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

Optics Express

Spin polarization characteristics of hybrid optically pumped comagnetometers with different density ratios

Tian Zhao, Yueyang Zhai, Chang Liu, Hong-Tai Xie, Qian Cao, Xiujie Fang

Published Jul 5, 2022• 17 citations
Publisher

Abstract

We investigate the effects of the density ratio of K-Rb hybrid cells on the alkali metal-noble gas comagnetometers. Bloch equations simplified with the density ratio and average-pumping-rate model are presented for numerical simulation, which simplifies equations of complete hybrid spin ensemble and problem of polarization gradient. The spin polarizations of electron and nucleon, total electronic relaxation rates, and the spin-exchange efficiencies are measured with cells of different density ratios. The results are in good agreement with our equivalent model. Based on our theoretical analysis, the K-Rb- 21 Ne comagnetometer achieves maximum output signal by optimizing the combination of density ratio and optical power density. The density ratio is critical to the homogeneity of spin polarization and efficiency of hyperpolarization. The method in this work finds a way to optimize the sensitivity of comagnetometers, which is significant for angular-rotation sensors and new physics research.

DOI
10.1364/oe.463651

Related papers

Density-ratio dependence of spin polarization and spatial homogeneity in hybrid Rb–Cs vapor cells

Ge Jin, Tao shi, Yuxin Chen +2 more

Abstract Hybrid spin-exchange optical pumping (hybrid SEOP) using multiple alkali-metal species is commonly employed to improve the spatial homogeneity of alkali spin polarization in atomic magnetometers and comagnetometers. We investigate the dependence of spin polarization and its spatial homogeneity on the alkali density ratio D r = [ Rb ] / [ Cs ] in Rb–Cs hybrid vapor cells. A series of cells with controlled D r were fabricated and characterized using absolute electron paramagnetic resonance polarimetry at multiple positions along the cell axis. The results show that the density ratio strongly influences both the magnitude and spatial uniformity of alkali polarization through the competition among optical pumping, spin exchange, and spin-destruction processes. An optimal density ratio is observed near D r ≈ 6.59 ± 0.47 , where the polarization reaches its maximum while maintaining high spatial homogeneity (end-to-end ratio ∼89% and RMS homogeneity > 95 % ). Under typical operating conditions, the optimal density ratio lies in the range D r ≈ 4 –10. These results clarify the role of the alkali density ratio in Rb–Cs hybrid SEOP and provide practical guidance for optimizing hybrid vapor cells used in precision atomic magnetometers and comagnetometers.

Journal of Physics D Applied Physics•Apr 21, 2026•1 citation

Density-ratio dependence of angular-momentum-transfer efficiencies in hybrid Rb–Cs– 129 Xe vapor cells

Ge Jin, Tao shi, Yuxin Chen +2 more

Abstract We investigate angular-momentum transfer efficiencies in hybrid Rb–Cs– 129 Xe vapor cells with different alkali compositions. Experiments were performed at a pump power of 40 mW and a cell temperature of 110 ∘ C, where the Rb–Cs spin-exchange rate is comparable to the alkali electron-spin relaxation rate and complete spin-temperature equilibrium is not established. Using Rb-rich cells under Cs pumping and Cs-rich cells under Rb pumping, we measured the steady-state 129 Xe polarization and build-up time and determined the corresponding spin-exchange and photon efficiencies. Within each cell series, both efficiencies exhibit systematic composition-dependent trends arising from the combined effects of optical pumping, incomplete Rb–Cs polarization transfer, alkali relaxation, and alkali–Xe spin exchange. The Rb–Cs polarization-transfer factor converts the nominal alkali density ratio into an effective polarization-weighted ratio, which governs the relative contributions of the Rb–Xe and Cs–Xe spin-exchange channels. These results clarify angular-momentum transfer in hybrid Rb–Cs– 129 Xe systems and provide guidance for optimizing low-power hybrid spin-exchange optical pumping and alkali–noble-gas sensor platforms.

Journal of Physics D Applied Physics•Sep 4, 2026•0 citations

Research on the influence of alkali polarization on an all-optical atomic spin magnetometer based on hybrid pumping potassium and rubidium

Hong Zhang, Sheng Zou, Xiyuan Chen +1 more

An all-optical atomic spin magnetometer using a hybrid cell of K and Rb atoms is demonstrated in this paper. Via deriving and solving the Bloch equations, we established the models for the polarization rate of Rb and the magnetometer’s output signal, respectively. In order to achieve the maximum sensitivity, we carried out research on the influence of the pump power on the polarization rate and magnetometer’s output signal. The magnetometer’s sensitivity was found to be proportional to the polarization rate of Rb, which was confined by the pump power. In a certain context, theoretical predictions indicated that the larger the pump power was, the higher magnetometer’s sensitivity that could be realized. However, the theoretical estimate deviated from the experimental results. An analysis of the errors between the actual value and the theoretical value showed that the different molar ratio between the two species of alkali-metal atoms was the primary reason causing the deviation. By comparing the experimental measurement result with simulation result, we found the difference in the molar ratio to be approximate 4 times. After various parameters had been optimized, a sensitivity of 18 fT/Hz 1/2 was achieved by analyzing the signal-to-noise ratio.

Journal of the Korean Physical Society•Apr 1, 2015•9 citations

Effects of pump laser power density on the hybrid optically pumped comagnetometer for rotation sensing

Liwei Jiang, Wei Quan, Yixiang Liang +3 more

We investigate the effects of pump laser power density on the hybrid optically pumped comagnetometer operated in the spin-exchange relaxation-free (SERF) regime. The analytic steady-state output model for the comagnetometer considering two alkali metal species and one nuclear species is presented for the first time. And the effects of pump laser power density on the rotation sensitivity, suppression of low-frequency magnetic noise and long-term stability of the comagnetometer are studied experimentally. The results indicate that when the product of pumping rate and density ratio of pumped atom to probed atom is equal to the spin relaxation rate of the probed atom, the maximum response and highest sensitivity of the comagnetometer are achieved. However, the suppression of low-frequency magnetic noise and long-term stability improve with the increasing of pump laser power density due to the increasing of nuclear spin polarization. Our focus is to optimize the performance of the comagnetometer for rotation sensing, but the theory and method presented here are relevant to all applications of the hybrid optical pumping technique.

Optics Express•Sep 16, 2019•62 citations

Balanced Light-Assisted Hybrid Spin Exchange Optical Pumping in SERF Comagnetometers

Zitong Xu, Kai Wei, Xiaofei Huang +7 more

Ultrasensitive spin exchange relaxation-free (SERF) comagnetometers have been widely applied in various new physics experiments and show great potential for inertial navigation. However, the spatially nonuniform spin polarization of alkali metal (AM) and noble gas (NG) atoms results in an effective magnetic field gradient on the order of 100 nT/cm which is much larger than that is produced by the coils and remanence on the magnitude of 1 nT/cm, thereby reducing the suppression ability of the magnetic noise and limiting the scale factor and noise floor of the comagnetometers. In this study, we establish a model of the effective magnetic field gradient caused by uneven spin polarization and analyze the influencing factors. Our results indicate that optimizing the density ratio of hybrid AM atoms can suppress the effective magnetic field gradient. Nevertheless, the available pump light power imposes a limitation on the density ratio. To further address this issue, we propose a balanced light-assisted hybrid spin exchange optical pumping (HSEOP) method. Our experimental results confirm the effectiveness of the mentioned approach, with 67% suppression of the nuclear transverse relaxation rate and a nearly threefold increase in the scale factor. Furthermore, the optimal density ratio in experimental applications can be reduced from 200 to below 80, thereby overcoming the limitation of laser power in SERF comagnetometers and providing the possibility for wider applications. Finally, the suppression factor of magnetic noise is enhanced by 89% by optimizing the density ratio and the balanced light-assisted HSEOP method. This research sheds light on the fundamental physics experiments and potential for inertial navigation.

IEEE Transactions on Instrumentation and Measurement•Jan 1, 2023•5 citations

In-Situ Measurement of the Density Ratio of the K-Rb-21Ne Comagnetometer Based on Electron Spin Relaxation Rate

Tian Zhao, Kai Wei, Yueyang Zhai +1 more

Abstract Accurate measurement of alkali metal density ratio in hybrid vapor cells is essential for high sensitivity of comagnetometers. We introduce and investigate a new method of measuring the density ratio based on electron spin-relaxation rate. The Bloch equations including the parameter of density ratio are studied, and the density measurement results show that measurement uncertainty is less than 12%. The advantage of this method is measuring the in-situ density ratio, which is more precise and useful for optimizing sensitivity of comagnetometers by adjusting the density ratio in real time.

Journal of Physics Conference Series•Nov 1, 2021•1 citation
We investigate the effects of the density ratio of K-Rb hybrid cells on the alkali metal-noble gas comagnetometers. Bloch equations simplified with the density ratio and average-pumping-rate model are presented for numerical simulation, which simplifies equations of complete hybrid spin ensemble and problem of polarization gradient. The spin polarizations of electron and nucleon, total electronic relaxation rates, and the spin-exchange efficiencies are measured with cells of different density ratios. The results are in good agreement with our equivalent model. Based on our theoretical analysis, the K-Rb- 21 Ne comagnetometer achieves maximum output signal by optimizing the combination of density ratio and optical power density. The density ratio is critical to the homogeneity of spin polarization and efficiency of hyperpolarization. The method in this work finds a way to optimize the sensitivity of comagnetometers, which is significant for angular-rotation sensors and new physics research.
Abstract Hybrid spin-exchange optical pumping (hybrid SEOP) using multiple alkali-metal species is commonly employed to improve the spatial homogeneity of alkali spin polarization in atomic magnetometers and comagnetometers. We investigate the dependence of spin polarization and its spatial homogeneity on the alkali density ratio D r = [ Rb ] / [ Cs ] in Rb–Cs hybrid vapor cells. A series of cells with controlled D r were fabricated and characterized using absolute electron paramagnetic resonance polarimetry at multiple positions along the cell axis. The results show that the density ratio strongly influences both the magnitude and spatial uniformity of alkali polarization through the competition among optical pumping, spin exchange, and spin-destruction processes. An optimal density ratio is observed near D r ≈ 6.59 ± 0.47 , where the polarization reaches its maximum while maintaining high spatial homogeneity (end-to-end ratio ∼89% and RMS homogeneity > 95 % ). Under typical operating conditions, the optimal density ratio lies in the range D r ≈ 4 –10. These results clarify the role of the alkali density ratio in Rb–Cs hybrid SEOP and provide practical guidance for optimizing hybrid vapor cells used in precision atomic magnetometers and comagnetometers.
Abstract We investigate angular-momentum transfer efficiencies in hybrid Rb–Cs– 129 Xe vapor cells with different alkali compositions. Experiments were performed at a pump power of 40 mW and a cell temperature of 110 ∘ C, where the Rb–Cs spin-exchange rate is comparable to the alkali electron-spin relaxation rate and complete spin-temperature equilibrium is not established. Using Rb-rich cells under Cs pumping and Cs-rich cells under Rb pumping, we measured the steady-state 129 Xe polarization and build-up time and determined the corresponding spin-exchange and photon efficiencies. Within each cell series, both efficiencies exhibit systematic composition-dependent trends arising from the combined effects of optical pumping, incomplete Rb–Cs polarization transfer, alkali relaxation, and alkali–Xe spin exchange. The Rb–Cs polarization-transfer factor converts the nominal alkali density ratio into an effective polarization-weighted ratio, which governs the relative contributions of the Rb–Xe and Cs–Xe spin-exchange channels. These results clarify angular-momentum transfer in hybrid Rb–Cs– 129 Xe systems and provide guidance for optimizing low-power hybrid spin-exchange optical pumping and alkali–noble-gas sensor platforms.
An all-optical atomic spin magnetometer using a hybrid cell of K and Rb atoms is demonstrated in this paper. Via deriving and solving the Bloch equations, we established the models for the polarization rate of Rb and the magnetometer’s output signal, respectively. In order to achieve the maximum sensitivity, we carried out research on the influence of the pump power on the polarization rate and magnetometer’s output signal. The magnetometer’s sensitivity was found to be proportional to the polarization rate of Rb, which was confined by the pump power. In a certain context, theoretical predictions indicated that the larger the pump power was, the higher magnetometer’s sensitivity that could be realized. However, the theoretical estimate deviated from the experimental results. An analysis of the errors between the actual value and the theoretical value showed that the different molar ratio between the two species of alkali-metal atoms was the primary reason causing the deviation. By comparing the experimental measurement result with simulation result, we found the difference in the molar ratio to be approximate 4 times. After various parameters had been optimized, a sensitivity of 18 fT/Hz 1/2 was achieved by analyzing the signal-to-noise ratio.
We investigate the effects of pump laser power density on the hybrid optically pumped comagnetometer operated in the spin-exchange relaxation-free (SERF) regime. The analytic steady-state output model for the comagnetometer considering two alkali metal species and one nuclear species is presented for the first time. And the effects of pump laser power density on the rotation sensitivity, suppression of low-frequency magnetic noise and long-term stability of the comagnetometer are studied experimentally. The results indicate that when the product of pumping rate and density ratio of pumped atom to probed atom is equal to the spin relaxation rate of the probed atom, the maximum response and highest sensitivity of the comagnetometer are achieved. However, the suppression of low-frequency magnetic noise and long-term stability improve with the increasing of pump laser power density due to the increasing of nuclear spin polarization. Our focus is to optimize the performance of the comagnetometer for rotation sensing, but the theory and method presented here are relevant to all applications of the hybrid optical pumping technique.
Ultrasensitive spin exchange relaxation-free (SERF) comagnetometers have been widely applied in various new physics experiments and show great potential for inertial navigation. However, the spatially nonuniform spin polarization of alkali metal (AM) and noble gas (NG) atoms results in an effective magnetic field gradient on the order of 100 nT/cm which is much larger than that is produced by the coils and remanence on the magnitude of 1 nT/cm, thereby reducing the suppression ability of the magnetic noise and limiting the scale factor and noise floor of the comagnetometers. In this study, we establish a model of the effective magnetic field gradient caused by uneven spin polarization and analyze the influencing factors. Our results indicate that optimizing the density ratio of hybrid AM atoms can suppress the effective magnetic field gradient. Nevertheless, the available pump light power imposes a limitation on the density ratio. To further address this issue, we propose a balanced light-assisted hybrid spin exchange optical pumping (HSEOP) method. Our experimental results confirm the effectiveness of the mentioned approach, with 67% suppression of the nuclear transverse relaxation rate and a nearly threefold increase in the scale factor. Furthermore, the optimal density ratio in experimental applications can be reduced from 200 to below 80, thereby overcoming the limitation of laser power in SERF comagnetometers and providing the possibility for wider applications. Finally, the suppression factor of magnetic noise is enhanced by 89% by optimizing the density ratio and the balanced light-assisted HSEOP method. This research sheds light on the fundamental physics experiments and potential for inertial navigation.
Abstract Accurate measurement of alkali metal density ratio in hybrid vapor cells is essential for high sensitivity of comagnetometers. We introduce and investigate a new method of measuring the density ratio based on electron spin-relaxation rate. The Bloch equations including the parameter of density ratio are studied, and the density measurement results show that measurement uncertainty is less than 12%. The advantage of this method is measuring the in-situ density ratio, which is more precise and useful for optimizing sensitivity of comagnetometers by adjusting the density ratio in real time.