Single beam radio frequency atomic magnetometer

Patent metadata

Field	Value
Publication number	US-9857441-B2
Application number	US-201313922376-A
Country	US
Kind code	B2
Filing date	Jun 20, 2013
Priority date	Jun 20, 2013
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

A radio-frequency atomic magnetometer comprises a laser, a photodetector, a vapor chamber, wherein the vapor chamber is in an optical path of laser light between the laser and photodetector, a circular polarizer configured to circularly polarize laser light emitted by the laser, wherein a circularly polarized laser beam is configured to pump into an oriented state, spins of atoms in the vapor chamber and to probe the atoms of the vapor chamber, wherein probing includes detecting a local radio frequency field; and a set of direct current (DC) field coils comprising at least one DC field coil, wherein the set of DC field coils is configured to generate a DC magnetic field oriented at 45 degrees relative to the optical axis of the laser light emitted by the laser and directed toward the vapor chamber; the set of DC field coils further configured to have adjustable DC magnetic field strength.

First claim

What is claimed is:

1. A radio-frequency atomic magnetometer comprising:
a laser;
a photodetector;
a vapor chamber, wherein the vapor chamber is in an optical path of laser light between the laser and photodetector;
a circular polarizer configured to circularly polarize laser light emitted by the laser, wherein a circularly polarized laser beam is configured to pump into an oriented state, spins of atoms in the vapor chamber and to probe the atoms of the vapor chamber, wherein probing includes detecting a local radio frequency field; and
a set of direct current (DC) field coils comprising at least one DC field coil, wherein the set of DC field coils is configured to generate a DC magnetic field oriented at 45 degrees relative to the optical axis of the laser light emitted by the laser and directed toward the vapor chamber; the set of DC field coils further configured to sweep the DC magnetic field strength.

2. The radio-frequency atomic magnetometer of claim 1 further comprising a vacuum package, wherein the set of DC field coils is located inside the vacuum package also containing the laser, photodetector, vapor chamber, and quarter wave plate and linear polarizer.

3. The radio-frequency atomic magnetometer of claim 1 further comprising a vacuum package, wherein the vacuum package contains the laser, photodetector, vapor chamber, and quarter wave plate and linear polarizer, the set of DC field coils located outside of the vacuum package.

4. The radio-frequency atomic magnetometer of claim 1 , wherein the set of DC field coils is configured such that the electrical DC bias applied to the DC field coil can be swept, in turn sweeping the DC magnetic field strength.

5. The radio-frequency atomic magnetometer of claim 1 , wherein the vapor chamber comprises a cell containing alkali atoms capable of coherent population transfer with the laser light of the laser; wherein the set of DC field coils is configured such that the set of DC field coils exerts a DC magnetic field effect on the alkali atoms of vapor chamber.

6. The radio-frequency atomic magnetometer of claim 1 , wherein the circular polarizer comprises a linear polarizer and quarter wave plate.

7. The radio frequency atomic magnetometer of claim 1 , wherein the laser light circularly polarized by the circular polarizer is configured as both a pump beam and a probe beam.

8. A radio frequency atomic magnetometer system comprising:
an atomic magnetometer further comprising:
a laser;
a photodetector;
a vapor chamber, wherein the vapor chamber is in an optical path of laser light between the laser and photodetector;
a circular polarizer configured to circularly polarize laser light emitted by the laser, wherein a circularly polarized laser beam is configured to pump into an oriented state, spins of atoms in the vapor chamber and to probe the atoms of the vapor chamber, wherein probing includes detecting a local radio frequency field; and
a set of direct current (DC) field coils comprising at least one DC field coil, wherein the set of DC field coils is configured to generate a DC magnetic field oriented at 45 degrees relative to the optical axis of the laser light emitted by the laser and directed toward the vapor chamber; the set of DC field coils further configured to sweep the DC magnetic field strength;

a microprocessor coupled to the atomic magnetometer;
a non-transitory computer readable medium; wherein,
the computer readable medium is configured to provide instructions to the microprocessor to indicate signals from the atomic magnetometer

an excitation probe coupled to the microprocessor configured to produce an excitation pulse.

9. The system of claim 8 further comprising a display coupled to the microprocessor, the display configured to indicate information about a sample being tested.

10. The system of claim 9 , wherein the display indicates a composition of the sample being tested.

11. The system of claim 9 , wherein the display indicates whether or not a specific material is present in the sample being tested.

12. The system of claim 9 , wherein the display is any one of an light emitting diode, incandescent light, or other such indicator.

13. The system of claim 9 , wherein the display is any of a cathode ray tube (CRT) display, an active matrix liquid crystal display (LCD), a passive matrix LCD, light emitting diode (LED) display, or plasma display.

14. The system of claim 8 , wherein the excitation pulse is swept.

15. The system of claim 8 , wherein the set of DC field coils is configured such that the electrical DC bias applied to the DC field coil can be swept, in turn sweeping the DC magnetic field strength.

16. The system of claim 8 further comprising a vacuum package, wherein the set of DC field coils is located inside the vacuum package also containing the laser, photodetector, vapor chamber, and quarter wave plate and linear polarizer.

17. The system of claim 8 further comprising a vacuum package, wherein the vacuum package contains the laser, photodetector, vapor chamber, and quarter wave plate and linear polarizer, the set of DC field coils located outside of the vacuum package.

18. A method for operating a radio frequency atomic magnetometer comprising:
pumping alkali atoms in a vapor chamber with a laser beam;
applying a direct current (DC) magnetic field using DC field coils oriented at 45 degrees to an optical axis of the laser beam to the alkali atoms, wherein the strength of the DC magnetic field applied by the DC field coils is swept;
exciting a sample with an excitation pulse;
detecting a modulation of a detector signal caused by an echo pulse, wherein the echo pulse originates from a sample caused by the excitation pulse applied to the sample, wherein the detector signal is a measurement of the laser beam used to pump the alkali atoms in the vapor chamber;
demodulating the detector signal with a reference signal derived from the excitation pulse.

19. The method of claim 18 , comprising:
detecting a modulation of a detector signal caused by a local radio frequency field, wherein the local radio frequency field originates from the sample; and
demodulating the detector signal to detect the local radio frequency field.

20. The method of claim 18 , wherein an electrical DC bias of the DC field coils is swept.

Assignees

• Honeywell Int Inc

Inventors

• Salit Mary K
• Salit Kenneth

Classifications

• G01R33/032 Primary

  using magneto-optic devices, e.g. Faraday {or Cotton-Mouton effect} · CPC title

• G01R33/26 Primary

  using optical pumping · CPC title