Two-dimensional (2D) van der Waals (vdW) heterostructures offer enhanced properties beyond their constituent monolayers, making them attractive for photocatalytic feasibility. Here, we investigate GaSe/BiI3 heterostructures (stack-I to stack-IV) as potential candidates for solar driven water-splitting applications. Structural stability is confirmed through binding energy, phonon spectra, and ab initio molecular dynamics. Spin-orbit-coupled bandstructure calculations reveal suitable bandgaps (similar to 1.63-1.73 eV) and a type-II alignment that promotes efficient charge separation. The pronounced spin-orbit coupling imparted by the heavy Bi atoms manifests as band splitting and bandgap reduction across all heterostructures. Optical analysis indicates strong absorption in the visible and UV regions. However, the conduction band minimum lies slightly below the hydrogen reduction potential (-4.44 eV), limiting intrinsic hydrogen evolution based on band-edge criteria. Strain engineering resolves this limitation, where 2% compressive strain shifts the band edges into the optimal range and yields an estimated solar to hydrogen (STH) efficiency of 17.1% under the adopted band-edge model. These results highlight GaSe/BiI3 heterostructures as promising optoelectronic and photocatalytic candidate, with tunable electronic and optical properties for solar-energy conversion.

Long-wave infrared thermal imaging has become indispensable for critical applications ranging from industrial facility maintenance to advanced security surveillance. While refractive-diffractive hybrid lenses offer potential for compact infrared optics, existing implementations face fundamental limitations in achieving performance parity with conventional thermal lenses-particularly regarding spatial resolution, restricted field of view (FOV), and inherent challenges in phase control under group delay constraints. Considering these issues, herein, a refractivemetasurface-based hybrid lens, enabled by equal-group-delay metasurfaces (EGDMs), was studied. The design combines optimized optical geometry to minimize oblique light incidence on the metasurface with the unique capabilities of EGDMs in providing large-aperture continuous phase modulation. The resulting system achieves diffraction-limited performance across the full 8-12 mu m spectral band without requiring aspheric components, featuring an F-number of 1.08 while maintaining a wide 60 degrees FOV. Notably, the lens demonstrates exceptional optical performance with a modulation transfer function of 0.44 at 29.4 lp/mm. Its compact size makes it compatible with handheld thermal imagers for versatile deployment scenarios. This work demonstrates the viability of EGDM-enabled hybrid designs for next-generation thermal imaging systems that combine commercial-grade performance with unprecedented compactness. (c) 2026 Chinese Laser Press

As a promising solution to the manufacturing challenges of modern super-large telescopes, the imaging performance of optical sparse aperture imaging systems (SAIS) is highly dependent on the aperture layout. This paper introduces a design-driven optimization method for SAIS that utilizes a self-adaptive genetic algorithm to concurrently optimize the number, dimensions, and spatial distribution of sub-apertures under given constraints. Departing from conventional approaches that employ fixed sub-aperture counts, this technique achieves comprehensive parameter co-optimization. Applied to a 2 m aperture system with fill factors of 15%, 20%, and 25%, the proposed method demonstrates superior performance over both classical configurations and prior optimized arrays. Our methodology provides a novel tool, to our knowledge, to fundamentally bridge theoretical design and practical implementation challenges in SAIS development.

Broadband ultraviolet photodetectors (BUVPDs), with spectral sensitivity spanning from the deep-ultraviolet band (DUV) to near-ultraviolet band (NUV), offer compact, high-speed, and versatile detection solutions for environmental monitoring, safety, and advanced imaging applications. Herein, we propose and demonstrate a self-powered BUVPD based on a homojunction composed of gallium nitride (GaN) quantum dots and epitaxial GaN. By harnessing the synergistic effects of the pyroelectric and photovoltaic responses, the device exhibits excellent performance, including a high responsivity of 149 mA/W, a specific detectivity of 4.5 x 1011 Jones, and a fast response time of 10 ms. The underlying photo-response mechanism is elucidated via energy band diagram analysis of the GaN homojunction. Furthermore, the influence of ambient temperature on device performance is systematically investigated. Notably, the dark current remains at the pA level across a wide temperature range from 83 K to 373 K. At 373 K, the responsivity shows only a slight deviation from room-temperature values, highlighting the detector's robustness under extreme thermal conditions. Benefiting from its outstanding optoelectronic properties, the device also demonstrates promising deep-UV transmission-mode imaging capabilities under weak light conditions. This work presents a novel design strategy for high-performance BUVPDs and paves the way for next-generation, high-sensitivity deep-ultraviolet imaging technologies.

A multiple stepped impedance resonator (SIR)based microwave measuring system is designed to effectively retrieve the complex permittivity of liquid samples in this article. The microwave measuring system is constituted by an SIR, a radio frequency (RF) oscillator, and a frequency demodulation circuit. The optimal geometrical parameters for multiple SIRs operating in low- or high-loss regimes are derived by considering the loss of the liquid sample. As the multiple SIRs operating in a low-loss regime are easier to manufacture, it is utilized as the load network to design an RF oscillator based on the negative resistance principle. To facilitate the reading of measurement values and reduce measurement costs, an envelope detector/frequency demodulation circuit is integrated to convert the output power level/oscillation frequency of the RF signal into a direct current (dc) voltage for the inversion of the permittivity of liquid samples. During measurement, the proposed system in this study displays an average sensitivity of approximately 28.2/29.6mV/Delta epsilon(r)' for measuring sunflower-mineral oil mixtures, and 15.9 and 2.2mV/Delta epsilon(r)' for measuring water-ethanol mixtures. This makes the system's sensitivity much higher than other literature. The proposed system is a prospective contender in the field of measuring liquid samples.

Solar‐blind photodetection plays a crucial role in environmental monitoring, corona detection, and covert battlefield communication due to its unique high signal‐to‐noise ratios in the UVC band. Aluminum quantum dots (AlQDs) emerge as promising optical materials owing to their extended photoresponse in the ultraviolet region, along with their low cost and compatibility with optoelectronic devices. Herein, an AlQDs‐based cascade solar‐blind photodetector is presented with enhanced sensitivity, achieved through the quantum confinement effect. By employing a gradient double‐layer AlQDs stack integrated with β ‐Ga₂O₃, the heterojunction demonstrates a significantly suppressed dark current, reduced from 3 nA to 2 pA, and a spectral noise density of 2.8 × 10 −11 A Hz⁻ 1 / 2 compared to the single‐layer device. The optimized photodetector achieves a high UV–vis rejection ratio ( R 250 / R 400 ) of 2.5 × 10 3 , a specific detectivity of ≈2.3 × 10 1 2 Jones, a relatively fast response time of 25 ms, and a responsivity of 35.1 mA W −1 under a 1 V bias. Furthermore, the device demonstrates robust interference‐resistant imaging capabilities, enabling ultra‐weak photodetection down to 23 nW cm −2 . These results highlight the potential of AlQDs‐based cascade devices for advanced solar‐blind photodetection applications.

We propose a vibration sensor based on dual-frequency optoelectronic oscillator (OEO) for self-suppression of leading-fiber-induced noise. In the two OEO loops, the acousto-optic modulator (AOM) is used as a modulator to direct the carriers and sidebands into a Michelson interferometer, significantly enhancing sensitivity. Additionally, the two OEO loops share the same leading fiber and sensing interferometer, forming a cross-reference structure through dense wavelength-division multiplexing (DWDM). Environmental disturbances are significantly reduced through beat frequency detection, and the measurement signal is further amplified. In experiments, the noise suppression ratio of the leading fiber was 41.98 dB (200 Hz to 1 kHz), with a 5.58 dB enhancement in the measurement signal. This method allows for the separation of the sensing unit and optoelectronic system while maintaining high signal-to-noise ratio (SNR), improving the system's reliability, maintainability, and convenience.

An active differential microwave sensor with enhanced anti-interference capability for analyzing complex permittivity of liquid samples is proposed in this article. The proposed microwave sensor system is constituted by a differential microwave microstrip sensor and a low-noise amplifier (LNA). The differential microstrip sensor is composed of a splitter, a combiner, and a pair of double-planar circular spiral resonators (DPCSRs), wherein, each DPCSR is etched under each branch of the splitter/combiner. In the experiment, the RF signal produced by the vector network analyzer (VNA) enters into the input port of the microstrip sensor, and exports from the output port of the microstrip sensor. As the insertion loss of splitter/combiner, the magnitude of the output signal is lower than that of the input signal, i.e., S-21 < 0 dB . As known, the small signal would be easily affected by the noise signal, which would cause a detection error. In order to diminish the interference and reduce the error, the LNA is cascaded to the output port of the microstrip sensor, and the transmission coefficient ( S21 ) of the system is significantly enhanced to be about 6.84 dB. In addition, one branch of the microstrip sensor is regarded as a reference, and another branch is used as a test for the differential structure, which can decrease a certain error. The average sensitivity of the proposed active microwave sensor, in measurement, is about 0.698%, and its maximum detection errors in testing epsilon '(r) and epsilon ''(r) amount to approximately 6.144% and 3.105%, respectively. Generally speaking, the proposed active differential microwave sensor is a good candidate in the field of characterizing liquid samples.

A high-sensitivity demodulation method for the vibration-induced frequency shift of an optoelectronic oscillator (OEO) using an acousto-optic modulator (AOM) has been proposed and experimentally demonstrated. This is achieved by separating the optical carrier (OC) and the first-order sideband, directing them into the reference and sensing arms of a Michelson interferometer (MI), respectively. Additionally, since the system sensitivity depends on the optical frequency rather than the oscillating frequency, high-sensitivity vibration sensing can be achieved at OEO oscillating frequencies as low as 80 MHz. Experimental results indicate that for low-frequency vibration signals in the range of 200-800 Hz, the system achieves a vibration amplitude sensitivity of up to 1.77 GHz/cm and a minimum detectable vibration amplitude of 5.1 pm, representing the best result within our current knowledge for low-frequency vibration demodulation using OEO.

Environmental disturbances in the leading fiber are a significant source of noise in remote fiber optic interferometric sensors (FOIS). As the two interrogation lightwaves propagate through the leading fiber, environmental disturbances can induce undesired demodulated phase noises, collectively referred to as leading-fiber-induced noise. This study proposes what we believe to be a novel method for leading-fiber-induced noises self-suppression, utilizing dual-wavelength optical signals as mutual reference signals, thereby eliminating the need for a reference interferometer. Furthermore, the FOIS doubles the amplitude of the measurement signal, providing a better signal-to-noise ratio (SNR) compared to the traditional reference interferometer method. Experimental results demonstrate that the FOIS achieves an average measurement signal enhancement of 5.93 dB and an average leading-fiber-induced noise suppression of 41.53 dB within the frequency range of 200 Hz to 1800 Hz. leading-fiber-induced noises are significantly suppressed over a 20 km bi-directional transmission, and the system’s SNR is comparable to that of a conventional FOIS using identical performance devices. The remote FOIS shows huge advantages for hydrophone shore-based array and towed array applications.

The reliability of Insulated Gate Bipolar Transistor (IGBT) significantly impacts the performance and efficiency of power conversion systems, making them crucial in industry and energy storage applications. With the ongoing trend towards higher power density in power conversion devices, IGBTs are increasingly vulnerable to interference from external sources during operation. This study investigates the high-power near-field modulation pulse magnetic field interference in the IGBT switching circuit during practical operation, with a focus on the impact of parasitic parameters on output waveform. Experimental verification under various interference conditions provides insight into actual interference effects.

Noise floor is an important metric for fiber optic sensors. In particular, common-mode noise (CMN) suppression is critical to improving the system's ability to detect weak signals. In this letter, an innovative method for reducing noise in white-light-driven sensors is proposed. This structure fully utilizes the broad spectrum of white light and the wavelength selectivity of fiber gratings. The proposed CMN suppression method is capable of suppressing the phase noise of the light source, as well as the noise due to environmental disturbances. The experiments demonstrate that the noise floor of this vibration sensor is about -88 dB/Hz above 30Hz with 10km disturbed transmission fiber. The max 1/f noise reduction can reach approximately 60 dB near 5 Hz, while the max transmission path noise suppression exceeds 103 dB at hundreds of Hz. The proposed structure has the potential to achieve higher resolution in wavelength division multiplexing (WDM) sensor arrays without excessive cost.

We present a novel higher-order space-harmonics-enabled leaky wave antenna (LWA) based on a half-mode substrate integrated waveguide (HMSIW) and microstrip phase delay (PD) lines, a design that allows for multibeam radiation. The unit cells (UCs) of the proposed LWA are connected by microstrip PD lines, which allows for the excitation of different nth higher-order space harmonics, resulting in an n-beam radiation pattern. Notably, by appropriate design of the microstrip PD lines, a pair of phase constants with equal amplitude but reverse lateral directions can be created, which ensures that the radiation beam remains fixed in the lateral direction. Furthermore, the inclusion of microstrip PD lines provides phase compensation (PCs) for each UC. Computer simulations demonstrate that the microstrip PD lines significantly improve the realized gain of the LWA while reducing the operating bandwidth. Consequently, the scanning rates, i.e., scanning range divided by operating bandwidth, experience a remarkable increase. The radiation from the proposed LWA is emitted from the open edges of the HMSIW, with tilt slots etched on the HMSIW to facilitate continuous beam scanning. A protype of a tri-beam LWA was fabricated and characterized, and the measurement results confirm excellent performance with a high peak gain ranging from 11 to 13.98 dBi across a continuous beam-scanning angle range from -48 degrees to +47 degrees. The achieved scanning rate is 6.02.

Colloidal quantum dots are semiconductor nanocrystals endowed with unique optoelectronic properties. A major challenge to the field is the lack of methods for synthesizing quantum dots exhibit strong photo-response in the deep-ultraviolet (DUV) band. Here, a facile solution-processed method is presented for synthesizing ultrawide bandgap aluminium nitride quantum dots (AlN QDs) showing distinguished UV-B photoluminescence. Combined with the strong optical response in solar blind band, a solution-processed, self-powered AlN-QDs/beta-Ga2O3 solar-blind photodetector is demonstrated. The photodetector is characterized with a high responsivity of 1.6 mA W-1 under 0 V bias and specific detectivity 7.60 x 10-11 Jones under 5 V bias voltage with good solar blind selectivity. Given the solution-processed capability of the devices and extraordinary properties of AlN QDs, this study anticipates the utilization of AlN QDs will open up unique opportunities for cost-effective industrial production of high-performance DUV optoelectronics for large-scale applications. Colloidal aluminum nitride quantum dots exhibit unique photoresponse in DUV band and the photodetector based on the AlN-QD/beta-Ga2O3 heterojunction demonstrates high wavelength-selective solar blind photodetection. image

This paper presents bandpass filter (BPF) comprising substrate integrated waveguide (SIW) and spoof surface plasmon polaritons (SSPPs), achieving miniaturized size, low insertion loss in the millimeter-wave band. SIW with single-slotted SSPP structure is employing to obtain the transmission zero (TZ) at the low-frequency part, and by introducing the SIW with rhombic periodic walls to enhance the low-frequency rejection. The target passband and TZ of the high-frequency part are realized by increasing the number of etching slots. Furthermore, we innovatively incorporate nonradiative (NR) slots etched below the SSPP structure to gain high out-of-band rejection level. SIW with rhombic periodic walls and slotted SSPP structure as one unit cell is analyzed and demonstrated. Ultimately, the two SIW unit cells are cascaded together to get better out-of-band rejection characteristics and serve as our final design. To validate the proposed design, the BPF prototype is fabricated and measured, showing good electrical performance in terms of high selectivity, low loss, and compact size.

A novel endfire antenna utilizing spoof surface plasmon polaritons (SSPP) and a traveling-wave feeding mechanism is introduced. The proposed endfire antenna operates in the millimeter-wave (mmW) band. The placement of a Vivaldi antenna at the front end of the SSPP endfire antenna allows for the efficient transmission of surface waves and the generation of an end-fire beam. The electromagnetic waves are coupled from the travelingwave feeding mechanism to the slot located between the Vivaldi antenna and the SSPP endfire antenna. Furthermore, we conducted a comparison between the effects of a standing-wave feeding mechanism and a traveling-wave feeding mechanism on the transmission performance and radiation pattern of the designed endfire antennas. The numerical analysis demonstrates that employing a traveling-wave feeding mechanism leads to a reduction of 63% in impedance bandwidth, while concurrently increasing the gain by 0.42dB. The ultimate configured antenna aperture measures 0.21λ 0 × 0.02λ 0 , showcasing its low-profile attributes.

This paper presents a millimeter-wave bandpass filter (BPF) that has a narrow-band and miniature dimension. The proposed BPF employs a half-mode substrate integrated waveguide (HMSIW) topology to attain decreased dimensions. We etched compact spoof surface plasmon polaritons (SSPPs) structures onto two rhombus-shaped HMSIW cavities in order to obtain the ability to filter a narrow range of frequencies. In addition, two HMSIW cavities with rhombus-shaped configurations are connected in series to achieve a high selectivity. In order to obtain a transmission zero in high-frequency part, the microstrip line located at the center of the SSPP structure is enlarged and a metallic via is introduced. Numerical results demonstrate that, the center frequency of the proposed HMSIW-SSPP hybrid BPF is at 30.585 GHz, insertion loss is 2.2 dB, 3-dB bandwidth is as narrow as 3.2%, and the profile is 1.48λ × 0.51λ, which has strong potential for use in millimeter-wave communication and radar applications.

The white light interferometer is advantageous for wavelength division multiplexing (WDM), but the excessive noise floor limits its application in practicality. In this Letter, we propose a fiber-optic sensor driven by a broadband light source, which uses a fiber-optic Fabry–Perot cavity and a reference interferometer to enhance strain resolution. In the experiment, the strain resolution of a 5.86 m resonant sensor is 18.5 fɛ/Hz at 1.5 kHz, while the maximum detectable signal is over 230 rad at 1 kHz. With low cost, this method provides a new, to the best of our knowledge, solution for WDM sensing arrays with a large dynamic range.