Optical waveguide displacement sensor

• US 20050180678A1
• Filed: 02/18/2004
• Published: 08/18/2005
• Est. Priority Date: 02/18/2004
• Status: Active Grant

• Current Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Original Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Inventors: Ilic, Bojan, Lipson, Michal, Panepucci, Roberto R., Almeida, Vilson Rosa de
• Granted Patent: US 7,274,835 B2
• Time in Patent Office: Days
• US Class Current: 385/13
• CPC Class Codes: G01D 5/266 by interferometric means G01D5/353 takes precedence
• CPC Class Codes: G01D 5/268 using optical fibres G01D5/28 - G01D5/38 take precedence
• CPC Class Codes: G02B 6/305 and having an integrated mode-size expanding section, e.g. tapered waveguide
• CPC Class Codes: G02B 6/3502 involving direct waveguide displacement, e.g. cantilever type waveguide displacement involving waveguide bending, or displacing an interposed waveguide between stationary waveguides
• CPC Class Codes: G02B 6/3566 involving bending a beam, e.g. with cantilever
• CPC Class Codes: G02B 6/3578 Piezoelectric force piezoelectric forces controlling reflecting elements in general G02B26/0858; piezo-optic devices G02F1/0131

Abstract

A substrate incorporates a mechanical cantilever resonator with passive integrated optics for motion detection. The resonator acts as a waveguide, and enables optical detection of deflection/displacement amplitude, including oscillations. In one embodiment, the cantilever comprises a silicon waveguide suspended over a substrate. A reflector structure faces a free end of the suspending cantilever, or a waveguide is supported facing the free end of the suspended cantilever to receive light transmitted through the silicon waveguide cantilever. Deflection/displacement of the cantilever results in modulation of the light received from its free end that is representative of the displacement. Ring resonators may be used to couple different wavelength light to the waveguides, allowing formation of an array of cantilevers.

Claims

1. An optical sensor comprising:

a substrate having an opening;

a cantilevered waveguide having a first portion supported by the substrate and a second portion suspended over the opening in the substrate; and

a receiving structure positioned to receive light transmitted from an end of the second portion of the cantilevered waveguide.

2. The optical sensor of claim 1 wherein the receiving structure comprises a waveguide having an end facing the light transmitting end of the second portion of the cantilevered waveguide.

3. The optical sensor of claim 1 wherein the receiving structure comprises a reflector facing the light transmitting end of the second portion of the cantilevered waveguide.

4. The optical sensor of claim 3 wherein the reflector is supported by the substrate and reflects light back into the light transmitting end of the second portion of the cantilevered waveguide.

5. The optical sensor of claim 1 and further comprising an optical fiber that supplies light to the cantilevered waveguide.

6. The optical sensor of claim 5 wherein the cantilevered waveguide comprises a nano-taper at a second end of the waveguide that contacts a light emitting end of the optical fiber.

7. The optical sensor of claim 1 wherein the cantilever waveguide comprises a selectively receptive substance attached to the second portion of the cantilever waveguide a desired distance from the light transmitting end of the second portion of the cantilevered waveguide.

8. The optical sensor of claim 7 wherein the cantilever waveguide has a resonant frequency of oscillation that changes when something attaches to the selectively receptive substance.

9. The optical sensor of claim 8 wherein the selectively receptive substance is bio-receptive.

10. The optical sensor of claim 1 and further comprising a stress layer formed on the cantilevered waveguide.

11. The optical sensor of claim 10 wherein the stress layer comprises silicon nitride.

12. An optical sensor comprising:

a substrate having an opening;

a cantilevered waveguide having a first portion supported by the substrate and a second portion suspended over the opening in the substrate;

means for receiving light transmitted from an end of the second portion of the cantilevered waveguide; and

means for actuating the cantilevered waveguide.

13. The optical sensor of claim 12 wherein the means for actuating comprises a piezoactuator.

14. The optical sensor of claim 13 wherein the piezoactuator is positioned below the substrate.

15. The optical sensor of claim 12 wherein the means for actuating increases sensitivity of the cantilevered waveguide without significantly degrading a quality factor.

16. The optical sensor of claim 12 wherein the means for actuating comprises an electrostatic actuator.

17. An optical sensor comprising:

a substrate having an opening;

a supply waveguide;

multiple cantilevered waveguides having first portions supported by the substrate and second portions suspended over the opening in the substrate;

multiple corresponding receiving structures positioned to receive light transmitted from the ends of the second portion of the cantilevered waveguides; and

multiple ring resonators optically coupled between the cantilever waveguides and the supply waveguide.

18. The optical sensor of claim 17 wherein multiple ring resonators couple light of different wavelengths between the cantilever waveguides and the supply waveguides.

19. The optical sensor of claim 17 wherein the cantilevered waveguides have different resonant frequencies.

20. The optical sensor of claim 17 wherein the receiving structures comprise reflectors.

21. The optical sensor of claim 17 wherein the receiving structures comprise waveguides.

22. The optical sensor of claim 17 and further comprising:

a receiving waveguide;

multiple ring resonators optically coupled to the receiving structures and the receiving waveguide, wherein such multiple ring resonators are tuned to corresponding ring resonators optically coupled between the cantilever waveguides and the supply waveguide.

23. The optical sensor of claim 22 wherein the multiple ring resonators are tuned to desired wavelengths.

24. The optical sensor of claim 17 wherein the second portions of the cantilever waveguides are of different length.

25. The optical sensor of claim 17 and further comprising a stress layer formed on at least one of the cantilevered waveguides.

26. An optical sensor comprising:

a substrate having an opening;

a supply waveguide;

multiple cantilevered waveguides having first portions supported by the substrate and second portions suspended over the opening in the substrate;

means for receiving light transmitted from the end of the second portion of the cantilevered waveguides;

multiple ring resonators optically coupled between the cantilever waveguides and the supply waveguide; and

means for actuating the cantilevered waveguides.

27. A method comprising:

forming a selectively receptive cite on a suspended end of a cantilever waveguide;

supplying light to the cantilever waveguide; and

measuring light modulated by motion of the cantilever waveguide.

28. The method of claim 27 wherein the receptive cite is bioreceptive.

29. The method of claim 28 and further comprising actuating the cantilever waveguide.

30. A method of sensing vibration, the method comprising:

supplying light to a cantilever waveguide;

coupling the cantilever waveguide to a vibrating surface; and

measuring light modulated by motion of the cantilever waveguide.