System and method for using slow light in optical sensors

• US 8,300,231 B2
• Filed: 02/11/2011
• Issued: 10/30/2012
• Est. Priority Date: 06/15/2007
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Terrel, Matthew A., Digonnet, Michel J. F., Fan, Shanhui
• Primary Examiner(s): Chowdhury, Tarifur
• Assistant Examiner(s): Cook, Jonathon
• Application Number:
  US13/026,049
• Publication Number:
  US 20110134432A1
• Time in Patent Office: 627 Days
• Field of Search: 356/477, 356/482, 356/483, 356/486, 356/493, 356/498, 356459-461
• US Class Current: 356/477
• CPC Class Codes: G01C 19/721 Details
• CPC Class Codes: G01D 5/35303 using a reference fibre, e.g. interferometric devices
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

An optical sensor includes at least one optical coupler and an optical waveguide in optical communication with the at least one optical coupler. The optical waveguide is configured to receive a first optical signal from the at least one optical coupler. The first optical signal has a group velocity and a phase velocity while propagating through at least a portion of the optical waveguide, the group velocity less than the phase velocity. An interference between the first optical signal and a second optical signal is affected by relative movement between the optical waveguide and the at least one optical coupler.

Claims

1. An optical sensor comprising:

at least one optical coupler;

an optical waveguide comprising a plurality of loops, the optical waveguide in optical communication with the at least one optical coupler and mechanically decoupled from the at least one optical coupler such that the at least one optical coupler and the optical waveguide can be moved relative to one another with a rotation of the optical waveguide about an axis of symmetry of the plurality of loops, the coiled optical waveguide configured to receive a first optical signal from the at least one optical coupler, wherein the first optical signal has a group velocity and a phase velocity while propagating through at least a portion of the optical waveguide, the group velocity less than the phase velocity, wherein an interference between the first optical signal and a second optical signal is affected by the rotation of the optical waveguide about the axis of symmetry; and

an optical detector configured to detect interference between the first optical signal and the second optical signal.

2. The optical sensor of claim 1, wherein the interference has a sensitivity to the relative movement which is dependent on the group velocity.

3. The optical sensor of claim 1, wherein the optical waveguide comprises a Bragg fiber.

4. The optical sensor of claim 1, wherein the optical waveguide comprises a photonic-bandgap fiber.

5. The optical sensor of claim 1, wherein the optical waveguide comprises a hollow-core optical fiber.

6. The optical sensor of claim 1, wherein the optical waveguide comprises a solid-core optical fiber.

7. The optical sensor of claim 1, wherein the group velocity is less than 50% of the speed of light in vacuum.

8. The optical sensor of claim 1, wherein the group velocity is less than 20% of the speed of light in vacuum.

9. The optical sensor of claim 1, wherein the interference is indicative of a rate of rotation of the optical waveguide.

10. The optical sensor of claim 1, wherein the at least one optical sensor comprises a first optical coupler and a second optical coupler, and the first optical signal comprises a first portion of an optical signal received by the first optical coupler.

11. The optical sensor of claim 10, further comprising a light source in optical communication with the first optical coupler, the light source configured to provide the optical signal to the first optical coupler.

12. The optical sensor of claim 10, wherein the second optical signal comprises a second portion of the optical signal received by the first optical coupler.

13. The optical sensor of claim 12, further comprising a second optical waveguide configured to receive the second optical signal, the optical waveguide in optical communication with the second optical coupler, the second optical waveguide in optical communication with the second optical coupler, wherein the second optical coupler is configured to receive the first optical signal and the second optical signal.

14. The optical sensor of claim 13, wherein the optical detector is in optical communication with the second optical coupler, the optical detector configured to detect interference between the first and second optical signals.

15. An optical sensor comprising:

at least one optical coupler;

an optical waveguide comprising a plurality of loops, the optical waveguide configured to receive a first optical signal and a second optical signal from the at least one optical coupler and mechanically decoupled from the at least one optical coupler such that the at least one optical coupler and the optical waveguide can be moved relative to one another with a rotation of the optical waveguide along a first direction about an axis of symmetry of the plurality of loops, wherein light propagates through at least a portion of the optical waveguide with a group velocity and a phase velocity, the group velocity less than the phase velocity, wherein, while the optical waveguide rotates along the first direction about the axis of symmetry, the first optical signal propagates through the optical waveguide in the first direction and the second optical signal propagates through the optical waveguide in a second direction generally opposite to the first direction, wherein an interference between the first optical signal and the second optical signal is affected by the rotation of the optical waveguide along the first direction about the axis of symmetry; and

an optical detector configured to detect interference between the first optical signal and the second optical signal.

16. The optical sensor of claim 15, wherein the group velocity is less than 50% of the speed of light in vacuum.

17. The optical sensor of claim 15, wherein the interference has a sensitivity to the rotation which is inversely proportional to the group velocity.

18. An optical sensor comprising:

a fiber coupler configured to receive light from a light source and to transmit light to a light detector; and

a fiber coil optically coupled to the fiber coupler and mechanically decoupled from the fiber coupler such that the fiber coupler and the fiber coil can be moved relative to one another with a rotation of one of the fiber coil and the fiber coupler about an axis of symmetry of the fiber coil such that a first optical pathlength between a first portion of the fiber coil and the fiber coupler increases and a second optical pathlength between a second portion of the fiber coil and the fiber coupler decreases, at least a portion of the fiber coil comprising an optical fiber through which light propagates with a group velocity and a phase velocity, the group velocity less than the phase velocity, wherein a first portion of the light received by the fiber coupler from the light source propagates from the fiber coupler, through the fiber coil in a first direction, and back to the fiber coupler and a second portion of the light received by the fiber coupler from the light source propagates from the fiber coupler, through the fiber coil in a second direction opposite to the first direction, and back to the fiber coupler, the first portion of the light and the second portion of the light propagating to the light detector and interfering with one another, wherein the interference between the first portion of the light and the second portion of the light is indicative of the rotation.

19. The optical sensor of claim 18, wherein the fiber coil is configured to rotate about a direction generally perpendicular to the fiber coil with a rotation rate, the interference indicative of the rotation rate.

20. The optical sensor of claim 19, wherein the fiber coupler comprises a prism coupler.

21. The optical sensor of claim 19, wherein the rotation of the fiber coil is less than 20 degrees.

22. The optical sensor of claim 18, wherein the first portion of the fiber coil comprises a first end of the fiber coil and the second portion of the fiber coil comprises a second end of the fiber coil.

23. The optical sensor of claim 22, wherein the fiber coupler comprises a first port and a second port, the first port optically coupled to the first end of the fiber coil and the second port optically coupled to the second end of the fiber coil.

24. The optical sensor of claim 23, further comprising a first gap between the first port and the first end such that optical signals traveling between the first port and the first end propagate in free space.

25. The optical sensor of claim 24, further comprising a second gap between the second port and the second end such that optical signals traveling between the second port and the second end propagate in free space.

26. The optical sensor of claim 23, further comprising a first lengthwise stretchable optical waveguide between the first port and the first end.

27. The optical sensor of claim 26, further comprising a second lengthwise stretchable optical waveguide between the second port and the second end.

28. The optical sensor of claim 18, wherein the optical fiber comprises a Bragg fiber.

29. The optical sensor of claim 18, wherein the optical fiber comprises a photonic-bandgap fiber.

30. The optical sensor of claim 18, wherein the group velocity is less than 50% of the speed of light in vacuum.

31. The optical sensor of claim 18, wherein the interference has a sensitivity to the rotation which is dependent on the group velocity.