Abstract:Infrared optical field compression provides an effective route to control mode dispersion and spatial distribution. In free space or homogeneous media， infrared propagating modes are diffraction-limited and difficult to achieve deep-subwavelength field compression. Optical field compression requires dispersion control and structure geometry design. In recent years， advances in low-dimensional materials and micro-nano fabrication broaden the physical implementation path of mode volume modulation. This review classifies infrared optical field into two fundamental types based on axial symmetry， including out-of-plane compression and in-plane compression. Out-of-plane compression forms normal （axial） compression states through interface dispersion and boundary conditions. Representative mechanisms include surface plasmon polaritons （SPPs）， surface phonon polaritons （SPhPs）， and waveguide modes. In-plane compression suppresses lateral propagation through disorder-induced interference， defect states， or geometric compression. This review compares physical origins and characteristic spatial scales of different mechanisms and summarizes research progress in infrared photodetection， surface-enhanced infrared absorption， and light-emission modulation. Further discussion examines the potential of hybrid in-plane-out-of-plane compression for enhancing optical field compression and tailoring mode distribution， and outlines future research directions.

Abstract:Pyroelectric detectors， a typical type of uncooled infrared detectors， are widely used in fields such as flame and fire warning， moving target sensing， gas detection， temperature measurement， and even terahertz detection， owing to their high sensitivity， fast response speed， low power consumption， and broad spectral response. Beyond conventional applications， pyroelectric detectors offer irreplaceable advantages in several specialized scenarios， including laser parameter measurement， high-precision spectrometers， spectral response calibration for infrared detectors， as well as applications in space science such as infrared earth sensors and earth radiation budget measurement. However， in the compelling field of infrared imaging， pyroelectric detectors indeed lose the competition against bolometers， which are another important type of uncooled infrared detectors. The review summarizes the intrinsic technical challenges faced by traditional pyroelectric detectors in imaging applications， including difficulties in integration with readout circuits， the requirement for a chopper， and the limitations in miniaturizing pixel size. This article summarizes two technical solutions that can address the difficulties of traditional pyroelectric detectors in infrared imaging： the thermal reset mode and the active detection mode. Through technological development and iteration， pyroelectric focal plane array devices are expected to achieve higher sensitivity and lower cost， securing a place in the application field of infrared imaging technology.

Abstract:Chaos in semiconductor lasers has developed into a rapidly advancing field that bridges nonlinear dynamics and modern photonic technologies. Owing to their intrinsic nonlinearity and strong carrier-photon interactions， semiconductor lasers serve as an ideal platform for the generation and control of deterministic chaos. This review summarizes the fundamental physical mechanisms underlying chaos generation in semiconductor lasers， including external perturbations and intrinsic nonlinear interactions. Various configurations for inducing chaotic dynamics， such as optical feedback， optical injection， and optoelectronic feedback， are discussed in detail. Recent advances in free-running chaotic lasers and integrated photonic platforms are also highlighted. Furthermore， emerging applications in secure optical communication， high-speed random number generation， and chaos-based sensing are presented. Finally， current challenges and future directions are outlined， underscoring the significant potential of semiconductor laser chaos for next-generation photonic systems. This work aims to offer a coherent and comprehensive perspective on the development and prospects of chaos in semiconductor lasers.

Abstract:Full Stokes polarization detection plays a significant role in various fields， such as environmental monitoring， remote sensing， biomedical detection， and optical communication. Conventional full Stokes detection systems rely on assemblies of discrete optical components， which are inherently bulky， complex， and difficult to integrate. With the advancement of photonic technologies， there is an increasing demand for compact， high-performance， and integrated full Stokes polarization detectors. In this review， we focus on three advanced research areas concerning integrated full Stokes detectors： those based on material platforms， metasurface-enabled architectures， and in-situ integrated optical structures. We summarize recent advances in each domain and discuss emerging opportunities and persistent challenges for the development of integrated full Stokes polarization detectors.

Abstract:Quantum well infrared photodetectors （QWIPs） are widely utilized in long-wave infrared detection applications， yet they are constrained by low quantum efficiency. Although metallic microcavities can enhance local coupling， achieving a field strength that perfectly coincides with the quantum well layers remains challenging， and such approaches are often incompatible with thick active regions. In this study， we developed an all-dielectric metasurface-coupled QWIP （MS-QWIP） to enhance device response. The metasurface features a square micropillar array etched directly into the 80-period GaAs/AlGaAs multi-quantum well active region. By leveraging the guided-mode resonance effect， this structure excites a strong longitudinal electric field component， effectively satisfying the intersubband transition selection rule for enhanced absorption within the active region. Experimental results at 50 K and a 5 V bias show that the peak responsivity of the MS-QWIP reaches 545 mA/W， a twofold increase over a conventional 45° facet-coupled device. Furthermore， the blackbody responsivity is improved by approximately 1.6 times. Notably， the architecture also reduces the effective electrical area of the photosensitive element， thereby suppressing dark current. This work demonstrates that all-dielectric metasurfaces can significantly enhance the sensitivity and signal-to-noise ratio of QWIPs.

Abstract:Semiconductor saturable absorber mirrors （SESAMs） are vital for enabling ultrafast fiber lasers， yet their mode-locking performance is often constrained by recovery time and nonlinear absorption parameters. Current optimization studies on SESAM mode-locking properties mainly focus on structural and material parameters of the quantum well absorption layer， while systematic research on the directional influence of a key fabrication parameter—the substrate miscut angle during epitaxial growth—remains scarce. This study presents the first systematic investigation into the impact of substrate miscut angles （0°， 2°， and 6° toward the ［110］ direction） on the structural properties of epitaxially grown InGaAs/GaAsP SESAMs and their mode-locking characteristics， revealing the regulatory effect of different substrate miscut angles on SESAM performance. Comprehensive characterization via high-resolution X-ray diffraction （HRXRD）， atomic force microscopy （AFM）， photoluminescence （PL） spectroscopy， and spectrophotometry reveals that increasing the miscut angle introduces lattice defects， significantly shortening recovery time. However， larger miscut angles also increase surface roughness and nonsaturable losses， degrading nonlinear absorption. In the mode-locking experiment of a Yb-doped fiber laser， SESAMs with the 2°-miscut angle achieved stable mode-locking， outputting 8.2 ps pulses at 1 064 nm， while the 6°-miscut sample exhibited deteriorated mode-locking performance due to material quality degradation. This work fills a critical gap in understanding how the substrate miscut angle influences SESAM mode-locking properties， providing a new optimization dimension and theoretical foundation for designing high-performance ultrafast lasers.

Abstract:GaSb and InAs demonstrate significant potential photoelectric applications in mid-wave infrared （3-5 μm） and long-wave infrared （8-12 μm） spectral regions. However， their weak optical absorption properties hinder accurate determination of absorption coefficients via conventional transmission spectroscopy due to multi-pass transmission effects. This study introduces a combined reflection-transmission analysis method based on Fourier-transform infrared spectroscopy （FTIR）， achieving enhancement in measurement accuracy within the low-absorption regime （α < 10 cm?1）. For samples with doping concentrations of N_D = 2.46×10¹⁶ cm^-3 （InAs） and N_D = 8.76×10¹⁶ cm^-3 （GaSb）， the analysis reveals that free carrier absorption in the 8-18 μm range is predominantly governed by acoustic phonon scattering and ionized impurity scattering. Notably， GaSb exhibits significantly enhanced scattering intensity compared to InAs， with a 10-fold increase in ionized impurity scattering coefficient and a 450-fold amplification in acoustic phonon scattering coefficient. The developed methodology provides a technical framework for determining absorption coefficients in low-absorption materials.

Abstract:The spatial distribution of lunar surface minerals provides essential constraints on magmatic activity， material differentiation， and subsequent impact modification， and is fundamental for reconstructing the Moon’s evolutionary history from remote-sensing observations. In this study， visible–near infrared （415–950 nm） mineral abundance products derived from the Multiband Imager （MI） onboard SELENE （Kaguya） were integrated with digital elevation model （DEM）–derived topographic parameters to conduct a quantitative， unified-scale spatial analysis of mineral–geomorphology relationships within lunar mare units. Representative large-scale impact structures and mare basins， including the Von Kármán crater and Mare Crisium， were selected as study areas to characterize the spatial correlation between near-infrared-sensitive mineral abundances and geomorphological features across different geological units. The results reveal significant regional-scale spatial clustering of mineral abundances and topographic parameters， along with pronounced spatial non-stationarity across varying geological and structural settings. These spatial patterns reflect the coupled long-term effects of magmatic activity， subsequent impact modification， and their interaction with pre-existing topography， thereby establishing a quantitative framework for lunar surface geological interpretation and evolutionary analysis using remote-sensing data.

Abstract:Accurate retrieval of Land Surface Temperature （LST） from satellite thermal infrared data remains challenging due to the reliance of physical models on real-time atmospheric profiles and the difficulty in characterizing surface emissivity over heterogeneous landscapes. To address these limitations， this study proposes SE-ResUNet， a deep learning framework for Landsat 9 thermal infrared images. To overcome the scarcity of large-scale in-situ measurements for training， we construct a high-quality synthetic dataset by coupling the MODTRAN 5 radiative transfer model with ERA5 atmospheric reanalysis data. The network adopts a U-Net encoder-decoder structure with a modified ResNet50 backbone to capture multi-scale features. Squeeze-and-Excitation （SE） attention modules are embedded in the residual blocks， and physical prior knowledge is directly added to the input tensor. By integrating skip connections and an adaptive calibration mechanism for thermal signals under physical constraints， our method achieves precise pixel-by-pixel temperature reconstruction. Experiments show that SE-ResUNet effectively mitigates the overfitting problem linked to spatial autocorrelation. The model shows strong robustness against simulated noise and complicated terrain variability. Evaluations on multiple datasets show that it achieves a Root Mean Square Error （RMSE） of around 0.7 K and a Mean Absolute Error （MAE） of 0.5 K. These results confirm the effectiveness of SE-ResUNet as a high-precision， end-to-end solution for LST retrieval without real-time external atmospheric inputs at the inference stage.

Abstract:This work presents a novel high-linearity AlGaN/GaN high electron mobility transistor （HEMT） featuring a multi-cycle graded gate recess （MCGGR）. The MCGGR-HEMT is realized through a designed periodically graded barrier layer along the gate width direction fabricated using optimized electron beam lithography （EBL） photoresist reflow process. The fabricated MCGGR-HEMT successfully achieves transconductance （G_m） compensation via the parallel connection of multiple periodic devices with graded threshold voltages along the gate width， exhibiting a recordable broadened gate voltage swing （GVS） of 3.5 V. This represents an extension of 1.8 V compared to the 1.7 V of conventional devices. Owing to its continuous graded modulation effect on the 2DEG channel， the higher-order peak transconductance values （G_m′ and G_m"） are simultaneously reduced by 37% and 35%， respectively. Meanwhile， the MCGGR-HEMT demonstrates a flatter f_T curve over a wider gate voltage range. At 10 GHz under single-tone continuous-wave （CW） over measurement （drain bias of 30 V）， it achieves a power density of 5 W/mm and a power-added efficiency （PAE） of 49%. In two-tone CW power measurement at the same frequency （10 MHz tone spacing， drain bias of 30 V）， the proposed device delivers a third-order output intercept point （OIP3） of 38 dBm， an OIP3/width of 63.1 W/mm， a linearity figure-of-merit （OIP3/P_DC） of 10 dB， and a third-order intermodulation distortion （IMD3） of -57.7 dBc. These performance metrics represent improvements of 5.2 dB， 44 W/mm， 4.8 dB， and 13.7 dB， respectively， over the conventional device. This innovative technology is highly compatible with the conventional GaN HEMT fabrication processes， offering a simplified and cost-effective route for enhancing device linearity.

Abstract:A terahertz （THz） spectrometer plays an essential role in THz astronomy. Coplanar waveguides （CPWs） are critical components in such THz spectrometers and relative permittivity is one of the most important parameters of a dielectric material. It decides the resonant frequency and the quality factor of the device. Since accurate electromagnetic field solutions of a CPW are hard to get due to its complex structure， the conformal mapping technique （CMT） is widely used to get approximative analytical expressions for effective permittivity . However， it makes a difference when a thin-film dielectric is involved. In this paper， we utilized high frequency structural simulator （HFSS） to get the effective permittivity of CPW based on resonator structure and compared it with that from conformal mapping technique. Provide the possibility to characterize the thin-film dielectric through simulation.

Abstract:Real-time spectral imaging of dynamic scenes is critical for industrial safety monitoring， atmospheric remote sensing， and aerial target recognition. Traditional spectral imaging methods are constrained by sequential sampling and low optical throughput， limiting simultaneous achievement of high temporal resolution and high detection sensitivity. Computational spectral imaging offers a promising solution， yet LWIR implementations remain challenging due to difficulties in coding element fabrication， response matrix calibration， and training data scarcity. A LWIR computational video spectral imaging method based on a broadband random coding array was developed， addressing coding element fabrication， system calibration， and dataset construction. Using 9 broadband randomly coded channels， 32 band spectral data cubes were reconstructed at 200 nm spectral resolution and 30 Hz frame rate， with detection sensitivity 5-10 times higher than equivalent narrowband filter schemes. In a gas leakage scenario， 16 gas species were identified with 98.97% average accuracy using a characteristic absorption spectral library. These results confirm the potential of this approach for gas spectral measurement and recognition in real dynamic scenes.

Abstract:The photoelectric characteristics of GaAsSb/InAlAs separate absorption， charge， and multiplication （SACM） avalanche photodetectors were investigated. This heterojunction has a small conduction band offset （=0.089 eV）， which facilitates carrier injection into the multiplication region. Three SACM APDs were designed with charge layer doping concentrations of 2×10¹⁷ cm^-3， 3×10¹⁷ cm^-3， and 4×10¹⁷ cm^-3. Results show that the device with 4×10¹⁷ cm^-3 exhibited the best performance. At room temperature， it achieved a cutoff wavelength of 1.7 ， a punch-through voltage of -10.8 V， a gain of 20.3 at -34.6 V， and a corresponding dark current density of 0.058 A/cm2. Compared with the GaAsSb PIN APD， the gain increased by 6.8 times， and the dark current was effectively reduced. Adjusting the charge layer doping concentration suppresses the dark current and improves the gain， providing a new approach for highly sensitive short-wave infrared APDs.

Abstract:A cascaded deep learning network model with physically consistent constraints was proposed for the modeling and design of terahertz metasurface biosensors. In this model， key resonance parameters， including resonance frequency， full width at half maximum， and quality factor， were explicitly treated as network outputs， and physically consistent constraints were imposed during training to ensure that the predictions obey fundamental resonance physics. Numerical results showed that the proposed model exhibited good convergence behavior and reliable prediction accuracy for the key resonance parameters. Based on the proposed model， a terahertz metasurface biosensor was designed and experimentally validated. The measured spectral response agreed well with the theoretical prediction， and trace detection of homocysteine molecules was successfully achieved. These results demonstrate that the proposed approach provides an effective modeling method for reliable and interpretable design of terahertz metasurface biosensors.

Abstract:A polarization-independent "Tian" shaped dynamic unit has been designed， which is composed of vanadium dioxide （VO₂） thin films and gold patterns. Leveraging the phase transition characteristics of VO₂， the designed unit structure can effectively modulate the amplitude of incident terahertz waves. Furthermore， based on this dynamic "Tian" shaped metasurface unit structure， the other static "Tian" shaped unit structure （without VO₂） is designed in this paper for the design of encrypted holography. Simulation results show that in the insulating state， both dynamic and static unit structures produce the same amplitude modulation on the incident terahertz waves， achieving information encryption. When VO₂ transitions to the metallic state upon heating， the dynamic unit changes its original amplitude state， thus realizing polarization-independent holographic imaging. Unlike previous dynamic metasurface research based on VO₂， which mostly focused on polarization-dependent or single image switching， this work is the first to combine the dynamic regulation capability of VO₂ with the "Tian" shaped polarization-independent structure， achieving reversible， polarization-independent switching between encryption and holographic imaging， with broadband operating characteristics. This scheme has broad application prospects in dynamic optical encryption， information storage， and anti-counterfeiting fields.

Abstract:Successful terahertz （THz） wave manipulation using dielectric metasurfaces is demonstrated. By employing optical pumping at different wavelengths， the metasurface modulates THz waves in either mode-selective or non-selective manner. Distinct transmittance relaxation processes are observed when varying the excitation photon energy， reflecting the band characteristics of silicon. Furthermore， we reveal an alternative optical control strategy through active adjustment of the pump-probe delay stage''s optical path， enabling continuous tuning of THz polarization states via metasurface functionality control. We also offer corresponding physical explanations. Our study proves that optical pumping serves as an effective external approach for dynamic THz wave manipulation， facilitating the development of versatile metasurface-based devices.

Abstract:Hyperspectral LiDAR （HSL） is an emerging active sensing technique that can simultaneously acquire spectral and spatial information for quantitative remote sensing applications. However， most existing HSL systems acquire spectral and spatial information point by point， which limits the acquisition of image-like hyperspectral data and dense 3D point clouds. In this paper， the authors presented a hyperspectral imaging LiDAR system based on a chip-scale single-photon avalanche diode （SPAD） array （768 × 576） and a supercontinuum laser source （SPAD-HSL）. A focus-tunable emitting system was designed to provide broadband illumination， while a SPAD-array-based receiving system was developed to enable wavelength-selective detection using optical filters. Based on the proposed SPAD-HSL system， hyperspectral measurements were conducted on a total of 12 leaf samples， including 5 species and various physiological states， under different detection distances and angles. The acquired spectral data were subsequently compared with spectrometer measurements， demonstrating that the proposed system enables active hyperspectral imaging acquisition and achieves high spectral consistency.

Abstract:During the imaging process of hyperspectral remote sensing images， the quality of the images often deteriorates due to various types of noise such as detector noise， optical system noise， environmental noise， and statistical noise， which in turn affects the accuracy and credibility of information extraction in subsequent applications. Especially in the infrared spectral band， due to factors such as the thermal vibration of the detector material itself， it is significantly affected by thermal noise. To address this issue， this paper proposes a hyperspectral denoising method based on scale-adaptive spectral dictionary learning. Firstly， an adaptive scale constraint is introduced into the dictionary learning process to obtain the spectral dictionary of the image to be denoised. Secondly， the spatial domain information of the image is utilized as prior knowledge for encoding， and the total variation-variational decomposition and augmented Lagrangian sparse regression methods are applied to solve the sparse coding of the image. Finally， the denoised hyperspectral image is reconstructed using the spectral dictionary and sparse coding. Experimental results demonstrate that， compared to existing hyperspectral denoising algorithms， the proposed method achieves superior performance on both simulated and real datasets.