Dielectric microcavity fluorosensors excited with a broadband light source

• US 20050263679A1
• Filed: 05/27/2004
• Published: 12/01/2005
• Est. Priority Date: 05/27/2004
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Wilson, Robert W., Guo, Chunmei, Fan, Xudong
• Granted Patent: US 7,271,379 B2
• Time in Patent Office: Days
• US Class Current: 250/214.100
• CPC Class Codes: G01N 21/6428 Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" in vivo A61B5/00; immunoassay G01N33/53
• CPC Class Codes: G01N 21/648 using evanescent coupling or surface plasmon coupling for the excitation of fluorescence
• CPC Class Codes: G02B 6/29341 Loop resonators operating in a whispering gallery mode evanescently coupled to a light guide, e.g. sphere or disk or cylinder evanescent coupling for sensing fluorescence G01N21/648
• CPC Class Codes: G02B 6/4246 Bidirectionally operating package structures

Abstract

A microresonator sensor apparatus has a microcavity resonator that defines equatorial whispering gallery modes (EWGMs), whose frequencies are separated by the free spectral range (FSR). The EWGMs lie in a plane perpendicular to a microcavity resonator axis. A light source is optically coupled to inject light into the microcavity resonator. The light source produces output light having an output spectrum whose bandwidth is approximately equal to or broader than the FSR of the EGWMs. One or more fluorescent materials are excited using the excitation light coupled into the microcavity resonator. A fluorescent signal arising from fluorescence of the one or more fluorescent materials is then detected.

Claims

1. A microresonator sensor apparatus, comprising:

a microcavity resonator defining equatorial whispering gallery modes (EWGMS) whose frequencies are separated by the free spectral range (FSR), the EWGMs lying in a plane perpendicular to a microcavity resonator axis; and

a light source optically coupled to inject light into the microcavity resonator, the light source producing output light having an output spectrum whose bandwidth is approximately equal to or greater than the FSR of the EWGMs.

2. An apparatus as recited in claim 1, wherein the microcavity comprises a bulge-like microcavity resonator.

3. An apparatus as recited in claim 2, wherein the bulge-like microcavity resonator is elongated along an axis, and further comprising a waveguide coupling the output light from the light source to the microcavity resonator.

4. An apparatus as recited in claim 1, further comprising a first optical waveguide disposed to couple light from the light source to the microcavity resonator.

5. An apparatus as recited in claim 4, wherein the first optical waveguide comprises a tapered optical fiber.

6. An apparatus as recited in claim 4, wherein the first optical waveguide comprises a planar waveguide on a substrate.

7. An apparatus as recited in claim 4, further comprising at least a first optical detector disposed to detect light associated with the first microcavity resonator.

8. An apparatus as recited in claim 7, wherein the first optical detector is optically coupled to receive light propagating along the first optical waveguide from the microcavity resonator.

9. An apparatus as recited in claim 7, wherein the first optical detector is disposed proximate the microcavity resonator so as to detect the light propagating through free space from the microcavity resonator.

10. An apparatus as recited in claim 7, further comprising a second optical waveguide optically coupled to the microcavity resonator, wherein the first optical detector is optically coupled to receive light propagating along the second optical waveguide from the microcavity resonator.

11. An apparatus as recited in claim 7, further comprising a wavelength selective element disposed to wavelength select light propagating to the first optical detector.

12. An apparatus as recited in claim 1, wherein the light source comprises a semiconductor laser.

13. An apparatus as recited in claim 1, wherein the light source comprises a light emitting diode.

14. An apparatus as recited in claim 1, wherein the bandwidth is at least equal to five times the FSR.

15. An apparatus as recited in claim 1, wherein the bandwidth is at least equal to ten times the FSR.

16. A method of taking fluorescent measurements, comprising:

coupling excitation light into a first microcavity resonator, the first microcavity resonator defining equatorial whispering gallery modes (EWGMs), the excitation light having a bandwidth sufficiently broad so as to be couplable into at least two adjacent EWGMs;

exciting one or more fluorescent materials using the excitation light coupled into the first microcavity resonator; and

detecting a fluorescent signal arising from fluorescence of the one or more fluorescent materials.

17. A method as recited in claim 16, wherein coupling the excitation light comprises generating the excitation light using a light source and passing the excitation light from the light source to the microcavity resonator via an optical waveguide.

18. A method as recited in claim 17, wherein generating the excitation light comprises generating the excitation light in a laser.

19. A method as recited in claim 17, wherein generating the excitation light comprises generating the excitation light in a light emitting diode.

20. A method as recited in claim 17, wherein the optical waveguide comprises a tapered fiber.

21. A method as recited in claim 17, wherein the optical waveguide comprises a planar waveguide on a substrate.

22. A method as recited in claim 16, wherein detecting the fluorescent signal comprises detecting light propagating in free space from the microcavity resonator.

23. A method as recited in claim 16, further comprising optically filtering the fluorescent signal before detecting the fluorescent signal.

24. A method as recited in claim 16, wherein the light source comprises a semiconductor laser.

25. A method as recited in claim 16, further comprising attaching an analyte to the microresonator cavity, the fluorescent material being associated with the analyte.

26. A method as recited in claim 25, further comprising attaching the fluorescent material to the analyte before attaching the analyte to the microresonator cavity.

27. A method as recited in claim 25, further comprising attaching the fluorescent material to the analyte after attaching the analyte to the microresonator cavity.

28. A method as recited in claim 16, wherein the excitation light has a bandwidth sufficiently broad so as to be couplable into at least five adjacent EWGMs.

29. A method as recited in claim 16, wherein the excitation light has a bandwidth sufficiently broad so as to be couplable into at least ten adjacent EWGMs.