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Review of Scientific Instruments

Simultaneous excitation of 85Rb and 87Rb isotopes inside a microfabricated vapor cell with double-RF fields for a chip-scale MZ magnetometer

Qi Gan, Jintang Shang, Yu Ji, Lei Wu

Published Nov 1, 2017• 9 citations
Publisher

Abstract

We report a novel method adopting two RF fields to simultaneously excite 85Rb and 87Rb isotopes for an MZ type atomic magnetometer. The MZ magnetometer adopts a 6 mm3 microfabricated vapor cell with natural abundance rubidium and 0.74 amagat nitrogen as buffer gas inside. The excessively broadened magnetic resonance signals of the two rubidium isotopes overlap with each other and cause deterioration in accuracy and sensitivity performance. To solve this problem, a Double-RF Field Method (DRFM) is proposed, which adopts two RF fields with a central frequency ratio of 2:3. Compared with traditional Single-RF Field Method (SRFM), the DRFM reduces the detection error by over 50% and improves the sensitivity by more than 10%. The experiments are conducted at three temperatures and under various static magnetic fields. Theoretical models are also built to discuss the performance improvement of the magnetometer by the DRFM against the SRFM. This method provides a way to improve the performance of chip-scale MZ atomic magnetometers with low cost natural abundance rubidium.

DOI
10.1063/1.5013032

Related papers

Publisher’s Note: “Simultaneous excitation of 85Rb and 87Rb isotopes inside a microfabricated vapor cell with double-RF fields for a chip-scale MZ magnetometer” [Rev. Sci. Instrum. 88, 115009 (2017)]

Qi Gan, Jintang Shang, Yu Ji +1 more

Simultaneous excitation of 85 Rb and 87 Rb isotopes

Review of Scientific Instruments•Dec 1, 2017•1 citation

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Jianwei Sheng, Ziao Liu, Xiaoyu Li +3 more

Due to high sensitivity and compactness, spin-exchange relaxation-free (SERF) atomic magnetometers have found widespread applications. These devices rely on alkali atoms to sense magnetic fields, with87Rb being the commonly used isotope. However,87Rb must be extracted from natural abundance rubidium (natRb) through isotopic separation, making it expensive. Replacing87Rb with natRb reduces the cost to approximately just 1%. Nevertheless, it is generally believed that the isotopic mixture of87Rb and85Rb in natRb affects the coherence of the atomic ensemble. Using a dual-beam SERF magnetometer, we systematically compared 3 mm inner-size cubic vapor cells filled with natRb and87Rb. By optimizing the buffer gas pressure and optical parameters, we demonstrate that the natRb magnetometer can achieve performance comparable to that of the87Rb magnetometer. Experimental results show that both cells achieved a sensitivity of 4 1T/Hz1/2. These findings demonstrate that natRb can effectively replace87Rb in miniaturized dual-beam SERF magnetometers, enabling low-cost, high-sensitivity magnetic field measurements.

IEEE International Conference on Electronic Measurement & Instruments•Aug 22, 2025•0 citations

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The designs of microfabricated alkali vapor cells play an important role when the atomic magnetometers are developing toward on-chip integration. This paper presents microfabricated spherical alkali vapor cells with improved sensitivity for chip-scale atomic magnetometers. A microfabricated spherical rubidium vapor cell and a traditional microfabricated planar rubidium vapor cell are designed for comparison, which are of the same volume and interconnected by a microchannel to acquire equal inner buffer gas pressure. In chip-scale spin-exchange relaxation-free (SERF) atomic magnetometers, the rubidium polarization lifetimes of three pairs of spherical and planar vapor cells at different buffer gas pressures of 0.35, 0.73, and 2.00 amg are measured, respectively. The sensitivity of SERF atomic magnetometers using the vapor cells at a 0.35-amg buffer gas pressure is also measured. The results show that the transverse polarization lifetime of the spherical vapor cell is 2.46, 1.44, and 1.05 times that of the planar one at 0.35-, 0.73-, and 2.00-amg buffer gas pressures, respectively. Combining the improved polarization lifetime and increased optical path length, chip-scale SERF atomic magnetometer using the microspherical vapor cell has the sensitivity of 60 fT/Hz1/2from 5 to 15 Hz, while that based on the planar one is demonstrated with the sensitivity of 400 fT/Hz1/2from 5 to 15 Hz.

IEEE Transactions on Components Packaging and Manufacturing Technology•Sep 3, 2018•22 citations

Improvement of polarization lifetime by using wafer-level micro spherical rubidium vapor cells for chip-scale atomic magnetometers

Yu Ji, Qi Gan, Lei Wu +1 more

The paper presents a novel design for chip-scale atomic magnetometers using a micro spherical rubidium vapor cell. By modeling and calculation, it was found that compared with the traditional planar rubidium vapor cell with approximately the same internal volume and buffer gas pressure, the micro spherical rubidium vapor cell was demonstrated with improved polarization lifetime and optical length. Experiments show that chip-scale atomic magnetometers based on the micro spherical cell has a significantly improved signal to noise(S/N) and sensitivity for both85Rb and87Rb. The wafer-level micro spherical rubidium vapor cells are also of interests for applications on chip-scale atomic clocks, gyroscope, vector microwave electrometries and other quantum sensors.

IEEE International Conference on Micro Electro Mechanical Systems (MEMS)•Jan 1, 2016•1 citation

Influence of Buffer-Gas Pressure Inside Micro Alkali Vapor Cells on the Performance of Chip-Scale SERF Magnetometers

Lei Wu, Jintang Shang, Yu Ji +2 more

Spin-exchange-relaxation-free (SERF) optical atomic magnetometers are facing the challenges of dramatic decrease of sensitivity when the alkali vapor cells become small. This paper focuses on the sensitivity improvement of the chip-scale atomic magnetometer (CSAM) by changing buffer-gas pressures inside the microfabricated vapor cells. The rubidium vapor cells with three different buffer-gas pressures were tested in the SERF magnetometer. The influences of vapor cell temperature and pumping laser power on the device sensitivity are also characterized for further optimization. Results show that the three atomic vapor cells, with N2buffer-gas pressure of 0.20, 0.88, and 2.35 amg, have sensitivities of 900, 500, and 150 fT/Hz1/2, respectively. Results indicated that when the alkali vapor cells continue to be smaller, high buffer-gas pressure would provide an effective way to reduce the wall collision and improve the performance of CSAMs.

IEEE Transactions on Components Packaging and Manufacturing Technology•Dec 21, 2017•18 citations

Integration of Micro-Fabricated Scalar Magnetometer with the Combination of Mx and Mz Techniques

Qi Gan, Jintang Shang, Lei Wu +1 more

The importance of the atomic magnetometer hasalready been widely recognized and it is an emergency to come up with portable atomic magnetometers with highperformance. The scalar magnetometer with its uniqueproperty of merely sensitive to the magnitude but relativelyinsensitive to the direction of the ambient magnetic field. This work presents a novel solution which combines two types of scalar atomic magnetometers, namely the MX magnetometer and the MZ magnetometer. A micro-fabricated rubidium vapor cell, which is the key component in an atomic magnetometer, was integrated in the prototype to enable the reduction of its volume. With a brief review of the theoretical model of scalar atomic magnetometers, the principle is demonstrated. Both thescheme of the magnetometer and the fabrication process of the vapor cell are illustrated. The results of the dispersive signals were measured and are presented. The magnetic field noise spectrum of both the MX and MZ magnetometers are also presented in this work, which shows the sensitivities are in the order of 100pT/Hz1/2.

IEEE Electronic Components and Technology Conference (ECTC)•May 1, 2016•3 citations
We report a novel method adopting two RF fields to simultaneously excite 85Rb and 87Rb isotopes for an MZ type atomic magnetometer. The MZ magnetometer adopts a 6 mm3 microfabricated vapor cell with natural abundance rubidium and 0.74 amagat nitrogen as buffer gas inside. The excessively broadened magnetic resonance signals of the two rubidium isotopes overlap with each other and cause deterioration in accuracy and sensitivity performance. To solve this problem, a Double-RF Field Method (DRFM) is proposed, which adopts two RF fields with a central frequency ratio of 2:3. Compared with traditional Single-RF Field Method (SRFM), the DRFM reduces the detection error by over 50% and improves the sensitivity by more than 10%. The experiments are conducted at three temperatures and under various static magnetic fields. Theoretical models are also built to discuss the performance improvement of the magnetometer by the DRFM against the SRFM. This method provides a way to improve the performance of chip-scale MZ atomic magnetometers with low cost natural abundance rubidium.
Due to high sensitivity and compactness, spin-exchange relaxation-free (SERF) atomic magnetometers have found widespread applications. These devices rely on alkali atoms to sense magnetic fields, with87Rb being the commonly used isotope. However,87Rb must be extracted from natural abundance rubidium (natRb) through isotopic separation, making it expensive. Replacing87Rb with natRb reduces the cost to approximately just 1%. Nevertheless, it is generally believed that the isotopic mixture of87Rb and85Rb in natRb affects the coherence of the atomic ensemble. Using a dual-beam SERF magnetometer, we systematically compared 3 mm inner-size cubic vapor cells filled with natRb and87Rb. By optimizing the buffer gas pressure and optical parameters, we demonstrate that the natRb magnetometer can achieve performance comparable to that of the87Rb magnetometer. Experimental results show that both cells achieved a sensitivity of 4 1T/Hz1/2. These findings demonstrate that natRb can effectively replace87Rb in miniaturized dual-beam SERF magnetometers, enabling low-cost, high-sensitivity magnetic field measurements.
The designs of microfabricated alkali vapor cells play an important role when the atomic magnetometers are developing toward on-chip integration. This paper presents microfabricated spherical alkali vapor cells with improved sensitivity for chip-scale atomic magnetometers. A microfabricated spherical rubidium vapor cell and a traditional microfabricated planar rubidium vapor cell are designed for comparison, which are of the same volume and interconnected by a microchannel to acquire equal inner buffer gas pressure. In chip-scale spin-exchange relaxation-free (SERF) atomic magnetometers, the rubidium polarization lifetimes of three pairs of spherical and planar vapor cells at different buffer gas pressures of 0.35, 0.73, and 2.00 amg are measured, respectively. The sensitivity of SERF atomic magnetometers using the vapor cells at a 0.35-amg buffer gas pressure is also measured. The results show that the transverse polarization lifetime of the spherical vapor cell is 2.46, 1.44, and 1.05 times that of the planar one at 0.35-, 0.73-, and 2.00-amg buffer gas pressures, respectively. Combining the improved polarization lifetime and increased optical path length, chip-scale SERF atomic magnetometer using the microspherical vapor cell has the sensitivity of 60 fT/Hz1/2from 5 to 15 Hz, while that based on the planar one is demonstrated with the sensitivity of 400 fT/Hz1/2from 5 to 15 Hz.
The paper presents a novel design for chip-scale atomic magnetometers using a micro spherical rubidium vapor cell. By modeling and calculation, it was found that compared with the traditional planar rubidium vapor cell with approximately the same internal volume and buffer gas pressure, the micro spherical rubidium vapor cell was demonstrated with improved polarization lifetime and optical length. Experiments show that chip-scale atomic magnetometers based on the micro spherical cell has a significantly improved signal to noise(S/N) and sensitivity for both85Rb and87Rb. The wafer-level micro spherical rubidium vapor cells are also of interests for applications on chip-scale atomic clocks, gyroscope, vector microwave electrometries and other quantum sensors.
Spin-exchange-relaxation-free (SERF) optical atomic magnetometers are facing the challenges of dramatic decrease of sensitivity when the alkali vapor cells become small. This paper focuses on the sensitivity improvement of the chip-scale atomic magnetometer (CSAM) by changing buffer-gas pressures inside the microfabricated vapor cells. The rubidium vapor cells with three different buffer-gas pressures were tested in the SERF magnetometer. The influences of vapor cell temperature and pumping laser power on the device sensitivity are also characterized for further optimization. Results show that the three atomic vapor cells, with N2buffer-gas pressure of 0.20, 0.88, and 2.35 amg, have sensitivities of 900, 500, and 150 fT/Hz1/2, respectively. Results indicated that when the alkali vapor cells continue to be smaller, high buffer-gas pressure would provide an effective way to reduce the wall collision and improve the performance of CSAMs.
The importance of the atomic magnetometer hasalready been widely recognized and it is an emergency to come up with portable atomic magnetometers with highperformance. The scalar magnetometer with its uniqueproperty of merely sensitive to the magnitude but relativelyinsensitive to the direction of the ambient magnetic field. This work presents a novel solution which combines two types of scalar atomic magnetometers, namely the MX magnetometer and the MZ magnetometer. A micro-fabricated rubidium vapor cell, which is the key component in an atomic magnetometer, was integrated in the prototype to enable the reduction of its volume. With a brief review of the theoretical model of scalar atomic magnetometers, the principle is demonstrated. Both thescheme of the magnetometer and the fabrication process of the vapor cell are illustrated. The results of the dispersive signals were measured and are presented. The magnetic field noise spectrum of both the MX and MZ magnetometers are also presented in this work, which shows the sensitivities are in the order of 100pT/Hz1/2.