Optical gyroscope sensors based on optical whispering gallery mode resonators

• US 8,514,400 B2
• Filed: 03/23/2011
• Issued: 08/20/2013
• Est. Priority Date: 03/23/2010
• Status: Active Grant

• Current Assignee: Oewaves Incorporated
• Original Assignee: Oewaves Incorporated
• Inventors: Mohageg, Makan, Maleki, Lute, Seidel, David, Ilchenko, Vladimir S., Matsko, Andrey B., Savchenkov, Anatoliy A., Liang, Wei
• Primary Examiner(s): Chowdhury, Tarifur
• Assistant Examiner(s): HANSEN, JONATHAN M
• Application Number:
  US13/065,587
• Publication Number:
  US 20110255094A1
• Time in Patent Office: 881 Days
• Field of Search: 356459-461, 356/483
• US Class Current: 356/459
• CPC Class Codes: G01C 19/72 with counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers

Abstract

Optical gyroscope devices based on optical whispering gallery mode resonators that measure rotations based on rotation-induced optical phase shift in optical whispering gallery mode resonators.

Claims

1. An optical gyroscope device, comprising:

a laser that produces laser light;

an optical resonator fixed in position relative to the laser and made of an optical material and structured to support optical whispering gallery modes that propagate in opposite directions in a closed optical loop in the optical resonator;

an optical coupler fixed relative to the optical resonator and evanescently coupled to the optical resonator to couple the laser light into one or more optical whispering gallery modes of the optical resonator and to couple the laser light in a particular optical whispering gallery mode inside the optical resonator as an injection laser beam back to the laser to cause injection locking of the laser to the particular optical whispering gallery mode;

a beam splitter fixed in position in an optical path of the laser light between the laser and the optical coupler to split a portion of the laser propagating towards the optical coupler as a first laser beam and to split a portion of the injection laser beam propagating towards the laser into a second laser beam;

a beam combiner fixed in position relative to the beam splitter to receive the first and second laser beam and to spatially overlap the received first and second laser beams to produce a combined laser beam;

an optical detector that receives the combined laser beam to produce a detector output that contains phase shift information in the optical interference between the first and second laser beams indicating a rotation of the optical resonator.

2. The device as in claim 1, comprising:

an optical modulator fixed in position between the laser and the beam splitter to cause a modulation of the laser light at a modulation frequency that is further modulated at a ramp frequency;

a laser lock circuit coupled to receive the detector output and information of the modulation frequency which is modulated at the ramp frequency and to produce a laser control signal based on the detector output and the information of the modulation frequency to lock the laser in frequency.

3. The device as in claim 2, comprising:

an output circuit that receives the laser control signal from the laser lock circuit and to demodulates the laser control signal with respect to the ramp frequency to produce a gyro output signal indicating the rotation of the optical resonator.

4. The device as in claim 3, comprising:

a resonator temperature sensor placed near the optical resonator to measure a local temperature;

a resonator temperature compensation servo circuit that receives the measured local temperature from the resonator temperature sensor to provide a correction to the gyro output signal.

5. The device as in claim 3, comprising:

a laser temperature sensor to measure a temperature of the laser

a laser temperature compensation servo circuit that receives the measured laser temperature from the laser temperature sensor to provide a shift to laser modulation frequency that compensates for a change in the laser temperature.

6. The device as in claim 3, comprising:

a laser temperature sensor to measure a temperature of the laser

a laser temperature compensation servo circuit that controls the laser temperature to compensate for a change in the laser temperature.

7. An optical gyroscope device, comprising:

a laser that produces laser light at a laser carrier frequency;

an optical set up that splits the laser light into a first laser beam and a second laser beam in opposition directions;

an optical resonator fixed in position relative to the laser and made of an optical material and structured to support optical whispering gallery modes that propagate in opposite directions in a closed optical loop in the optical resonator;

a first optical modulator in a path of the first beam to modulate the first laser beam to produce a first modulated laser beam;

a second optical modulator in a path of the second beam to modulate the second laser beam to produce a second modulated laser beam;

an input optical coupler fixed in position relative to the optical resonator and evanescently coupled to the optical resonator to couple the first modulated laser beam into one or more optical whispering gallery modes of the optical resonator circulating in the optical resonator in a first direction and to couple second modulated laser beam into the optical resonator circulating in a second direction opposite to the first direction;

an output optical coupler fixed in position relative to the optical resonator and evanescently coupled to the optical resonator to couple the first modulated laser beam out of the optical resonator as a first output beam and to couple the second modulated laser beam out of the optical resonator as a second output beam;

a first optical filter to filter the first output beam to remove light at the laser carrier frequency to produce filtered first output beam;

a second optical filter to filter the second output beam to remove light at the laser carrier frequency to produce filtered second output beam;

a first optical detector to receive the filtered first output beam to produce a first detector signal;

a second optical detector to receive the filtered second output beam to produce a second detector signal;

a laser lock circuit that stabilizes the laser in frequency;

a first lock circuit that controls the first optical modulator based on the first detector signal to stabilize a frequency of the first modulated laser beam at a first whispering gallery mode of the optical resonator;

a second lock circuit that controls the second optical modulator based on the second detector signal to stabilize a frequency of the second modulated laser beam at a second whispering gallery mode of the optical resonator; and

a signal mixer that mixes outputs of the first and second lock circuits to produce a gyro output indicating a rotation of the optical resonator.

8. An optical gyroscope device, comprising:

a first laser that produces first laser light at a first laser carrier frequency;

a second laser that produces second laser light at a second laser carrier frequency;

a laser lock circuit that stabilizes the second laser relative to the first laser in frequency;

a first optical modulator that modulates the first laser beam at a first modulation frequency to produce a first modulated laser beam;

a second optical modulator that modulates the second laser beam at a second modulation frequency to produce a second modulated laser beam;

an optical resonator fixed in position relative to the first and second lasers and made of an optical material and structured to support optical whispering gallery modes that propagate in opposite directions in a closed optical loop in the optical resonator;

a first optical coupler fixed in position relative to the optical resonator and evanescently coupled to the optical resonator to couple the first modulated laser beam into one or more optical whispering gallery modes of the optical resonator circulating in the optical resonator in a first direction and to couple light in the optical resonator circulating in a second direction opposite to the first direction out of the optical resonator as a first output beam;

a second optical coupler fixed in position relative to the optical resonator and evanescently coupled to the optical resonator to couple the second modulated laser beam into one or more optical whispering gallery modes of the optical resonator circulating in the optical resonator in the second direction and to couple light in the optical resonator circulating in the first direction out of the optical resonator as the second output beam;

a first optical detector to receive the second output beam to produce a first detector signal;

a second optical detector to receive the first output beam to produce a second detector signal;

a first signal mixer that mixes the first detector signal with a signal at the first modulation frequency to produce a gyro output indicating a rotation of the optical resonator;

a second signal mixer that mixes the second detector signal with a signal at the second modulation frequency to produce a laser control signal; and

a laser lock circuit that applied the laser control signal to the first laser to stabilize the first laser.

9. An optical gyroscope device, comprising:

a laser that produces laser light at a laser carrier frequency;

an optical modulator in a path of the laser light to modulate the laser light to produce a modulated laser beam;

an optical set up that splits the modulated laser beam into a first laser beam and a second laser beam in opposition directions;

an optical resonator fixed in position relative to the laser and made of an optical material and structured to support optical whispering gallery modes that propagate in opposite directions in a closed optical loop in the optical resonator;

a first optical filter in a path of the first beam to transmit light at the laser carrier frequency while rejecting other light to produce the first filtered laser beam;

a second optical filter in a path of the second beam to transmit light at a modulation sideband while rejecting other light including light at the laser carrier frequency to produce the second filtered laser beam;

an input optical coupler fixed in position relative to the optical resonator and evanescently coupled to the optical resonator to couple the first filtered laser beam into one or more optical whispering gallery modes of the optical resonator circulating in the optical resonator in a first direction and to couple second filtered laser beam into the optical resonator circulating in a second direction opposite to the first direction;

an output optical coupler fixed in position relative to the optical resonator and evanescently coupled to the optical resonator to couple the first filtered laser beam out of the optical resonator as a first output beam and to couple the second filtered laser beam out of the optical resonator as a second output beam;

a beam combiner that combines the first and second output beams to produce a combined beam;

an optical detector to receive the combined beam to produce a detector signal; and

a gyro circuit that uses the detector signal to control the optical modulator and to produce a gyro output indicating a rotation of the optical resonator.

10. An optical gyroscope device, comprising:

a laser that produces laser light at a laser carrier frequency;

an optical resonator fixed in position relative to the laser and made of an optical material and structured to support optical whispering gallery modes that propagate in opposite directions in a closed optical loop in the optical resonator;

an input optical coupler fixed in position relative to the optical resonator and evanescently coupled to the optical resonator to couple the laser light into one or more optical whispering gallery modes of the optical resonator circulating in the optical resonator in a first direction and in a second direction opposite to the first direction, the input optical resonator further configured to couple light out of the optical resonator as an injection beam back to the laser to lock the laser;

an output optical coupler fixed in position relative to the optical resonator and evanescently coupled to the optical resonator to couple light in the first direction out of the optical resonator as a first output beam and to couple light in the second direction out of the optical resonator as a second output beam;

a first optical filter to filter the first output beam to remove light at the laser carrier frequency to produce a first filtered beam;

a second optical filter to filter the second t output beam to remove light at the laser carrier frequency to produce a second filtered beam;

a first detector that converts the first filtered beam into a first detector signal;

a second detector that converts the second filtered beam into a second detector signal; and

a mixer that mixes the first and second detector signals to produce a gyro output indicating a rotation of the optical resonator,

wherein the optical resonator is configured to produce a frequency comb at different frequencies in light circulating inside the optical resonator.

11. An optical gyroscope device, comprising:

a laser that produces laser light at a laser carrier frequency;

an optical resonator fixed in position relative to the laser and made of an optical material and structured to support optical whispering gallery modes that propagate in opposite directions in a closed optical loop in the optical resonator, the optical resonator structured to produce Raman frequency bands via stimulated Raman scattering;

an input optical coupler fixed in position relative to the optical resonator and evanescently coupled to the optical resonator to couple the laser light into one or more optical whispering gallery modes of the optical resonator circulating in the optical resonator in a first direction and in a second direction opposite to the first direction, the input optical resonator further configured to couple light out of the optical resonator as an injection beam back to the laser to lock the laser;

an output optical coupler fixed in position relative to the optical resonator and evanescently coupled to the optical resonator to couple light in the first direction out of the optical resonator as a first output beam and to couple light in the second direction out of the optical resonator as a second output beam;

a first optical filter to filter the first output beam to remove light at the laser carrier frequency to produce a first filtered beam;

a second optical filter to filter the second t output beam to remove light at the laser carrier frequency to produce a second filtered beam;

a beam combiner that combines the first and second filtered beams to produce a first output beam and a second output beam;

a first detector that converts the first output beam into a first detector signal;

a second detector that converts the second output beam into a second detector signal; and

a mixer that mixes the first and second detector signals to produce a gyro output indicating a rotation of the optical resonator.