We demonstrate a single-beam atomic magnetometer (AM) capable of measuring a three-axis magnetic field with high-sensitivity, achieved by applying a small DC offset field and a high frequency modulation field. To satisfy the miniaturization demand of AMs, an elliptically polarized light detuned by 50 GHz from the resonance transition center is employed. The circularly polarized component is used to polarize the alkali-metal atoms, while the linearly polarized light is used to detect the dynamics of the polarized spin under a magnetic field. Based on theoretical analysis, parameters that significantly affect the performance are optimized, and a sensitivity of 20 fT/Hz^1/2 in x-axis, 25 fT/Hz^1/2 in y-axis, 30 fT/Hz^1/2 in z-axis is achieved with a miniature 4 × 4 × 4 mm ⁸⁷Rb vapor cell. Moreover, we also verify that the operation principle of AMs can be used to null background magnetic fields in-situ with isotropic compensation resolution of 6.7 pT, which provides an effectively precise method for zeroing ambient magnetic field. The high-sensitivity operating of an elliptically-polarized-laser-based magnetometer provides prospective futures for constructing a compact, low-cost AM, which is particularly applicable for non-invasive bio-magnetic imaging such as array-based magnetoencephalography (MEG) and magnetocardiography (MCG).

Alkali metal optically pumped magnetometers, with a particular emphasis on Spin-Exchange Relaxation-Free atomic magnetometers, has garnered considerable attention due to their remarkable sensitivity. In this comprehensive review, we present a succinct overview of the fundamental principle of the magnetometer and the various categories of its central sensitive unit, namely the cell. We then proceed to elaborate on the vital aspect of establishing an extremely feeble magnetic field environment that is crucial for its operation, inclusive of both active magnetic shielding and passive magnetic compensation methodologies. In furtherance, we conduct a thorough evaluation of the pros and cons of single-beam and dual-beam pump-probe scheme magnetometers, followed by a detailed investigation of their potential applications in the cardiology and brain magnetism fields. Finally, we conclude with an analysis of the hurdles and prospective development directions for alkali metal-based atomic magnetometers in the domains of magnetocardiography and magnetoencephalography, which hold the promise of substantial progress and widespread adoption in the biomedical area.

Atomic magnetometers operated in spin-exchange relaxation-free (SERF) have the potential to replace superconducting quantum interference devices (SQUIDs) in the field of biomagnetism. Here, we demonstrate the dual-axis closed-loop control of a single-beam SERF magnetometer that allows sensing of two orthogonal magnetic fields simultaneously and independently with suppressed crosstalk effect, achieved by applying a rotating modulation field and using the negative feedback. Operating in the dual-axis closed-loop mode with a miniature 4 $\times $ 4 $\times $ 4 mm ⁸⁷ Rb cell, we achieve the magnetic field sensitivity of 20 fT/Hz ^1/2 and a bandwidth of 1.8 kHz. In addition to the experimental study of the sensitivity and bandwidth, we perform a theoretical analysis of the dual-axis response and develop an effective decoupling method. The implementation of closed-loop control enables the magnetometer to be robust against the disturbance of the ambient field, which could enlarge the dynamic range, enhance the systematic stability, and suppress the crosstalk effect. Such a simple, yet high-performance SERF magnetometer could be suitable as a promising candidate in the field of biomagnetism, allowing for a denser sensor array and opening up new possibilities for noninvasive biomagnetic imaging.

The negatively charged nitrogen vacancy (NV^-) center ensembles in diamond have been demonstrated to be a promising platform for quantum metrology, but the poor fluorescence collection efficiency of a microscope objective limits the sensitivity of the NV^- based sensors. Here we present a method for increasing the collected fluorescence intensity with a total internal reflection (TIR) lens. The detected fluorescence intensity is increased by approximately a factor of 56 compared with detection using a microscope objective with NA = 0.55, leading to a collection efficiency of 47.7% ± 3.1%. The signal-to-noise ratio is improved by a factor of 7.6 using the TIR lens. The proposed method is of great significance for collecting fluorescence from NV^- centers in a large volume and can be used in weak fluorescence detection systems.

Polarization holography has the unique capacity to record and retrieve the amplitude, phase, and polarization of light simultaneously in a polarization-sensitive recording material and has attracted widespread attention. Polarization holography is a noteworthy technology with potential applications in the fields of high-capacity data storage, polarization-controlled optical elements, and other related fields. The choice of its high-performance materials is particularly important. To further develop polarization holography applications and improve the quality of the information recorded (i.e., material sensitivity and resolution), a deeper understanding of such materials is needed. We present an overview of the polarization-sensitive materials, which introduced polarization holographic technology and the development of polarization holographic materials. The three main types of polarization holographic materials are described, including azopolymer materials, photopolymer material, and photorefractive polymer material. We examine the key contributions of each work and present many of the suggestions that have been made to improve the different polarization-sensitive photopolymer materials.

In recent years, significant developments have occurred in the field of optically pumped magnetometers (OPMs), which are widely used in biomagnetic measurements. In this study, we propose a temperature optimization model for a single-beam miniaturized atomic magnetometer. Based on this model, we find that there is an optimal operating temperature for each individual vapor cell, under which the OPM achieves optimal performance. We construct a single-beam zero-field modulation OPM to prove this model. The sensitivity of the magnetometer reaches 18 fT/Hz ^1/2 (close to the theoretical sensitivity) when we adjust the temperature of the vapor cell through our model, and a detection bandwidth of more than 160 Hz is achieved. It is also discovered that the system bandwidth is reduced when the temperature is increased, whereas the sensitivity of the system does not show notable variation during this process. Our model enables a quick definition of the best working temperature for each individual magnetometer, ensuring the best performance at the lowest operating temperature. This model is especially advantageous for miniaturized OPMs and can also be further applied to arrayed integration for biomagnetic measurement in the future work.