Dual-Species All-Optical Magnetometer Based on a Cs-K Hybrid Vapor Cell

Yudong Ding, Wei Xiao, Yixin Zhao, Teng Wu, Xiang Peng, and Hong Guo

Phys. Rev. Applied 19, 034066 – Published 21 March 2023

Abstract

We build and characterize a dual-species all-optical magnetometer based on a Cs-K hybrid vapor cell with a paraffin coating. Using the amplitude-modulated Bell-Bloom scheme and Faraday-rotation measurement, we show that the spin polarization of Cs and K atoms can be generated and detected independently. The noise floor of the Cs channel is $35 fT / \sqrt{Hz}$ , whereas that of the K channel is $260 fT / \sqrt{Hz}$ , which is affected mainly by the magnetic resonance broadening in the presence of mutual spin-exchange collisions. With use of the proposed device, in situ magnetic field stabilization is realized by use of (i) the K channel to monitor and compensate for the magnetic field noise and (ii) the Cs channel to read out the magnetic field after active stabilization. The low-frequency magnetic field noise can be suppressed by a factor of more than $1000$ in the presence of magnetic field gradients. When applied to magnetic field stabilization, such in situ measurement is achieved more compactly and is more accurate than ex situ measurement that is realized with two spatially separated vapor cells. In addition, the proposed scheme could also be applied in a practical ground-surveying magnetometer based on dual working species.

Received 14 March 2022
Revised 7 October 2022
Accepted 14 February 2023

DOI:https://doi.org/10.1103/PhysRevApplied.19.034066

Physics Subject Headings (PhySH)

Magneto-optical spectra Magnetometry Quantum sensing Zeeman effect

Alkali metals Atomic gases

Magnetic moment Polarization

Quantum Information, Science & TechnologyAtomic, Molecular & Optical

Authors & Affiliations

Yudong Ding , Wei Xiao , Yixin Zhao , Teng Wu, Xiang Peng ^*, and Hong Guo ^†

State Key Laboratory of Advanced Optical Communication Systems and Networks, School of Electronics, and Center for Quantum Information Technology, Peking University, 100871 Beijing, China

^*xiangpeng@.pku.edu.cn
^†hongguo@.pku.edu.cn

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Issue

Vol. 19, Iss. 3 — March 2023

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Images

Figure 1
Experimental setup of an all-optical Cs-K magnetometer. The bias magnetic field is along the axial direction of the magnetic shield and is perpendicular to the propagation direction of both the pump laser and the probe laser. AOM, acousto-optic modulator (which is used to modulate the pump beam); DAVLL, dichronic atomic vapor laser lock (which is used to lock the laser frequency); FC, fiber coupler; L, convex lens; LIA, lock-in amplifier; LP, linear polarizer; PBS, polarization beam splitter; PD, photodetector; PID, proportional-integral-derivative controller; PMF, polarization-maintaining fiber; R, reflector; SG, signal generator; VCO, voltage-controlled oscillator; WP, Wollaston prism; $λ / 2$ , half-wave plate; $λ / 4$ , quarter-wave plate; 50%, semitransparent and semireflective mirror.
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Figure 2
Power spectral density (PSD) of magnetic field noise measured with the Cs channel (blue line) and the K channel (gray line) in our design. The inset shows the signal frequency responses.
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Figure 3
Simulation and measurement of (a) Cs magnetic resonance linewidth using the hybrid cell (orange) and a pure Cs cell (gray) and (b) K magnetic resonance linewidth using the hybrid cell (blue) and a pure K cell (red).
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Figure 4
Simulated and measured dependence of transfer of transverse spin polarization on the bias magnetic field. The transfer of spin polarization is detected by our optically pumping the Cs atoms and measuring the Faraday rotation of the K atoms. SEC, spin-exchange collision.
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Figure 5
(a) Experimental scheme of active magnetic field (current-source) stabilization with a Cs-K all-optical magnetometer. Here, the K channel is used to measure and compensate for the magnetic field noise, while the Cs channel is used to read out the noise-suppressed magnetic field. $B_{C}$ is the magnetic field that generated by the magnetic field coils. (b) Magnetic field noise measured before and after in situ magnetic field stabilization; the bias magnetic field is $25 μ T$ . (c) Sinusoidal test field (gray line) with a frequency of 0.01 Hz and an amplitude of 8000 pT (peak-to-peak value) generated to characterize the magnetic-field-noise suppression in the time domain. The orange line (blue line) represents the magnetic field measurement after active stabilization using the hybrid cell (independent Cs and K cells). (d) Frequency dependence of test-field suppression in active magnetic field stabilization.
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