This paper presents a novel method to measure the magnetic gradient by an Mz atomic magnetometer using a micro-fabricated shaped rubidium vapor cell. The shaped vapor cell is fabricated by a chemical foaming process. Four micro radio frequency (RF) coils are mounted on the shaped rubidium vapor cell. Magnetic fields at the four points corresponding to the RF coils along the laser beam propagation are obtained by measuring Larmor frequency of the rubidium atoms inside the vapor cell. The magnetic gradients are also acquired with the measured magnetic fields. The measurement is performed in a magnetic shield environment. A dc electrical coil is taken to produce an existed magnetic field for the measurement and the theoretical magnetic field distribution is calculated. It is demonstrated that the measured magnetic fields and magnetic gradients correspond well with the calculated ones. Results show that the absolute error of the magnetic field is less than 0.1 μT, the relative error of the magnetic field is below 0.8%, and the relative error of the magnetic gradient is below 5.5%. Results also indicate that the atomic magnetometer has a sensitivity of 5 pT/Hz1/2from 1 to 2 Hz. The Mz atomic magnetometer is potentially useful for applications requiring gradient field information.
This paper presents a novel method to measure the magnetic gradient by an Mz atomic magnetometer using a micro-fabricated shaped rubidium vapor cell. The shaped vapor cell is fabricated by a chemical foaming process. Four micro radio frequency (RF) coils are mounted on the shaped rubidium vapor cell. Magnetic fields at the four points corresponding to the RF coils along the laser beam propagation are obtained by measuring Larmor frequency of the rubidium atoms inside the vapor cell. The magnetic gradients are also acquired with the measured magnetic fields. The measurement is performed in a magnetic shield environment. A dc electrical coil is taken to produce an existed magnetic field for the measurement and the theoretical magnetic field distribution is calculated. It is demonstrated that the measured magnetic fields and magnetic gradients correspond well with the calculated ones. Results show that the absolute error of the magnetic field is less than 0.1 μT, the relative error of the magnetic field is below 0.8%, and the relative error of the magnetic gradient is below 5.5%. Results also indicate that the atomic magnetometer has a sensitivity of 5 pT/Hz1/2from 1 to 2 Hz. The Mz atomic magnetometer is potentially useful for applications requiring gradient field information.
In this letter, we present a novel microfabricated shaped rubidium vapor cell with 3 cm optical path length for miniaturized atomic magnetometers. The novel shaped rubidium vapor cells are manufactured by a wafer-level fabrication process, and the process consists of the following three steps sequentially: first, wet etching to form oblong shallow cavity arrays; second, anodic bonding, glass reflowing, and wet etching to obtain a glass wafer with shaped structures; third, anodic bonding and chemical reaction to obtain the wafer-level shaped rubidium vapor cells. A miniaturized atomic magnetometer using the novel shaped rubidium vapor cell is characterized in the geomagnetic environment. The performance of the novel shaped rubidium vapor cell is compared with the traditional microfabricated rubidium vapor cell of a “glass–silicon–glass” sandwich structure. Results show that the measured geomagnetic field is 47.85 μT. It is demonstrated that the dispersive signal's slope of the novel shaped rubidium vapor cell is 15 times larger than that of the traditional one. Results also indicate that the miniaturized atomic magnetometer working in the geomagnetic environment has a magnetic noise spectral density of 3.5 pT/Hz1/2from 1 to 2 Hz.
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.
Currently, medical magnetic localization necessitates complex and costly gradient coil systems, primarily due to the limited sensitivity of the magnetic sensors in use. This article presents a highly sensitive, compact multipoint quantum magnetometer (CMQM) characterized by a straightforward design and low cost. The core of the sensor is a MEMS 3D Rubidium (Rb) atomic cell with an optical path of 3.0 cm, which is manufactured through a mold foaming process. The size of the compact sensor head is less than 11.5 cm3. The CMQM obtains magnetic field magnitude at six points by measuring Larmor frequency of rubidium atoms within corresponding positions. A uniform magnetic field coils is calibrated with the CMQM within a ferromagnetic shield. The vector synthesis method is used to enhance the accuracy by reducing interference from remanent magnetic field. The deviation between the measured magnetic field and those predicted using closed cylinder approximation (CCA) is less than 1.1%. The magnetic noise density at different points varies between 2.289 pT/Hz1/2and 6.015 pT/Hz1/2. The effective magnetic resolution of the CMQM is ~0.65 nT. Theoretical spatial resolution of the CMQM can reach to$17.5~\mu $m with a simple circular coil. [2024-0230]
High sensitive atomic magnetometers play an important role in many fields including geophysical mapping, space science, nuclear magnetic resonance, health care and perimeter and remote monitoring. In this study, a novel method to fabricate the micro spherical Rubidium vapor cell has been investigated and the integration of micro spherical rubidium vapor cell in 3-axis atomic magnetometer has been demonstrated successfully. First of all, a fabrication process for micro spherical alkali vapor cells is introduced. Then the prepared uniform wafer-level micro spherical rubidium vapor cell has been characterized by Ultraviolet spectrophotometer as well as a laser frequency locking system. At last, 3-axis atomic magnetometer based on the micro spherical rubidium vapor cell has been demonstrated. Results show that micro spherical rubidium vapor cell has been fabricated successfully. Results also indicate that a 3-axis atomic magnetometer based on the micro spherical rubidium vapor cell could measure magnetic fields along three directions (BX, BYand BZ).
This paper introduces measurement of weak magnetic field using a novel design of chip-scale Spin Exchange Relaxation Free (SERF) atomic magnetometer based on a microfabricated Rubidium (Rb) vapor cell. The sensor, which integrates a micro-fabricated Rb vapor cell, a heater and related components, is fabricated by stacking printed circuit boards (PCB) and Micro Electro Mechanical Systems (MEMS) process technology. During the experiments, the noise of the measurement using the atomic magnetometer was obtained. In addition, a test of the simulated magnetic field was performed in a shielding cylinder, and the signal of the simulated magnetic field about 100 pT at 1.2 Hz was measured. The signal is processed by the software using a notch filter to suppress the Direct Current (DC) noise and 50Hz noise. This paper provides a novel micro-fabricated device for detecting weak magnetic field.
We report a rubidium atomic magnetometer based on pump-probe nonlinear magneto-optical rotation. The rubidium vapor cell is placed in a five-layer magnetic shield with inner coils that can generate uniform magnetic fields along the direction of pump beam, and the cell is also placed in the center of a Helmholtz coil that can generate an oscillating magnetic field perpendicular to the direction of pump beam. The atoms are optically pumped by circularly polarized pump beam along a constant magnetic field in a period of time, then the pump beam is turned off and a /2 pulse of oscillating magnetic field for 87Rb atoms is applied. After the above process, the individual atomic magnetic moments become phase coherent, resulting in a transverse magnetization vector precessing at the Larmor frequency in the magnetic field. The linearly polarized probing beam is perpendicular to the direction of magnetic field, and can be seen as a superposition of the left and right circularly polarized light. Because of the different absorptions and dispersions of the left and right circularly polarized light by rubidium atoms, the polarization direction of probing beam rotates when probing beam passes through rubidium vapor cell. The rotation of the polarization is subsequently converted into an electric signal through a polarizing beam splitter. Finally, the decay signal related to the transverse magnetization vector is measured. The Larmor frequency proportional to magnetic field is obtained by the Fourier transform of the decay signal. The value of magnetic field is calculated from the formula:B=(2/) f, where and f are the gyromagnetic ratio and Larmor frequency, respectively. In order to measure the magnetic field in a wide range, the tracking lock mode is proposed and tested. The atomic magnetometer can track the magnetic field jump of 1000 nT or 10000 nT, indicating that the atomic magnetometer has strong locking ability and can be easily locked after start-up. The main performances in different magnetic fields are tested. The results show that the measurement range of the atomic magnetometer is from 100 nT to 100000 nT, the extreme sensitivity is 0.2 pT/Hz1/2, and the magnetic field resolution is 0.1 pT. The transverse relaxation times of the transverse magnetization vector in different magnetic fields are obtained, and the relaxation time decreases with the increase of the magnetic field. When the measurement range is from 5000 nT to 100000 nT, the magnetic field sampling rate of the atomic magnetometer can be adjusted in a range from 1 Hz to 1000 Hz. The atomic magnetometer in high sampling rate can measure weak alternating magnetic field at low frequency. This paper provides an important reference for developing the atomic magnetometer with large measurement range, high sensitivity and high sampling rate.