UNIT-CELL ARRAY OPTICAL SIGNAL PROCESSOR

• US 20090208162A1
• Filed: 06/01/2008
• Published: 08/20/2009
• Est. Priority Date: 02/14/2008
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Yap, Daniel
• Granted Patent: US 8,019,185 B2
• Time in Patent Office: Days
• US Class Current: 385/3
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/29343 Cascade of loop resonators
• CPC Class Codes: G02B 6/29383 Adding and dropping
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02F 1/212 Mach-Zehnder type
• CPC Class Codes: G02F 1/3132 of directional coupler type
• CPC Class Codes: G02F 2203/15 involving resonance effects, e.g. resonantly enhanced interaction
• CPC Class Codes: G02F 2203/50 Phase-only modulation

Abstract

This invention provides a versatile unit cell as well as programmable and reconfigurable optical signal processors (such as optical-domain RF filters) that are constructed from arrays of those unit cells interconnected by optical waveguides. Each unit cell comprises an optical microdisk, an optical phase shifter, and at least one input/output optical waveguide, wherein the microdisk and the phase shifter are both optically connected to a common waveguide.

Claims

1. A unit cell comprising an optical microdisk, a separate optical phase shifter, and at least two input/output optical waveguides, wherein said microdisk and said phase shifter are both optically connected to a first input/output optical waveguide, and wherein said microdisk is optically connected to a second input/output optical waveguide.

2. The unit cell of claim 1, wherein said optical microdisk and said optical phase shifter are separately programmable, and wherein said optical microdisk comprises two programmable coupling regions and a programmable resonance frequency.

3. The unit cell of claim 1, wherein said unit cell comprises a thin layer of semiconductor material in optical connection with said at least two input/output optical waveguides.

4. The unit cell of claim 3, wherein said layer of semiconductor material includes an undoped region and a doped region, wherein said undoped region and said doped region are configured substantially laterally.

5. The unit cell of claim 4, wherein said at least one input/output optical waveguide includes a core region, and wherein said undoped region is located vertically above said core region and said doped region is not adjacent to said core region.

6. The unit cell of claim 4, wherein the combination of said undoped region and said doped region forms a lateral P-i-N diode, and wherein application of a voltage or current to said P-i-N diode is capable of producing a change in the optical refractive index of the undoped region in said P-i-N diode.

7. The unit cell of claim 4, wherein the combination of said undoped region and said doped region forms a lateral N-i-N device, and wherein application of a voltage to said lateral N-i-N device is capable of producing an electrical current suitable to change the optical refractive index of the undoped region in said lateral N-i-N device.

8. The unit cell of claim 1, further comprising two or more input optical ports and two or more output optical ports for optically connecting to other unit cells, wherein a first pair of input and output optical ports comprise terminations of said first input/output optical waveguide, and wherein a second pair of input and output optical ports comprise terminations of said second input/output optical waveguide.

9. The unit cell of claim 1, wherein said microdisk includes a phase-shifting section.

10. The unit cell of claim 1, wherein said microdisk further comprises two coupling regions and two phase shifters on said microdisk.

11. The unit cell of claim 1, wherein said microdisk includes a heating element.

12. An optical signal processor comprising a plurality of unit cells each described according to claim 1, said unit cells arranged in an array pattern, and said signal processor further comprising a plurality of optical waveguides, wherein each optical waveguide of said plurality of optical waveguides interconnects two unit cells of said plurality of unit cells.

23. A programmable signal-processing building block comprising a combination of four unit cells each described according to claim 1, wherein said building block has up to four optical inputs and up to four optical outputs.

24. The programmable building block of claim 23, wherein said building block can be programmed in a manner suitable for a filter function selected from the group consisting of finite impulse response filter, infinite impulse response filter, delay line with adjustable phase shift, optical power splitter, optical power coupler, optical switch, and recursive optical delay line.

13. An optical filter comprising a plurality of unit cells, wherein each unit cell includes an optical microdisk, a separate optical phase shifter, a first input/output optical waveguide, and a second input/output optical waveguide, wherein said microdisk and said phase shifter are both optically connected to said first input/output optical waveguide, and wherein said second input/output optical waveguide is optically connected to said microdisk.

14. The optical filter of claim 13, wherein said unit cell comprises a thin layer of semiconductor material, having an undoped region and a doped region, in optical connection with at least one input/output optical waveguide.

15. The optical filter of claim 14, wherein said filter is a programmable delay-line filter constructed by interconnecting a plurality of said unit cells with optical waveguides.

16. The optical filter of claim 15, wherein at least some of said unit cells are used as 2×

2 optical couplers.

17. The optical filter of claim 15, wherein at least some of said unit cells are used as 2×

2 optical combiners.

18. The optical filter of claim 15, wherein at least some of said unit cells are used as optical power splitters.

19. The optical filter of claim 15, wherein at least some of said unit cells are used as recursive delay lines.

20. The optical filter of claim 15, wherein at least some of said unit cells are used as optical path switches.

21. The optical filter of claim 15, wherein at least some of said unit cells are used as optical phase shifters.

22. The optical filter of claim 13, wherein said plurality of unit cells are configured in a two-dimensional array, and wherein substantially all of said unit cells are identical in composition.

25. A method of constructing an optical signal processor comprising a plurality of unit cells, said method comprising:

(i) providing a plurality of unit cells, wherein each unit cell includes an optical microdisk including a circular path, an optical phase shifter, a first input/output optical waveguide, and a second input/output optical waveguide, wherein said microdisk and said phase shifter are optically connected by means of said first input/output optical waveguide, and wherein said second input/output optical waveguide is optically connected to said microdisk; and

(ii) interconnecting at least some of said plurality of unit cells with a plurality of optical waveguides, said plurality of optical waveguides being connected to said unit cells by means of said first and second input/output optical waveguides in said unit cells.

26. The method of claim 25, further comprising the step of providing a thin layer of semiconductor material, having an undoped region and a doped region, in optical connection with at least one input/output optical waveguide, in substantially each unit cell.

27. The method of claim 25, further comprising programming at least some of said unit cells to function as 2×

2 optical couplers each comprising two inputs and two outputs, wherein said optical microdisk of said unit cells includes two coupling regions, said two coupling regions suitably programmed to establish the relative amount of power coupled between each of said first and second input/output waveguides and said circular path.

28. The method of claim 25, further comprising programming at least some of said unit cells to function as 1×

2 optical power splitters, wherein said optical microdisk of said unit cells includes a first and second coupling region, said first coupling region suitably programmed to partially couple light between said first input/output optical waveguide and said circular path of said microdisk, and said second coupling region suitably programmed to fully couple light between said circular path and said second input/output optical waveguide.

29. The method of claim 25, further comprising programming at least some of said unit cells to function as 2×

1 optical power combiners, wherein said optical microdisk of each of said unit cells includes first and second coupling regions, said first coupling region suitably programmed to partially couple light from said first input/output optical waveguide into said circular path of said microdisk, and said second coupling region suitably programmed to fully couple light from said circular path to said second input/output optical waveguide.

30. The method of claim 25, further comprising programming at least some of said unit cells to function as recursive delay lines, wherein said optical microdisk of said unit cells includes first and second coupling regions, said first coupling region suitably programmed to couple light between said first input/output optical waveguide and said circular path of said microdisk, and said second coupling region suitably programmed to not couple light between said circular path and said second input/output optical waveguide.

31. The method of claim 25, further comprising programming at least some of said unit cells to function as optical path switches, wherein said optical microdisk of said unit cells includes two coupling regions, said two coupling regions both suitably programmed to either fully couple light between said first and second input/output optical waveguide and said circular path of said microdisk or both suitably programmed to not couple light between said first and second input/output optical waveguide and said circular path of said microdisk.

32. The method of claim 25, further comprising programming at least some of said unit cells to function as optical phase shifters, wherein said optical microdisk of said unit cells includes two coupling regions, said two coupling regions being suitably programmed to not couple light between first and/or second input/output optical waveguide and said circular path of said microdisk.

33. The method of any of claims 27-32, further comprising the step of providing a thin layer of semiconductor material, having an undoped region and a doped region, in optical connection with at least one input/output optical waveguide, in substantially each unit cell, wherein programming is implemented by appropriately electrically energizing said undoped and doped regions of said semiconductor material.