Reconfigurable optical switch and method

• US 6,542,654 B1
• Filed: 07/10/2001
• Issued: 04/01/2003
• Est. Priority Date: 07/10/2001
• Status: Expired due to Fees

• Current Assignee: Optical Switch Corporation
• Original Assignee: Optical Switch Corporation
• Inventors: Reed, Jeffrey A., Miller, Robert O.
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Dinh, Jack
• Application Number:
  US09/902,908
• Time in Patent Office: 630 Days
• Field of Search: 385/15, 385/16, 385/17, 385/14, 385/129, 385/130, 385/131, 385/122, 385/125, 385/40, 359/241
• US Class Current: 385/16
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 2006/12145 Switch
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: G02B 6/3548 1xN switch, i.e. one input and a selectable single output of N possible outputs
• CPC Class Codes: G02B 6/3594 Characterised by additional functional means, e.g. means for variably attenuating or branching or means for switching differently polarized beams
• CPC Class Codes: G02F 1/0147 based on thermo-optic effects G02F1/132 takes precedence
• CPC Class Codes: G02F 1/313 in an optical waveguide structure
• CPC Class Codes: G02F 2202/32 Photonic crystals

Abstract

A method for reconfiguring an optical switch includes selecting a first path through a photonic crystal. The crystal includes the first path having a plurality of first regions and a second path having a plurality of second regions. The crystal also includes a third path that provides an optical signal for propagation through one of the first and second paths. The method also includes heating at least one of the first regions and at least one of the second regions. The method further includes cooling the first region at a first rate to place the first region in a first state. The first state allows propagation of the optical signal through at least a portion of the crystal. In addition, the method includes cooling the second region at a second rate to place the second region in a second state. The second state reduces the propagation of the optical signal through at least a portion of the crystal.

Claims

1. A photonic crystal, comprising:

a first path comprising a plurality of first regions, at least one of the first regions set to a first state to allow an optical signal to propagate through at least a portion of the crystal;

a second path comprising a plurality of second regions, at least one of the second regions set to the first state;

a third path coupling the first path and the second path and providing the optical signal for propagation through at least one of the first and second paths;

a first actuator coupled to at least one of the first regions, the first actuator operable to switch the first region between the first state and a second state, the second state reducing the propagation of the optical signal through at least a portion of the crystal; and

a second actuator coupled to at least one of the second regions, the second actuator operable to switch the second region between the first state and the second state.

2. The photonic crystal of claim 1, wherein the first region is amorphous in the first state and polycrystalline in the second state.

3. The photonic crystal of claim 1, wherein:

the first region enters the first state when heated and then cooled at a first rate; and

the first region enters the second state when heated and then cooled at a second rate.

4. The photonic crystal of claim 3, wherein:

the first rate is between approximately one and approximately two nanoseconds; and

the second rate is between approximately ten and approximately fifty nanoseconds.

5. The photonic crystal of claim 1, wherein the first actuator comprises two electrodes coupled to the first region.

6. The photonic crystal of claim 5, wherein a current flowing through the first actuator switches the first region between the first state and the second state.

7. The photonic crystal of claim 6, wherein the current is generated by creating a voltage differential between the electrodes.

8. The photonic crystal of claim 6, wherein:

the current heats the first region; and

the first region enters the first state or the second state based on a rate at which the first region cools.

9. The photonic crystal of claim 8, wherein the rate at which the first region cools depends on at least one of an amplitude of the current, a duration of the current, and a rate at which the current is reduced.

10. The photonic crystal of claim 1, wherein the first and second regions comprise a chalcogenide.

11. The photonic crystal of claim 1, wherein the first and second regions comprise Ge₂Sb₂Te₅.

12. The photonic crystal of claim 1, wherein the first and second regions comprise rods.

13. The photonic crystal of claim 1, wherein the first and second regions are planar.

14. The photonic crystal of claim 1, further comprising at least one confinement cladding disposed around the first and second regions and operable to reduce the propagation of the optical signal through the cladding.

15. The photonic crystal of claim 1, wherein the first and second regions form a triangular lattice.

16. The photonic crystal of claim 1, wherein the crystal has a normalized bandgap of between fifteen percent and twenty five percent.

17. The photonic crystal of claim 1, wherein the crystal has an area of ten square micrometers or less.

18. An optical switch, comprising:

a photonic crystal comprising;

a first path comprising a plurality of first regions, at least one of the first regions set to a first state to allow an optical signal to propagate through at least a portion of the crystal;

a second path comprising a plurality of second regions, at least one of the second regions set to the first state;

a third path coupling the first path and the second path and providing the optical signal for propagation through at least one of the first and second paths;

a first actuator coupled to at least one of the first regions; and

a second actuator coupled to at least one of the second regions; and

a controller coupled to the first and second actuators, the controller operable to switch the first and second regions between the first state and a second state, the second state reducing the propagation of the optical signal through at least a portion of the crystal.

19. The optical switch of claim 18, wherein:

the first region enters the first state when heated and then cooled at a first rate; and

the first region enters the second state when heated and then cooled at a second rate.

20. The optical switch of claim 19, wherein:

the first rate is between approximately one and approximately two nanoseconds; and

the second rate is between approximately ten and approximately fifty nanoseconds.

21. The optical switch of claim 18, wherein:

the first actuator comprises two electrodes coupled to the first region; and

the controller is operable to generate a voltage differential across the electrodes to create a current that heats the first region.

22. The optical switch of claim 21, wherein:

the first region enters the first state or the second state based on a rate at which the first region cools; and

the rate at which the first region cools depends on at least one of an amplitude of the current, a duration of the current, and a rate at which the current is reduced.

23. The optical switch of claim 18, wherein the first and second regions comprise a chalcogenide.

24. The optical switch of claim 18, wherein the controller is operable to determine the state of the first and second regions based on an input control signal.

25. The optical switch of claim 18, wherein:

the first, second, and third paths form a 1×

2 switch;

the crystal comprises at least one million 1×

2 switches; and

the switches have a combined area of one square centimeter or less.

26. A method for reconfiguring an optical switch, comprising:

selecting a first path through a photonic crystal, the crystal comprising the first path and a second path, the first path comprising a plurality of first regions, the second path comprising a plurality of second regions, the crystal also comprising a third path coupling the first path and the second path and providing an optical signal for propagation through one of the first and second paths;

heating at least one of the first regions and at least one of the second regions;

cooling the first region at a first rate to place the first region in a first state, the first state allowing propagation of the optical signal through at least a portion of the crystal; and

cooling the second region at a second rate to place the second region in a second state, the second state reducing the propagation of the optical signal through at least a portion of the crystal.

27. The method of claim 26, wherein:

the first rate is between approximately one and approximately two nanoseconds; and

the second rate is between approximately ten and approximately fifty nanoseconds.

28. The method of claim 26, wherein the first and second regions comprise a chalcogenide.

29. The method of claim 26, further comprising receiving an input control signal;

and

wherein selecting the first path through the photonic crystal comprises selecting the first path using the input control signal.

30. The method of claim 26, wherein heating at least one of the first regions comprises generating a current through the first region.

31. The method of claim 30, wherein:

two electrodes are coupled to the first region; and

generating the current through the first region comprises generating a voltage differential across the electrodes.

32. The method of claim 30, wherein:

the first region enters the first state or the second state based on a rate at which the first region cools; and

the rate at which the first region cools depends on at least one of an amplitude of the current, a duration of the current, and a rate at which the current is reduced.

33. A photonic crystal, comprising:

a first path comprising a plurality of first rods, at least one of the first rods comprising a chalcogenide and set to a first state;

a second path comprising a plurality of second rods, at least one of the second rods comprising a chalcogenide and set to the first state;

a third path coupling the first path and the second path and providing an optical signal for propagation through at least one of the first and second paths;

at least one first electrode coupled to at least one of the first rods and operable to switch the first rod between the first state and a second state;

at least one second electrode coupled to at least one of the second rods and operable to switch the second rod between the first state and the second state;

the first state allowing propagation of the optical signal through at least a portion of the crystal, the first and second rods entering the first state when heated and then cooled at a rate of between approximately one and approximately two nanoseconds;

the second state reducing the propagation of the optical signal through at least a portion of the crystal, the first and second rods entering the second state when heated and then cooled at a rate of between approximately ten and approximately fifty nanoseconds;

the first rod heated by an electric current flowing through the first electrode, the second rod heated by an electric current flowing through the second electrode, the rate at which the first and second rods cool depending on at least one of an amplitude of the current, a duration of the current, and a rate at which the current is reduced.

34. An optical switch, comprising:

a photonic crystal comprising;

a first path comprising a plurality of first rods, at least one of the first rods comprising a chalcogenide and set to a first state;

a second path comprising a plurality of second rods, at least one of the second rods comprising a chalcogenide and set to the first state;

a third path coupling the first path and the second path and providing an optical signal for propagation through at least one of the first and second paths;

at least one first electrode coupled to at least one of the first rods and operable to switch the first rod between the first state and a second state;

at least one second electrode coupled to at least one of the second rods and operable to switch the second rod between the first state and the second state;

the first state allowing propagation of the optical signal through at least a portion of the crystal, the first and second rods entering the first state when heated and then cooled at a rate of between approximately one and approximately two nanoseconds; and

the second state reducing the propagation of the optical signal through at least a portion of the crystal, the first and second rods entering the second state when heated and then cooled at a rate of between approximately ten and approximately fifty nanoseconds; and

a controller operable to switch the first and second rods between the first state and the second state, the controller operable to heat at least one of the first or second rods by generating a current through the first or second electrodes, the controller operable to cool the rod at at least two rates by varying at least one of an amplitude of the current, a duration of the current, and a rate at which the current is reduced.

35. A method for reconfiguring an optical switch, comprising:

selecting a first path through a photonic crystal, the crystal comprising the first path and a second path, the first path comprising a plurality of first rods, the second path comprising a plurality of second rods, the first and second rods comprising a chalcogenide, the crystal also comprising a third path coupling the first path and the second path and providing an optical signal for propagation through one of the first and second paths;

generating a current through at least one of the first rods and a current through at least one of the second rods, the currents operable to heat the rods;

cooling the first rod at a rate of between approximately one and approximately two nanoseconds to place the first rod in a first state, the first state allowing propagation of the optical signal through at least a portion of the crystal;

cooling the second rod at a rate of between approximately ten and approximately fifty nanoseconds to place the second rod in a second state, the second state reducing the propagation of the optical signal through at least a portion of the crystal; and

the rate at which a rod cools depending on at least one of an amplitude of the current flowing through the rod, a duration of the current flowing through the rod, and a rate at which the current flowing through the rod is reduced.