In this work, we experimentally measure the broadened linewidth of magneto-optical resonance signal due to magnetic-field gradient with an alkali buffer-gas-free anti-relaxation-coated cell. We also study how the temperature of the atomic vapor cell affects the magneto-optical resonance signal linewidth under different magnetic-field gradients. Theoretical calculations show that the relaxation caused by magnetic-field gradient could be suppressed with increased temperature, which could be useful to optimize the working parameters for unshielded atomic magnetometer based on anti-relaxation-coated cells.
In this work, we experimentally measure the broadened linewidth of magneto-optical resonance signal due to magnetic-field gradient with an alkali buffer-gas-free anti-relaxation-coated cell. We also study how the temperature of the atomic vapor cell affects the magneto-optical resonance signal linewidth under different magnetic-field gradients. Theoretical calculations show that the relaxation caused by magnetic-field gradient could be suppressed with increased temperature, which could be useful to optimize the working parameters for unshielded atomic magnetometer based on anti-relaxation-coated cells.
In this work, a sensitivity of the rate of relaxation of ground-state atomic coherences to magnetic-field inhomogeneities is studied. Such coherences give rise to many interesting phenomena in light-atom interactions, and their lifetimes are a limiting factor for achieving better sensitivity, resolution, or contrast in many applications. For atoms contained in a vapor cell, some of the coherence-relaxation mechanisms are related to magnetic-field inhomogeneities. We present a simple model describing relaxation due to such inhomogeneities in a buffer-gas-free antirelaxation-coated cell. A relation is given between relaxation rate and magnetic-field inhomogeneities including the dependence on cell size and atomic species. Experimental results, which confirm predictions of the model, are presented. Different regimes, in which the relaxation rate is equally sensitive to the gradients in any direction and in which it is insensitive to gradients transverse to the bias magnetic field, are predicted and demonstrated experimentally.
One of the peculiar phenomenons in non-zero magnetic resonance magnetometer is that, with the increase of the temperature, the magnetic resonance linewidth is narrowed at first instead of broadened due to the increasing collision rate. The magnetometer usually operates at the narrowest linewidth temperature to obtain the best sensitivity. Here, we explain this phenomenon quantitatively considering the nonlinear of the optical pumping in the cell and did experiments to verify this explanation. The magnetic resonance linewidth is measured using one amplitude-modulated pump laser and one continuous probe laser. The field is along the direction orthogonal to the plane of pump and probe beams. We change the temperature from 53 °C to 93 °C and the pumping light from 0.1 mW to 2 mW. The experimental results agree well with the theoretical calculations.
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.
Using a detection technique of microwave (MW) magnetic field based on Rabi resonance, we have constructed a SI-traceable MW magnetic field sensor. Unlike the uncoated cylindrical Cs vapor cell filled with buffer gas presented in our previous work, here we developed an experimental setup based on an alkali vapor cell with anti-relaxation coating. Rabi resonance signal lineshape are successfully observed when alkali atoms interact with a phase-modulated MW field. Several experimental parameters, such as optical laser intensity and cell temperature, are detailly studied and characterized. The optimal amplitude of Rabi resonance lineshape were obtained, which is well-agreed with the theoretical model.
Atomic spin relaxation in a vapor cell, which can be characterized by the magnetic resonance linewidth (MRL), is an important parameter that eventually determines the sensitivity of an atomic magnetometer. In this paper, we have extensively studied how the pump intensity affects the spin relaxation. The experiment is performed with a cesium vapor cell, and the influence of the pump intensity on MRL is measured at room temperature at zero-field resonance. A simple model with five atomic levels of a Λ-like configuration is discussed theoretically, which can be used to represent the experimental process approximately, and the experimental results can be explained to some extent. Both the experimental and the theoretical results show a nonlinear broadening of the MRL when the pump intensity is increasing. The work helps to understand the mechanism of pump induced atomic spin relaxation in the atomic magnetometers.
Magnetic field gradients interfere with the coherence of the atomic ensemble and degrade the performance of the spin-exchange relaxation-free (SERF) atomic magnetometer. In this paper, the influence of magnetic field gradients is incorporated into the response model of single-beam atomic magnetometer, and the theoretical models of transverse relaxation rate, spin polarization and scale factor are established. Based on this model,we find that magnetic field gradients in different directions can cause varying degrees of degradation in the performance parameters of the magnetometer. The magnetic linewidths under different light power and magnetic field gradients are measured using the designed dedicated magnetic field gradients coils, and the spin polarization and magnetic field gradients relaxation rate are obtained through fitting. An unevenness and deviation of the curve are also observed in the experiments, indicating the presence of the magnetic field gradient of approximately 2 nT/cm in the magnetic shields. Furthermore, in a magnetic field gradient environment of 20 nT/cm, the mean of the long-term sensitivity decreased by 3.5 times and the standard deviation increased by 11 times. It shows that the magnetic field gradients will not only affect the signal-to-noise ratio, but also make the magnetometer more vulnerable to external interference when working. The sensitivity and stability of magnetometer will be greatly reduced. The research in this article provides a theoretical and experimental basis for eliminating the influence of magnetic field gradients and improving the accuracy of magnetic field measurements.