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Bulletin of the American Physical Society

A miniature differential atomic magnetometer based on a diverging laser beam

E. Hodby, Elizabeth A. Donley, John E. Kitching

Published Jun 6, 2007• 0 citations
OpenAlex

Abstract

We demonstrate a novel miniature atomic magnetometer that uses differential detection of the spatially diverging components of a light field to monitor the Larmor precession frequency of alkali atoms confined in a micromachined vapor cell.

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A miniature differential atomic magnetometer based on a diverging laser beam

E. Hodby, Elizabeth A. Donley, John E. Kitching

We demonstrate a novel miniature atomic magnetometer that uses differential detection of the spatially diverging components of a light field to monitor the Larmor precession frequency of alkali atoms confined in a micromachined vapor cell.

Frontiers in Optics•Jan 1, 2007•0 citations

Differential atomic magnetometry based on a diverging laser beam

E. Hodby, Elizabeth A. Donley, John E. Kitching

The authors demonstrate a novel atomic magnetometer that uses differential detection of the spatially diverging components of a light field to monitor the Larmor precession frequency of atoms in a thermal vapor. The design is implemented in compact form with a micromachined alkali vapor cell and a naturally divergent light field emitted by a vertical-cavity surface-emitting laser. Operating the magnetometer in differential mode cancels common-mode noise and improves the sensitivity by a factor of 26 over single-channel operation. They also suggest ways in which the current sensitivity of 28pT∕√Hz may be improved further without sacrificing size or simplicity.

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Remote detection magnetometry

Simon Rochester, James Higbie, Bob J. Patton +3 more

Introduction Shortly after the inception of atomic magnetometry, alkali-vapor magnetometers were being used to measure the Earth's magnetic field to unprecedented precision. During the same era, Bell and Bloom first demonstrated all-optical atomic magnetometry through synchronous optical pumping [1] (see Chapters 1 and 6). In this approach, optical-pumping light is frequency- or amplitude-modulated at harmonics of the Larmor frequency ω L to generate a precessing spin polarization within an alkali vapor at finite magnetic field [2, 3]. Although this technique received considerable attention from the atomic physics community for its applicability to optical pumping experiments, Earth's-field alkali-vapor atomic magnetometers continued to rely on radiofrequency (RF) field excitation for several decades (see Chapter 4). Upon the advent of diode lasers addressing alkali and metastable helium transitions, synchronously pumped magnetometers experienced a revival beginning in the late 1980s. In recent years, such magnetometers have found applications in nuclear magnetic resonance detection [4] (see also Chapter 14), quantum control experiments [5], and chip-scale devices intended for spacecraft use [6] (see also Chapters 7 and 15). All-optical magnetometers possess several advantages over devices that employ RF coils. RF-driven magnetometers can suffer from cross-talk if two sensors are placed in close proximity, since the AC magnetic field driving resonance in one vapor cell can adversely affect the other. All-optical magnetometers are free from such interference. When operated in self-oscillating mode [7], RF-driven magnetometers require an added ±90° electronic phase shift in the feedback loop to counter the intrinsic phase shift between the RF field and the probe-beam modulation.

Cambridge University Press eBooks•Mar 7, 2013•0 citations

Pulsed operation of a miniature scalar optically pumped magnetometer

Vladislav P. Gerginov, Sean Krzyzewski, Svenja A. Knappe

A scalar magnetic field sensor based on a millimeter-size Rb87 vapor cell is described. The magnetometer uses nearly copropagating pump and probe laser beams, amplitude modulation of the pump beam, and detection through monitoring the polarization rotation of the detuned probe beam. The circularly polarized pump laser resonantly drives a spin precession in the alkali atoms at the Larmor frequency. A modulation signal on the probe laser polarization is detected with a lock-in amplifier. Since the Larmor precession is driven all-optically, potential cross talk between sensors is minimized. And since the pump light is turned off during most of the precession cycle, large offsets of the resonance, typically present in a single-beam Bell–Bloom scheme, are avoided. At the same time, relatively high sensitivities can be reached even in millimeter-size vapor cells: The magnetometer achieves a sensitivity of 1 pT/Hz1/2 in a sensitive volume of 16 mm3, limited by environmental noise. When a gradiometer configuration is used to cancel the environmental noise, the magnetometer sensitivity reaches 300 fT/Hz1/2. We systematically study the dependence of the magnetometer performance on the optical duty cycles of the pump light and find that better performance is achieved with shorter duty cycles, with the highest values measured at 1.25% duty cycle.

Journal of the Optical Society of America B•Jun 15, 2017•57 citations

Chip Scale Atomic Magnetometers

Peter D. D. Schwindt, B. J. Lindseth, Svenja A. Knappe +5 more

An optically pumped magnetometer was drastically miniaturized, by taking advantage of MEMS techniques, producing the chip-scale atomic magnetometers (CSAM) physics package. The key component of the package is an alkali vapor cell. To probe the magnetic field experienced by the atoms, the injection current to the VCSEL was modulated at 3.4 GHz near half the hyperfine frequency of87Rb. Lock-in detection is used to determine the center of the resonance, and the magnetic field is determined by counting the modulation frequency, which is related to the Larmor precession frequency under these locked conditions. The ITO heaters create a large magnetic field gradient, which broadens the resonance and reduces the sensitivity.

IEEE International Magnetics Conference•May 1, 2006•15 citations
The authors demonstrate a novel atomic magnetometer that uses differential detection of the spatially diverging components of a light field to monitor the Larmor precession frequency of atoms in a thermal vapor. The design is implemented in compact form with a micromachined alkali vapor cell and a naturally divergent light field emitted by a vertical-cavity surface-emitting laser. Operating the magnetometer in differential mode cancels common-mode noise and improves the sensitivity by a factor of 26 over single-channel operation. They also suggest ways in which the current sensitivity of 28pT∕√Hz may be improved further without sacrificing size or simplicity.
Introduction Shortly after the inception of atomic magnetometry, alkali-vapor magnetometers were being used to measure the Earth's magnetic field to unprecedented precision. During the same era, Bell and Bloom first demonstrated all-optical atomic magnetometry through synchronous optical pumping [1] (see Chapters 1 and 6). In this approach, optical-pumping light is frequency- or amplitude-modulated at harmonics of the Larmor frequency ω L to generate a precessing spin polarization within an alkali vapor at finite magnetic field [2, 3]. Although this technique received considerable attention from the atomic physics community for its applicability to optical pumping experiments, Earth's-field alkali-vapor atomic magnetometers continued to rely on radiofrequency (RF) field excitation for several decades (see Chapter 4). Upon the advent of diode lasers addressing alkali and metastable helium transitions, synchronously pumped magnetometers experienced a revival beginning in the late 1980s. In recent years, such magnetometers have found applications in nuclear magnetic resonance detection [4] (see also Chapter 14), quantum control experiments [5], and chip-scale devices intended for spacecraft use [6] (see also Chapters 7 and 15). All-optical magnetometers possess several advantages over devices that employ RF coils. RF-driven magnetometers can suffer from cross-talk if two sensors are placed in close proximity, since the AC magnetic field driving resonance in one vapor cell can adversely affect the other. All-optical magnetometers are free from such interference. When operated in self-oscillating mode [7], RF-driven magnetometers require an added ±90° electronic phase shift in the feedback loop to counter the intrinsic phase shift between the RF field and the probe-beam modulation.
A scalar magnetic field sensor based on a millimeter-size Rb87 vapor cell is described. The magnetometer uses nearly copropagating pump and probe laser beams, amplitude modulation of the pump beam, and detection through monitoring the polarization rotation of the detuned probe beam. The circularly polarized pump laser resonantly drives a spin precession in the alkali atoms at the Larmor frequency. A modulation signal on the probe laser polarization is detected with a lock-in amplifier. Since the Larmor precession is driven all-optically, potential cross talk between sensors is minimized. And since the pump light is turned off during most of the precession cycle, large offsets of the resonance, typically present in a single-beam Bell–Bloom scheme, are avoided. At the same time, relatively high sensitivities can be reached even in millimeter-size vapor cells: The magnetometer achieves a sensitivity of 1 pT/Hz1/2 in a sensitive volume of 16 mm3, limited by environmental noise. When a gradiometer configuration is used to cancel the environmental noise, the magnetometer sensitivity reaches 300 fT/Hz1/2. We systematically study the dependence of the magnetometer performance on the optical duty cycles of the pump light and find that better performance is achieved with shorter duty cycles, with the highest values measured at 1.25% duty cycle.
An optically pumped magnetometer was drastically miniaturized, by taking advantage of MEMS techniques, producing the chip-scale atomic magnetometers (CSAM) physics package. The key component of the package is an alkali vapor cell. To probe the magnetic field experienced by the atoms, the injection current to the VCSEL was modulated at 3.4 GHz near half the hyperfine frequency of87Rb. Lock-in detection is used to determine the center of the resonance, and the magnetic field is determined by counting the modulation frequency, which is related to the Larmor precession frequency under these locked conditions. The ITO heaters create a large magnetic field gradient, which broadens the resonance and reduces the sensitivity.