Abstract:To solve the spectral demand and material design conflicts of multifunctional coupling and integration of optical materials， a collaborative design method based on ［TiAlN/Ag］²/TiAlN sequential structure film for visible transmission induction and infrared radiation suppression is proposed， interpreting the new principles and mechanisms of multifunctional coupling of sequential structure film materials. Meanwhile， its optical compatibility performance is characterized. It shows that the ［TiAlN （thickness of 30 nm）/Ag （thickness of 15 nm）］ ²/TiAlN （thickness of 30 nm） sequential composite film has the optical characteristics of band-pass selective transmission and mid-far infrared low radiation， which can better realize the multifunctional compatibility effects of perspective， shading， low radiation temperature control， and infrared stealth， and can be used in the radiation temperature control and infrared stealth application fields of special glasses such as military vehicles and green buildings.

Abstract:Vanadium dioxide materials， which show semiconductor-metal phase transition， can be used for protection of photoelectric detectors against laser blinding weapons. The structure， morphology and optical properties of vanadium dioxide thin films prepared by radio frequency magnetron sputtering at different temperatures were reported. The visible to infrared ellipsometric parameters of vanadium dioxide film at 20-100 were measured by an ellipsometer. The optical properties of vanadium dioxide films before the phase transition were obtained by Gaussian and Lorentz model， and the optical properties after the phase transition were obtained by adding a Drude model. The refractive index and extinction coefficient at varied temperatures between 300 nm and 1 700 nm were obtained. The transmittance spectra of 1 550 nm infrared laser at varied power densities show that the threshold power of phase transformation for the VO₂ film is about 12 W/cm²， where the transmittance decreases sharply from 51% to 15%-17%， and the switching rate is about 69%.

Abstract:A numerical calculation model of the narrow ridge waveguide was established based on the effective refractive index method. The relationship between the polarization characteristics and the transverse mode of the InGaAs quantum well narrow ridge waveguide semiconductor laser was studied experimentally. According to theoretical calculations， the effective refractive index difference of the TM-like mode in the ridge waveguide is larger in the direction of the slow axis. The confinement factors of the TM-like mode are larger than those of the TE-like mode， and the slow-axis high-order mode is more likely to appear. As the height of the ridge waveguide increases， the fast-axis high-order modes are truncated， and the confinement factor of the TE₀₀-like mode gradually increases to be similar to that of the TM₀₀-like mode. The slow-axis high-order mode is suppressed due to its large scattering loss， theoretically achieving high polarization， and near diffraction limit beam-quality laser output. In terms of experiments， a narrow ridge waveguide semiconductor laser with a high polarization extinction ratio and a fundamental transverse mode was fabricated by the gain polarization characteristics of quantum well materials and by designing the height and width of the ridge.

Abstract:The demand for high-speed response mid-wave infrared （MWIR） photodetectors （PDs） is gradually increasing in emerging fields such as free-space optical communication and frequency comb spectroscopy. The XB_nn barrier infrared photodetectors greatly suppress shot noise originated from the device dark current. In this work， InAsSb/AlAsSb/AlSb-based nBn and pBn barrier MWIR PDs were grown on GaSb substrates using molecular beam epitaxy （MBE）. The GSG PDs were fabricated to realize the radio frequency （RF） response testing. X-ray diffraction （XRD） and atomic force microscopy （AFM） results indicate that both epitaxial structures exhibit good crystal quality. The 90 μm diameter pBn PDs exhibit a lower dark current density of 0.145 A/cm2 compared to the nBn PDs operating at room temperature （RT） and a reverse bias of 400 mV， which indicates the uncooled barrier PDs perform with low noise. Capacitance tests reveal that the pBn PDs， operating at zero bias， show a fully depleted barrier layer and partially depleted absorption region， while the nBn absorption region also exhibits partial depletion. RF response characterization demonstrates that the 90 μm diameter pBn PDs achieve 3 dB bandwidth of 2.62 GHz at room temperature and under a 3 V reverse bias， which represents a 29.7% improvement over the corresponding nBn PDs， only achieving 3 dB bandwidth of 2.02 GHz. This signifies a preliminary achievement of uncooled barrier MWIR PDs capable of fast detection.

Abstract:In this paper， we investigated the crystal quality of Mercury Cadmium Telluride （HgCdTe） materials in the key avalanche region of avalanche photodiode detectors （APDs） with MWIR PIN structure. We simulated the entire process of the PIN APD device on the experimental materials and used differential Hall testing and differential minority lifetime testing to evaluate the material’s real crystal quality in the key avalanche area. It is found that the crystal quality of the avalanche region under the optimized process is good. Its Shockley-Read-Hall （SRH） lifetime is 20.7 μs， which can be comparable to that of the primary HgCdTe materials. This meets the development requirements for high-quality MWIR HgCdTe avalanche devices. Additionally， based on the obtained SRH lifetime in the avalanche region， we conducted corresponding two-dimensional numerical simulations on HgCdTe APD structural devices to determine the theoretically optimal dark current density of 8.7×10^-10 A/cm².

Abstract:Spectral polarization imaging technology is a novel optical imaging technique that not only enhances the amount of information acquired from targets， but also reduces background noise， which can capture target details and detect disguised targets. This paper presents a spectro-polarimetric device by integrating subwavelength gratings with Fabry-Perot （F-P） filter， which can obtain ultra-high spectral resolution and polarization extinction ratio with high control flexibly on both spectrum and polarization. A spectro-polarimetric filter （SPF） has been designed to obtain 4 spectral channels of stokes parameters simultaneously. Simulation results show that it has a spectral resolution （SR， ） of 217 and a polarization extinction ratio （PER） of . The polarization extinction ratio of subwavelength grating is measured to be over 500 PER with 90% transmission efficiency. The spectral resolution of all-dielectric F-P filter is measured to be 30 with 60% transmission efficiency in the long wave infrared band. The designed method is universal and can be used in a wide range of wavelength bands such as visible， infrared， and even terahertz. It has great potential applications in fields such as micro-polarization spectrometers and full-stokes polarization detection， benefiting from these advantages.

Abstract:A wideband low noise amplifier （LNA） covering the whole W-band in 0.1-μm GaAs pHEMT technology is designed. To reduce the inter-stage crosstalk and obtain wideband matching， a bypass circuit composed of dual shunt capacitors is proposed to provide wideband RF grounding. The wideband input matching and optimal noise matching are implemented by a dual-resonance input matching network. The measurement results exhibit a peak gain of 20.4 dB at 108 GHz. The measured small signal gain is 16.9-20.4 dB across 66-112.5 GHz. The measured noise figure （NF） is 3.9 dB at 90 GHz. The measured input 1-dB compression point （IP_1dB） is around -12 dBm in W-band.

Abstract:A dual-tunable "perfect" metamaterial absorber composed of a "Tian-zi"-shaped bulk Dirac semimetal （BDS） resonator and strontium titanate （STO） is proposed in this work and systematically studied by performing numerical simulations. From the acquired results， it is demonstrated that the absorber can achieve 99% absorption rate at 2.613 1 THz when the BDS Fermi energy is 40 meV and the STO temperature is 400 K. Moreover， both dynamics dual-tuning of the absorption frequency and absorption rate of the absorber can be successfully achieved by varying the BDS Fermi energy level and the STO temperature. Additionally， the absorber''s performance is theoretically analyzed using both coupled mode theory （CMT） and equivalent circuit model （ECM）. Finally， the changes in the absorber''s absorption spectrum are further discussed when each parameter of the model is modified， providing thus a solid theoretical basis for the design of dual-tunable filters and absorbers.

Abstract:In this paper， we demonstrated SiN_x/AlN/GaN metal-insulator-semiconductor high electron mobility transistors （MIS-HEMTs） with low noise and high linearity， by in-situ growth of SiN_x gate dielectrics on ultra-thin barrier AlN/GaN heterostructure. Deep-level transient spectroscopy （DLTS） shows a traps-level depth of 0.236 eV， a capture cross-section of 3.06×10^-19 cm^-2， and an extracted interface state density of 10¹⁰-10¹² cm^-2eV^-1， which confirms that the grown SiN_x can reduce the interface state. The devices exhibit excellent DC， small signal， and power performance， with a maximum saturation output current （I_dmax） of 2.2 A/mm at the gate voltage （V_gs） of 2 V and the gate length of 0.15 μm， a maximum current cutoff frequency （f_T） of 65 GHz， a maximum power cutoff frequency （f_MAX） of 123 GHz， a minimum noise figure （NF_min） of the device of 1.07 dB and the gain of 9.93 dB at 40 GHz. The two-tone measurements at the V_ds of 6V， yield a third-order intermodulation output power （OIP3） of 32.6 dBm， and OIP3/P_dc of 11.2 dB. Benefited from the high-quality SiN_x/AlN interface， the MIS-HEMTs exhibited excellent low noise and high linearity， revealing its potential in applications of millimeter waves.

Abstract:The absorption peaks of three cinnamic acid derivatives （CADs）： p-coumaric acid （PCA）， trans o-coumaric acid （OCA）， and 4-fluorocinnamic acid （4-FCA） were measured using terahertz time-domain spectroscopy （THz-TDS） in the range of 0.5-3.5 THz. To identify the origins of the THz absorption peaks in the three samples， the density functional theory （DFT） was employed along with the vibrational mode automatic relevance determination （VMARD） method. Additionally， the molecular force field energy decomposition analysis （EDA-FF） was used to analyze the forms of weak intermolecular forces in the molecular systems. Visualization analysis was conducted through the visualization of molecular dynamics （VMD） using atom coloring to study the contribution types and strengths of weak intermolecular forces by atoms in the molecular systems. This combination of THz-TDS， DFT， VMARD， and EDA-FF methods not only effectively distinguishes organic molecules with structural isomers or structural similarities but also provides valuable reference data for uncovering their biochemical functionalities.

Abstract:The high radiation intensity and weak self-absorption effect of the O₂（a¹?_g） airglow in the 1.27 μm band make it an ideal target source for retrieval of the atmospheric temperature in the near-space. Based on the theory of O₂ airglow spectral and the "onion-peeling" algorithm， the near-infrared limb-viewing data of the SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY （SCIAMACHY） were successfully used to retrieve the atmospheric temperature profiles in the range of 50-100 km. Comparison with SABER， ACE-FTS and LIDAR observations shows that the temperature measurement error is better than ±10 K in the tangential altitude of 55-85 km. However， in the space region below 55 km and above 85 km， the temperature retrieval results show significant bias due to the influences of self-absorption effects， atmospheric scattering， and spectral contamination from OH airglow.

Abstract:The correct use of the product is possible only when the land surface temperature （LST） data is calculated by an accurate and reliable inversion algorithm. In this paper， we compare the inversion results of five commonly used LST inversion algorithms based on Landsat-8， Landsat-9 data， and weather station data. The inversion results and parameter sensitivity analysis of different algorithms are tested. The results show that the inversion results of the Radiative Transfer Equation （RTE） and Single Channel （SC） algorithms calculated based on land surface emissivity （LSE） are in good agreement with the ground measured. The inversion results of the SC algorithm based on the atmospheric water vapor inversion and the Split Window （SW） algorithm based on the atmospheric water vapor inversion are higher than the measured temperature. The inversion accuracy of the Mono Window （MW） algorithm based on average temperature parameters is not ideal. In addition， the consistency of the inversion temperature of the two data on different ground objects is compared. Our study can provide a reference for land surface temperature inversion based on Landsat-9 data.

Abstract:The detection of ships and other sea targets is of great significance to sea surface management， national defense security， search and rescue， and other fields. Space-borne infrared remote sensing has a wide coverage ， which is an effective means to achieve wide-area detection of ship targets. Affected by the diurnal cycle of the solar zenith angle， the temperature difference between the ship and the sea surface changes periodically， resulting in a thermal crossover period twice a day in the ship detection scene on the sea surface. In this paper， taking the mid-latitude summer and winter sea surface environment as an example， the 24-hour infrared radiation characteristics of the sea surface ship detection scene are established， and a multi-spectrum optimal combination scheme is proposed， which is realized by the detection of dual detection spectrum bands of 3.50 -4.10 μm and 10.25-10.75 μm day and night continuous observation with signal-to-noise ratio better than 15. The proposed dual-spectrum detection method provides technical support for the application of wide-area all-time sea surface target detection.

Abstract:The spaceborne photon counting laser ranging radar system has significant advantages such as high repetition rate and high precision， but it also faces the problem of large amount of original data and high proportion of noise data. In order to adapt to the transmission capacity of the satellite data channel， it is necessary to compress the original data volume and ensure the recall rate of signal photons， so it is necessary to develop a hardware based real-time denoising algorithm. This article proposes a fast denoising algorithm that combines coarse and fine processing. Firstly， based on the laser emission pulse width， system noise rate， target characteristics， and local density information of received photon events， coarse denoising is performed to remove some noisy photons； then， using histogram statistics， fine denoising is performed on the retained photon events to determine the signal photon interval and the final signal photon and its time information. The algorithm is verified by Monte Carlo simulation and ICESat-2 measured data. The test results show that the recall ratio， precision ratio and harmonic average of the algorithm are more than 94%， 93% and 94% respectively， and the operational efficiency is improved by 10%. The algorithm can achieve fast and real-time denoising of photon events， providing a theoretical basis for real-time denoising processing of onboard hardware.

Abstract:Infrared small target denoising is widely used in military and civilian fields. Existing deep learning-based methods are specially designed for optical images and tend to over-smooth the informative image details， thus losing the response of small targets. To both denoise and maintain informative image details， this paper proposes a gradient-aware channel attention network （GCAN） for infrared small target image denoising before detection. Specifically， we use an encoder-decoder network to remove the additive noise of the infrared images. Then， a gradient-aware channel attention module is designed to adaptively enhance the informative high-gradient image channel. The informative target region with high-gradient can be maintained in this way. After that， we develop a large dataset with 3981 noisy infrared images. Experimental results show that our proposed GCAN can both effectively remove the additive noise and maintain the informative target region. Additional experiments of infrared small target detection further verify the effectiveness of our method.

Abstract:Chaotic dynamics is a significant systematic feature of infrared electromagnetic wavefields that requires further study. Understanding the chaotic dynamics of infrared radiation wavefields can lead to advancements in high-performance detection， imaging， and recognition of weak， moving， time-varying signals. To extract the time series of the dynamic system， we have established a 4D time-space observing system. We then use the FFT transform on a random time series of frequency-band infrared data to obtain the fractional Brownian motion dimension， indicating a fractal structure in the atmospheric infrared radiation wavefield. By using time-delay analysis， we construct a dimensional phase space and compute the fractal dimension. We also observe that the first Lyapunov exponent remains positive in different phase spaces， leading to the initial conclusion that the atmospheric infrared wavefield is chaotic. To measure the chaotic strength of real cases in the time-space domain， we use the permutation entropy. These results serve as a foundation for further research， such as understanding the dynamic evolution mechanism of moving objects and their background wavefields， capturing time-varying signals， and making long-term nonlinear predictions of infrared wave behaviors in different domains.

Abstract:Low noise is a key requirement of readout integrated circuit （ROIC） in hyperspectral applications for its low radiation. Correlated double sampling （CDS） is commonly used to suppress noise. In this paper， CDS is improved by adjusting the time interval between the clamp and sample-and-hold （SH）， which can filter low-frequency noise flexibly. A 640×512， 15 μm pixel pitch ROIC is designed and fabricated in 180 nm CMOS process. The input stage consists of low-noise capacitive trans-impedance amplifier （CTIA） and CDS with adjustable intervals （AICDS）. A timing generator is proposed to extend the CDS reset time from 0 to 270 clock cycles. By extending the reset time to decrease the time interval， the noise electrons are significantly decreased from 39 e^- to 18.3 e^-. The SPECTRE simulation and the experimental results corroborate that the proposed structure AICDS can optimize noise performance of hyperspectral ROIC， thus can be widely used.

Abstract:To investigate the mechanism of infrared radiation suppression on solid surfaces by spraying water film and to establish an accurate calculation method for infrared radiation， the theoretical and experimental research was conducted to study the influence of water film on the infrared radiation of solid surfaces. The results showed that in the 8-12 μm wavelength range， the infrared radiation characteristics of a solid surface covered with a water film （with a thickness greater than 100 μm） mainly relied on the infrared radiation emitted by the water film. An infrared radiation transfer model was developed to encompass solid surfaces covered by the water film， and the accuracy of commonly used calculation methods in the literature was analyzed. The error in calculating infrared radiation using the free surface temperature of the water film was less than 0.3%， while the maximum error in calculating infrared radiation using the temperature of the solid surface was 8.32%.

Abstract:High image quality is crucial for cell experiments in space， as it requires the ability of remotely monitoring to grasp the progress and direction of experiments. However， due to space limitations and environmental factors， imaging equipment is strongly constrained in some performance， which directly affects the imaging quality and observation of cultivated targets. Moreover， experimental analysis on the ground requires tasks such as feature extraction and cell counting， but uneven lighting can seriously affect computer processing. Therefore， a method called STAR-ADF is proposed， and experimental results show that the proposed method can effectively remove noise， equalize illumination， and increase the enhancement evaluation index by 12.5% in comparison with original figures， which has certain robustness.