Liquid crystal planar non-blocking NxN cross-connect

• US 20030142262A1
• Filed: 01/07/2003
• Published: 07/31/2003
• Est. Priority Date: 11/01/1999
• Status: Abandoned Application

• Current Assignee: Robert G. Lindquist, Thomas M. Leslie
• Original Assignee: Robert G. Lindquist, Thomas M. Leslie
• Inventors: Leslie, Thomas M., Lindquist, Robert G.
• Application Number:
  US10/337,549
• Publication Number:
  US 20030142262A1
• Time in Patent Office: Days
• US Class Current: 349/198
• CPC Class Codes: G02F 1/1326 Liquid crystal optical waveguides or liquid crystal cells specially adapted for gating or modulating between optical waveguides
• CPC Class Codes: G02F 1/133738 for homogeneous alignment
• CPC Class Codes: G02F 1/133742 for homeotropic alignment
• CPC Class Codes: G02F 1/3137 with intersecting or branching waveguides, e.g. X-switches and Y-junctions

Abstract

A non-blocking N×N cross-connect is provided that has an array of liquid crystal (LC) switches in a grid of planar optical waveguides within a light optical circuit (LOC). LC filled trenches are used in a planar optical waveguide and each trench provides the functionality of a waveguide polarization splitter, a transverse electric (TE) switch cross point, a transverse magnetic (TM) switch cross point, or a waveguide polarization combiner. By combining these elements, a cross-connect system is fabricated.

Claims

1. An optical device for directing a light signal, comprising:

an optical path for propagating the light signal;

a trench formed in the optical path, said trench including a surface region;

an alignment layer disposed on said surface region; and

a liquid crystal material disposed in said trench, said liquid crystal material having a plurality of molecules that are aligned in a first direction by said alignment layer.

2. The optical device according to claim 1, wherein the alignment layer is a homogeneous alignment layer, such that the first direction is parallel to the surface region.

3. The optical device according to claim 1, wherein the alignment layer is a homeotropic alignment layer, such that the first direction is orthogonal to the surface region.

4. The optical device according to claim 1, wherein the optical path comprises:

at least one first waveguide; and

at least one second waveguide intersecting said at least one first waveguide at a cross-point, wherein the trench is disposed at said cross-point.

5. The optical device according to claim 4, further comprising a switching device coupled to the liquid crystal material.

6. The optical device according to claim 5, wherein the switching device is a pair of electrodes.

7. The optical device according to claim 4, wherein the alignment layer comprises at least one of a copolymer, a polymer, obliquely evaporated SiO, and silane couple agents.

8. The optical device according to claim 1, wherein the trench is a slot in the optical path.

9. The optical device according to claim 1, wherein the trench is a canal substantially extending the length of the optical device.

10. The optical device according to claim 1, wherein the optical path comprises a substrate and an optical waveguide structure.

13. The method according to claim 10, wherein the alignment layer is a homogeneous alignment layer, such that the first direction is parallel to the surface region.

14. The method according to claim 10, wherein the alignment layer is a homeotropic alignment layer, such that the first direction is orthogonal to the surface region.

11. The optical device according to claim l, wherein the optical device is disposed within one of a polarization splitter, a polarization combiner, a TM switch, a TE switch, a variable optical attenuator, a signal splitter, and an N×

N TE-TM array.

12. A method of directing a light signal in an optical device, said optical device having a first optical path and a second optical path, said method comprising:

forming a trench in a cross-point, wherein said cross-point is a location where the first optical path intersects the second optical path;

forming an alignment layer on a surface region of the trench;

disposing a liquid crystal material having a plurality of molecules in the trench, wherein said alignment layer causes said plurality of molecules to align in a first direction; and

applying a voltage to said liquid crystal material to thereby change an alignment of said plurality of molecules from said first direction to a second direction to cause a portion of the light signal to be directed from the first optical path into the second optical path.

15. A method of directing a light signal in an optical device, said optical device including an optical path, a trench formed in said optical path, and an alignment layer disposed on a surface of said trench, said method comprising:

disposing a switch element in the trench, said switch element including a plurality of liquid crystal molecules that are aligned in a first direction by the alignment layer when no electrical energy is applied to said switch element; and

applying electrical energy to said switch element to thereby cause said plurality of molecules to align in a second direction.

16. The method according to claim 15, wherein the first direction is parallel to the surface of the trench.

17. The method according to claim 15, wherein the first direction is orthogonal to the surface of the trench.

18. The method according to claim 15, wherein the plurality of molecules comprises liquid crystal molecules.

19. An optical device for directing a light signal, said optical device including a substrate having an optical waveguide layer disposed thereon, said optical device comprising:

at least one first electrode disposed between the substrate and the optical waveguide;

a trench formed in the optical waveguide, said trench having a surface area;

a first alignment layer disposed on the surface area of said trench;

a liquid crystal material disposed in said trench and covering said first alignment layer;

a top plate connected to the substrate; and

a second alignment layer disposed on the top plate and adjacent to said liquid crystal material.

20. The device according to claim 19, wherein the top plate comprises:

a cover glass connected to the substrate; and

a second electrode disposed between said cover glass and the second alignment layer.

21. The device according to claim 20, wherein the first electrode is a grounding electrode and the second electrode is an address electrode.

22. The device according to claim 19, wherein the first and second alignment layers each comprise at least one of a copolymer, a polymer, obliquely evaporated SiO, and silane coupling agents.

23. The device according to claim 19, wherein the liquid crystal material is disposed in a layer that has a thickness of less than about 25 μ

m.

24. The device according to claim 19, wherein the liquid crystal layer comprises at least one of a nematic class liquid crystal material and a ferroelectric class liquid crystal material.

25. The device according to claim 19, wherein the liquid crystal layer comprises liquid crystal molecules that are oriented responsive to an applied voltage.

26. The device according to claim 25, wherein the liquid crystal molecules align with the electric field when a voltage exceeding a predetermined threshold voltage is applied.

27. The device according to claim 25, wherein the liquid crystal molecules align substantially perpendicular to any interface coated with the first alignment layer when substantially no voltage is applied.

28. The device according to claim 25, wherein the liquid crystal molecules align substantially perpendicular to any interface coated with the second alignment layer when substantially no voltage is applied.

29. A liquid crystal cross-connect device, comprising:

an input port for receiving light;

a polarization splitter to split the received light into transverse magnetic (TM) and transverse electric (TE) components;

a TM switch array connected to receive the TM components from the polarization splitter;

a TE switch array connected to receive the TE components from the polarization splitter;

a polarization combiner coupled to the TM switch array and the TE switch array to combine the outputs of the TM switch array and the TE switch array; and

an output port coupled to the polarization combiner.

30. The device according to claim 29, wherein each switch array has a plurality of paths, each path comprising a switching element.

31. The device according to claim 29, wherein each of the switch arrays is in the range between about 50 and 500 μ

m center to center.

32. The device according to claim 29, wherein each of the polarization splitter, the TM switch array, the TE switch array, and the polarization combiner comprises a liquid crystal trench device comprising:

a substrate;

at least one first electrode disposed on the substrate;

a first cladding layer disposed on the first electrode;

a core layer disposed on the first cladding layer;

a second cladding layer disposed on the core layer;

a trench formed in the first cladding layer, the core layer, and the second cladding layer;

a first alignment layer disposed in the trench and on the second cladding layer;

a liquid crystal layer disposed on the first alignment layer;

a second alignment layer disposed on the liquid crystal layer; and

a top plate layer disposed above the second alignment layer.

33. The device according to claim 32, wherein the top plate layer comprises a second electrode disposed above the second alignment layer above the trench and above a portion of the liquid crystal layer over the second cladding layer;

and a cover glass disposed above the second electrode and the second alignment layer.

34. The device according to claim 33, wherein the first electrode is a grounding electrode and the second electrode is an address electrode.

35. The device according to claim 32, wherein the first and second alignment layers each comprise at least one of a copolymer, a polymer, obliquely evaporated SiO, and silane coupling agents.

36. The device according to claim 32, wherein the first cladding layer has a thickness between about 12 and 50 μ

m, the core layer has a thickness between about 4 and 10 μ

m, and the second cladding layer has a thickness between about 12 and 50 μ

m.

37. The device according to claim 32, wherein the liquid crystal layer has a thickness less than about 25 μ

m.

38. The device according to claim 32, wherein the liquid crystal layer comprises at least one of a nematic class liquid crystal material and a ferroelectric class liquid crystal material.

39. The device according to claim 32, wherein the liquid crystal layer comprises liquid crystal molecules that are oriented responsive to an applied voltage.

40. The device according to claim 39, wherein the liquid crystal molecules align with the electric field when a voltage exceeding a predetermined threshold voltage is applied.

41. The device according to claim 39, wherein the liquid crystal molecules align substantially perpendicular to any interface coated with the first alignment layer when substantially no voltage is applied.

42. The device according to claim 39, wherein the liquid crystal molecules align substantially perpendicular to any interface coated with the second alignment layer when substantially no voltage is applied

43. The device according to claim 32, wherein the TM switch array is an N×

N waveguide having N² trenches, N₂ being an integer.

44. The device according to claim 43, wherein all but one of the N trenches are set in a transmission state.

45. The device according to claim 43, wherein the TE switch array is the voltage dual of the TM switch array.