Non-spherical whispering-gallery-mode microcavity

• US 20020018611A1
• Filed: 03/22/2001
• Published: 02/14/2002
• Est. Priority Date: 03/22/2000
• Status: Active Grant

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Yao, Xiaotian S., Ilchenko, Vladimir, Maleki, Lutfollah
• Granted Patent: US 6,795,481 B2
• Time in Patent Office: Days
• US Class Current: 385/15
• CPC Class Codes: G02B 6/29332 Wavelength selective couplers, i.e. based on evanescent coupling between light guides, e.g. fused fibre couplers with transverse coupling between fibres having different propagation constant wavelength dependency non wavelength-selective light guide couplers G02B6/28
• 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 6/34 utilising prism or grating G02B6/293 takes precedence
• CPC Class Codes: G02B 6/4206 Optical features G02B6/4207, G02B6/421 take precedence
• CPC Class Codes: H01S 3/0078 Frequency filtering
• CPC Class Codes: H01S 3/083 Ring lasers fibre ring lasers H01S3/06791
• CPC Class Codes: H01S 5/141 using a wavelength selective device, e.g. a grating or etalon H01S5/146 takes precedence
• CPC Class Codes: H01S 5/142 which comprises an additional resonator

Abstract

Devices based on a non-spherical whispering-gallery-mode optical resonator.

Claims

1. A device comprising a whispering-gallery-mode resonator formed of a spheroid made of an optical dielectric material and shaped with an eccentricity sufficiently large so that free spectral ranges of two different sets of whispering-gallery modes circulating along an equator of said spheroid around a short ellipsoid axis are compatible in magnitude.

2. The device as in claim 1, wherein said eccentricity is greater than 0.5.

3. The device as in claim 1, further comprising an optical coupling element disposed adjacent to said equator to evanescently couple optical energy into said resonator in at least one of said whispering-gallery modes, or out of said resonator from at least one of said whispering-gallery modes.

4. The device as in claim 3, wherein said optical coupling element includes a fiber tip with an angle-polished end facet to couple said optical energy.

5. The device as in claim 3, wherein said optical coupling element includes an optical planar waveguide with an angle-polished end facet to couple said optical energy.

6. The device as in claim 3, wherein said optical coupling element includes a prism.

7. The device as in claim 1, wherein said dielectric material is doped with active ions to produce optical gain at a laser emission wavelength by absorbing pump light at a pump wavelength shorter than said laser emission wavelength.

8. The device as in claim 1, wherein said dielectric material is an electro-optic material, and further comprising electrodes positioned to apply an electrical control voltage to said spheroid to modulate optical energy in said resonator.

9. The device as in claim 1, wherein said spheroid has a dimension less than 10 mm.

10. A method, comprising:

providing a whispering-gallery-mode resonator formed of a spheroid made of an optical dielectric material; and

shaping the spheroid to produce a sufficiently large eccentricity so that free spectral ranges of two different sets of whispering-gallery modes circulating along an equator of said spheroid around a short ellipsoid axis are compatible in magnitude.

11. The method as in claim 10, further comprising coupling optical energy into said resonator in at least one of said whispering-gallery modes.

12. The method as in claim 10, further comprising:

coupling an output laser beam from a CW laser into said resonator in at least one of said whispering-gallery modes;

coupling optical energy out of said resonator from at least one of said whispering-gallery modes to produce a feedback signal; and

feeding said feedback signal back to said laser to control a laser frequency.

13. The method as in claim 10, further comprising using said resonator to filter an optical beam to produce a filtered optical beam in a frequency of one of said whispering-gallery modes.

14. The method as in claim 10, further comprising:

using an optical modulator to modulate a cw laser beam in response to an electrical control signal;

coupling a portion of said modulated laser beam into said resonator in at least one of said whispering-gallery modes;

converting an optical output from said resonator into an electrical signal; and

using at least a portion of said electrical signal as said electrical control signal to control said optical modulator.

16. The device as in claim 15, wherein said laser includes a diode laser.

18. The device as in claim 17, wherein said optical modulator includes:

a whispering-gallery-mode resonator formed of a spheroid made of an electro-optic material to receive said input optical beam; and

electrodes positioned to apply an electrical control voltage to said spheroid to modulate optical energy in said resonator to produce said modulated signal.

15. A device, comprising:

a cw laser operable to produce a laser beam at a laser frequency;

a whispering-gallery-mode resonator formed of a spheroid made of an optical dielectric material and shaped with an eccentricity sufficiently large so that free spectral ranges of two different sets of whispering-gallery modes circulating along an equator of said spheroid around a short ellipsoid axis are compatible in magnitude; and

a coupling element disposed adjacent to said resonator to evanescently couple said laser beam in optical energy into said resonator in at least one of said whispering-gallery modes and a feedback optical signal out of said resonator from at least one of said whispering-gallery modes into said laser to control said laser frequency.

17. A device, comprising:

an optical modulator operable to respond to an electrical control signal to modulate an input optical beam to produce a modulated signal;

a whispering-gallery-mode resonator formed of a spheroid made of an optical dielectric material and shaped with an eccentricity sufficiently large so that free spectral ranges of two different sets of whispering-gallery modes circulating along an equator of said spheroid around a short ellipsoid axis are compatible in magnitude; and

a coupling element disposed adjacent to said resonator to evanescently couple a portion of said modulated signal into said resonator in at least one of said whispering-gallery modes; and

a photodetector coupled to receive an optical output from said resonator to produce said electrical control signal.