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11 pages, 3109 KiB

Open AccessArticle

Far-Detuning Laser Frequency Disturbance Suppression for Atomic Sensor Based on Intrinsic Fiber Fabry–Pérot Cavity

by Guanghui Li, Lihong Duan, Xinxiu Zhou and Wei Quan

Photonics 2024, 11(11), 1027; https://doi.org/10.3390/photonics11111027 - 30 Oct 2024

Viewed by 405

The method of laser far-detuned frequency locking is proposed based on a fiber Fabry–Perot cavity which transfers the ultra-stable atomic reference frequency stability to the target laser utilized for atomic sensors. The control transfer function of the closed-loop system is established to elucidate [...] Read more.

The method of laser far-detuned frequency locking is proposed based on a fiber Fabry–Perot cavity which transfers the ultra-stable atomic reference frequency stability to the target laser utilized for atomic sensors. The control transfer function of the closed-loop system is established to elucidate the process of perturbation suppression. It is illustrated that this method is robust against the disturbance to the laser and cavity by controlling the cavity with different parameters. After the long-term experimental test, the stability of the laser frequency locked on the fiber cavity achieves an Allan deviation of

9.9 \times 10^{- 11}

and the detuning of the nearest atomic frequency resonance point is more than 200 GHz. Its stability and detuning value exceed previous reports. Full article

(This article belongs to the Special Issue Optically Pumped Magnetometer and Its Application)

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17 pages, 5263 KiB

Open AccessArticle

The Optimization of Microwave Field Characteristics for ODMR Measurement of Nitrogen-Vacancy Centers in Diamond

by Zhenxian Fan, Li Xing, Feixiang Wu, Xiaojuan Feng and Jintao Zhang

Photonics 2024, 11(5), 436; https://doi.org/10.3390/photonics11050436 - 8 May 2024

Viewed by 1541

Abstract

A typical solid-state quantum sensor can be developed based on negatively charged nitrogen-vacancy (NV⁻) centers in diamond. The electron spin state of NV⁻ can be controlled and read at room temperature. Through optical detection magnetic resonance (ODMR) technology, temperature measurement [...] Read more.

A typical solid-state quantum sensor can be developed based on negatively charged nitrogen-vacancy (NV⁻) centers in diamond. The electron spin state of NV⁻ can be controlled and read at room temperature. Through optical detection magnetic resonance (ODMR) technology, temperature measurement can be achieved at the nanoscale. The key to ODMR technology is to apply microwave resonance to manipulate the electron spin state of the NV⁻. Therefore, the microwave field characteristics formed near the NV⁻ have a crucial impact on the sensitivity of ODMR measurement. This article mainly focuses on the temperature situation in cellular applications and simulates the influence of structural parameters of double open loop resonant (DOLR) microwave antennas and broadband large-area (BLA) microwave antennas on the microwave field’s resonance frequency, quality factor Q, magnetic field strength, uniformity, etc. The parameters are optimized to have sufficient bandwidth, high signal-to-noise ratio, low power loss, and high magnetic field strength in the temperature range of 36 °C to 42.5 °C. Finally, the ODMR spectra are used for effect comparison, and the signal-to-noise ratio and Q values of the ODMR spectra are compared when using different antennas. We have provided an optimization method for the design of microwave antennas and it is concluded that the DOLR microwave antenna is more suitable for living cell temperature measurement in the future. Full article

(This article belongs to the Special Issue Optically Pumped Magnetometer and Its Application)

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16 pages, 987 KiB

Open AccessArticle

Theoretical Study on Performing Movement-Related MEG with ⁸³Kr-Based Atomic Comagnetometer

by Yao Chen, Ruyang Guo, Jiyang Wang, Mingzhi Yu, Man Zhao and Libo Zhao

Photonics 2023, 10(12), 1302; https://doi.org/10.3390/photonics10121302 - 24 Nov 2023

Cited by 1 | Viewed by 1171

Abstract

A K–Rb–

^{83}

Kr-based atomic comagnetometer for performing movement-related Magnetoencephalography (MEG) is theoretically studied in this paper. Parameters such as the spin-exchange rates, the spin-dephasing rates and the polarization of the nuclear spins are studied to configure the comagnetometer. The results show that [...] Read more.

A K–Rb–

^{83}

Kr-based atomic comagnetometer for performing movement-related Magnetoencephalography (MEG) is theoretically studied in this paper. Parameters such as the spin-exchange rates, the spin-dephasing rates and the polarization of the nuclear spins are studied to configure the comagnetometer. The results show that the nuclear spin can generate a magnetic field of around 700 nT, at which the nuclear spin can compensate for a wide range of magnetic fields. In this paper, we also show the fabrication process for hybrid optical-pumping vapor cells, whereby alkali metals are mixed in a glove box that is then connected to the alkali vapor-cell fabrication system. Full article

(This article belongs to the Special Issue Optically Pumped Magnetometer and Its Application)

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11 pages, 2836 KiB

Open AccessArticle

Laser Heating Method for an Alkali Metal Atomic Cell with Heat Transfer Enhancement

by Yang Li, Guoqing Zhou, Shencheng Tian, Xuejing Liu, Xiangmei Dong and Xiumin Gao

Photonics 2023, 10(6), 637; https://doi.org/10.3390/photonics10060637 - 1 Jun 2023

Cited by 2 | Viewed by 1818

Abstract

Alkali metal atomic cells are crucial components of atomic instruments, such as atomic magnetometers, atomic gyroscopes, and atomic clocks. A highly uniform and stable heating structure can ensure the stability of the alkali metal atom density. The vapor cell of an atomic magnetometer [...] Read more.

Alkali metal atomic cells are crucial components of atomic instruments, such as atomic magnetometers, atomic gyroscopes, and atomic clocks. A highly uniform and stable heating structure can ensure the stability of the alkali metal atom density. The vapor cell of an atomic magnetometer that uses laser heating has no magnetic field interference and ease of miniaturization, making it superior to hot air heating and AC electric heating. However, the current laser heating structure suffers from low heating efficiency and uneven temperature distribution inside the vapor cell. In this paper, we designed a non-magnetic heating structure based on the laser heating principle. We studied the temperature distribution of the heating structure using the finite element method (FEM) and analyzed the conversion and transfer of laser energy. We found that the heat conduction between the vapor cell and the heating chips (colored filters) is poor, resulting in uneven temperature distribution and low heating efficiency in the vapor cell. Therefore, the addition of graphite film to the four surfaces of the vapor cell was an important improvement. This addition helped to balance the temperature distribution and improve the conduction efficiency of the heating structure. It was measured that the power of the heating laser remained unchanged. After the addition of the graphite film, the temperature difference coefficient (CVT) used to evaluate the internal temperature uniformity of the vapor cell was reduced from 0.1308 to 0.0426. This research paper is crucial for improving the heating efficiency of the non-magnetic heating structure and the temperature uniformity of the vapor cell. Full article

(This article belongs to the Special Issue Optically Pumped Magnetometer and Its Application)

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12 pages, 3335 KiB

Open AccessArticle

Internal Dynamic Temperature Measurement of Alkali Metal Vapor Cell by Kalman Filter

by Yang Li, Shencheng Tian, Junpeng Zhao, Guoqing Zhou, Xiangmei Dong, Xiumin Gao and Xuejing Liu

Photonics 2023, 10(5), 492; https://doi.org/10.3390/photonics10050492 - 24 Apr 2023

Cited by 1 | Viewed by 1576

Abstract

Measuring the internal dynamic temperature of alkali metal vapor cells is crucial for enhancing the performance of numerous atomic devices. However, conventional methods of measuring the internal dynamic temperature of the cell are prone to errors. To obtain a more accurate internal dynamic [...] Read more.

Measuring the internal dynamic temperature of alkali metal vapor cells is crucial for enhancing the performance of numerous atomic devices. However, conventional methods of measuring the internal dynamic temperature of the cell are prone to errors. To obtain a more accurate internal dynamic temperature of the alkali metal vapor cell, a temperature measuring method based on the data fusion of the Kalman filter has been proposed. This method combines the indirect temperature measurement signal from a resistance temperature detector with the atomic absorption spectrometric temperature measurement signal. This provides a high-accuracy set of internal dynamic temperatures in the cell. The atomic vapor density calculated from the final fusion results is 37% average lower than that measured by external wall temperature measurements, which is in line with the conclusions reached in many previous studies. This study is highly beneficial to measure the temperature of alkali metal vapor cells. Full article

(This article belongs to the Special Issue Optically Pumped Magnetometer and Its Application)

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11 pages, 6109 KiB

Open AccessCommunication

Nonzero-Order Resonances in Single-Beam Spin-Exchange Relaxation-Free Magnetometers

by Kun Wang, Kaixuan Zhang, Nuozhou Xu, Yifan Yan, Xiaoyu Li and Binquan Zhou

Photonics 2023, 10(4), 458; https://doi.org/10.3390/photonics10040458 - 15 Apr 2023

Cited by 1 | Viewed by 1882

Abstract

Zero-field optically pumped magnetometers operating in the spin-exchange relaxation-free (SERF) regime have been extensively studied, and usually depend on zeroth-order parametric resonance to measure the magnetic field. However, the studies conducted on this topic lack thorough analyses and in-depth discussion of nonzero-order magnetic [...] Read more.

Zero-field optically pumped magnetometers operating in the spin-exchange relaxation-free (SERF) regime have been extensively studied, and usually depend on zeroth-order parametric resonance to measure the magnetic field. However, the studies conducted on this topic lack thorough analyses and in-depth discussion of nonzero-order magnetic resonances in single-beam SERF magnetometers. In this paper, we analyzed the nonzero-order resonance, especially the first-order resonance, based on a single-beam SERF magnetometer, and discussed its various applications. A comprehensive theoretical analysis and experiments were conducted with respect to multiple functions, including nonzero finite magnetic field measurements, spin polarization measurement, and in situ coil constant calibration. The results showed that first-order resonance can be utilized for nonzerofinite magnetic field measurements, and the spin polarization of alkali-metal atoms can be determined by measuring the slowing-down factor using the resonance condition. Furthermore, acquiring the first-order resonance point at an equivalent zero pump light power through fitting offers an approach for quick and precise in situ coil constant calibration. This study contributes to the applications of SERF magnetometers in nonzero finite magnetic fields. Full article

(This article belongs to the Special Issue Optically Pumped Magnetometer and Its Application)

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9 pages, 662 KiB

Open AccessCommunication

Suppression of the Equivalent Magnetic Noise Caused by Electron Spin Polarization in a Xe Isotope Comagnetometer

by Zekun Wu, Zhen Chai, Lan Xiao and Zhanchao Liu

Photonics 2023, 10(4), 423; https://doi.org/10.3390/photonics10040423 - 9 Apr 2023

Viewed by 1395

Abstract

The Xe isotope comagnetometer in the nuclear magnetic resonance regime can be used as a promising high-precision inertial measurement unit because of the absolute frequency measurement and high bandwidth. The fluctuation of the electron spin polarization leads to equivalent magnetic noise in the [...] Read more.

The Xe isotope comagnetometer in the nuclear magnetic resonance regime can be used as a promising high-precision inertial measurement unit because of the absolute frequency measurement and high bandwidth. The fluctuation of the electron spin polarization leads to equivalent magnetic noise in the Xe isotope comagnetometer, which is one of the main factors limiting the stability of the comagnetometer. Here, we demonstrate systematic research of equivalent magnetic noise suppression and analyze the influence of the electron spin polarization on the Xe isotope comagnetometer. Based on the spin–exchange method between Xe isotopes and alkali metal atoms through the Fermi contact hyperfine interaction, the error equation of the Xe Larmor frequency is established. The equivalent magnetic noise can be suppressed by controlling the static magnetic field. This suppression method for Xe isotope comagnetometers improved the stability while maintaining high bandwidth. The experimental results show that this method can reduce the fluctuations of the

^{129}

Xe and

^{131}

Xe frequencies by 75% and 68.6%, respectively. Full article

(This article belongs to the Special Issue Optically Pumped Magnetometer and Its Application)

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16 pages, 2822 KiB

Open AccessArticle

Precise Determination of Magnetic Gradient Relaxation of Coupled Atomic Spin Ensemble in Spin-Exchange Relaxation-Free Co-Magnetometer

by Xiujie Fang, Kai Wei, Wenfeng Fan, Siran Li, Qian Cao, Wei Quan, Yueyang Zhai and Zhisong Xiao

Photonics 2023, 10(4), 400; https://doi.org/10.3390/photonics10040400 - 3 Apr 2023

Cited by 1 | Viewed by 1493

Abstract

Inside a spin-exchange relaxation-free (SERF) co-magnetometer with a high-pressure buffer gas atomic cell, the magnetic field gradient causes the decoherence of atomic spins to produce magnetic-field gradient relaxation. This paper presents a new method for the accurate measurement of magnetic field gradient relaxation [...] Read more.

Inside a spin-exchange relaxation-free (SERF) co-magnetometer with a high-pressure buffer gas atomic cell, the magnetic field gradient causes the decoherence of atomic spins to produce magnetic-field gradient relaxation. This paper presents a new method for the accurate measurement of magnetic field gradient relaxation of alkali metal atoms and inert atoms of strongly coupled spin systems under triaxial magnetic field gradients in the K-Rb-²¹Ne co-magnetometer. The magnetic field gradient relaxation of alkali metal atoms is measured using a step magnetic field modulation method, and the magnetic field gradient relaxation of inert atoms is measured using a combined free induction decay and spin growth method. The method does not require the use of large background magnetic fields and RF fields to maintain the atoms in the SERF state, does not require additional optics, and is not affected by the pumping or detecting of optical power. A kinetic model that considers a large electron-equivalent magnetic field was designed and a gradient relaxation model was developed. The quadratic coefficients of the experimentally measured gradient relaxation curves fit the theoretical model well over the range of the applied magnetic field gradients, confirming the validity of the proposed method. Full article

(This article belongs to the Special Issue Optically Pumped Magnetometer and Its Application)

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14 pages, 2320 KiB

Open AccessArticle

A Novel Measurement Method for Spin Polarization Three Axis Spatial Distribution in Spin-Exchange Relaxation Free Atomic Magnetometer

by Xiujie Fang, Jin Li, Yanning Ma, Kai Wei, Wenfeng Fan, Yueyang Zhai, Wei Quan and Zhisong Xiao

Photonics 2023, 10(3), 332; https://doi.org/10.3390/photonics10030332 - 20 Mar 2023

Viewed by 2002

Abstract

The measurement of atomic spin polarization distribution in spin-exchange relaxation free (SERF) magnetometer is an important topic for improving the sensitivity and consistency of multi-channel magnetic field measurement applications. A novel spin polarization spatial distribution measurement method is presented based on the transient [...] Read more.

The measurement of atomic spin polarization distribution in spin-exchange relaxation free (SERF) magnetometer is an important topic for improving the sensitivity and consistency of multi-channel magnetic field measurement applications. A novel spin polarization spatial distribution measurement method is presented based on the transient response of the magnetometer after modulating the pumped light with a chopper. Polarization is obtained by a slow-down factor based on the fast spin-exchange interaction effects. Longitudinal and transverse polarization distributions are measured simultaneously without interrupting the operation of the SERF status. Under different oscillating magnetic fields, the spin polarization is measured at the cell centroid. Residual magnetic field inside the magnetometer is obtained from the linear relationship between the precession frequency and the oscillating magnetic field. The one-dimensional polarization distributions in the x, y, and z axes are measured using a digital micromirror device with a resolution of 0.25 cm. The measurement results conform to the Lambert-Bier absorption law and the Gaussian distribution law. Furthermore, 7 × 7 two-dimensional spatial distribution measurements of polarization on the xy and yz planes are performed. Nonuniformity of 1.04 in the xy plane and 1.82 in the yz plane in the built magnetometer. Compared with other measurement methods, the distribution measurement method proposed is independent of optical depth and suitable for low polarization and high polarization applications. Based on the results of the proposed measurement method of spin polarization spatial distribution, further compensation can improve the application consistency of multi-channel magnetic field measurements and improve the sensitivity of single-channel differential measurements. Full article

(This article belongs to the Special Issue Optically Pumped Magnetometer and Its Application)

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