The spin-exchange relaxation-free (SERF) atomic magnetometer is one of the ultra-sensitive magnetometers, which must be operated in a low magnetic field and heated more than 100°C. One of the main engineering difficulties in fabricating a SERF atomic magnetometer is to develop a heater that introduces no additional magnetic noise into the measurement system. In this paper, a novel compact current-heating scheme and apparatus for the SERF atomic magnetometer are proposed. The thermal and magnetic simulations of this apparatus are carried out and the results of the simulations demonstrate the feasibility of this heating apparatus: the vapor cell can be heated to a temperature of 103°C and magnetic field introduced in the magnetometer can be limited in 10nT.
The spin-exchange relaxation-free (SERF) atomic magnetometer is one of the ultra-sensitive magnetometers, which must be operated in a low magnetic field and heated more than 100°C. One of the main engineering difficulties in fabricating a SERF atomic magnetometer is to develop a heater that introduces no additional magnetic noise into the measurement system. In this paper, a novel compact current-heating scheme and apparatus for the SERF atomic magnetometer are proposed. The thermal and magnetic simulations of this apparatus are carried out and the results of the simulations demonstrate the feasibility of this heating apparatus: the vapor cell can be heated to a temperature of 103°C and magnetic field introduced in the magnetometer can be limited in 10nT.
Atomic magnetometers based on spin-exchange relaxation free (SERF) regime typically operate with the high optical density and low magnetic fields. We present SERF magnetometer with a compact heating system for compact and efficient temperature control. A resistive heating system with high frequency alternating current was used to achieve high optical density. The current frequency was carefully chosen to avoid resonance with the atomic magnetometer. This resulted in a compact heating system that also allows independent operation of multiple heating systems. Optical rotation signal was obtained at 200 oC and width was about 3 nT with pump laser power of 55 mW. Bandwidth of the magnetometer with the compact heater was 40 Hz. Consequently, the compact resistive heating system proved to be a good alternative to the air-flow heating system. Additionally, residual field effect and signal-to-noise yielded a sensitivity of 50 fT/Hz1/2 at 10 Hz.
Heating the alkali metal vapor cell to obtain high atomic density is a prerequisite for realizing the high-precision measurement for spin-exchange relaxation-free (SERF) co-magnetometer. However, the thermo-magnetic and thermo-optical coupling noise caused by the temperature diffusion from the alkali vapor cell is one of the main factors restricting the co-magnetometer performance at present. Here the influence of heating on the SERF co-magnetometer was comprehensively studied, and the thermal error model of the system was established. A novel heat insulation structure for the co-magnetometer was designed, and the effectiveness was verified through monitoring of characteristic temperature points. Compared to the conventional oven support, the average maximum temperature difference within 12 h of the optical path and magnetic shielding systems (OPMSS) decreased by 52%, the bias instability of the co-magnetometer decreased by 24%, and the noise of the co-magnetometer at 1 Hz decreased by 33%. The experimental results demonstrate that this method reduces the temperature fluctuation of the OPMSS, effectively suppresses the thermal coupling noise, and thus improves the performance of the SERF co-magnetometer. Moreover, this method is also applicable to other quantum sensors based on alkali metal vapor cell.
Nowadays, quantum sensor research is a very interesting and popular topic. High-sensitivity magnetic field measurements using quantum sensors have evolved into the most sensitive magnetic field sensor category today with the invention of atomic magnetometers operating in the spin-exchange relaxation-free (SERF) regime. This letter was prepared to investigate the magnetic field sensitivity changes depending on the buffer gas, temperature, and laser intensity using indigenously produced atomic vapor cells. In addition, the aim was to determine the optimum operating conditions of the atomic magnetometer operating in the SERF regime. As a result, the resonance linewidth and signal-to-noise ratio were measured, and the minimum detectable magnetic field was calculated. According to the obtained results, the lowest magnetic field for Cells I–III was measured as 5.12, 4.21, and 4.81 pT, respectively. The lowest magnetic field of all conditions was obtained in vapor cell (Cell-II) at 100 °C with 5 mW laser intensity. As a result, it has been experimentally proven that under the same conditions, increasing the buffer gas pressure in vapor cells can narrow the resonance linewidth, and the magnetic field sensitivity can be improved by increasing the laser intensity applied to the vapor cells.
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.
Wafer-level integration of micro heater on an alkali vapor cell for chip-scale SERF magnetometers is presented. In order to obtain a suitable resistivity, polysilicon and aluminum are mixed as the target material. Magnetron sputtering is adopted to fabricate the heater on the surface of the alkali vapor cell. Various voltages are applied to the heater, of which the temperatures are measured by thermal sensitive sensors. Spin exchange relaxation free (SERF) atomic magnetometer with the heater integrated on the alkali vapor cell is characterized. Results show that the micro heater is successfully integrated on the alkali vapor cell. With the integrated heater, the rubidium vapor cell is heated up to 120°C by a 445kHz AC current. The sensitivity of the SERF magnetometer is 6.3pT/Hz1/2. Results also indicate that it provides an effective and low-cost solution for the miniaturization of atomic magnetometers.
Spin-exchange relaxation-free (SERF) atomic magnetometers are the promising non-cryogenic sensors to potentially replace the superconducting quantum interference device (SQUID) in the ultra-weak magnetic-field measurements. Although the SERF magnetometers have achieved a sensitivity of sub-femtotesla, the bandwidth is limited at a narrow range. In this work, we developed a closed-loop SERF magnetometer under proportional-integral (PI) control, the bandwidth could be adaptively tuned and extended above 1.2 kHz. A nearly 40-fold enhancement of the typical bandwidth was achieved in comparison with the open-loop system and the sensitivity was maintained at 15 fT/Hz1/2from 30 Hz to 750 Hz. Moreover, the magnetic field dynamic range could also be greatly improved. This proposed atomic magnetometer with higher bandwidth, sensitivity, and dynamic range has a good prospect in developing a compact, portable, and non-cryogenic magnetic field sensor and may find more applications in biomedical, nuclear magnetic resonance, and fundamental physics research.