• Time in Patent Office: 1,112 Days
• Field of Search: 359/10, 359/11, 359/21, 359/22, 359/24, 359/25, 365/125, 365/216
• US Class Current: 359/22
• CPC Class Codes: G03H 1/0005 Adaptation of holography to specific applications holographic optical element G02B5/32; holographic scanner G02B26/106; recognition using holographic mask G06V10/88; holographic memories G11B7/0065, G11C13/042
• CPC Class Codes: G03H 1/26 Processes or apparatus specially adapted to produce multiple sub- holograms or to obtain images from them, e.g. multicolour technique
• CPC Class Codes: G03H 2001/0268 Inorganic recording material, e.g. photorefractive crystal [PRC]
• CPC Class Codes: G03H 2001/2675 Phase code multiplexing, wherein the sub-holograms are multiplexed according to spatial modulation of the reference beam
• CPC Class Codes: G03H 2222/34 Multiple light sources
• CPC Class Codes: G03H 2225/60 Multiple SLMs
• CPC Class Codes: G11C 13/046 using other storage elements storing information in the form of an interference pattern

Abstract

An architecture for holographic data storage and processing integrates multifunctional silicon-based optoelectronic devices, rewritable holographic material, optical devices and other electro-optical elements in compact and high-performance systems. A dynamic hologram refresher based on optoelectronic integrated circuits has a smart pixel structure including an electrically addressed SLM to write a new data page, a thresholding detector array for readout, and a memory to latch the data from the detector to the modulator in each pixel. In particular, conjugate reconstruction is used in combination with the dynamic hologram refresher to retrieve data from volume multiplexed holograms in the rewritable holographic material.

Claims

1. An optoelectronic holographic system, comprising:

an optoelectronic integrated circuit, having a plurality of pixels to form a pixel array on an interface thereof and a plurality of electrical terminals for both feeding information to said pixel array and exporting information from said pixel array, each of said plurality of pixels having a light modulation mode and a light detection mode;

a holographic recording medium with a plurality of superimposed holograms therein, having a plurality of surfaces to receive light beams and being attached to said interface of said integrated circuit with a first surface of said plurality of surfaces to provide an optical path between said pixel array on said interface and said recording medium; and

said integrated circuit in said light modulation mode modulating an incident light beam to produce a spatially modulated light beam propagating towards said recording medium, said integrated circuit in said light detection mode operating to receive and detect light signals from said recording medium.

2. A system as in claim 1, further including an optical beam coupling element that is disposed between said integrated circuit and said recording medium, said beam coupling element operating to inject an optical signal beam to said pixel array of said integrated circuit in said light modulation mode, which modulates said signal beam and produces a modulated beam propagating towards said recording medium.

3. A system as in claim 2, further comprising:

a first optical beam steering element disposed on a second surface of said plurality of surfaces of said recording medium, operating to change the propagating direction of an optical reference beam that enters said recording medium through said first optical beam steering element and said second surface; and

a third surface of said plurality of surfaces of said recording medium being disposed in the optical path of said reference beam.

4. A system as in claim 3, further comprising:

a phase conjugator that is positioned adjacent to said third surface and in the optical path of said reference beam, operating to receive at least a portion of said reference beam and to produce a phase-conjugated reference beam that retraces the optical path of said reference beam and propagates from said phase conjugator towards said recording medium; and

said phase-conjugated reference beam diffracting from said holograms in said recording medium to produce a plurality of conjugate reconstruction beams, each propagating to a predetermined position within one of said pixels in said pixel array of said integrated circuit.

5. A system as in claim 4, wherein said first optical beam steering element further operating to add a fixed and predetermined biasing angle in the direction of said optical reference beam entering said recording medium through said second surface when said integrated circuit operates in said light detection mode so as to direct said conjugated reconstruction beam to a desired and predetermined position within one of said plurality of pixels of said integrated circuit.

6. A system as in claim 4, wherein said phase conjugator is self-pumped.

7. A system as in claim 4, wherein said phase conjugator has a photorefractive crystal.

8. A system as in claim 3, wherein said beam steering element is a diffractive optical element.

9. A system as in claim 8, wherein said diffractive optical element has a liquid crystal material.

10. A system as in claim 9, wherein said diffractive optical element is a liquid crystal device comprising:

a plurality of cells made from substrates, each having an etched surface to form a blazed grating with a different spatial period and enclosing a liquid crystal material therein, each of said cells having electrodes upon which electrical control signals are applied; and

said cells cascading relative to each other to change phase profile of a light beam passing through said cells based on said electrical control signals and thereby to generate a plurality of deflection angles of said light beam.

11. A system as in claim 3, wherein said first optical beam steering element is a micro-mirror based on micro-mechanical electromagnetic systems.

12. A system as in claim 3, further including:

a third surface of said plurality of surfaces of said recording medium facing said second surface and being disposed in the optical path of said reference beam;

a second optical beam steering element being disposed on said third surface of said recording medium; and

a plurality of optical guiding elements, operating in combination with said second beam steering element to direct a conjugate reference beam to propagate in the opposite direction of said reference beam and to retrace the optical path thereof, said conjugate reference beam entering said recording medium through said second beam steering element and said third surface.

13. A system as in claim 12, wherein said second beam steering element is capable of deflecting said phase-conjugated reference beam with a predetermined angle with respect to the optical path of said reference beam when said integrated circuit operates in said light detection mode, said predetermined angle being so predetermined such that said phase-conjugated reference beam diffracts from said holograms in said recording medium to produce a plurality of conjugate reconstruction beams, each propagating toward a predetermined position within one of said plurality of pixels in said pixel array of said integrated circuit.

14. A system as in claim 12, wherein said optical guiding elements are mirrors.

15. A system as in claim 12, wherein said first beam steering element and said second beam steering element are diffractive optical elements.

16. A system as in claim 3, further including a reflecting mirror, disposed adjacent to said third surface and in the optical path of said reference beam, operating to receive at least a portion of said reference beam and to produce a phase-conjugated reference beam by reflection that retraces the optical path of said reference beam and propagates from said reflecting mirror towards said recording medium;

and

said phase-conjugated reference beam diffracting from said holograms in said recording medium to produce a plurality of conjugate reconstruction beams, each propagating to a predetermined position in one of said pixels in said pixel array of said integrated circuit.

17. A system as in claim 16, wherein said reflecting mirror further operates to reflect said reference beam, which propagates through said first optical beam steering element and said recording medium to said reflecting mirror, to produce a reflected read beam that retraces the optical path of said reference beam with a fixed biasing angle relative to the optical path thereof when said integrated circuit operates in said light detection mode, said biasing angle being so predetermined such that said reflected read beam diffracts from said holograms in said recording medium to produce a plurality of conjugate reconstruction beams, each propagating toward a predetermined position within one of said plurality of pixels in said pixel array of said integrated circuit.

18. A system as in claim 1, further including:

an optical beam coupling element, disposed between said integrated circuit and said recording medium, operating to inject an optical reference beam into said recording medium through said first surface thereof for retrieving information encoded in said holograms therein;

a second surface of said plurality of surfaces of said recording medium facing said first surface and being disposed in an optical path that connects said pixel array on said integrated circuit, said beam coupling element, and said first surface of said recording medium;

at least one tunable laser, operating to produce light of a plurality of wavelengths in a spectral range to which said recording medium is responsive, said laser operable to produce an optical signal beam that propagates along said optical path, entering said recording medium via said second surface and propagating to said pixel array in said integrated circuit via said first surface of said recording medium and said beam coupling element;

means in said integrated circuit in light modulation mode for modulating said signal beam and producing a spatially modulated signal beam, said spatially modulated signal beam propagating back to said recording medium along said optical path and interfering with said signal beam to record said plurality of holograms superimposed in said recording medium with each of said holograms being at a different wavelength in said spectral range; and

said reference beam propagating along said optical path towards said recording medium and diffracting from said plurality of holograms to produce a phase-conjugated reconstruction beam that propagates in the opposite direction of said spatially modulated signal beam towards said pixel array of said integrated circuit.

19. A system as in claim 18, further including:

a beam steerer, attached to said beam coupling element, operating to bias the propagation direction of said reference beam in a way such that said reference beam propagates along said optical path towards said recording medium with a fixed biasing angle; and

said biasing angle being so predetermined that said reference beam diffracts from said holograms in said recording medium to produce a plurality of reconstruction beamlets in said conjugate reconstruction beam, each of said reconstruction beamlets propagating to a desired and !predetermined position within one of said plurality of pixels in said pixel array of said integrated circuit.

20. A system as in claim 2, further including:

a second surface and a third surface of said plurality of surfaces of said recording medium, said second surface facing said third surface;

a first diode laser, operating to produce light of different wavelengths in a spectral range to which said recording medium is responsive, said first diode laser emanating a writing reference beam into said recording medium through said second surface, said writing reference beam being coherent with said signal beam;

a second diode laser, operating to produce light of different wavelengths in a spectral range to which said recording medium is responsive, said second diode laser being attached to said third surface to emanate a reading reference beam into said recording medium; and

said first diode laser and said second diode laser being positioned such that said writing reference beam and said reading reference beam counter propagate relative to each other within said recording medium.

21. A system as in claim 20, wherein said second diode laser is positioned in a way that said reading reference beam counter propagates said writing reference beam at a fixed biasing angle with respect to the direction of said writing reference beam, said biasing angle being so predetermined that said reading reference beam diffracts from said holograms in said recording medium to produce a plurality of conjugate reconstruction beams, each propagating to a desired and predetermined position within one of said plurality of pixels in said pixel array of said integrated circuit.

22. A system as in claim 20, further including a beam steerer, disposed between said second diode laser and said third surface of said recording medium, operating to bias said reading reference beam with a fixed basing angle relative to said writing reference beam, said biasing angle being so predetermined that said reading reference beam diffracts from said holograms in said recording medium to produce a plurality of conjugate reconstruction beams, each propagating to a desired and predetermined position within one of said plurality of pixels in said pixel array of said integrated circuit.

23. A system as in claim 2, further comprising:

a phase modulator capable of producing a plurality of phase codes that are mutually orthogonal to each other, operating to modulate phase of an optical reference beam passing therethrough with said plurality of phase codes;

a second surface and a third surface of said plurality of surfaces of said recording medium;

said second surface facing said third surface;

a first lens, a second lens, and a mirror;

said phase modulator and said first lens being disposed relative to said second surface of said recording medium so that said first lens is positioned between said phase modulator and said second surface;

said second lens and said mirror being disposed relative to said third surface of said recording medium so that said second lens is positioned between said third surface and said mirror;

said phase modulator, said first lens, said second lens, and said mirror being arranged relative to each other in such a way that said reference beam having an optical path through said phase modulator, said first mirror, and said recording medium retraces said optical path upon reflection by said mirror.

24. A system as in claim 23, further including a beam steerer, disposed between said second lens and said third surface of said recording medium, operating to bias said reflection of said reference beam with a fixed basing angle relative to said optical path, said biasing angle being so predetermined that said reflection diffracts from said holograms in said recording medium to produce a plurality of conjugate reconstruction beams, each propagating to a desired and predetermined position within one of said plurality of pixels in said pixel array of said integrated circuit.

25. A system as in claim 23, wherein said phase modulator, said first lens, said second lens, and said mirror being arranged relative to each other to form a 4f optical system.

26. A system as in claim 23, wherein said first lens and said second lens are diffractive optical lenses.

27. A system as in claim 2, further including:

a phase modulator, engaging a second surface of said recording medium and being operable to produce a plurality of phase codes that are mutually orthogonal to each other, operating to modulate the phase of an optical reference beam passing therethrough with said plurality of phase codes;

a reference beam, coherent with said signal beam, propagating through said phase modulator and said recording medium;

a phase conjugator, engaging a third surface of said recording medium which faces said second medium, operating to receive said reference beam and to produce a phase conjugate beam thereof; and

said phase conjugate beam diffracting from said holograms to produce a conjugated reconstruction beam propagating to said pixel array of said integrated circuit.

28. A system as in claim 27, wherein said phase conjugator has a nonlinear optical medium and two counter-propagating pump beams therein;

said pump beams being disposed relative to each other and to said incident optical beam to generate an optimal amount of said phase conjugate beam.

29. A system as in claim 27, wherein said phase modulator is capable of biasing the direction of said optical reference beam entering said recording medium through said second surface with a predetermined biasing angle, said biasing angle being so determined that said conjugated reconstruction beam propagates to a desired and predetermined position within one of said plurality of pixels of said integrated circuit in said light detection mode.

30. A system as in claim 2, further including:

a focusing lens and a reflecting element;

a second surface and a third surface of said plurality of surfaces of said recording medium;

said second surface and said third surface facing and being parallel to each other and being perpendicular to the optic axis of said focusing lens, said focusing lens being disposed relative to said second surface to emanate light along the optic axis thereof into said recording medium via said second surface, said reflecting element being positioned relative to said third surface to receive light from said recording medium;

a moving assembly, holding said integrated circuit, said beam coupling element, said recording medium, and said reflecting element relative to each other, operating to move in a direction perpendicular to the optic axis of said focusing lens; and

said focusing lens and said reflecting element being positioned relative to each other such that a collimated plane-wave reference beam, propagating along the optic axis of said focusing lens having a optical path going through said focusing lens and said recording medium to reach said reflecting element, is reflected by said reflecting element as a reflected reference beam to retrace said optical path.

31. A system as in claim 30, wherein said reflecting element is operable to shift said reflected reference beam in parallel to the optic axis of said lens and perpendicular to said direction of moving assembly in a predetermined amount of displacement relative to the optic axis of said lens, said predetermined amount of displacement being set forth such that said reflected reference beam diffracts from said holograms in said recording medium to produce a plurality of conjugate reconstruction beams, each propagating to a desired and predetermined position within one of said plurality of pixels in said pixel array of said integrated circuit.

32. A system as in claim 30, wherein said focusing lens is a diffractive optical element.

33. A system as in claim 2, further comprising:

a reconfigurable lens having an optical material and an electrical element, said electrical element producing electrical signals to change refractive index of said optical material and thereby to shift the focus of said lens;

a second surface and a third surface of said plurality of surfaces of said recording medium;

said second surface and said third surface facing and being parallel to each other and being perpendicular to the optic axis of said lens, said lens being disposed relative to said second surface to emanate light along the optic axis thereof into said recording medium via said second surface; and

a reflecting element, being positioned relative to said third surface to receive light from said recording medium, said reflecting element and said lens being positioned relative to each other such that a collimated plane-wave reference beam, propagating along the optic axis of said lens having an optical path going through said focusing lens and said recording medium to reach said reflecting element, is reflected by said reflecting element as a reflected reference beam to retrace said optical path.

34. A system as in claim 2, further including:

a second surface and a third surface of said plurality of surfaces of said recording medium, said second surface and said third surface facing and being parallel to each other;

a focusing lens, said focusing lens being disposed relative to said second surface to emanate light along the optic axis thereof into said recording medium via said second surface;

a beam guiding element, disposed relative to said focusing lens, operating to couple a reference beam to said focusing lens along the optics axis thereof, said focusing lens focusing said reference beam into said recording medium;

a reflecting element being positioned relative to said third surface to receive light from said recording medium;

a moving assembly, holding said beam guiding element and said focusing lens, operating to move in a direction perpendicular to the optic axis of said focusing lens; and

said focusing lens and said reflecting element being positioned relative to each other such that said reference beam, propagating along the optic axis of said focusing lens having a optical path going through said focusing lens and said recording medium to reach said reflecting element, is reflected by said reflecting element as a reflected reference beam to retrace said optical path.

35. A system as in claim 34, wherein said focusing lens is a diffractive optical element.

36. A system as in claim 1, further including:

a set of fixed illumination holograms in said recording medium, superimposing said plurality of holograms therein;

a light source to produce a reference writing beam having a relationship with said illumination holograms in said recording medium;

said reference writing beam interacting with said illumination holograms to produce a plurality of illumination beams that propagate to said pixel array of said integrated circuit and converge to said plurality of said pixels thereof;

said reference writing beam and said pixel array in said light modulation mode working in combination to store information in said plurality of holograms in said recording medium; and

a means to produce a reference read beam that propagates in the opposite direction of said reference writing beam.

37. A system as in claim 36, wherein said means to produce said reference read beam includes a second light source to generate said reference read beam.

38. A system as in claim 36, wherein said means to produce said reference read beam includes at least two optical elements to partition a portion of said referee writing beam to produce said reference read beam.

46. A system as in claim 10, wherein said substrates are made of a semiconductor material or a glass.

47. A system as in claim 27, wherein said phase conjugator is self-pumped.

39. A multifunctional holographic system, comprising:

a holographic recording medium with a plurality of holograms therein, having a first surface, a second surface, and a third surface to receive and transmit light, said second surface and said third surface facing and opposing each other;

a first lens disposed relative to said first surface, providing optical conduit to said recording medium via said first surface;

a second lens disposed relative to said second surface, providing optical conduit to said recording medium via said second surface;

a first optoelectronic integrated circuit, having a plurality of pixels to form a pixel array, each of said pixels capable of detecting light signals and modulating light beams operating to perform said modulating by using information from said detecting, said first integrated circuit being positioned relative to said first lens such that said first lens is between said first integrated circuit and said first surface of said recording medium;

a second optoelectronic integrated circuit, substantially similar to said first integrated circuit in structure and function, being positioned relative to said second lens such that said first lens is between said second integrated circuit and said second surface of said recording medium;

a signal beam generating means, operating to produce and couple an incident beam propagating to said first integrated circuit along the optic axis of said first lens, each of said pixels in said first integrated circuit modulating and reflecting said signal beam to generate a signal beam propagating towards said recording medium;

a reference beam generating means, operating to produce a reference beam coherent with said signal beam, said reference beam propagating through said recording medium via said third surface and said second surface thereof;

said signal beam and said reference beam interfering each other to record said holograms in said recording medium; and

said second lens and said second integrated circuit being disposed relative to each other such that said reference beam is reflected back to produce a conjugate reference beam retracing said reference beam.

40. A system as in claim 39, further comprising a beam steerer, disposed relative to said third surface, changing propagating direction of said reference beam to angularly multiplex said holograms in said recording medium and to retrieve said holograms.

41. A system as in claim 39, wherein said first lens and said second lens are diffractive optical elements.

42. A system as in claim 39, wherein said second lens and said second integrated circuit are separated to each other by a focal length, said second lens focusing said reference beam to a pixel on said second integrated circuit.

43. A system as in claim 39, further including volume multiplexing means to superimpose said holograms in said recording medium by a multiplexing scheme that is selected from a group consisting of phase-code multiplexing, wavelength multiplexing, and shift multiplexing.

44. A system as in claim 39, wherein said signal beam generating means includes a beam splitter that is disposed between said first lens and said integrated circuit.

45. A method of forming an optical holographic system, comprising:

providing a rewritable holographic recording medium;

providing an optoelectronic device that has a plurality of pixels to form a pixel array, each of said pixels detecting and modulating light signals and being capable of using information from said detecting to control said modulating;

integrating said optoelectronic device and said recording medium relative to each other;

recording multiplexed holograms in said recording medium by using a modulated signal beam from said pixel array and a reference beam; and

generating a conjugate readout beam that counterpropagates with respect to said reference beam, said readout beam diffracting from said multiplexed holograms to produce a conjugate reconstruction retracing said modulated signal beam to said pixel array.

48. A photonic device, comprising:

an optoelectronic integrated circuit, having a plurality of pixels to form a pixel array on an interface thereof and a plurality of electrical terminals for both feeding information to said pixel array and exporting information from said pixel array, each of said plurality of pixels operable to emit and to detect light;

a rewritable holographic recording medium, having a first surface, a second surface, and a third surface to provide optical conduits to said recording medium, said first surface and said optoelectronic integrated circuit being disposed relative to each other such that said pixels emit light beams into said recording medium and receive light beams from said recording medium, said second surface and said third surface opposing to each other;

a laser, operating to produce an optical reference beam entering said recording medium via said second surface and having a phase relationship with said pixels in said optoelectronic integrated circuit; and

a first optical beam steering element disposed on said second surface of said recording medium, operating to change the propagating direction of said optical reference beam that enters said recording medium through said first optical beam steering element and said second surface.

49. A device as in claim 48, wherein each of said pixels in said optoelectronic integrated circuit includes a vertical cavity surface-emitting laser.

50. A device as in claim 48, further comprising:

a second optical beam steering element disposed on said third surface of said recording medium, operating to change the propagating direction of an optical reference readout beam that enters said recording medium through said second optical beam steering element and said third surface.

51. A device as in claim 48, wherein said second optical reference readout beam has a relation with said optical reference beam.