Abstract:Microstrip transmission lines connecting to the millimeter wave radar chip and antenna significantly affect the radiation efficiency and bandwidth of the antenna. Here， a wideband non-uniform wavy microstrip line for complex impedance in automotive radar frequency range is proposed. Unlike the gradient transmission line， the wavy structure is composed of periodically semi-circular segments. By adjusting the radius of the semi-circular， the surface current is varied and concentrated on the semi-circular segments， allowing a wider tunability range of the resonant frequency. The results reveal that the bandwidth of the loaded wavy transmission line antenna improves to 9.37 GHz， which is 5.81 GHz wider than that of the loaded gradient line. The gain and the half power beam width of the loaded antenna are about 14.69 dB and 9.58°， respectively. The proposed non-uniform microstrip line scheme may open up a route for realizing wideband millimeter-wave automotive radar applications.

Abstract:The effect of external vibration on the velocity uniformity of the moving mechanism of the angular mirror translational Fourier transform interferometer （hereinafter referred to as interferometer） can be quantitatively analysed by the interferometer optical range difference velocity stability. The article proposes a more comprehensive method of analysing the optical range difference velocity uniformity for the reliability of the interferometer kinematic mechanism under the influence of on-orbit microvibration in the process of space spectroscopy detection. The method incorporates the structural response of the interferometer caused by external excitation into the stability analysis as one of the influencing factors， so as to reflect the reliability of the interferometer in orbit more realistically， and judge the microvibration criticality that the interferometer can withstand more accurately. At the same time， an optical surface model of the interferometer is established to further theoretically characterise the effect of microvibration on the homogeneity of the interferometric mechanism. The method discussed in the article provides a way of thinking for the judgement of the reliability of the mechanism movement under the external excitation perturbation as well as the research on the optimisation of the mechanism control.

Abstract:To enhance the net photoelectric conversion efficiency of quantum well infrared photodetectors， this study investigates the matching conditions between radiative dissipation and coupling strength in devices operating in the strong light-matter coupling regime. A critical coupling model distinct from the conventional intrinsic and radiative dissipation matching is proposed. Through an analytical model， the contributions of intrinsic thermal dissipation and coupling strength to the critical conditions are quantified. The results indicate that， with optimized matching parameters， the net photoelectric absorption efficiency， excluding thermal dissipation， can exceed 95%. Moreover， under the synergistic regulation of the strong coupling mechanism and critical coupling conditions， the photodetection response can be enhanced by up to 160%. This work highlights the importance of optimizing dissipation and coupling parameters under strong coupling conditions， providing theoretical and design guidance for improving photoelectric conversion efficiency and enhancing the performance of quantum well infrared photodetectors.

Abstract:The polarization properties of light are widely applied in imaging， communications， materials analysis， and life sciences. Various methods have been developed that can measure the polarization information of a target. However， conventional polarization detection systems are often bulky and complex， limiting their potential for broader applications. To address the challenges of miniaturization， integrated polarization detectors have been extensively explored in recent years， achieving significant advancements in performance and functionality. In this review， we focus mainly on integrated polarization detectors with innovative features， including infinitely high polarization discrimination， ultrahigh sensitivity to polarization state change， full Stokes parameters measurement， and simultaneous perception of polarization and other key properties of light. Lastly， we discuss the opportunities and challenges for the future development of integrated polarization photodetectors.

Abstract:This study involved a comprehensive investigation aimed at achieving efficient multi-millijoule THz wave generation by exploiting the unique properties of cylindrical GaAs waveguides as effective mediators of the conversion of laser energy into THz waves. Through meticulous investigation， valuable insights into optimizing THz generation processes for practical applications were unearthed. By investigating Hertz potentials， an eigenvalue equation for the solutions of the guided modes （i.e.， eigenvalues） was found. The effects of various parameters， including the effective mode index and the laser pulse power， on the electric field components of THz radiation， including the fundamental TE （transverse electric） and TM （transverse magnetic） modes， were evaluated. By analyzing these factors， this research elucidated the nuanced mechanisms governing THz wave generation within cylindrical GaAs waveguides， paving the way for refined methodologies and enhanced efficiency. The significance of cylindrical GaAs waveguides extends beyond their role as mere facilitators of THz generation； their design and fabrication hold the key to unlocking the potential for compact and portable THz systems. This transformative capability not only amplifies the efficiency of THz generation but also broadens the horizons of practical applications.PACS codes Each manuscript must be given 2-4 PACS

Abstract:NIR-II fluorescence imaging demonstrates significant advantages in biological imaging with its high signal-to-background ratio (SBR) and deep tissue penetration, showing broad application prospects in biomedical fields. The classification of NIR-II imaging windows facilitates the optimization of imaging processes. Among these, the 1400-1500 nm imaging window benefits from its unique water absorption characteristics, enabling effective suppression of scattering background and achieving high-contrast imaging. This study systematically evaluates the imaging potential of the 1400-1500 nm window through simulation studies and in vivo experiments. To advance the clinical translation of fluorescence imaging in the 1400-1500 nm window, indocyanine green (ICG), an organic small-molecule dye approved by the U.S. Food and Drug Administration (FDA), was employed as the fluorescent probe. Utilizing its extended fluorescence emission tail in the NIR-II region, high-contrast and high-resolution imaging of mouse vasculature and intestinal structures was achieved in the 1400-1500 nm window. Furthermore, in combination with methylene blue (MB), another FDA-approved agent, high-quality dual-channel NIR-II imaging was successfully implemented enabling precise localization of blood vessels and lymph nodes in mice. This research further explores the unique advantages of the 1400-1500 nm imaging window in biological imaging and its clinical application potential. It also provides valuable references for the clinical translation of NIR-II fluorescence imaging.

Abstract:This paper presents a high-speed and robust dual-band infrared thermal camera based on an ARM CPU. It is composed of a low-resolution long-wavelength infrared detector， a digital temperature and humidity sensor， and a CMOS sensor. In view of the phenomenon of large contrast between face and background in thermal infrared image， this paper we search for a suitable accuracy-latency tradeoff for thermal face detection and propose a tiny-lightweight detector named YOLO-Fastest-IR. Four different scale YOLO-Fastest-IR0 to IR3 thermal infrared face detectors based on YOLO-Fastest are designed. To train and test four tiny-lightweight models， a multi-user low-resolution thermal face database （RGBT-MLTF） is collected， and the four networks are trained. Experiments reveal that the lightweight convolutional neural network can also perform well in the thermal infrared face detection task. And the algorithm is superior to the existing face detection algorithms in positioning accuracy and speed， which is more suitable for deployment in mobile platforms or embedded devices. After obtaining the region of interest in the infrared image （IR）， the RGB camera is guided by the results of thermal infrared face detection， to realize the fine positioning of RGB face. The experimental results show that YOLO-Fastest-IR has a frame rate of 92.9 FPS on a Raspberry Pi 4B and can successfully locate 97.4% of the face in the RGBT-MLTF test set. The integration of infrared temperature measurement system with low cost， strong robustness and high real-time performance was ultimately achieved， the temperature measurement accuracy can reach 0.3 degrees Celsius.

Abstract:Enamel demineralization often occurs in the early stage of dental caries. Studying the microscopic mechanism of enamel demineralization is essential to prevent and treat dental caries. Terahertz （THz） technology， especially continuous wave （CW） THz near-field scanning microscopy （THz-SNOM） with its nanoscale resolution， can be promising in biomedical imaging. In addition， compared with traditional THz time-domain spectroscopy （TDS）， portable solid-state source as the emission has higher power and SNR， lower cost， and can obtain more precise imaging. In this study， we employ CW THz-SNOM to further break the resolution limitations of conventional THz imaging techniques and successfully achieve the near-field imaging of demineralized enamel at the nanoscale. We keenly observe that the near-field signal of the enamel significantly lowers as demineralization deepens， mainly due to the decrease in permittivity. This new approach offers valuable insights into the microscopic processes of enamel demineralization， laying the foundation for further research and treatment.

Abstract:As a valuable Chinese herbal medicine, Panax notoginseng exhibits therapeutic efficacy and quality closely associated with its saponin content, which demonstrates significant geographical variations. To accurately authenticate the geographical origin and ensure medicinal quality, a novel method integrating terahertz precision spectroscopy with a convolutional neural network (CNN) algorithm was proposed. 40 Panax notoginseng samples from 4 regions in Yunnan Province, China—Honghe Autonomous Prefecture, Kunming, Qujing, and Wenshan Autonomous Prefecture—were analyzed using terahertz spectroscopy and high-performance liquid chromatography (HPLC). A CNN model was constructed and trained based on the acquired spectral and chromatographic data to classify the geographical origins. Experimental results revealed that the terahertz spectroscopy combined with the CNN model achieved a classification accuracy of 92.5%, significantly outperforming the 82.5% accuracy attained by the HPLC-CNN model. This finding highlights the potential of terahertz spectroscopy in component analysis and geographical traceability of herbal medicines, providing a novel scientific approach for rapid, non-destructive, and precise identification of Chinese medicinal materials.

Abstract:This study used a terahertz metamaterial sensor for the rapid and accurate detection of the antithrombotic drug Plavix， addressing the increasing demand for efficiency and sensitivity in drug content monitoring. Utilizing the terahertz vibration characteristics of Plavix， characteristic absorption peaks within the 1~3 THz band were identified. Based on these findings， a dual-polarization resonance metamaterial sensor was designed to simultaneously enhance the sensing signals of these characteristic absorption peaks. Experimental results indicate that the sensor attains a high level of fit （R²>0.97） for quantitative analysis in the quantitative detection of Plavix through the established two-indicator decision model. Consequently， the terahertz metamaterial sensing technology presented in this study exhibits superior performance in monitoring Plavix content and offers a new tool for clinical drug monitoring and broader biochemical sample analysis.