Flexible polymer-based magnetoelectric (ME) materials have broad application prospects and are considered as a new research field. In this article, FeCoSiB thin films were deposited on poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) substrate by DC magnetron sputtering. The structure of PVDF-TrFE/FeCoSiB heterostructure thin films was similar to 2-2. Under a bias magnetic field of 70 Oe, the composites have a dramatically increased ME voltage coefficient as high as 111 V/cm⋅Oe at a frequency of about 85 kHz. The piezoelectric coefficient of PVDF-TrFE thin films is 34.87 pC/N. The surface morphology of PVDF-TrFE thin films were studied by FESEM, and the results of XRD and FTIR showed that the β-phase of PVDF-TrFE thin films was dominant. Meanwhile, the effects of different heating conditions on the crystallization and piezoelectric properties of PVDF-TrFE films were also studied. The flexible ME heterojunction composite has a significant ME voltage coefficient and excellent piezoelectric properties at room temperature, which allows it to be a candidate material for developing flexible magnetoelectric devices.

A calibration and measurement method based on an autocollimator and a manual turntable are proposed to calibrate the mounting error of a three-axis microelectromechanical system (MEMS) gyroscope in a wearable inertial measurement unit (IMU). In this system, with extension of the angle range of the autocollimator to ±9° and setting the mutual orthogonal structure of the two autocollimators, the measurement angle range of the MEMS gyroscope mounting error and the evaluation reference of the three-axis attitude angle data are obtained respectively, and the common data acquisition serial port between the autocollimator camera and the IMU host computer is built. As a result, the acquisition time is synchronized between the two systems. Additionally, the angular rate reading value of the MEMS gyroscope is integrated by time to unify the reading value scale between the calibration system and the MEMS gyroscope. This method is further compared with the traditional precision three-axis angular rate output turntable calibration method, and the accuracy deviation of the MEMS gyroscope mounting error after calibration is less than 0.3%. This method helps facilitate the development of inertial sensing calibration techniques toward traceability, which significantly reduces and simplifies laboratory equipment costs and maintenance requirements.

High-performance interconnection between hollow-core fiber and conventional solid-core fiber is of great significance for a lot of promising applications of hollow-core fibers. The current problems for high-performance hollow-core fiber/solid-core fiber interconnection mainly involve mode field mismatch of the two fibers and the complex splicing process. Subject of study. We study fusion splicing of anti-resonant hollow-core fiber with low loss (0.52 dB) and conventional single-mode fiber using a convenient graded-index bridge fiber. Purpose of the work. We aim to eliminate the mode field diameter mismatch between anti-resonant hollow-core fiber and single-mode fiber and simplify the mode field diameter adaptation method and process. Method. We employ a convenient graded-index bridge fiber approach, where a gradient index fiber is first spliced with the single-mode fiber, and the mode interference within the graded-index bridge fiber causes periodic enlargement and shrinkage of the mode field diameter. By precise cutting of the graded-index bridge fiber, the mode field diameter can be well controlled and made approximately equal to the mode field diameter of the anti-resonant hollow-core fiber. After mode field diameter adaptation, an optimized arc discharge fusion splicing procedure is applied for the anti-resonant hollow-core fiber/single-mode fiber fusion splicing. Main results. A fusion splicing loss of about 0.52 dB is achieved, which involves nearly 0.42 dB mode-field-diameter-mismatch-induced loss and about 0.1 dB fusion splicing loss that is caused by the deformation of the anti-resonant hollow-core fiber. Practical significance. The developed approach is convenient and cost-effective, which can benefit a lot of applications of anti-resonant hollow-core fibers in future telecommunications, fiber gas lasers as well as fiber-optic sensing.

This paper proposes a terahertz absorber based on a U-shaped metal patch that exhibits both narrowband and wideband absorption characteristics. The absorber comprises a metal–medium–metal structure, with a U-shaped metal patch as the top layer, a lossy medium as the middle layer, and a fully covered metal base plate at the bottom. There are two narrowband absorption peaks at 1.368 THz and 2.648 THz and a broadband absorption band from approximately 4 to 5 THz. The formation of resonance frequencies was elucidated by analyzing the current and electric field distributions at the resonance frequency. The resonant mechanism of the U-shaped patterned structure was clarified using equivalent circuit models to evaluate the resonant frequencies of different absorption peaks. Subsequently, the absorber’s characteristics were examined under varying structural parameters. Dual-function terahertz absorbers are applicable in terahertz communications, imaging, and various other fields.

A new type of fluid sensing system based on side-polished fiber is proposed, which realizes fluid fluidity and effective biological solution concentration sensing characteristics. Numerical studies have shown that the light guiding characteristics of the mixed-filled photonic crystal fiber when filled with high refractive index materials are similar to that of the photonic band gap fiber, so the liquid sensing sensitivity can be obtained by analyzing the variation of the band gap. The linear relationship between solution concentration and refractive index is obtained theoretically and experimentally. The concentration of salmon sperm DNA solution was effectively measured by optical fiber fluid sensing system. The results show that the wavelength of the bandgap edge has a red shift as the concentration increases. The concentration sensing sensitivity is 6.1989×10 ⁵ nm ·ml/mol. Similarly, the sensing sensitivity of glutamate solution is 1.6981×10 ⁵ nm ·ml/mol. The proposed sensing system can be flexibly applied to other biological fluid characteristic sensing fields, which provides the possibility for real-time biological monitoring.