Abstract:A method for judging the performance of image intensifiers is described and used for night vision devices. Based on the operating distance model， some factors affecting the detection ability are analyzed. The difference between test conditions for integral sensitivity， ultimate resolution and actual night vision environment is studied. The influences of night sky radiation spectral characteristics， spectral attenuation characteristics of atmospheric transmission， and spectral difference of background reflection characteristics on detection distance are analyzed. The shortcomings of traditional methods for judging the quality of the image intensifiers are sorted out. Figure of Capability （FOC） is proposed， which consists of signal-to-noise ratio， resolution tested in low illumination and low contrast， and technical features. The performance echelon and intergenerational of two major technology routes （including GaAs tubes and multi-alkali tubes） are analyzed with FOC， and one kind of Gen.3rd development route is designed. Experimental results show that FOC can accurately reflect the developing law of the technical route and grade of image intensifiers.

Abstract:The main factor affecting the vacuum life of the infrared detector Dewar is the internal material outgassing. The Langmuir adsorption model outgassing equation is used to calculate the vacuum lifetime， considering the outgassing mechanism and the long-term degassing procedure of the Dewar. An innovative method of changing the temperature at the end of the degassing procedure was proposed to obtain the outgassing activation energy. The outgassing rate was measured at different temperatures while simultaneously removing the influence of coverage on the outgassing rate. The outgassing rates at storage temperature and the rule of outgassing rate changing over time were deduced. The difference among the three Dewar outgassing activation energies obtained in different conditions was 8.8%. The heat load of the Dewar was tracked for two years to verify the method. The estimated error of Dewar''s vacuum lifetime was 7.2%. It is a non-destructive testing estimation method for the vacuum life of small and diverse Dewar.

Abstract:A 760 nm single-mode， wavelength-tunable Vertical Cavity Surface-Emitting Laser （VCSEL） for oxygen sensing has been reported. The design method and device fabrication results of the 760 nm VCSEL have been reported in detail. By analyzing the gain characteristics of AlGaAs quantum wells， the composition and thickness of the quantum wells were determined， and the VCSEL structure with a gain peak and cavity mode mismatch of 10 nm at room temperature was designed. The single-mode power of the VCSEL exceeds 2 mW when the operating temperature is 25 °C， the side-mode suppression ratio （SMSR） is 28.1 dB， and the full angle of the divergence angle is 18.6°. As the operating current increases， the divergence angle of the VCSEL laser increases， but the far-field is still a circular and symmetrical spot with a Gaussian shape. By tuning the operating temperature and operating current of the VCSEL laser， the single-mode wavelength of the VCSEL can be continuously tuned from 758.740 nm to 764.200 nm. The current tuning coefficient of the laser wavelength changes from 1.120 nm/mA to 1.192 nm/mA， and the temperature tuning coefficient changes from 0.072 nm/℃ to 0.077 nm/℃ when the VCSEL operates at 15-35 °C. The SMSR of the VCSEL laser reaches 32.6 dB and 30.4 dB near the two characteristic absorption wavelengths of oxygen.

Abstract:InAs DWELL quantum dot lasers were grown on GaAs（100） substrate by molecular beam epitaxy technology. The effect of Be doping in active regions on the performance of InAs quantum dot lasers has been studied. The results show that Be-doped in the active region could effectively reduce the threshold current density， improve the output power， and increase the temperature stability of the InAs quantum dot laser.The threshold current of Be-doped InAs quantum dot laser was reduced to 12 mA， and the corresponding threshold current density was 100 A/cm². The highest output power of the laser was 183 mW， and the highest operating temperature reached 130 ℃. This is of great significance for the application of InAs quantum dot laser device in the optical communication system.

Abstract:850 nm vertical cavity surface-emitting lasers are the core light source of the short-range optical interconnect. With the increasing demands for data center traffic， achieving NRZ modulated high speed error-free transmission is a hot current research topic. This paper designed and fabricated a high-speed 850 nm vertical cavity surface-emitting laser with six oxide limiting layers in a λ/2 short cavity. At room temperature， the -3 dB bandwidth was up to 23.8 GHz. Clear eye diagrams were obtained under the test conditions of 50 Gbit/s （1 m） and 40 Gbit/s （100 m）. Transmission tests showed that error-free transmission was achieved at transmission distances of 1 m and 100 m with transmission rates of 40 Gbit/s and 30 Gbit/s， respectively， by NRZ modulation without the use of pre-emphasis， equalization， and forward error correction.

Abstract:The structure of a novel ring-shaped top-DBR etched microstructure VCSEL with a proton implantation high resistance region was designed. A ring column structure was formed from the upper electrode to the active region， which directly generated a hollow laser beam output. The optical field distribution of the etched microstructure VCSEL was calculated by FDTD software， and the obtained ring-shaped patterns maintained the hollow beam characteristics under the different mode numbers. We fabricated the etched microstructure VCSEL with a lasing wavelength of 848 nm at room temperature and investigated its performance. The threshold current was 0.27 A and the peak power was up to 170 mW. The near-field patterns of different currents clearly displayed hollow ring-shaped spots. The distribution curves of far-field light intensity matched the characteristics of a hollow beam as well. This novel VCSEL provides a new approach for the development of hollow beams and even array devices.

Abstract:InGaAs photodetector is widely used in SWIR detection. Bi incorporation into InGaAs can reduce the bandgap， extending the detection wavelength. By controlling of the In and Bi compositions， the detection wavelength could be extended to over 3 μm from In_yGa_1-yAs_1-xBi_x， lattice-matched to InP. An In_0.394Ga_0.606As_0.913Bi_0.087 p-i-n photodetector is designed and its performance is numerically investigated. Dark currents and responsivity spectra are calculated with different temperatures， absorption layer thicknesses and doping concentrations. A 50% cutoff wavelength of 3 μm is achieved. The proposed structure provides a feasible way to fabricate InGaAsBi based SWIR detector with longer detection wavelength.

Abstract:Near-infrared light-driven terahertz modulators are an important component in terahertz/infrared fiber-optic hybrid communication systems. Here， a near-infrared driven terahertz modulator based on silver nanoparticles/carbon quantum dots （Ag NPs/CDs） is proposed. Experimental results show that the combination of silver nanoparticles （Ag NPs） and carbon quantum dots （CDs） induces quantum size effect and dielectric confinement effect of nanoparticles， and the absorption of NIR light by silicon substrate can be enhanced by using Ag NPs/CDs to achieve NIR-driven terahertz wave modulation. The terahertz transmission characteristics of the sample were characterized in the range of 0.22-0.33 THz with the 808 nm NIR modulation excitation source， and the modulation depth of the Ag NPs/CDs NIR terahertz modulator could reach about 83% compared with the reference silicon substrate， which was significantly higher than the modulation depth of the reference silicon substrate （~54%）， realizing the terahertz wave modulation with large modulation depth. This research work has important applications in terahertz/infrared fiber hybrid communication systems.

Abstract:In this work， high-efficiency AlN/GaN metal-insulator-semiconductor high electron mobility transistors （MIS-HEMTs） have been fabricated for millimeter wave applications. A 5-nm SiN_x insulator is grown in-situ as the gate insulator by metal-organic chemical vapor deposition （MOCVD）， contributing to remarkably suppressed gate leakage， interface state density and current collapse. The fabricated MIS-HEMTs exhibit a maximum drain current of 2.2 A/mm at V_GS=2 V， an extrinsic peak G_m of 509 mS/mm， and a reverse Schottky gate leakage current of 4.7×10^-6 A/mm when V_GS = -30 V. Based on a 0.15 μm T-shaped gate technology， an f_T of 98 GHz and f_MAX of 165 GHz were obtained on the SiN/AlN/GaN MIS-HEMTs. Large signal measurement shows that， in a continuous-wave mode， the MIS-HEMTs deliver an output power density （P_out） of 2.3 W/mm associated with a power-added efficiency （PAE） of 45.2% at 40 GHz， and a P_out （PAE） of 5.2 W/mm （42.2%） when V_DS was further increased to 15 V.

Abstract:The transmission line structures such as coplanar waveguide （CPW） and microstrip ring resonator （MRR） were designed on a high-purity quartz substrate （99.9997%） with a thickness of 127 μm. The average insertion loss for the CPW line varied from 0.096 to 0.176 dB/mm in the frequency range of 40-110 GHz. Furthermore， the relative permittivity and loss tangent of the quartz were extracted by the MRR method. The relative permittivity of the quartz substrate in the V-band and W-band ranged with 3.7-3.85 and 3.85-4， respectively. The loss tangent value was approximately 0.004 in the V-band and 0.004-0.006 in the W-band. The performance comparison with other substrates shows that this high-purity quartz has excellent and stable electrical properties and its potential for designing high-performance passive and packaging structures.

Abstract:Semiconductor heterostructures have great ability to bind carriers and the potential to produce high power terahertz radiation. However， the intensity of terahertz radiation is substantially reduced， due to the interference effects of incoherent oscillations of plasma in the heterostructure. Thus in the AlGaAs ） multilayer heterostructure， it is able to adjust the absorption coefficient of the narrow band-gap layer by adjusting the aluminum molar fraction， which makes the excitation carriers number in each narrow band-gap layer approximately the same， achieving the goal of almost completely eliminating the interference effects. Based on the AlGaAs multilayer heterostructure terahertz radiation model， the properties of broadband terahertz radiation are studied with the numerical calculations， the quantitative relationships between the pump laser pulse width and the generated terahertz pulse are obtained， and the influence of pump laser pulse parameters on the parameters of generated terahertz pulse is also analyzed. This study provides a reference for the development of broadband terahertz radiation sources based on the semiconductor.

Abstract:A novel resonator has been proposed for the klystron that operates at mode. The electric fields of both the middle cavity and the side cavity are effectively enhanced by discretizing the field in the side cavity. The novel resonator demonstrates a higher characteristic impedance than the traditional barbell shape cavity when both cavities operate at mode. Sensitivity analysis has been performed on these two kinds of cavities. Moreover， an RF circuit in the W-band has been designed based on the proposed novel cavity. The RF circuit can achieve a high gain of 52.4 dB and a peak output power of 7.8 kW when 45 mW input power is injected. The circuit is driven by a 25 kV and 2 A pencil beam. The electronic efficiency and 3-dB bandwidth are 15.6% and 120 MHz， respectively.

Abstract:A dual-polarized active phased array antenna module is presented for 5G millimeter-wave communications. The array antennas and multi-channel beamforming chips are printed and implemented on the top and bottom layers of the multilayer PCB （2 mm thickness）， respectively. Besides the interconnection of the antenna and chip， power supply and digital control are realized within the middle layers of the multilayer PCB. The measured results show that the beam-scanning range larger than ± 40 degrees （power level declines smaller than 3 dB） and normalized cross-polarization level smaller than -18 dB are both achieved in E- and H-planes. Besides 42.6-45.7 dBm and 43.5-46.1 dBm transmitting equivalent isotropically radiated powers （EIRPs） for V polarization and H polarization are realized respectively.

Abstract:Mismatch elimination is an important means of improving the accuracy of feature matching. Due to the large amount of data， texture duplication， light intensity changes， and other characteristics of satellite-borne optical remote sensing images， the performance of existing mismatch elimination methods is degraded. To solve this problem， a method based on local and guided global geometric constraints is proposed to eliminate mismatches. Based on the initial matching set， local consistency of features is used to filter out mismatches. Then， according to the transformation relationship between images， a feature topological structure is constructed， and its geometric attributes are extracted to describe structural similarity. Based on this， a feature global structure consistency constraint model is established， and residual mismatches are eliminated by deriving the optimal solution of the model. A guided matching strategy is adopted for global constraint， and matching points with high local consistency are selected to form a high internal point rate matching set， which is applied as the feature global neighborhood to improve the robustness and efficiency of the algorithm. The experimental results show that， in comparison with existing methods， the proposed method has better matching performance for satellite-borne optical remote sensing images， with an average accuracy and recall of 0.9 and 0.89， respectively. It is robust on the initial matching set with different internal point rates， and the average F score is 0.86.

Abstract:In order to solve the problem of detecting infrared small targets of unknown size in complex background， an infrared small target detection algorithm based on the clustering idea is proposed. First， the original infrared image is preprocessed by using small target morphological features to generate a new density feature map. Secondly， the potential candidate targets are coarsely localized with an improved density-peak clustering algorithm. Then， the local candidate sets of potential targets are constructed. A weighted fuzzy set clustering algorithm is used to finely segment the target and background regions of the image block， and then the difference between the target and background is adopted to suppress false alarms while enhancing the target. Finally， an adaptive threshold is applied to the processed local candidate set to extract the real target. Experimental results show that the proposed algorithm has good robustness and detection performance for small targets of unknown size in comparison with the other seven methods.

Abstract:Sub-pixel mapping technology can analyze mixed pixels and realize the transformation from fractional images to fine a land-cover mapping image at the sub-pixel level. However， the spectral information used by the traditional sub-pixel mapping methods is usually constructed in a specified rectangular local window， and the spectral information of all bands is rarely used， affecting the performance of sub-pixel mapping. To solve this issue， sub-pixel mapping based on spectral information of irregular scale areas （SIISA） for hyperspectral images is proposed in this paper. The experimental results on three remote sensing images show the proposed SIISA outperforms the existing sub-pixel mapping methods.

Abstract:Infrared point target detection is one of the key technologies of the infrared guidance system. On the one hand， due to the long observation distance， the point target is often submerged in the background clutter and large noise in the process of atmospheric transmission and scattering， and the signal-to-noise ratio is low. On the other hand， the target in the image appears in the form of fuzzy points， so that the target has no obvious features and texture information. Therefore， due to these two factors， infrared point target detection becomes intensely difficult. In order to address the issue， the relevant algorithms of point infrared target detection are studied， and a combination algorithm of non-convex rank approximation minimization algorithm and the modified random walker algorithm （NRAM-MRW） is proposed， which has a better detection effect of point infrared target detection under complex background.

Abstract:Accurate， robust， and fast feature representation and automatic registration are urgent needs for far infrared image in aerial scenes. Since the existing Multiple Line Descriptors （MLD） have the problems of “isolated feature” and “limited scale transformation”， thus a feature description method that combines feature points and line descriptors partition statistics is proposed. This paper refers to the feature descriptor as the Segmented MLD （sMLD）. Combining the characteristics that sMLD feature connect with each other to form a mesh topology structure， a coarse-to-fine branch accelerated matching （RF-BA） algorithm is also proposed. The RF-BA coarse matching improves the matching efficiency by making full use of the topology structure and local optimal algorithm. The RF-BA fine matching improves the registration accuracy by using the minimum circumscribed convex quadrilateral principle and GMS verification principle. Experimental results show that compared with other existing registration methods， the method has better performance in terms of registration accuracy and running time.