With the development of infrared technology, characterizing the response nonlinearity of infrared detectors has become a key focus for domestic and international research. However, traditional test methods cannot effectively distinguish between linear and nonlinear responses, making the accuracy of nonlinear testing limited. By using harmonic signals to characterize the impedance nonlinearity of photoconductive detectors and extract their nonlinear components, the interference of linear signals can be excluded and the accuracy of the tests can be increased. In this study, two detectors of different materials and structures were tested using the harmonic method. The results show that the harmonic signals due to the impedance nonlinearity of the detector prepared from the liquid-phase epitaxial material are approximately 100 times higher than those of the bulk-material detector. This may be due to the inconsistent effect of thermal excitation on different detectors, resulting in different degrees of nonlinearity. The feasibility of the harmonic method in impedance nonlinearity testing of photoconductive detectors is demonstrated by a combination of experimental and mathematical analyses.

To address the compatibility issue of photodetection units with standard processes and the difficulty in combining monolithic integration with process technology, a monolithic integrated high-response photodetection device based on complementary bipolar standard process is proposed. A monolithic integration scheme for photodetectors accompanied by a signal-processing circuit is adopted to conduct the design and simulation of a high-response photodetection unit and a low-latency, high-rate signal-processing unit, thus realizing the monolithic integration of the device, process-technology merging, and high-response photodetection. Test results show that the photoelectric response characteristics and signal-processing functions are normal, and the required photoelectric detection parameters such as high response (peak response reaching 0.462 A/W), high data output rate (maximum of 12 Mbd), low transmission delay (less than 41.8 ns), low output logic level (0.15 V), and low output leakage (less than 1.5 A) are achieved. The overall technical performance of the proposed device is excellent and satisfies the application requirements of miniaturized, highly integrated, and low-cost photodetection systems.

Electro-optic modulators are critical components of optical communication systems. With an increasing demand for the near-infrared spectrum in optical communication, the 2 m mid-infrared band has emerged as a promising option for expanding the bandwidth of fiber optic communications. This study proposes a mid-infrared electro-optic modulator based on barium titanate on an insulator platform at a wavelength of 2 m. Theoretical analyses and structural optimizations are performed on the barium titanate ridge waveguide and slow-wave electrode. The simulation results demonstrate that at a wavelength of 2 m and a modulation length of 5 mm, the designed electro-optic modulator exhibits high modulation efficiency and achieves a large electro-optic bandwidth, with a half-wave voltage-length product (V·L) of 0.677 V·cm and a 3 dB electro-optic bandwidth of 229.6 GHz.

Self-powered heterojunction photodetectors have attracted significant attention as they can detect signals driven by a built-in electric field without external power. They are characterized by low power consumption, high sensitivity, and a fast response speed. This study employs a simple vacuum thermal sublimation method to prepare highly crystalline CuI thin films. Additionally, a smooth and dense polycrystalline film is prepared by improving the smoothness and density using confined space annealing. By building a p-CuI/u-GaN heterojunction, self-powered blue-UV photodetectors are constructed. The device responds to the blue-UV light spectrum with wavelengths <420 nm and exhibits excellent performance, including high responsivity (51 mA/W-1), high detectivity (6.5×1011 Jones), fast response times (approximately 32 ms rise time and 36 ms decay time), good stability at the 360 nm wavelength, and self-powering capabilities. This study provides a simple method for preparing high-quality semiconductor CuI films and offers new insights for the fabrication of high-performance photodetectors.

In the terahertz band, high-resistivity silicon and sapphire are commonly used as substrates for terahertz devices owing to their low absorption, high resistivity, and low spectral dispersion. However, the high refractive index results in most of the incident terahertz waves being reflected at the interface, leading to a reduced wave transmittance and a potential Fabry-Perot resonant cavity effect, limiting the operating bandwidth and sensitivity of the terahertz device. To reduce the reflection of terahertz waves at the interface, this study proposes a three-layer anti-reflection structure. By using the transfer matrix method (TMM) in MATLAB and the finite-difference method in the time-domain (FDTD) in electromagnetic simulation, Mylar/Al2O3/AlN is selected as the anti-reflection structure in the terahertz range. The simulation results show that this structure can maintain a reflectivity <-20 dB in the range of 275~405 GHz. Furthermore, the terahertz detector applying this anti-reflection structure exhibits a -3 dB bandwidth enhancement of >50 GHz and a 3.2-fold increase in responsivity at 340 GHz. Additionally, the structure has a straightforward and cost-effective fabrication process, providing an economical and effective solution for broadband reflection reduction in the terahertz band.

To meet the design requirements of integration, volume, and resolution for the signal readout circuit of optical encoders, this study analyzes the encoding principles of incremental and absolute optical encoders, based on the pseudo-random coding principle and Moir fringe optical signal theory. A dedicated integrated circuit for high-resolution optical encoders, based on the incremental and pseudo-random mixed encoding scheme, is designed and fabricated. Utilizing a 350 nm CMOS process, full integration of the photodetector and readout circuitry is achieved. The chip size is only 4.6 mm×3.5 mm, with a resolution of up to 22 bit. It can simultaneously generate precise sine and cosine output signals within a signal period of 50 kHz, as well as output digital pseudo-random code signals at a clock frequency of 2 MHz, meeting the design specifications of the system.

Based on TSMC 65 nm CMOS technology, in this study, a double-clamp counting circuit is designed for a high-precision current matching charge pump circuit in a wide voltage range. The double-clamp technology avoids the complicated circuit structure caused by the rail-to-rail operation amplifier. Moreover, the influence of non-rational effects, such as charge sharing, clock feedthrough, and charge injection, on the circuit are effectively optimized by adding the count of the regulating switch tube and the complementary switch. The simulation results show that, compared with the traditional charge pump circuit, when the power supply voltage is 1.2 V and the charge pump current is 50 A, the power supply voltage is 1.2 V. The current matching degree of the double-clamp charge pump circuit can be maintained within 0.03% in the range of 0.2~1.0 V.

A novel temperature sensing structure and packaging process for metal-encapsulated fiber Bragg grating (FBG) temperature sensors were proposed to overcome issues such as aging, creep, and other long-term effects typically seen in traditional adhesive-encapsulated FBG temperature sensors. Finite element analysis was used to design a strain-insensitive sensor. In this new design, glass solder replaced traditional epoxy resin adhesive to secure the FBG to a stainless steel substrate through two-point welding, while a metal shell and silicone rubber provided sealing protection. The FBG temperature sensor demonstrated a temperature sensitivity of 27.46 pm/℃ within the range of -20 to 55 ℃, with a linear fitting degree of 0.999. The sensor exhibited excellent temperature stability and repeatability, achieving a measurement standard deviation of less than 0.003 ℃ across a broader temperature range of 0 to 150 ℃. This packaging structure offers a simple, cost-effective, and easily implementable sensor technology, with promising application prospects in the field of structural health monitoring.

To improve the sensitivity of fluorescence detection, a microfluidic channel structure using silicon-based photonic crystals is proposed. The microfluidic channel can effectively enhance the excitation light field and realize fluorescence-directed emission of quantum dots. The band structure of the photonic crystal was determined by the plane wave expansion method. The effects of quantum dot polarization, channel structure parameters, and the position of quantum dots in the channel on fluorescence emission were examined using the finite-difference time-domain method. In addition, the enhancement effect of the structure during the excitation of quantum dots was analyzed. The simulation results show that, compared with the traditional silicon microfluidic channel, the photonic crystal microfluidic channel has a higher far-field emission power and a narrower radiation angle. Compared with the glass substrate, the far-field power of quantum dots in the microfluidic channel of the photonic crystal achieves a 16.9-fold enhancement and a narrow-angle emission within 9°. The photonic crystal microfluidic channel achieves an average 7.9-fold enhancement of the excitation field at 945 nm.

This study proposes a terahertz branching waveguide directional coupler with a switchable coupling degree. The coupling degree is switched by controlling the conductivity of the vanadium dioxide film on the surface of the first four branches. The simulation results demonstrate that within the frequency range of 180~250 GHz, the coupling degree is (3±0.6) dB. The isolation and return losses exceed 17 dB when the vanadium dioxide conductivity is 2×105 S/m. Similarly, for a vanadium dioxide conductivity of 10 S/m, the coupling degree is (10±0.7) dB. The isolation and return losses are >18 and 20 dB, respectively. The coupler performs exceptionally well under both coupling states, satisfying the design expectations.

This study presents the fabrication process of quartz microlens arrays (MLAs) using a combination of photoresist thermal reflow and plasma etching techniques. Key fabrication steps, including thermal reflow and inductively coupled plasma reactive ion etching (ICP-RIE), were investigated in detail. The optimal process parameters were determined, enabling the preparation of quartz MLAs in various sizes and shapes. The geometrical morphology and optical properties of the fabricated MLAs were evaluated, showing high uniformity and excellent surface quality. The measured focal lengths were found to be in close agreement with theoretical predictions. The results demonstrate that the fabricated MLAs exhibit excellent imaging performance, making them highly suitable for various optical applications.

In this study, a terahertz metasurface label based on a frequency-selective surface (FSS) was designed. The overall structure is composed of a surface metal pattern, intermediate medium, and a bottom metal plate. The structural unit of the FSS consists of symmetrical octagonal nesting rings etched onto an intermediate polyimide medium. When a nested ring disappears, the absorption peak of the corresponding resonant frequency point disappears through different coding. Effective bandwidth utilization is also achieved through frequency coding. The simulation results show that the proposed structure achieves a 4 bit coding capacity, with a working frequency range of 0.1~0.5 THz and a label area of only 0.25 mm2. The proposed structure has a high coding density, the angular stability is ≥45°, polarization insensitivity is present, the requirements of label recognition accuracy are satisfied, and the coding performance is strong. In addition, a frequency shift coding rule is proposed, which introduces a frequency shift by changing the resonant structural parameters to increase the coding capacity and label coding density without changing the label volume, which can satisfy the practical application requirements more flexibly. The metasurface-based flexible terahertz tag proposed in this study is different from the popular RF tag and has strong application prospects for miniature objects, such as medical and industrial components, automotive parts, and silicon chips.

Optical fiber temperature sensors gave attracted significant interest owing to their compact structure and resistance to electromagnetic interference. Nevertheless, it is imperative to enhance the detection sensitivity to adequately fulfill the existing requirements. This study proposes and demonstrates a sensitivity-enhanced optical fiber temperature sensor using the cascaded Lyot filter and Mach-Zehnder interferometer (MZI), based on the Vernier effect. The MZI has two consecutive bubble-type upper tapers and is employed as a reference interferometer, owing to the exceptional stability of its totally polarization-maintaining fiber (PMF) construction. A Lyot filter is created by fusion splicing a segment of PMF at a 45° angle between two linear polarizers, functioning as a sensing interferometer. The sensitivity of the cascaded sensor is improved through the Vernier effect, which is produced when the length of the sensing PMF in the Lyot filter is modified to closely match the free spectral range (FSR) of the MZI. Experimental results reveal the sensitivity of the Lyot filter is -1.4 nm/℃, while the cascaded sensor achieves an increased sensitivity of -28.3 nm/℃, with a sensitivity amplification factor of 20.2. The proposed PMF sensor structure leverages the controllable polarization characteristics to enhance system performance, effectively addressing the issue of detection errors that arise from the fluctuating polarization state of the optical signal being transmitted throughout the sensitivity test. This proposed optical fiber temperature sensor, with a robust polarization stability, simple fabrication, and high sensitivity, is suitable for high-precision industrial applications.

Under different structural parameters, the flow and heat transfer characteristics of TF-MCHS are studied using numerical methods. The results show that the rib height () has the most significant effect on the total thermal resistance (Rth) and pressure decrease (p). As increases, the Rth of the microchannel decreases rapidly, but p increases rapidly. To obtain the best parameter, a multi-objective optimization was performed using the response surface methodology (RSM), non-dominated sorting genetic algorithm (NSGA-Ⅱ), and the technique for order preference by similarity to the ideal solution (TOPSIS). According to the field synergy principle and the performance evaluation criteria (PEC), the overall performance of the microchannel before and after optimization was assessed. The results show that when Rth is 0.185 8 K/W, the pumping power (Wpp) of the optimized microchannel is 53.38% lower than that of the unoptimized microchannel, at only 0.006 2 W. When Wpp is 0.013 2 W, the Rth of the optimized microchannel decreases by 13.04%, compared with that of the unoptimized microchannel, at only 0.16 K/W. The PEC of the TOPSIS optimal microchannel is higher than that of the unoptimized microchannel. At Re=231, the PEC increases from 1.163 to 1.253, an increase of 7.74%. At Re= 631, the PEC is 1.451 5. The field synergy principle indicates that the velocity field and temperature field of the TOPSIS optimal microchannel have the best synergy effect (Fc=0.018 89).

This study proposes a hybrid structure consisting of a double-layer dislocated metal grating and an inclined dielectric grating to address the issues of low fluorescence intensity and omnidirectional divergence in fluorescence detection. Using the finite-difference time-domain method, we investigated the effects of polarization state and position, quantum dot positioning, and metal grating period on enhancing directed fluorescence emission. Additionally, we analyzed the enhancement effect during fluorescence excitation. By embedding the up-conversion quantum dots as fluorescent materials within the polymethyl methacrylate layer, the proposed structure achieved significant fluorescence far-field directional enhancement. The results demonstrated that, compared to free space, when quantum dots were placed in dislocated metal gratings, fluorescence excitation was enhanced by 40-fold, directional fluorescence emission was increased by 26-fold, and the far-field radiation angle was reduced, thereby improving the sensitivity of fluorescence-based biological detection.

In this study, the dynamic properties of current-driven RKKY-coupled Skyrmion are analyzed. In particular, the manipulation of Skyrmion oscillation and precession by different RKKY ferromagnetic coupling intensities is explored. The results show that the Skyrmion of the Top and Bottom layers can achieve stable oscillation under certain conditions, and the precession of the Skyrmion presents a circular trajectory. Furthermore, the precession position of the Top layer is ahead of that of the Bottom layer, and the coupling strength changes the difference of the Skyrmion precession radius between the upper and lower layers. In addition, the effects of different driving currents on the dynamic characteristics of Skyrmion are analyzed, and the results show that the driving currents can effectively manipulate the dynamic properties such as the initial oscillation time and stable oscillation radius.

To reduce the influence of the zero-drift problem on the measurement accuracy of an accelerometer and satisfy the measurement accuracy and drift requirements of a low-range micro-electro-mechanical system (MEMS) accelerometer, a high-precision MEMS accelerometer signal processing system based on AD7124 is designed. The hardware uses STM32F303CBT6 as the core controller to drive AD7124, and a high-precision analog-to-digital (A/D) conversion chip is used for data acquisition. In the software, the pulse width modulation (PWM) output square wave is designed as the excitation signal of the accelerometer, and the weighted moving average filter is used to denoise and smooth the signal. An algorithm for zero-drift suppression and tracking is proposed, which solves the problem of excessive zero-drift. After testing, the sensitivity of the accelerometer is 146 mV/g at the ±1 g range, the output stability of the accelerometer after digital filtering is increased by 5.97 times, and the final bias stability is improved from 45.850 mg/h to 0.055 mg/h.

A spintronic theory is proposed for a magnetic tunnel junction with a single-crystal barrier. This theory is founded on optical theory and the Patterson function approach and can adequately account for the influences of the barrier periodicity and lattice distortion. Based on the proposed theory, we investigated the temperature characteristics of the tunnel magneto-Seebeck effect in MgO-based magnetic tunnel junctions. In low-temperature approximation, the temperature only influences the Seebeck coefficients through the Fermi distribution function. However, in the proposed theory, the temperature can modify the potential parameter of the barrier through lattice distortion and further alter the Seebeck coefficients. As the tunneling electrons are scattered by the single-crystal barrier, the corresponding coherence leads to the oscillation of the Seebeck coefficients. The results can theoretically interpret the non-monotonic temperature characteristics of the Seebeck coefficient in the parallel configuration and TMS in MgO-based magnetic tunnel junctions. Furthermore, the physical mechanism of the non-monotonic temperature characteristics is elucidated. In addition, we investigated the influences of the parameters of the lattice distortion, such as strain, defect concentration, and recovery temperature, on the temperature characteristics of the tunnel magneto-Seebeck effect. It is found that the amplitudes of the non-monotonic variations of the Seebeck coefficient in the parallel configuration can be modulated by the defect concentration and recovery temperature.

Infrared imaging technology is widely used in fields such as medical diagnosis, spectroscopy, and molecular sensing. In recent years, metalens technology has provided a miniaturized and integrated platform for infrared imaging. However, the inherent dispersion of metalenses greatly hinders their application in infrared imaging. The current mainstream method for designing achromatic metalenses involves simulating the metalens and then analyzing relevant performance parameters, which is time-consuming. To address this issue, this study utilizes the field stitching technique, combined with a particle swarm optimization algorithm, to design a full-silicon achromatic metalens with a diameter of 100 m, operating in the range of 3.7~4.8 m. The calculated effective focal length of the designed metalens is 219.01 m, with a coefficient of variation of 1.87% and a maximum focusing efficiency of 49.3%. The designed metalens was simulated and validated using Lumerical FDTD software. A systematic comparison between the simulation results and the stitching results was conducted in terms of the focal length, coefficient of variation, computational time, full width at half maximum, focusing efficiency, and modulation transfer function, confirming the feasibility and accuracy of the field stitching technique. This method can be extended to other wavelength bands and provides a novel approach for designing larger metalenses.

Indium antimonide (InSb) has attracted significant attention owing to its exceptional performance in various fields, including infrared detection, high-speed electronics, and quantum computing. This study explores the heteroepitaxial growth of InSb thin films on Si(111) vicinal substrates and investigates their visible light photoconductive properties. To address the lattice mismatch and thermal expansion coefficient discrepancy between Si and InSb, a Bi buffer layer was employed in conjunction with a two-step growth strategy, enabling the successful fabrication of high-quality single-crystalline InSb(111) thin films on Si(111) planar substrates. However, on Si(111) vicinal substrates exhibiting a high-density step structure, the grown Bi(001) buffer layers exhibited numerous anti-phase domain defects, leading to the formation of polycrystalline InSb thin films on these surfaces. The fabricated InSb/Bi/Si heterostructures displayed a negative photoconductivity effect under simulated solar illumination, which is attributed to the trapping of photogenerated charge carriers in the interfacial states of the heterostructure.

This research focused on the numerical simulation of fluid-solid conjugate heat transfer in natural convection conditions, specifically addressing an independently designed and manufactured LED light. Employing Computational Fluid Dynamics (CFD) methods, the study aimed to optimize the multi-scheme design of the heat dissipation of the light in underwater environments. Validation efforts involved water tank testing, demonstrating 2.9% average relative error between simulated and measured temperatures under thermal equilibrium. Furthermore, the study delved into predicting the inner operating temperature of the LED light in large underwater spaces. Comparative analysis of temperature variations under varying seawater velocities and fin orientation provided valuable insights, guiding the refinement of the heat dissipation of the light for enhanced performance in specific underwater contexts.

A reconfigurable intelligence surface (RIS) consists of a large-scale array of optoelectronic devices that can modulate the electromagnetic characteristics, such as the amplitude and phase, of an incident electromagnetic wave to obtain a customized reflected beam and improve the wireless positioning service problem in non-line-of-sight (NLOS) environments. In this study, a non-orthogonal multiple access (NOMA) positioning system with intelligent reflective surfaces is constructed, which uses multiple RISs deployed in the air to reflect the signals transmitted from the base station to the user for easy reception. In addition, the RISs use pseudo-random sequences to remodulate the signals transmitted from the base station and then reflect them back to the user, making it easier to identify the signals reflected from different RISs. Finally, the user estimates multiple signal angles of arrival (AOA) using the multiple signal classification (MUSIC) algorithm to obtain the positioning coordinates. The simulation results show that the method proposed in this study can achieve centimeter-level positioning accuracy in NLOS environments.

To address the issue where the traditional critical set (CS) of polar codes includes bit positions that may result in the elimination of the correct path, we proposed a successive cancellation list (SCL)-Flip (SCLF) decoding algorithm with an optimized critical set (OCS-SCLF). In the proposed algorithm, the initial critical set was taken as the starting point, and the Gaussian approximation principle was applied to estimate the reliability of the polarized subchannels. The selection rules of the initial critical set were then modified to address the incompleteness of the CS in SCL decoding. The OCS was constructed and arranged in ascending order of channel reliability, effectively improving the flipping accuracy and reducing the number of re-decoding attempts. The simulation results showed that the proposed algorithm achieved better performance gains while significantly reducing the number of flips.

A remote sensing image sharpening method is proposed that combines cross stage local network (CSPNet) and parameter free attention (SimAM) to address the issues of uneven spectral distribution and missing spatial details in pansharpening of remote sensing images. Firstly, CSPNet is introduced into the backbone structure to replace the residual blocks in feature extraction with ordinary convolution and skip connections, in order to alleviate gradient redundancy and improve model learning power. Secondly, add SimAM blocks to directly derive 3D weights from the features, and then reverse optimize the extracted features to enable the model to extract deeper level feature information. Finally, design a learnable subtraction parameter to control the subtraction weights, in order to highlight the edge information of the fused image. The experimental results show that the proposed method can not only improve the gradient redundancy of the model, but also further enhance the spatial spectral resolution of the fused image.

To address the detection challenges of infrared images, such as a low signal-to-noise ratio, blurred edge information, and clutter interference, a generative adversarial network infrared image denoising method based on subspace projection is proposed. First, the generator consists of a U-Net structure and a subspace attention network. The encoding stage extracts image features through four layers of downsampling, while the decoding stage reconstructs the image through four layers of upsampling. Second, a subspace projection network is added to each skip connection, and the feature maps of each layer are combined with upsampled images from the same layer to form a subspace projection network for image feature fusion. The projected feature maps are then fused with the original high-level features to achieve image denoising. Finally, the image is input to the discriminator for adversarial training to obtain a clear reconstructed image. The comparative experiments with BM3D（Block-Matching and 3D Filtering）, DnCNN（Deep Neural Neural Network For Image Denoising）, and other algorithms show that the improved generative adversarial network algorithm has better objective evaluation index effects, with PSNR and SSIM reaching 34.36 dB and 0.985 2, respectively, thus verifying the strong denoising performance of this algorithm.

To mitigate the impact of interference clutter in the detection of infrared small targets within complex backgrounds, a dual-neighborhood local weighted contrast algorithm is proposed. First, considering the background characteristics of small targets of different sizes, a dual-neighborhood window strategy is employed to effectively capture target and background features. Subsequently, directional information feature and weight coefficient enhancement maps are computed separately. The former fully utilizes the dispersal direction information of the target, while the latter generates weight information by utilizing the intensity and dispersion of grayscale responses in different regions. The combination of these two maps through image fusion results in a target saliency map. Finally, adaptive threshold segmentation is applied to extract targets from the saliency map. Comparative evaluations were conducted on four publicly available datasets with different backgrounds, involving six different algorithms. The proposed algorithm demonstrates robust anti-interference capabilities and accurate detection performance.