Abstract:According to the structure of the InP diode, 3-D high frequency simulate software was adopted to create accurate physical model and matching circuits of the diode. Harmonic balance simulation was used to simulate the whole circuits. Based on this type of InP Schottky diode, a 270GHz zero bias detector was designed and measured for the first time in China. The measured responsivity is near 1600 V/W at 260 GHz, as well as 1400 V/W over 260～280GHz typically, which corresponds to typical noise equivalent power level(NEP)of 18 pW/ Hz1/2. The measured and simulated results are highly similar, indicating that this solution has the advantages of accurate, simplified and easily optimized.

Abstract:A 190~225GHz high multiplying efficiency frequency doubler was developed with discrete GaAs planar Schottky diode. The 50μm thick quartz circuit substrate is flip-chip mounted for diode thermal dissipation, as well as RF signals and DC grounding effectively. Diode embedding impedances were calculated by full-wave analysis with lumped port to represent the nonlinear junction for circuit matching. The doubler is self-biasing and fix-tuned. The highest efficiency of 9.6% and corresponding output power of 8.25mW were obtained at 202GHz with pumping power of 85.5mW. The typical tested efficiency is 7.5% in 190~225GHz. The multiplying efficiency features flat and broadband operation. The doubler reaches the state-of-the-art performance reported worldwide.

Abstract:The thermal crosstalk characteristics in high-power 808 nm AlGaAs/GaAs laser diode bar were investigated experimentally and theoretically using infrared thermography and finite element method. We have performed the steady-state and transient analysis. A detailed profile of thermal crosstalk in laser diode bar was presented in this paper. The steady-state temperature rise has a logarithmical dependence on the total operation current, and the thermal crosstalk between emitters increases with the current density. Furthermore, the transient thermal analysis suggested that the thermal crosstalk occurred mainly in chip. Using thermal resistance parallel connection model, we explained the phenomena that the time constant of chip decreased with the increase of total operation current.

Abstract:The temperature-and voltage bias dependent photocurrent spectra of very long wavelength GaAs/AlGaAs quantum well infrared photodetectors were studied by spectroscopic measurements and the corresponding theoretical calculations. It is found that the peak response wavelength will shift with the changing of voltage bias and temperature. With the assistance of band structure calculations, we proposed a model of the double excited states which explains the experimental observations very well. Meanwhile, the working mechanism of the quasi-bound state confined in the quantum well, including the processes of tunneling and thermionic emission, were also investigated in detail. Based on our model, two transition processes, including the ground state to the first excited state transition and the ground state to the continuous state transition have been separated from the photocurrent spectrum. The two normalized photocurrent spectra peak wavelength agreed reasonably well with the calculating results. The results allow a better understanding of bound-to-quasibound state transition and bound-to-quasi-continuous state transition and thus a better optimization of the QWIP performance.

Abstract:Silicon oxide(SiOx) films on GaN were synthesized at 75℃, using the inductively coupled plasma chemical vapor deposition(ICPCVD) with different radio-frequency chuck power(RF power). The physical and electrical properties of the deposited SiOx thin films were characterized by various methods. It is found that as the RF power increased, the films’ stress increased while the surface roughness and the film density increased. With optimized RF power, the SiOx/n-GaN metal-insulator-semiconductor(MIS) structures were fabricated. The electrical properties of the SiOx films were investigated by current density-voltage(J-V) and capacitance-voltage(C-V) measurements. The results show that the leakage current density is lower than 1×10-7A/cm2 at 90V, the minimum interface state density is 2.4×1010eV-1cm-2, indicating good electrical properties of ICPCVD deposited SiOx films.

Abstract:In order to improve the quantum efficiency of THz detectors made of p-GaAs homojunction, the effects of temperature and bias voltage were taken into account. By optimizing the materials and structure parameters of the resonant cavity enhanced p-GaAs HIWIP detectors, its quantum efficiency was increased to 17%. The relationships among the responsivity and detectivity of the detector, bias voltage, temperature and spectral frequency were simulated, leading to an optimized bias voltage range(10~40mV), an optimal temperature(< 8K) and a maximum detectivity(4.1×1010cm Hz1/2/W). By applying a pair of matched mirror, the ultimate quantum efficiency, the detectivity and the responsivity are 26%, 5.7×1010cm Hz1/2/W and 25.9 A/W, respectively.

Abstract:An interesting phenomenon of transient photo-voltage in the InGaAs p-i-n photo-detector induced by pico-second mode-locked lasers illumination was found. The response voltage presents an obvious negative valley after a rapid rising and a slow relaxation trailing. The amplitude of the negative and positive peak voltage increases with the fixed ratio about 20% with the linear characteristic of the photodiode, then the ratio decreases until the negative valley disappears with the pulse energy increasing with the nonlinear characteristic of the photodiode. By establishing the p-i-n equivalent circuit model and solving the RLC oscillation equation, the appearance and disappearance of the phenomenon can be explained by the non-negligible inductance and the increasing junction capacitance.

Abstract:Mn1.56Co0.96Ni0.48O4 thin films have been successfully deposited on Y-Al-O garnet(YAG) single crystal substrate via chemical solution method. X-Ray diffraction shows the films are of single spinel phase. Infrared spectrum characterization indicates the film has an obvious absorption band at 2.5~5μm. Moreover, the resistance-temperature dependence of the film was also studied. Using nearest-neighbor hopping model, we found that the characteristic temperature T0 is about 2530K and the temperature coefficient at 300K is about-3.66%K-1. All these results demonstrate that the MCN films deposited on YAG have potential applications in temperature sensors or near-infrared detectors under extreme conditions.

Abstract:Most materials in nature do not have electromagnetic response in the terahertz (THz) frequency range. THz metamaterials that were invented recently provide an opportunity for the development and application of THz technology. However, the conventional methods for modulating the THz metamaterials are complicated. In this paper, we present a novel and simple way to adjust the THz metamaterials just by zooming in and out the THz metamaterial’s unit. Simulation results show that THz metamaterials are still impedance-matching, even after the ratio change. In addition, the resonance frequency changes inversely with the unit ratio. Absorption bandwidth will be widened when the THz metamaterial’s unit is shrunk. According to our approach, any response frequency of THz metamaterials (a value of absorption peak is greater than 98%) can be acquired within specific frequency bands. This modulation simplifies the THz metamaterial design and broadens the applications of metamaterials in detectors.

Abstract:Thermal infrared hyperspectral imaging system is powerful at target detection and discrimination for its high spectral resolution. Advanced researches on these instruments have not been conducted in China. The relevant research works in the world including China were summarized and reviewed in this paper. The future development is prospected considering the undergoing research projects in China.

Abstract:The quasi-optical launcher is an important part of quasi-optical mode converter in high power gyrotron. The circular waveguide quasi-optical launcher was analyzed with the theory of geometrical optics. To form the Gaussian mode(TEM00) at the cut of the launcher, the coupled-wave theory was employed to design corrugated waveguide quasi-optical launcher. A high efficiency launcher has been designed for 140GHz, TE28,8 mode. Results show that total length of the launcher is only 205.2mm, and the cut length is 47.2mm. At the helical cut the scalar correlation efficiency of the Gaussian mode in the Brillouin zone is greater than 98%. The method can also be used for the designs of other frequency and mode gyrotron quasi-optical launcher.

Abstract:As anisotropy of land surface thermal emissivity (8~14μm) reduces the accuracy of the remotely sensed land surface temperature (LST) and its application, which is more important for urban surface, a kernel model was suggested in this paper to describe the urban surface emissivity anisotropy (USEA). The USEA is estimated by the ratio between off-nadir and nadir observed emissivity. The kernel model has two basic assumptions: (1) at daytime, USEA has apparent hot spot whose location approaches the sun’s location;(2) at nighttime, there is no apparent hot spot effect in USEA, but it has significant correlation with viewing zenith angle and weak correlation with azimuth angle. Three kernels named isotropic kernel, multi-scattering kernel, and temperature difference kernel constitute the kernel-based model, where the isotropic kernel is a constant equal to 1, the multi-scattering kernel describes the dependence on viewing zenith angle, and the temperature difference kernel describes the hot spot effect of USEA. Results, based on computer simulations, indicated that the kernel model can accurately describe the spatiotemporal variation of USEA but the thermal inertia of urban surface would reduce the applicability of the kernel model. The kernel model has many potential applications with MODIS directional land surface emissivity data.

Abstract:Conventional infrared spectral imaging detection can provide large amount spectrum information and has extensive applications, but it cannot provide spectrum tunablility with compact volume. A novel FET detector structure with electrically tunable plasmon absorption was proposed. Through electromagnetic simulation of infrared absorption variation with the structure parameters, more than 90% absorption is reached within specified spectral band under optimized condition for this kind of detector. When gate voltage is changed, the carrier concentration and complex refractive index vary simultaneously, which lead to obvious characteristics of tunable absorption. Based on this FET structure, uncooled infrared detector will have the ability of spectral imaging on one single chip, which opens a new route to miniaturization of spectral imaging systems.

Abstract:An accuratenoise model was established for the infrared imageinformation acquiring system.In the simulation and test, noise characteristics were analyzed. The results of the three are almost same, about 0.11mV. Both theory and experiment proved that signal conditioning circuit based on instrumentation amplifier can be used for low-noise infrared detectors. The noise level was analyzed together with the spectral characteristics of the circuit noise. The results show that the main components of the noise are 1/f noise and white noise. Both of the two meet the Gaussian distribution.

Abstract:Based on the analysis of the scanning procedure of single-sampling and over-sampling systems, we proposed a novel scanning image simulation method. The target energy gathering, clutter suppression, and dim target detection of single and over-sampling systems were performed in 3 different scenes, mild-cloudy, severe-cloudy, and cirrus-cloudy. Analysis and experiments indicate that over-sampling system has better performance at target energy gathering, clutter suppression, and dim target detection.

Abstract:It has an important application to blend multi-source remote sensing to generate high spatial-temporal resolution data. In this study, three spatial-temporal fusion algorithms were analyzed and compared with each other. They are spatial and temporal fusion method using high/low resolution time-series images(STIFM), spatial and temporal data fusion method based on decomposition of mixed pixels(STDFM) and an enhanced spatial and temporal adaptive reflectance fusion method(ESTATFM). The study area was located in Yingke irrigation districts. Temporal change information was detected from sequence MODIS and high-resolution spatial information was provided by ASTER/TM. Results showed that STDFM can make an optimal effect in red reflectance(r=0.91) and ESTATFM in near-infrared reflectance(r=0.71) which was compared with actual observations of ASTER. The blended NDVI from above three method were similar with r higher than 0.84. Results also indicate that ESTATFM is well adapted to the heterogeneous region, such as corn and wheat.

Abstract:As traditional target tracking based on compressive sensing has poor robustness in texture change, scale variation and illumination change, a real-time tracking algorithm using compressing sensing based on Gaussian differential graph was proposed. Firstly, Gaussian differential graph is acquired from multi-scale space of image. The features are extracted from the graph and taken as input signals of impressive sensing. Secondly, by compressing, dimension reduction, target neighborhood traversal, parameters update, the optimal search window is estimated. Thirdly, the search window is mapped onto the corresponding original image, and target tracking in the video sequences is finished. Gaussian differential graph had some characteristics such as single-channel, small grayscale range, low value, simple structure, small dimensions, which make the algorithm have strong robustness in scaling, texture and illumination changing. The real-time performance was inherited from the traditional algorithm. Experiments proved that with the proposed algorithm the moving target can be tracked quickly and accurately in a complex environment.

Abstract:A random finite sets(RFS) theory based joint detection and tracking algorithm was proposed for detecting dim small moving target and estimating its state parameters from scan image sequences. By analyzing the scan characteristics of shave-scan optical sensor, a target dynamic model and observation model were established, respectively. Then target state and measurements was described as a RFS variable. The joint detection and tracking problem was modeled as a Bayesian optimal estimation problem. Prediction and updating formulas of this algorithm were derived using RFS theory. The algorithm implementation problem was taken into account. A Gaussian mixture(GM) implementation is presented. Simulation results show that this algorithm can depress clutters strongly while has small influence on missing detections. It can accomplish the target detection and tracking task efficiently for shave-scan optical sensor.

Abstract:Anomaly detection is one of the most important applications in hyperspectral imagery. Real-time processing is the main issue we are facing due to the large data set. Real time causal processing algorithms were developed to perform anomaly detection. It is an innovational kalman filtering based processing by using Woodburys identity to update information which provides the pixel currently being processed without re-processing previous pixels. Experimental results demonstrated the proposed algorithm significantly improves processing efficiency in comparison with conventional anomaly detection without real time causal processing.

Abstract:A multi-channel multiplexing compressive sensing imaging approach based on compressive sensing is proposed for physical realizable remote sensing systems. First, multi-masks coded with random binary Bernoulli matrix are explored for different optical channels, and the undersampled data of an image are collected in an exposure time. Next, non-local similarity of spatial remote sensing images is presented as the regularization term for reconstruction to remove the reconstructed interference caused by local prominent features in remote sensing scene. The experimental results demonstrate the feasibility of this compressive remote sensing imaging. The proposed algorithm can preserve image details and achieve an effective image reconstruction compared with traditional algorithms.