Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Proceedings of IEEE Sensors/Proceedings of IEEE Sensors ...

Control loops for a Coupled Dark State Magnetometer

Andreas Pollinger, Roland Lammegger, Werner Magnes, Michaela Ellmeier, W. Baumjohann, Laurentius Windholz

Published Nov 1, 2010• 12 citations
Publisher

Abstract

The Coupled Dark State Magnetometer (CDSM) is a new type of scalar magnetometer, which is based on two-photon spectroscopy of free alkali atoms. CDSM measurements do not depend on the sensor temperature. Furthermore, it has no dead zones, no moving parts and no excitation coils at the sensor. This paper deals with the control loops which are developed for tracking the magnetic field dependent resonances and for avoiding drifts of the carrier frequency of the laser diode used as excitation light source. It is the first time that a magnetometer of this type is operated in a control loop. The implementation of several functional blocks in a Field Programmable Gate Array (FPGA) is a first step towards miniaturization for a future space application. The magnetic field magnitude is measured by a frequency. Therefore, the Direct Digital Synthesis (DDS) principle is used for accurate signal generation. A noise floor measurement has shown no 1/f dependence near DC and 70 pT/√Hz up to the corner frequency of 3 Hz for which the CDSM is designed.

DOI
10.1109/icsens.2010.5690766

Related papers

Enable the inherent omni-directionality of an absolute coupled dark state magnetometer for e.g. scientific space applications

Andreas Pollinger, Michaela Ellmeier, Werner Magnes +4 more

The Coupled Dark State Magnetometer (CDSM) is an optically-pumped absolute scalar magnetometer which is based on two-photon spectroscopy of free alkali atoms. Several magnetic field dependent resonances occur in the presence of an external magnetic field, reaching their maximal strengths at different angles between the magnetic field direction and the reference axis of the sensor defined by the optical path of the laser excitation field. Dependent on this angle the strongest available resonances are selected. This enables an omni-directional dead zone free measurement. The paper discusses the measurement principle, describes the technical realization of the resonance switching, investigates the influence of this transition on the magnetic field measurement and proposes a method to detect the angle of the magnetic field direction in relation to the optical axis. The results presented within this paper show that dead zone free magnetic field measurements are possible with the CDSM without the need of a complex sensor design, e.g. additional moving parts or excitation coils.

IEEE International Instrumentation and Measurement Technology Conference•May 1, 2012•18 citations

Lower magnetic field measurement limit of the coupled dark state magnetometer

Michaela Ellmeier, Alexander Betzler, Christoph Amtmann +9 more

Abstract The Coupled Dark State Magnetometer (CDSM) is an optically pumped magnetometer. For the Jupiter Icy Moons Explorer mission, the CDSM and two fluxgate magnetometers are combined in the J-MAG instrument to measure the static and low frequency magnetic field in the Jupiter system. During certain calibration manoeuvres, the CDSM has to be able to measure magnetic field strengths down to 100 nT with an accuracy of 0.2 nT ( 1 σ ). At such low magnetic fields, the CDSM’s operational parameters must be carefully selected to obtain narrow resonance structures. Otherwise, the coupled dark state resonances, used for the magnetic field detection in different instrument modes, overlap and result in a systematic error. The overlap of the resonances and therefore the systematic error mainly depends on the resonance line width and the selected modulation frequencies for the detection of the resonances. We show that a line width of less than 200 Hz and selecting a modulation frequency of about the resonance line width are beneficial at magnetic field strengths B < 1.5 μ T. In this paper we demonstrate that with the found instrument settings the CDSM is able to measure magnetic field strengths below 100 nT with a systematic error less than 0.2 nT resulting from the overlap of the resonances.

Measurement Science and Technology•Jul 22, 2024•6 citations

Frequency shift compensation for single and dual laser beam pass sensors of a coherent population trapping resonance based coupled dark state magnetometer

Michaela Ellmeier, Christoph Amtmann, Andreas Pollinger +7 more

The Coupled Dark State Magnetometer is an atomic magnetometer designed for magnetic field measurements in space. Its measurement principle is based on the excitation of coupled dark state resonances prepared via the coherent population trapping effect. The coupled dark state resonances enable the compensation of disturbing frequency shifts which degrade the measurement accuracy. Results with a sensor design based on a single laser beam pass through the sensor unit reveal a reduced ability to compensate these disturbing effects compared to theoretical predictions. Therefore, a new sensor design is presented which enables a dual laser beam pass through the sensor unit. For almost all angles between the external magnetic field and the light propagation direction, the dual pass sensor design enables a better compensation of disturbing frequency shifts than the single pass sensor design - up to a factor of nine.

Measurement Sensors•Nov 26, 2022•11 citations

Study on the sensitivity of laser-pumped cesium atomic magnetometer

Nan Li, Huang Kai-Kai, Xuanhui Lu

A cesium atomic magnetometer based on laser-pumped rf resonance has been investigated and demonstrated experimentally. Atoms are polarized and pumped to dark states by circularly polarized light. When there exists a magnetic field, the corresponding magnetization will be precessing around the magnetic field at Larmor frequency. By means of adding a resonant rf magnetic field, the atoms will be depolarized and absorb photons again. By detecting the spectrum of the transmitted light, one can obtain the information about the external magnetic field. We build an 894nm external cavity diode laser with a frequency stabilization device, and a low noise magnetic field measurement environment. After the optimization of the magnetometer parameter and closed-loop measurement, an ultimate sensitivity of 19 fT/Hz1/2 and an intrinsic sensitivity of 1.8 pT/Hz1/2 have been achieved with the spatial resolution smaller than 2 cm.

Acta Physica Sinica•Jan 1, 2013•4 citations

Dead-zone-free free-induction-decay alkali-metal atomic magnetometer

X.-K. Wang, J. He, HH Deng +2 more

The detection dead zone is an important systematic limitation in scalar atomic magnetometers, constraining their practical utility. In this work, we demonstrate a sensitive dead zone free scalar magnetometer by integrating previously established techniques into a FID magnetometer based on Bell Bloom optical pumping. The dead zone is eliminated by inserting a reflecting mirror within a multipass cavity assisted atomic cell, which folds the optical beam into orthogonal paths. Our analysis reveals that interregion cross talk is essential for interpreting the resulted experimental signals. The sensor exhibits oscillation signal amplitude variations within a factor of three across all orientations in three dimensional space, and a field sensitivity better than 80 fT/Hz^(1/2) over the full space. We further characterize the heading error in the geomagnetic field range, where experimental results agree with theoretical predictions within 0.7 nT. Additionally, the sensor can operate in a closed loop mode by feeding back the real time frequency extracted from the FID signal to modulate the pump beam, we characterize the magnetic field slew rate of the sensor. This work paves the way towards a sensitive vector FID magnetometer.

arXiv:2609.04847•Physical Review A•Aug 25, 2026•0 citations

Loop-locked coherent population trapping magnetometer based on a fiber electro-optic modulator

Yong Hu, Y. Y. Feng, Chi Xu +2 more

We have set up a coherent population trapping (CPT)-based magnetometer prototype with the D1 line of ⁸⁷Rb atoms. The dichromatic light field is derived from a fiber electro-optic modulator (FEOM) connected to an external cavity laser diode. A CPT resonance signal with a 516 Hz linewidth is observed. By feeding back the derivative of the resonance curve to the FEOM with a proportional integral controller, of which the voltage output is directly converted to the measured magnetic field intensity, the resonance peak is locked to the environmental magnetic field. The measurement data we have achieved are well matched with the data measured by a commercial fluxgate magnetometer within 2 nT, and the sensitivity is better than 8 pT/√Hz in a parallel B field.

Applied Optics•Mar 27, 2014•11 citations
The Coupled Dark State Magnetometer (CDSM) is a new type of scalar magnetometer, which is based on two-photon spectroscopy of free alkali atoms. CDSM measurements do not depend on the sensor temperature. Furthermore, it has no dead zones, no moving parts and no excitation coils at the sensor. This paper deals with the control loops which are developed for tracking the magnetic field dependent resonances and for avoiding drifts of the carrier frequency of the laser diode used as excitation light source. It is the first time that a magnetometer of this type is operated in a control loop. The implementation of several functional blocks in a Field Programmable Gate Array (FPGA) is a first step towards miniaturization for a future space application. The magnetic field magnitude is measured by a frequency. Therefore, the Direct Digital Synthesis (DDS) principle is used for accurate signal generation. A noise floor measurement has shown no 1/f dependence near DC and 70 pT/√Hz up to the corner frequency of 3 Hz for which the CDSM is designed.
The Coupled Dark State Magnetometer (CDSM) is an optically-pumped absolute scalar magnetometer which is based on two-photon spectroscopy of free alkali atoms. Several magnetic field dependent resonances occur in the presence of an external magnetic field, reaching their maximal strengths at different angles between the magnetic field direction and the reference axis of the sensor defined by the optical path of the laser excitation field. Dependent on this angle the strongest available resonances are selected. This enables an omni-directional dead zone free measurement. The paper discusses the measurement principle, describes the technical realization of the resonance switching, investigates the influence of this transition on the magnetic field measurement and proposes a method to detect the angle of the magnetic field direction in relation to the optical axis. The results presented within this paper show that dead zone free magnetic field measurements are possible with the CDSM without the need of a complex sensor design, e.g. additional moving parts or excitation coils.
Abstract The Coupled Dark State Magnetometer (CDSM) is an optically pumped magnetometer. For the Jupiter Icy Moons Explorer mission, the CDSM and two fluxgate magnetometers are combined in the J-MAG instrument to measure the static and low frequency magnetic field in the Jupiter system. During certain calibration manoeuvres, the CDSM has to be able to measure magnetic field strengths down to 100 nT with an accuracy of 0.2 nT ( 1 σ ). At such low magnetic fields, the CDSM’s operational parameters must be carefully selected to obtain narrow resonance structures. Otherwise, the coupled dark state resonances, used for the magnetic field detection in different instrument modes, overlap and result in a systematic error. The overlap of the resonances and therefore the systematic error mainly depends on the resonance line width and the selected modulation frequencies for the detection of the resonances. We show that a line width of less than 200 Hz and selecting a modulation frequency of about the resonance line width are beneficial at magnetic field strengths B < 1.5 μ T. In this paper we demonstrate that with the found instrument settings the CDSM is able to measure magnetic field strengths below 100 nT with a systematic error less than 0.2 nT resulting from the overlap of the resonances.
The Coupled Dark State Magnetometer is an atomic magnetometer designed for magnetic field measurements in space. Its measurement principle is based on the excitation of coupled dark state resonances prepared via the coherent population trapping effect. The coupled dark state resonances enable the compensation of disturbing frequency shifts which degrade the measurement accuracy. Results with a sensor design based on a single laser beam pass through the sensor unit reveal a reduced ability to compensate these disturbing effects compared to theoretical predictions. Therefore, a new sensor design is presented which enables a dual laser beam pass through the sensor unit. For almost all angles between the external magnetic field and the light propagation direction, the dual pass sensor design enables a better compensation of disturbing frequency shifts than the single pass sensor design - up to a factor of nine.
A cesium atomic magnetometer based on laser-pumped rf resonance has been investigated and demonstrated experimentally. Atoms are polarized and pumped to dark states by circularly polarized light. When there exists a magnetic field, the corresponding magnetization will be precessing around the magnetic field at Larmor frequency. By means of adding a resonant rf magnetic field, the atoms will be depolarized and absorb photons again. By detecting the spectrum of the transmitted light, one can obtain the information about the external magnetic field. We build an 894nm external cavity diode laser with a frequency stabilization device, and a low noise magnetic field measurement environment. After the optimization of the magnetometer parameter and closed-loop measurement, an ultimate sensitivity of 19 fT/Hz1/2 and an intrinsic sensitivity of 1.8 pT/Hz1/2 have been achieved with the spatial resolution smaller than 2 cm.
The detection dead zone is an important systematic limitation in scalar atomic magnetometers, constraining their practical utility. In this work, we demonstrate a sensitive dead zone free scalar magnetometer by integrating previously established techniques into a FID magnetometer based on Bell Bloom optical pumping. The dead zone is eliminated by inserting a reflecting mirror within a multipass cavity assisted atomic cell, which folds the optical beam into orthogonal paths. Our analysis reveals that interregion cross talk is essential for interpreting the resulted experimental signals. The sensor exhibits oscillation signal amplitude variations within a factor of three across all orientations in three dimensional space, and a field sensitivity better than 80 fT/Hz^(1/2) over the full space. We further characterize the heading error in the geomagnetic field range, where experimental results agree with theoretical predictions within 0.7 nT. Additionally, the sensor can operate in a closed loop mode by feeding back the real time frequency extracted from the FID signal to modulate the pump beam, we characterize the magnetic field slew rate of the sensor. This work paves the way towards a sensitive vector FID magnetometer.
We have set up a coherent population trapping (CPT)-based magnetometer prototype with the D1 line of ⁸⁷Rb atoms. The dichromatic light field is derived from a fiber electro-optic modulator (FEOM) connected to an external cavity laser diode. A CPT resonance signal with a 516 Hz linewidth is observed. By feeding back the derivative of the resonance curve to the FEOM with a proportional integral controller, of which the voltage output is directly converted to the measured magnetic field intensity, the resonance peak is locked to the environmental magnetic field. The measurement data we have achieved are well matched with the data measured by a commercial fluxgate magnetometer within 2 nT, and the sensitivity is better than 8 pT/√Hz in a parallel B field.