Phase projection errors in rf-driven optically pumped magnetometers

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Hauptverfasser: Grujić, Zoran D., Ćurĉić, Marija, Kocić, Aleksandra, Weis, Antoine, Scholtes, Theo
Format: Preprint
Veröffentlicht: 2024
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author Grujić, Zoran D.
Ćurĉić, Marija
Kocić, Aleksandra
Weis, Antoine
Scholtes, Theo
author_facet Grujić, Zoran D.
Ćurĉić, Marija
Kocić, Aleksandra
Weis, Antoine
Scholtes, Theo
contents We investigate the phase relationship between the oscillating (rf) excitation field and the detected (light) power modulation in scalar rf-driven optically pumped magnetometers (OPMs), in particular in the $M_x$ configuration. While the static dependence of the demodulation phase on the direction of the external static magnetic field vector can be largely mitigated by aligning the oscillating rf field along the light propagation direction, we demonstrate that a dynamic (transient) phase response arises under magnetic field tilts. We analytically solve the corresponding modified Bloch equation and confirm agreement with experimental observations obtained using an $M_x$ magnetometer incorporating a paraffin-coated Cs vapor cell. The results reveal fundamental limitations of $M_x$ magnetometers regarding response time and accuracy, in particular when employed with active electronic feedback, such as a phase-locked loop. Therefore, this work is highly relevant to important magnetometry applications where the direction of the quasi-static magnetic field of interest is unknown \textit{a priori} or varies over time, or in measurements requiring a large detection bandwidth. Such conditions are encountered in applications such as geomagnetic surveying, particularly with mobile platforms.
format Preprint
id arxiv_https___arxiv_org_abs_2409_20446
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Phase projection errors in rf-driven optically pumped magnetometers
Grujić, Zoran D.
Ćurĉić, Marija
Kocić, Aleksandra
Weis, Antoine
Scholtes, Theo
Atomic Physics
Instrumentation and Detectors
We investigate the phase relationship between the oscillating (rf) excitation field and the detected (light) power modulation in scalar rf-driven optically pumped magnetometers (OPMs), in particular in the $M_x$ configuration. While the static dependence of the demodulation phase on the direction of the external static magnetic field vector can be largely mitigated by aligning the oscillating rf field along the light propagation direction, we demonstrate that a dynamic (transient) phase response arises under magnetic field tilts. We analytically solve the corresponding modified Bloch equation and confirm agreement with experimental observations obtained using an $M_x$ magnetometer incorporating a paraffin-coated Cs vapor cell. The results reveal fundamental limitations of $M_x$ magnetometers regarding response time and accuracy, in particular when employed with active electronic feedback, such as a phase-locked loop. Therefore, this work is highly relevant to important magnetometry applications where the direction of the quasi-static magnetic field of interest is unknown \textit{a priori} or varies over time, or in measurements requiring a large detection bandwidth. Such conditions are encountered in applications such as geomagnetic surveying, particularly with mobile platforms.
title Phase projection errors in rf-driven optically pumped magnetometers
topic Atomic Physics
Instrumentation and Detectors
url https://arxiv.org/abs/2409.20446