Apparatus for simultaneous spatial modulation of incoherent/coherent angulary multiplexed optical beams

• US 6,445,470 B1
• Filed: 08/27/2000
• Issued: 09/03/2002
• Est. Priority Date: 04/06/1990
• Status: Expired due to Fees

• Current Assignee: University of Southern California
• Original Assignee: University of Southern California
• Inventors: Tanguay, Armand R. Jr., Jenkins, B. Keith
• Primary Examiner(s): HENRY, JON W
• Application Number:
  US09/648,794
• Time in Patent Office: 737 Days
• Field of Search: 359/7, 359/3, 359/4, 359/11, 359/21, 359/22, 359/24, 359/27, 359/32, 359/1, 359/35
• US Class Current: 359/11
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• 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 1/265 Angle multiplexing; Multichannel holograms G03H1/268 takes precedence
• CPC Class Codes: G03H 1/28 superimposed holograms only
• CPC Class Codes: G11B 7/0065 Recording, reproducing or erasing by using optical interference patterns, e.g. holograms
• CPC Class Codes: G11B 7/28 Re-recording, i.e. transcribing information from one optical record carrier on to one or more similar or dissimilar record carriers
• CPC Class Codes: G11C 13/042 using information stored in the form of interference pattern
• CPC Class Codes: H04Q 11/0001 using optical switching

Abstract

Novel apparatus for simultaneous spatial modulation of a set of angularly multiplexed individually coherent but mutually incoherent optical beams is disclosed, comprising means for generating a set of two or more individually coherent beams that have at least one optical wavelength in common, pairwise, and are assured to be mutually incoherent, and means for directing the set of individually coherent but mutually incoherent beams to a spatial modulation means, such that a spatially overlapping group of individually coherent but mutually incoherent beams overlap spatially in at least one region of the spatial modulation means and are angularly multiplexed within the region. Such simultaneous spatial modulation is a key feature, for example, in highly multiplexed photonic interconnection, memory, and display systems with maximum optical throughput efficiency and minimum crosstalk, based on parallel incoherent/coherent double angularly multiplexed holographic recording and readout principles. Simultaneous spatial modulation is also of importance for the provision for arbitrarily weighted and independent interconnections in the development of densely interconnected photonic implementations of neural networks, photonic interconnection networks for telecommunications switching and digital computing applications, optical information processors, optical memories, and optical displays. Variants of the apparatus are provided that allow for the incorporation of optically isolated semiconductor laser diode arrays, vertical cavity surface emitting laser arrays that are partially mutually incoherent and partially wavelength division multiplexed, the combination of laser diode and phase modulator arrays to provide for controllable mutual incoherence, both pixelated and non-pixelated spatial light modulators, and both planar and volume holographic or diffractive optical elements employed as spatial light modulation means.

Claims

1. Apparatus for simultaneous spatial modulation of angularly multiplexed individually coherent but mutually incoherent beams, comprising:

(a) means for generating a set of two or more individually coherent beams;

(b) means for simultaneously activating at least said set of individually coherent beams, said individually coherent beams having at least one optical wavelength in common, pairwise;

(c) means for assuring mutual incoherence among said individually coherent beams, thereby providing a set of two or more individually coherent but mutually incoherent beams; and

(d) means for directing said set of individually coherent but mutually incoherent beams to a spatial modulation means for spatially modulating said set of beams, such that;

(i) a spatially overlapping group of beams, comprising at least two of said individually coherent but mutually incoherent beams, overlap spatially in at least one region of said spatial modulation means, thereby providing a spatially modulated set of beams, and

(ii) said spatially overlapping group of beams is angularly multiplexed in said at least one region.

2. The apparatus of claim 1 wherein said means for generating said set of two or more individually coherent beams comprises a set of sources within a one-dimensional source array.

3. The apparatus of claim 2 wherein said one-dimensional source array comprises an array of semiconductor lasers, said semiconductor lasers being one of edge emitting and surface emitting, and said array of semiconductor lasers provided with laser-to-laser optical isolation and pixelation means to eliminate the potential for inadvertent phase locking among said set of sources.

4. The apparatus of claim 1 wherein said means for generating said set of two or more individually coherent beams comprises a set of sources within a two-dimensional source array.

5. The apparatus of claim 4 wherein said two-dimensional source array comprises an array of surface-emitting semiconductor lasers, said array of semiconductor lasers provided with laser-to-laser optical isolation and pixelation means to eliminate the potential for inadvertent phase locking among said set of sources.

6. The apparatus of claim 1 wherein each region of said at least one region covers substantially all of the active area of said spatial modulation means.

7. The apparatus of claim 1 wherein said means for directing said set of individually coherent but mutually incoherent beams further provides means for directing each said individually coherent beam of said set of individually coherent but mutually incoherent beams to a region of illumination within said spatial modulation means, thereby generating a set of regions of illumination, one said region of illumination for each said beam of said set of individually coherent but mutually incoherent beams, such that the area of each said region of illumination is substantially smaller than the active area of said spatial modulation means.

8. The apparatus of claim 7 wherein substantially all said regions of illumination of said set of regions of illumination are approximately the same size.

9. The apparatus of claim 8 wherein each region of said at least one region is smaller than each said region of illumination of said set of regions of illumination.

10. The apparatus of claim 1 further comprising means for generating a plurality of beams that are at least partially multiplexed in wavelength.

11. The apparatus of claim 1 wherein said means for generating said set of two or more individually coherent beams comprises a set of sources within a superset of sources that is at least partially multiplexed in wavelength.

12. The apparatus of claim 11 wherein said superset of sources comprises a two-dimensional source array.

13. The apparatus of claim 12 wherein said two-dimensional source array comprises a two-dimensional array of semiconductor lasers, said two-dimensional array of semiconductor lasers having wavelength varying across one dimension and said two-dimensional array of semiconductor lasers provided with pixelation means to eliminate the potential for inadvertent phase locking in the other dimension.

14. Apparatus for simultaneous spatial modulation of angularly multiplexed individually coherent but mutually incoherent beams, comprising:

(a) an incoherent/coherent source array, further comprising;

(i) a set of individually coherent light sources within a two-dimensional source array,

(ii) means for simultaneously activating at least a group of two or more of said individually coherent light sources, said group of two or more of said individually coherent light sources thereby generating a group of two or more Individually coherent beams that are substantially monochromatic, and

(iii) means for assuring mutual incoherence among substantially all of said individually coherent beams of said group, pairwise, thereby providing a group of two or more individually coherent but mutually incoherent beams; and

(b) means for directing said group of two or more individually coherent but mutually incoherent beams to a spatial modulation means for spatially modulating said group of beams, such that;

(i) a spatially overlapping subgroup of beams, comprising at least two of said individually coherent but mutually incoherent beams, overlap spatially in at least one region of said spatial modulation means, thereby providing a spatially modulated set of beams, and

(ii) said spatially overlapping subgroup of beams is angularly multiplexed in said at least one region.

15. The apparatus of claim 14 wherein said two-dimensional source array comprises an array of surface-emitting semiconductor lasers, said array of semiconductor lasers provided with laser-to-laser optical isolation and pixelation means to eliminate the potential for inadvertent phase locking among said set of sources.

16. The apparatus of claim 14 wherein each region of said at least one region covers substantially all of the active area of said spatial modulation means.

17. The apparatus of claim 14 wherein said means for directing said group of two or-more individually coherent but mutually incoherent beams further provides means for directing each said individually coherent beam of said group of individually coherent but mutually incoherent beams to a region of illumination within said spatial modulation means, thereby generating a set of regions of illumination, one said region of illumination for each said beam of said group of individually coherent but mutually incoherent beams, such that the area of each said region of illumination is substantially smaller than the active area of said spatial modulation means.

18. The apparatus of claim 17 wherein substantially all said regions of illumination of said set of regions of illumination are approximately the same size.

19. The apparatus of claim 18 wherein each region of said at least one region is smaller than each said region of illumination of said set of regions of illumination.

20. The apparatus of claim 14 wherein said two-dimensional source array is at least partially multiplexed in wavelength.

21. The apparatus of claim 20 wherein said two-dimensional source array comprises a two-dimensional array of semiconductor lasers, said two-dimensional array of semiconductor lasers having wavelength varying across one dimension and said two-dimensional array of semiconductor lasers provided with pixelation means to eliminate the potential for inadvertent phase locking in the other dimension.