Liquid crystal planar non-blocking NxN cross-connect

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.

What is claimed:  
     
         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.  
     
     
         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.    
     
     
         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.  
     
     
         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 μm.  
     
     
         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 μm 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 μm, the core layer has a thickness between about 4 and 10 μm, and the second cladding layer has a thickness between about 12 and 50 μm.  
     
     
         37 . The device according to  claim 32 , wherein the liquid crystal layer has a thickness less than about 25 μm.  
     
     
         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 N 2  trenches, N 2  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.