Optically pumped magnetometers can provide functionality for bio-magnetic field detection and mapping. This has attracted widespread attention from researchers in the biomedical science field. Magnetocardiography has been proven to be an effective method for examining heart disease. Notably, vector magnetocardiography obtains more spatial information than the conventional method by only taking a component that is perpendicular to the chest surface. In this work, a spin-exchange-relaxation-free (SERF) magnetometer with a compact size of 14 mm × 25 mm × 90 mm was developed. The device has a high sensitivity of 25 fT/ $\sqrt{\text{Hz}}$. Meanwhile, in the multichannel working mode, synchronous sensor manipulation and data acquisition can be achieved through our control software without additional data acquisition boards. Since a typical SERF magnetometer only responds to dual-axis magnetic fields, two sensors are orthogonally arranged to form a vector detection channel. Our system consists of seven channels and allows 7 × 9 vector MCG mapping by scanning. High-quality heart vector signals are measured, and P peak, QRS peak, and T peak can be distinguished clearly. To better demonstrate the vectorial information, a vector scatter plot form is also provided. Through a basic bio-electric current model, it demonstrates that triaxial MCG measurements capture a richer spatial current information than traditional uniaxial MCG, offering substantial diagnostic potential for heart diseases and shedding more light on the inversion of cardiac issues.

A novel and convenient color-tuning method by filling the porous alumina membrane (PAM) based on metal–dielectric–metal structure is proposed. The pore sizes of PAM as well as the thickness of ${\mathrm{TiO}}_2$ films, deposited by atomic layer deposition, causes various reflection colors due to multilayer interference effects. Overlapping films on top and within the PAM structure can be observed with a scanning electron microscope and will be used to show the change of the effective refractive index of the PAM composite layer. The color-tuning method resulting in changing the dynamics of the PAM layer can be widely applied in fields such as micro-optics, microstructures, nanomaterials, and micro/nanotechnology.

Magnetic particles (MPs), a group of engineered particles in the nanometer and microscale, are valuable tools for separation of chemical or biological substance in environmental research, for target delivery of antibodies or proteins in biomedical applications, and for quantification of cells or biomolecules in biological systems. Despite the estimation of the amount of magnetic nanoparticles that were realized by magnetic particle spectroscopy, accurate quantification of MPs at single-particle resolution is still a challenge. Here, we used an elliptically optically pumped M_x atomic magnetometer combined with a peristaltic pump system to perform magnetic field measurements to quantify magnetic particles at the single-particle level under aqueous solution condition. Quantitative analysis of cobalt micro-nanoparticles revealed the volume-field linear character of magnetic particles. From the measured intensity of the magnetic field generated by MPs, we calculated the geometric parameters and numbers of MPs and estimated the detection limit of our developed atomic magnetometer. Our work paves a way for the practical use of MPs in the biomedical field as well as other applications in industry.

Three-axis atomic magnetometers have great advantages for interpreting information conveyed by magnetic fields. Here, we demonstrate a compact construction of a three-axis vector atomic magnetometer. The magnetometer is operated with a single laser beam and with a specially designed triangular ${}^{87}\mathrm{Rb}$ vapor cell (side length is 5 mm). The ability of three-axis measurement is realized by reflecting the light beam in the cell chamber under high pressure, so that the atoms before and after reflection are polarized along two different directions. It achieves a sensitivity of 40 $fT/\sqrt{Hz}$ in x-axis, 20 $fT/\sqrt{Hz}$ in y-axis, and 30 $fT/\sqrt{Hz}$ in z-axis under spin-exchange relaxation-free regime. The crosstalk effect between different axes is proven to be little in this configuration. The sensor configuration here is expected to form further values, especially for vector biomagnetism measurement, clinical diagnosis, and field source reconstruction.

A chiral sensor with optical rotation detection based on weak measurement for the kinetic study of sucrose hydrolysis is presented. Based on the polarization modulation to the pre-selection state, the optical rotation of chiral sample was accurately determined through the central wavelength shift of the output spectrum. With this approach, the concentration response curves of sucrose and its hydrolysis products, i.e., fructose and glucose, were experimentally obtained for the hydrolysis analysis. By collecting the output spectrum with a frequency of 100 Hz and fitting the central wavelength shift synchronously during the measurement, the sucrose hydrolysis process was monitored in real time. Different hydrolysis conditions with varied concentration of invertase enzyme and citrate were implemented in this work. As a consequence, the real-time hydrolysis curves of the hydrolysis process with distinct velocities was achieved and analyzed. Such a kinetic monitoring about sucrose hydrolysis with optical rotation detection technology played a critical role in the researches involving sucrose, and also revealed the great potential of weak measurement in intersections, such as food safety inspection and chemical analysis.

In this paper, we present a glass-based double-side cascade film stack structure for visible-infrared ultrabroadband absorption. The proposed structure demonstrates an average absorption as high as ∼95% over an ultrawide range of wavelengths from 0.4 μm to 20 μm. The high absorption feature of the different bandgap materials is applied in this absorption device to realize the ultrabroadband absorption, combining with the metal-dielectric-like configuration for those unmatched-admittance wavelengths and the graded index profile arrangement for the 0.4–2.5 μm band. The proposed ultrabroadband absorber shows a great angular tolerance up to 60° with the average absorption of 90% remaining. The proposed approach can have tremendous potential in fields of optical sensing, camouflage, optical imaging, passive cooling, and sustainable power generation, profiting from the good mechanical characteristics of this compact multilayer film structure and the low manufacture costs with the simple physical vapor deposition.