Cunguang Lou

High-performance, self-powered, ultrabroadband photodetection at room temperature holds significant promise for a wide range of applications. However, existing ultrabroadband photodetectors (PDs) often suffer from limitations such as low sensitivity and poor responsivity. This work reports a dual-mechanism self-powered PD based on CH3NH3PbI3 perovskite, which demonstrates an ultrabroadband response across the wavelength range from 532 nm to 3000 μm. Within the visible light range, the PD operates primarily through the photovoltaic effect, whereas in the infrared to terahertz range, the dominant mechanism is the photothermoelectric effect. The results indicate that the PD achieves a high responsivity of up to 6 × 10–3 A/W at zero bias voltage, a detectivity as high as 5 × 1010 Jones, a low noise equivalent power of 4 pW/Hz1/2, and a rapid response time of 0.6 ms. Additionally, Fourier single-pixel imaging was conducted, offering a strategy for realizing high-performance, ultrabroadband photodetection.

Overheating of the stator and rotor in hydroelectric generators poses significant safety risks. Conventional temperature monitoring methods are unable to directly measure temperature and can be compromised by electromagnetic interference in dynamic environments, reducing measurement accuracy. To address these challenges, this paper introduces a fluorescence‐lifetime‐based optical fiber sensing system for distributed temperature monitoring of stator and rotor components under power generation conditions. The system simultaneously measures both components, exhibits strong electromagnetic interference resistance, and supports real‐time temperature visualization via a customized custom graphical user interface (GUI) platform for data storage and analysis. Installed in a hydropower station in Sichuan province, during summer operation, the system successfully collected real‐time stator and rotor temperature data at rotational speeds of 500 rpm, achieving measurement accuracy of ±0.3°C. This approach demonstrates significant potential for industrial deployment in advanced condition monitoring of hydroelectric generator.

Silicon has become a leading material in photoelectric detection, owing to its distinct advantages in both response speed and photoelectric conversion efficiency. However, due to the lack of intrinsic polarization selectivity, silicon still faces major challenges in achieving polarization detection in the broadband ultraviolet (UV) to infrared (IR) range. In this paper, we have successfully developed an ultrabroadband UV-IR polarization photodetector with a Ag/CsPbBr₂I/Si/Ag vertical structure based on the CsPbBr₂I and N-type pyramid-silicon composite structure, which is designed to achieve full Stokes polarization detection. The device exhibits excellent broadband polarization response in the ultraviolet to infrared band (405-1319 nm), especially at 1064 nm, showing an anisotropy ratio of up to 72.7. By optimizing the anisotropic optical response of CsPbBr₂I and nanoscale pyramid silicon structures, the device achieves a fast response time of 4 μs under 1064 nm illumination at a zero bias voltage. The experimental results show that the detector has a stable and fast optical switching response and excellent polarization sensitivity in the broadband range. The maximum response reaches 270 mA/W under 1064 nm illumination at zero bias voltage, the normalized detection rate is 2.6 × 10¹³ Jones, and the noise equivalent power is 44 pW/Hz^1/2. Through in-depth discussions, the photoelectric response mechanism at 1319 nm is attributed to the PTE effect and the heterojunction effect. In addition, the full Stokes parameter verifies the effectiveness of the device in polarization state characterization, and the single-point pixel imaging experiment further confirms its application potential in broadband polarization imaging. This study proposes a novel approach for advancing the next generation of the on-chip polarization imaging system and shows an important application prospect in the fields of safety detection, high-resolution medical imaging, and medico-industrial intersection.

In this study, we develop a gas detection system by employing a tunable diode laser absorption spectroscopy (TDLAS) and a nanopyramid structure-enhanced silicon heterojunction photodetector (PD). With oxygen as the target gas, the performance of the system is rigorously verified. Our results show that the silicon-based heterojunction PD achieves an impressive signal-to-noise ratio (SNR) of 427.98, significantly higher than the 140.36 of commercial indium gallium arsenide (InGaAs) PD and the 200.29 of commercial silicon PD. Compared to commercial InGaAs PD and silicon PD, our heterojunction PD has approximately 3.3-fold and 2.1-fold higher sensitivity, respectively. In addition, the minimum detection limit (MDL) has been significantly improved, with an MDL of 480 ppm for silicon-based heterojunction PDs, compared to 1500 ppm for commercial PDs and 1043 ppm for commercial silicon PDs. The normalized noise equivalent absorption coefficient of the system was determined to be 3.466×10 ^-11 cm ^-1 ·W·Hz ^-1/2 . The Allan bias analysis results show that the system achieves an accuracy level of 116 ppm in an average of 320 seconds. These advances underscore the potential of silicon-based heterojunction PD as a highly sensitive element in gas detection systems, marking a major innovation in laser spectroscopic gas detection.

Respiratory detection plays a significant role in the assessment of human health status and in aiding the diagnosis of diseases. This requires the development of fast, economical and non-invasive detection technologies. This research employed tunable diode laser absorption spectroscopy (TDLAS) to analyze exhaled methane (CH ₄ ) levels in patients with gastrointestinal diseases. The system achieving a minimum detection limit (MDL) of 42.12 ppbv, and an accuracy of 8.04 ppbv. A total of 451 samples of exhaled CH ₄ concentration from gastrointestinal surgery patients were detected, and several gastrointestinal diseases with high average CH ₄ concentration were screened out. Support vector machine (SVM) algorithms were used to investigate the relationship between CH ₄ levels and specific gastrointestinal diseases. The study achieved a classification accuracy, recall, and precision rate of 100% for ileus, ascending colon cancer (COAD), and cancers with liver metastasis. Meantime, the rate of CH ₄ positivity for patients undergone postoperative chemotherapy was observed to be significantly lower than patients with active cancer. However, the presence of CH ₄ was not significantly associated with gastrointestinal stromal tumors of the stomach (GIST), stomach cancer (SC), or rectal cancer (READ), indicating the need for a multifaceted diagnostic approach incorporating additional gas markers. In conclusion, CH ₄ analysis holds promise as a novel non-invasive diagnostic tool for gastrointestinal diseases, with significant potential for clinical application.

To facilitate temperature detection in industrial production settings, an optical fiber temperature transmitter was developed utilizing fluorescence lifetime as its basis. Comprising an upper computer, fiber optic temperature transmitter, and optical fiber probe, the system incorporates a scalable fluorescence detection module. Real‐time temperature calculation is achieved through a microcontroller based on the fluorescence lifetime, with results transmitted to the upper computer, the optical fiber sensor exhibits a resolution of 0.01°C and an accuracy of ±0.3°C.

A gas detection method based on CH₃NH₃PbI₃(MAPbI₃) and poly (3,4-ethylenedioxythiophene): poly (4-styrene sulfonate) (PEDOT:PSS) composite photodetectors (PDs) is proposed. The operation of the PD primarily relies on the photoelectric effect within the visible light band. Our study involves constructing a gas detection system based on tunable diode laser spectroscopy (TDLAS) and MAPbI₃/PEDOT:PSS PD, and O₂was selected as the target analyte. The system has achieved a minimum detection limit (MDL) of 0.12% and a normalized noise equivalent absorption coefficient (NNEA) of 8.83 × 10⁻¹¹cm^-1⋅W⋅Hz^-1/2. Furthermore, the Allan deviation analysis results indicate that the system can obtain sensitivity levels as low as 0.058% over an averaging time of 328 seconds. This marks the first use of MAPbI₃/PEDOT:PSS PD in gas detection based on TDLAS. Despite the detector's performance leaves much to be desired, this innovation offers a new approach to developing spectral based gas detection system.

Light-induced thermoelastic spectroscopy (LITES), boasting an extended effective optical path length, stands as a potent approach for trace gas detection. The indispensable factor for heightened measurement sensitivity lies in the quartz tuning fork (QTF) probe, possessing a robust thermoelastic conversion efficiency. In this study, we introduce a novel laser micro-machining technique for fabricating sensitive miniature QTFs (mQTFs) tailored to suit LITES applications. This innovation effectively addresses the issues of subpar sensitivity and the elevated laser response threshold commonly observed in commercial QTFs. As a proof of concept, we demonstrate its capabilities through the measurement of CO ₂ . Capitalizing on the utilization of mQTFs, the sensing sensitivity was increased by an impressive factor of ~5, outperforming the conventional QTF-LITES approach. The minimum detection limits (MDLs) for CO ₂ are also notably improved, measuring 351.34 ppm for the mQTF and 968.29 ppm for the standard commercial QTF. This cost-effective technological advancement paves the way for the development of highly responsive trace gas LITES sensing systems.

Ionogels have garnered great attention for fabricating flexible soft ionotronics as they can mimic human skin that responds to external stimuli. However, the low detection sensitivity and limited responsiveness as well as the complicated fabrication process significantly limit their wide applications. Herein, a skin-inspired stretchable, compressible, self-adhesive ionogel with gradient and hierarchical microstructures and properties has been prepared by a one-step electric-field assisted photo-polymerization method. By regulating the ions of ionic liquids (ILs) and poly(ionic liquid)s (PILs), these PIL ionogels also exhibit good adjustable hydrophilicity/hydrophobicity and environmental adaptability. Based on the gradient conductivity capacity along with the gradient mechanical structure, the gradient ionogel-based flexible ionotronic shows high sensitivity up to 1.0 kPa⁻¹ over a wide range of detection up to 400 kPa, low minimum detection (0.15 Pa), fast response time (8 ms), wide working temperature range (−85 to 360 °C), and good durability (5000 cycles). More importantly, the developed high-resolution pressure-sensing array can accurately detect the contour and output three-dimensional pressure distribution maps. Furthermore, advanced soft ionotronic sensors with multimodal sensation capabilities are further designed, which can detect various motions, such as liquid drop sensing, human joint motion detection, and real-time pulse wave monitoring.