Chip-scale optomechanical magnetometer

• US 9,897,666 B2
• Filed: 12/15/2014
• Issued: 02/20/2018
• Est. Priority Date: 12/16/2013
• Status: Active Grant

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Rogers, Daniel J., Papadakis, Stergios J., Churchill, Layne R., Wong, Chee Wei
• Primary Examiner(s): Hollington, Jermele M
• Assistant Examiner(s): Pothen, Feba
• Application Number:
  US14/569,893
• Publication Number:
  US 20150168504A1
• Time in Patent Office: 1,163 Days
• CPC Class Codes: G01R 33/032 using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
• CPC Class Codes: G01R 33/0327 with application of magnetostriction

Abstract

An optomechanical oscillator for measuring a magnetic field may include a fixed substrate, a moveable mass separated from the fixed substrate by a slot, a photonic crystal comprising an optomechanical cavity formed at the slot, and a current source operably coupled to provide current to the photonic crystal. The moveable mass may be moveable responsive to placement of the optomechanical oscillator in a magnetic field based on interaction of the magnetic field and the current. The magnetic field may be measureable based on displacement of the moveable mass.

Claims

1. An optomechanical oscillator for measuring a magnetic field comprising:

a fixed substrate;

a moveable mass separated from the fixed substrate by a slot;

a photonic crystal comprising an optomechanical cavity formed at the slot, wherein the photonic crystal is provided on the fixed substrate and the moveable mass on opposite sides of the slot to form the optomechanical cavity; and

a current source operably coupled to provide current to the photonic crystal,

wherein the moveable mass is moveable responsive to placement of the optomechanical oscillator in a magnetic field based on interaction of the magnetic field and the current, and

wherein the magnetic field is measureable based on displacement of the moveable mass.

2. The optomechanical oscillator of claim 1, wherein the current source comprises an oscillating source.

3. The optomechanical oscillator of claim 1, wherein the current source comprises a direct current source.

4. The optomechanical oscillator of claim 1, wherein the displacement of the moveable mass is a function of a width of the slot.

5. The optomechanical oscillator of claim 4, wherein a change in width of the slot is indicative of a shift in resonance of the optomechanical cavity.

6. The optomechanical oscillator of claim 1, wherein the optomechanical oscillator comprises a chip-scale optical oscillator, wherein the photonic crystal includes holes formed therein on opposite sides of the slot to form a waveguide for an optical signal to travel through the slot.

7. The optomechanical oscillator of claim 6, wherein a width of the slot is changeable based on the magnetic field such that a change in the width of the slot causes the shift in resonance of the optomechanical cavity, and wherein the shift in resonance is measured to provide an indication of the magnetic field.

8. An apparatus for measuring a magnetic field comprising:

a laser light source;

a sensing element exposable to a magnetic field and a current source, and

an optical detector configured to receive light from the laser light source passed through the sensing element,

wherein the sensing element comprises an optomechanical oscillator including;

a fixed substrate;

a moveable mass separated from the fixed substrate by a slot;

a photonic crystal comprising an optomechanical cavity formed at the slot, wherein the photonic crystal is provided on the fixed substrate and the moveable mass on opposite sides of the slot to form the optomechanical cavity; and

the current source operably coupled to provide current to the photonic crystal,

wherein the moveable mass is moveable responsive to placement of the optomechanical oscillator in the magnetic field based on interaction of the magnetic field and the current, and

wherein the magnetic field is measureable by the optical detector based on modulation of the light from the laser light source caused at least in part by displacement of the moveable mass.

9. The apparatus of claim 8, wherein the current source comprises a direct current source.

10. The apparatus of claim 8, wherein the current source comprises an oscillating source.

11. The apparatus of claim 10, further comprising a lock-in amplifier timed to the oscillating source and operably coupled to the optical detector to increase sensitivity of magnetic field amplitude detection by the optical detector.

12. The apparatus of claim 8, wherein the displacement of the moveable mass is a function of a width of the slot.

13. The apparatus of claim 12, wherein a change in width of the slot is indicative of a shift in resonance of the optomechanical cavity.

14. The apparatus of claim 8, wherein the optomechanical oscillator comprises a chip-scale optical oscillator, wherein the photonic crystal includes holes formed therein on opposite sides of the slot to form a waveguide for an optical signal to travel through the slot.

15. The apparatus of claim 13, wherein a width of the slot is changeable based on the magnetic field such that a change in the width of the slot causes the shift in resonance of the optomechanical cavity, and wherein the shift in resonance is measured to provide an indication of the magnetic field.

16. A method of measuring a magnetic field, the method comprising:

providing a current to an optomechanical oscillator structured to deform under a magnetic force to cause a shift in resonance associated with an optomechanical cavity formed in the optomechanical oscillator;

placing the optomechanical oscillator in a magnetic field capable of providing the magnetic force;

measuring light passed through the optomechanical oscillator to determine a change in resonance of the optomechanical cavity; and

determining a measurement of the magnetic field based on the change in resonance.

17. The method of claim 16, wherein providing the current to the optomechanical oscillator comprises providing the current to a photonic crystal disposed at a slot defined between a fixed substrate and a moveable mass.

18. The method of claim 17, wherein the optomechanical oscillator comprises a chip-scale optical oscillator including the photonic crystal, the photonic crystal having holes formed therein on opposite sides of the slot to form a waveguide for an optical signal to travel through the slot.