Abstract:This paper investigates the punch-through characteristics of separate absorption， charge and multiplication avalanche photodetector （SACM APD）. By analyzing the device''s spectral response， capacitance characteristics， and current-voltage （I-V） characteristics at various operating temperatures， and combining these with simulated internal electric field and energy band distributions from the SILVACO platform， we analyzed examined the performance of the SACM APD before and after punch-through and established a corresponding mathematical model. Through structural and process parameter optimization for silicon-based SACM APD devices， simulations revealed that when the ion implantation energy of the field-control layer was 580 keV， the optimized device exhibited a punch-through threshold voltage of -30 V and a capacitance reduction to one-third of the pre-punch-through value. Subsequently， a silicon SACM APD device was fabricated using the complementary metal-oxide-semiconductor （CMOS） process. Measurements confirmed a punch-through threshold voltage of -30 V， a 2.18-fold increase in photocurrent at 808 nm （punch-through）， a redshift of the peak responsivity wavelength from 590 nm （pre-punch-through） to 820 nm （post-punch-through）， and an elevation of the peak responsivity from 0.171 A/W@590 nm to 0.377 A/W@820 nm. The capacitance was also reduced to one-third of the pre-punch-through value at 1 MHz.

Abstract:Unmanned Aerial Vehicles（UAVs） have a wide range of applications in agriculture， logistics， rescue and disaster relief because of their compactness， lightness and flexibility. However， if they are used improperly or mismanaged， they may not only cause personal privacy leakage and property loss， but also pose a threat to public safety and even military security. Therefore， real-time and accurate detection and warning of UAVs in the airspace play an important role. In this regard， a multi-channel interactive attention mechanism and edge contour enhancement （MCIAECE） method for infrared UAV detection is proposed. Firstly， the shallow and deep features of the infrared image are extracted by a dual-channel consisting of a multi-channel interactive attention mechanism module and an edge contour enhancement module， after which the attention mechanism enhances the target features while the edge contour enhancement obtains more detailed information. Then the extracted features of each layer are fused and enhanced using the multilevel feature fusion module to obtain the detection results. The experimental results show that better results can be achieved with the MCIAECE method on all three datasets. Among them， the best results are obtained on the NUDT-SIRST infrared dataset， with the detection probability and intersection over union of 98.83% and 85.11% respectively， which increased by 1.95% and 6.88% compared to the baseline network， and the effect is significant in the edge contour restoration of the target compared with other methods.

Abstract:This study introduces a comprehensive theoretical framework for accurately calculating the electronic band-structure of strained long-wavelength InAs/GaSb type-II superlattices. Utilizing an eight-band Hamiltonian in conjunction with a scattering matrix method， the model effectively incorporates quantum confinement， strain effects， and interface states. This robust and numerically stable approach achieves exceptional agreement with experimental data， offering a reliable tool for analyzing and engineering the band structure of complex multilayer systems.

Abstract:A novel near-infrared all-fiber mode monitor based on a mini-two-path Mach-Zehnder interferometer （MTP-MZI） is proposed. The MTP-MZI mode monitor is created by fusing a section of （no-core fiber ，NCF） and a （single-mode fiber ，SMF） together with an optical fiber fusion splicer， establishing two distinct centimeter-level optical transmission paths. Since the high-order modes in NCF transmit near-infrared light more sensitively to curvature-induced energy leakage than the fundamental mode in SMF， the near-infrared high-order mode light leaks out of NCF when the curvature changes， causing the MTP-MZI transmission spectrum to change. By analyzing the relationship between the curvature， transmission spectrum， and spatial frequency spectrum， the modes involved in the interference can be studied， thereby revealing the mode transmission characteristics of near-infrared light in optical fibers. In the verification experiments， higher-order modes were excited by inserting a novel hollow-core fiber （HCF） into the MTP-MZI. When the curvature of the MTP-MZI changes， the near-infrared light high-order mode introduced into the device leaks out， causing the transmission spectrum to return to its original state before bending and before the HCF was spliced. The experimental results demonstrate that the MTP-MZI mode monitor can monitor the fiber modes introduced from the external environment， providing both theoretical and experimental foundations for near-infrared all-fiber mode monitoring in optical information systems.

Abstract:Electro-Optic Sampling （EOS） detection technique has been widely used in terahertz science and technology， and it also can measure the field time waveform of the few-cycle laser pulse. Its frequency response and band limitation are determined directly by the electro-optic crystal and duration of the probe laser pulse. Here， we investigate the performance of the EOS with thin GaSe crystal in the measurement of the mid-infrared few-cycle laser pulse. The shift of the central frequency and change of the bandwidth induced by the EOS detection are calculated， and then the pulse distortions induced in this detection process are discussed. It is found that this technique produces a red-shift of the central frequency and narrowing of the bandwidth. These changings decrease when the laser wavelength increases from 2 μm to 10 μm. This work can help to estimate the performance of the EOS detection technique in the mid-infrared band and offer a reference for the related experiment as well.

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:The existing deep learning-based image blind super-resolution algorithms only utilize neural networks to learn the end-to-end mapping from low-resolution （LR） images to high-resolution （HR） images， only allowing the network to implicitly learn image priors， resulting in algorithms that still produce blurry super-resolution results. To address the above issues， a deep learning image blind super-resolution algorithm guided by sparsity and self-similarity priors is proposed. Initially， for various LR image inputs， a dynamic linear kernel estimation module is employed to effectively estimate the corresponding blur kernels； Subsequently， a deep unfolding deconvolution filtering module based on the Fast Iterative Shrinkage-Thresholding Algorithm （FISTA） is utilized to explicitly model the sparsity prior of signal， achieving deconvolution restoration of the degraded images； Finally， a dual-path multi-scale large receptive field restoration module leverages the self-similarity prior of images for super-resolution recovery. The experimental results indicate that， compared to existing methods， the proposed algorithm achieves a peak signal-to-noise ratio （PSNR） of 31.66 and a structural similarity index （SSIM） of 0.8725 on the publicly available Gaussian8 dataset， and attains a PSNR of 29.08 and an SSIM of 0.8007 on the DIV2KRK dataset. The images restored by the proposed algorithm not only exhibit the highest restoration metrics but also superior visual quality.

Abstract:One of the key areas of advancement in space-based infrared sensing is the high-sensitivity detection of small and weak targets. A major innovation in this regard is the design of the infrared detection system indicator， which is influenced by the characteristics of the target background radiation. The effectiveness of space-based infrared detection is significantly challenged by airborne targets， especially civil aircraft. These targets are active in the upper troposphere and lower stratosphere. They exhibit weak and variable radiation characteristics due to complex background clutter and atmospheric attenuation. Aiming to address this issue， this paper proposes a multi-parameter joint optimization method for an airborne target infrared detection system based on the coupling of the multiple physical effects. Firstly， the initial optimization of the target detection spectral band in the sky is completed based on the spectral radiation characteristics of the target， the background， and the spectral atmospheric transmittance change characteristics of the target-sky-based detection platform. Subsequently， the detection sensitivity requirements are proposed. Then， a system parameter optimization method is established with the target motion speed limit， earth background limit， and detection sensitivity as the three major boundaries. This method facilitates the creation of an infrared detection index system for air targets.

Abstract:In the process of power scaling large-area Quantum Cascade Lasers （QCLs）， challenges such as degradation of beam quality and emission of multilobed far-field modes are frequently encountered. These issues become particularly pronounced with an increase in ridge width， resulting in multimode problems. To tackle this， an innovative multi ridge waveguide structure based on the principle of supersymmetry （SUSY） was proposed. This structure comprises a wider main waveguide in the center and two narrower auxiliary waveguides on either side. The high-order modes of the main waveguide are coupled with the modes of the auxiliary waveguides through mode-matching design， and the optical loss of the auxiliary waveguides suppresses these modes， thereby achieving fundamental mode lasing of the wider main waveguide. This paper employs the finite difference eigenmode （FDE） method to perform detailed structural modeling and simulation optimization of the 4.6 μm wavelength quantum cascade laser， successfully achieving a single transverse mode QCL with a ridge width of 10 μm. In comparison to the traditional single-mode QCL（with a ridge width of about 5 μm）， the MRW structure has the potential to increase the gain area of the laser by 100%. This offers a novel design concept and methodology for enhancing the single-mode luminous power of mid-infrared quantum cascade lasers， which is of considerable significance.