Microbubble optical resonator

• US 20100231903A1
• Filed: 02/02/2010
• Published: 09/16/2010
• Est. Priority Date: 03/13/2009
• Status: Active Grant

• Current Assignee: OFS Fitel LLC (Furukawa Electric Company Limited)
• Original Assignee: OFS Fitel LLC (Furukawa Electric Company Limited)
• Inventors: Sumetsky, Mikhail
• Granted Patent: US 8,515,227 B2
• Time in Patent Office: Days
• US Class Current: 356/246
• CPC Class Codes: G01N 2021/0346 Capillary cells; Microcells
• CPC Class Codes: G01N 2021/0378 Shapes
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 21/7746 the waveguide coupled to a cavity resonator
• CPC Class Codes: G02B 5/20 Filters polarising elements G02B5/30
• CPC Class Codes: G02B 6/29335 Evanescent coupling to a resonator cavity, i.e. between a waveguide mode and a resonant mode of the cavity wavelength selective means based on resonator cavity coupled non-evanescently G02B6/29356, G02B6/29358
• 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: H01S 3/083 Ring lasers fibre ring lasers H01S3/06791
• CPC Class Codes: H01S 5/10 Construction or shape of the optical resonator , e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region H01S5/20 takes precedence
• CPC Class Codes: H01S 5/1075 Disk lasers with special modes, e.g. whispering gallery lasers

Abstract

An optical microresonator is configured as an optical microbubble formed along a section of an optical microcapillary. The curvature of the outer surface of the microbubble creates an optical resonator with a geometry that encourages the circulating WGMs to remain confined in the central region of the bubble, creating a high Q optical resonator. The resonator may be tuned by modifying the physical properties of the microbubble, allowing the resonator to be used as an optical filter. The resonator may also be used as a sensor or laser by introducing the material to be sensed (or the active laser material) into the microcapillary along which the microbubble is formed.

Claims

1. An optical resonator comprising:

an optical microcapillary formed of an optically transparent material and having a predetermined wall thickness; and

an optical microbubble formed along the optical microcapillary and having a curved outer surface sufficient to confine optically-generated whispering gallery modes (WGMs) excited therein.

2. An optical resonator as defined in claim 1 wherein the optical microbubble curved outer surface is formed of the optically transparent material used to form the optical microcapillary.

3. An optical resonator as defined in claim 2 wherein the predetermined wall thickness of the optical microcapillary is reduced in the region of the optical microbubble.

4. An optical resonator as defined in claim 1 wherein the optical microcapillary and the optical microbubble are disposed within a low index encapsulating material.

5. An optical resonator as defined in claim 4 wherein the curved outer surface of the optical microbubble is removed to create a cavity region confined within the low index encapsulating material that will support optically-generated WGMs.

6. An optical device comprising:

an optical signal path for supporting the propagation of an optical signal;

an optical resonator comprising;

an optical microcapillary formed of an optically transparent material and having a predetermined wall thickness; and

an optical microbubble formed along the optical microcapillary and having a curved outer surface sufficient to confine optically-generated whispering gallery modes (WGMs) excited therein; and

an optical coupler for providing coupling between the optical signal propagating along the optical signal path and the optical microbubble of the optical resonator.

7. An optical device as defined in claim 6 wherein the optical coupler comprises an optical prism disposed adjacent to the curved outer surface of the optical microbubble.

8. An optical device as defined in claim 6 wherein the optical coupler comprises an optical waveguide disposed adjacent to the curved outer surface of the optical microbubble.

9. An optical device as defined in claim 6 wherein the optical coupler comprises an optical fiber taper disposed adjacent to the curved outer surface of the optical microbubble.

10. An optical device as defined in claim 6 wherein the optical coupler comprises an optical grating disposed adjacent to the curved outer surface of the optical microbubble.

11. An optical device as defined in claim 6 wherein the device comprises an optical filter and the optical resonator is tunable to adjust the wavelength of the optical signal propagating along the optical signal path.

12. An optical device as defined in claim 11 wherein the optical resonator is tuned by applying mechanical deformation to the optical microbubble.

13. An optical device as defined in claim 11 wherein the optical resonator is tuned by varying the temperature of the optical microbubble.

14. An optical device as defined in claim 11 wherein the optical resonator is tuned by applying electromagnetic radiation to the optical microbubble.

15. An optical device as defined in claim 6 wherein the device comprises an optical sensor and a sample material to be analyzed is introduced into the optical microbubble through the optical microcapillary.

16. An optical device as defined in claim 15 wherein the sample material is a fluid disposed within or flowing through the optical microcapillary.

17. An optical device as defined in claim 16 wherein the sample material is a gas disposed within or flowing through the optical microcapillary.

18. An optical device as defined in claim 6 wherein the device comprises an optical laser and an active optical material is disposed within the optical microbubble.

19. An optical device as defined in claim 18 wherein the active optical material comprises a liquid disposed within or flowing through the optical microbubble.

20. A method of fabricating an optical microbubble resonator, the method comprising the steps of:

providing an optical microcapillary of an optically transparent material;

heating a localized region of the optical microcapillary;

modifying the air pressure within the heated, localized region; and

deforming the localized region to create a curved outer surface defining an optical microbubble.

21. The method as defined in claim 20 wherein the air pressure is modified by blowing into the optical microcapillary.

22. The method as defined in claim 20 wherein the deforming step creates an essentially spherical microbubble.

23. The method as defined in claim 20 wherein the deforming step creates an elongated microbubble.

24. The method as defined in claim 20 wherein the deforming step creates a squeezed microbubble.

25. The method as defined in claim 20 wherein the method further comprises the step of:

encapsulating the microcapillary and the microbubble within a low-index encapsulant material.

26. The method as defined in claim 25 wherein the method further comprises the step of:

removing at least a portion of the microcapillary in the area of the microbubble, creating a cavity region defined by the low-index encapsulant material.

27. The method as defined in claim 26 wherein the material is removed by etching.

28. The method as defined in claim 20 wherein the method further comprises the step of splicing a section of optical fiber to the optical microcapillary.