High sensitivity solid state magnetometer

• US 8,947,080 B2
• Filed: 12/03/2008
• Issued: 02/03/2015
• Est. Priority Date: 12/03/2007
• Status: Active Grant

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Inventors: Lukin, Mikhail, Walsworth, Ronald L.
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): MCANDREW, CHRISTOPHER P
• Application Number:
  US12/746,020
• Publication Number:
  US 20100308813A1
• Time in Patent Office: 2,253 Days
• Field of Search: 324/244, 324/244.1, 324/262, 324/345
• US Class Current: 324/244.1
• CPC Class Codes: G01N 24/10 by using electron paramagnetic resonance G01N24/12 takes precedence
• CPC Class Codes: G01R 33/032 using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
• CPC Class Codes: G01R 33/1284 Spin resolved measurements; Influencing spins during measurements, e.g. in spintronics devices G01R33/093 takes precedence; semiconductor devices using spin polarized carriers H01L29/66984
• CPC Class Codes: G01R 33/24 for measuring direction or magnitude of magnetic fields or magnetic flux
• CPC Class Codes: G01R 33/60 using electron paramagnetic resonance G01R33/24, G01R33/62 take precedence

Abstract

A magnetometer for sensing a magnetic field may include a solid state electronic spin system, and a detector. The solid state electronic spin system may contain one or more electronic spins that are disposed within a solid state lattice, for example NV centers in diamond. The electronic spins may be configured to receive optical excitation radiation and to align with the magnetic field in response thereto. The electronic spins may be further induced to precess about the magnetic field to be sensed, in response to an external control such as an RF field, the frequency of the spin precession being linearly related to the magnetic field by the Zeeman shift of the electronic spin energy levels. The detector may be configured to detect output optical radiation from the electronic spin, so as to determine the Zeeman shift and thus the magnetic field.

Claims

1. A magnetometer for sensing an unknown external magnetic field, comprising:

a solid state electronic spin system containing one or more a plurality of electronic spins that are disposed within a solid state lattice, and that are substantially free of interaction with the solid state lattice;

wherein the plurality of electronic spins are configured to align with the unknown external magnetic field in response to optical excitation radiation applied thereto by the optical excitation system; and

wherein the plurality of electronic spins are further responsive to the external control system so as to induce a precession of the electronic spins about the unknown external magnetic field to be sensed, the frequency of the precession being linearly related to the unknown external magnetic field by the Zeeman shift of the electronic spin energy levels; and

a detector configured to detect output optical radiation correlated with the plurality of electronic spins, after the plurality of electronic spins have been subject to the optical excitation radiation and the external control, and wherein the detector is further configured to determine the Zeeman shift and use the determined Zeeman shift to calculate the unknown external magnetic field,

wherein the plurality of electronic spins include different sets of spin centers having different crystallographic orientations within the solid state lattice, and

wherein the magnetometer is configured to select one or more of the sets of spin centers in one or more crystallographic orientations and use the selected spin defects to determine the unknown external magnetic field.

2. The magnetometer of claim 1, further comprising an optical source configured to generate the optical excitation radiation that causes the electronic spins to align with the unknown external magnetic field.

3. The magnetometer of claim 2, wherein the optical source comprises a laser.

4. The magnetometer of claim 1, wherein the solid state electronic spin system comprises a diamond, and wherein the plurality of electronic spins are NV (Nitrogen vacancy) centers.

5. The magnetometer of claim 3, wherein the optical excitation radiation is laser light having a wavelength of about 530 nanometers.

6. The magnetometer of claim 1, wherein the external control comprises RF radiation, and wherein each electronic spin is configured to precess around an axis of the magnetic field in response to the RF radiation.

7. The magnetometer of claim 6, further comprising an RF source configured to generate the RF radiation that induces the precession of the electronic spins about the unknown external magnetic field when applied to the aligned electronic spins.

8. The magnetometer of claim 7, wherein the RF source comprises an RF pulse generator that generates an excitation RF field that can be applied in any desired direction relative to the unknown external magnetic field.

9. The magnetometer of claim 4, wherein the sensitivity of the magnetometer for a single NV center is about 200 nT Hz⁻

1/2 when the unknown external magnetic field is a DC magnetic field, and about 10 nT Hz<sup>−

1/2</sup> when the unknown external magnetic field is an AC magnetic field.

10. The magnetometer of claim 1, wherein the detector comprises a CCD (charge-coupled device) and one or more associated optical components.

11. The magnetometer of claim 1, wherein the detector comprises one of:

a confocal microscope; and

a super-resolution imaging system configured to implement one or more techniques for imaging below the conventional diffraction limit.

12. The magnetometer of claim 11, wherein the one or more techniques comprise STED (stimulated emission depletion).

13. The magnetometer of claim 6, wherein the detector is configured to employ magnetic field gradients to improve spatial resolution by localizing the spatial region in which the electronic spins are on resonance with the applied RF radiation.

14. The magnetometer of claim 1, wherein the detector comprises a control and data processing system configured to determine the Zeeman shift and the unknown external magnetic field from the detected output optical radiation, and wherein the Zeeman frequency shift δ

ω

is proportional to the unknown external magnetic field according to a formula given by;

15. The magnetometer of claim 2, further comprising one or more optical components configured to direct the optical excitation radiation from the optical source toward the electronic spin system, and further configured to direct the output optical radiation from the electronic spin system toward the detector.

16. The magnetometer of claim 1, wherein the density of the electronic spins is about 10¹⁸ cm⁻

3, and wherein an average distance between the electronic spins is about 10 nm.

17. The magnetometer of claim 15, wherein the one or more optical components comprises a dichroic mirror.

18. The magnetometer of claim 1, wherein the magnetometer is configured to select the one or more sets of spin centers by using a magnetic field to detune the other sets of spin centers.

19. The magnetometer of claim 1, wherein the magnetometer is configured to select each set of spin centers in turn to take magnetic field measurements thereby providing a full 3D vector and scalar magnetometer using more than one set of spin centers within the solid state lattice.

20. A magnetometer for sensing an unknown external magnetic field, comprising:

a solid state electronic spin system containing one or more electronic spins that are disposed within a solid state lattice, and that are substantially free of interaction with the solid state lattice;

wherein the one or more electronic spins are configured to align with the unknown external magnetic field in response to optical excitation radiation applied thereto by the optical excitation system; and

wherein the one or more electronic spins are further responsive to the external control system so as to induce a precession of the one or more electronic spins about the unknown external magnetic field to be sensed, the frequency of the precession being linearly related to the unknown external magnetic field by the Zeeman shift of the electronic spin energy levels; and

a detector configured to detect output optical radiation correlated with the plurality of electronic spins, after the one or more electronic spins have been subject to the optical excitation radiation and the external control, and wherein the detector is further configured to determine the Zeeman shift and use the determined Zeeman shift to calculate the unknown external magnetic field,

wherein the solid state electronic spin system is configured such that the one or more electronic spins are disposed close to a surface of the solid state lattice to enable the one or more electronic spins to be positioned sufficiently close to a source of the unknown external magnetic field to provide nanometer or micron scale spatial resolution.

21. The magnetometer of claim 20, wherein the solid state electronic spin system is in the form of a nanocrystal.

22. The magnetometer of claim 20, wherein the solid state electronic spin system is in the form of a thin crystal plate.

23. The magnetometer of claim 20, further comprising an AFM (atomic force microscope), and wherein the solid state spin system is mounted at the tip of the AFM.

24. The magnetometer of claim 20, wherein the magnetometer is configured to probe a single electronic spin close to the surface of the solid state lattice.

25. The magnetometer of claim 20, wherein the magnetometer is configured to probe a plurality of electronic spins close to the surface of the solid state lattice, the plurality of electronic spins including different sets of spin centers having different crystallographic orientations within the solid state lattice, and wherein the magnetometer is configured to select one or more of the sets of spin centers in one or more crystallographic orientations and use the selected spin defects to determine the unknown external magnetic field.

26. The magnetometer of claim 20, wherein the solid state electronic spin system comprises a diamond, and wherein the one or more electronic spins are NV (Nitrogen vacancy) centers.