Abstract:An experimental study of the minority carrier lifetime in a finite base HgCdTe n -on-p photodiode using pulse recovery technique (PRT) is presented in this paper. The reverse recovery storage time (ts) is functions of the forward current IF and reverse current IR. Average minority carrier (electron) lifetimes (τn) calculated from ts and IF/IR strongly increases with decreasing ratio of the base thickness to the diffusion length. The minority carrier (electron) lifetime extracted from the conventional theory is approximately 28 ns at 77 K, much less than the value of 51 ns obtained when short base effects are considered in the analysis. This reveals that the base thickness of the photodiode is an important parameter for the minority carrier lifetime measurement using PRT. The infinite base assumption is valid only if the base thickness is larger than about three times the diffusion length of minority carriers.

Abstract:A novel adaptive scene-based nonuniformity correction method for fixed-pattern noise removal was put forward. It is based on the multiframe registration and estimation of global translation between several adjacent frames. The resulting mean square error function was optimized making use of the least mean square algorithm. Combining the local variance of an error function with the correlation peak value, the convergence speed can be controlled adaptively. The proposed method takes advantage of the correlation of adjacent frames sufficiently, thus it can provide enhanced results for diverse simulated and real infrared image sequences with nonuniformity. The experimental results show that the accurate estimations of the nonuniformity parameters of each detector in a focal plane array speed up the convergence, meanwhile, retain few ghosting artifacts.

Abstract:The noise of HgCdTe medium-wave photoconductive devices was studied by vibration text table and spectrum analyzer. The random vibration experimental results showed that the noise measured in vibration environment increased linearly with the increase of vibration power spectrum density (PSD).The linear dependence can be divided into two parts. The coefficient is 32 μVHz1/2/g2 or 80 μVHz1/2/g2 with the vibration PSD of 0.01 g2/Hz as the kink point. In order to explain the experimental results, we suggested that the vibration energy is absorbed with a certain coefficient by HgCdTe material and transformed into thermal energy. This gives rise to an increased scattering of charge carriers by the phonons in the material, eventually produces an extra vibration noise in the device.

Abstract:The zero-field spin splitting and Zeeman splitting in the In0.53Ga0.47As/In0.52Al0.48As quantum well (QW) were extracted by a Shubnikov-de Haas oscillations (SdH) beating pattern analysis under different tilt angles between QW plane and external magnetic field. It is found that the zero-field spin splitting Δ0 increases with increasing carrier concentration while the effective g-factor |g*| decreases. The further calculation indicated that the decrease of |g*| with concentration is ascribed to the nonparabolic effect of the band structure.

Abstract:The micro/nano-scale Bi3.15Nd0.85Ti3O12/Si-MCP (BNT/Si-MCP) ferroelectric thin film arrays were fabricated successfully by the sol-gel, spin-coating and pumping filtration methods. Precursors of BNT were coated on the inner wall of Si-MCP. Bi3.15Nd0.85Ti3O12 thin film supported by Si-MCP were prepared via annealing in oxygen atmosphere at 600℃, 650℃, 700℃ and 750℃, respectively. The ferroelectric properties and microstructures of BNT/Si-MCP film arrays were characterized. The results show that with the increase of annealing temperature, the size of BNT grain localized on the inner wall of Si-MCP increases, the uniformity of the surface and the degree of orientation along the c-axis increase, too. The largest remanent polarization (93.8 μC/cm2) and lowest leakage current of the micro/nano-scale BNT/Si-MCP arrays were obtained annealing at 750℃.

Abstract:The pure metal thin films were fabricated on the F doped SnO2 conductive glass(FTO) substrates by DC magnetron sputtering at room temperature. Then the VO2 /FTO composite films were annealed in furnace. The structure and optical properties of the composite films were analyzed by instruments. Results show that FTO on the glass does not change the preferred orientation growth of VO2 thin films, but significantly change its surface morphology characteristics. Compared with the VO2 thin films that were prepared on glass substrates with the same process conditions, the phase transition temperature of the VO2 /FTO composite films is decreased about 18℃, the width of thermal hysteresis is narrowed by about 4℃, and the infrared transmittances before and after phase transition are 42% and 21% respectively. It suggested that the composite films can reduce the phase transition temperature, limit the thermal hysteresis loop as well as enhance the infrared light modulation capabilities of VO2 thin films.

Abstract:The CdS thin films were prepared on ITO, FTO and AZO substrates by RF magnetron sputtering technique and chemical bath deposition technique. The morphology, structure and optical properties of all samples were characterized by the scanning electron microscopy, X-ray diffraction and ultraviolet-visible spectroscopy. The results show that the microstructure of CdS thin films dependent on the type of substrate by different deposition techniques, the grain size is larger by chemical bath deposition technique, but the surface are relatively rough. All the prepared CdS thin films show a mixed phase structure of cubic and hexagonal. The diffraction peaks by sputtering is clear, sharp, and the crystalline is better than chemical bath deposition technique. The optical transmittance of CdS thin film by chemical bath deposition technique is inferior to those of CdS films by sputtering, but the advantage in the short wave direction is clearly.

Abstract:The design and simulation of polarization beam splitter(PBS) for Y type two-dimensional photonic crystal with the same beam splitting radius are presented. It is based on the different properties of the light waves with different polarization modes propagating in the two-dimensional photonic crystal. The function of the PBS were numerically simulated and analyzed using the finite difference time domain ( FDTD) method. It is shown that parallel splitting with high efficiency for TE and TM modes can be achieved. The transmission probability can reach over 97% for TE mode and over 93.5% for TM mode for a Gaussian pulse light with a wavelength of 1.55 μm. The size of the splitter is only 6.3 μm × 6.8 μm. Owing to these excellent features，the PBS is a promising candidate in the future photonic integrated circuits.

Abstract:Based on grating electromagnetic theory, initial values of the grating groove were computed with grating equivalence rule. The design was then optimized with the diffraction efficiency contour method. Gratings of arbitrary groove shape with a geometry symmetry center can be designed in this way. As examples, four kinds of groove gratings were designed and fabricated with groove shapes of sine, rectangle and trapeze. The peak efficiency of TM mode for sine groove grating is 95% theoretically and 92% experimentally in C band.

Abstract:According to the theory of the stereo mapping based on three-line, the simulation of three-line satellite images for cloud-top height retrieval is presented. The matching method SIFT was improved, and the cloud top height was retrieved by the improved SIFT and forward intersection. The correctness of the simulated three-line satellite images was verified and a new way was explored to retrieve the cloud top height in low light condition at night. Finally, the sources of the errors in the cloud top height were analyzed in detail. A new method was given to eliminate the error caused by cloud motion.

Abstract:We derived object temperature from emissivity spectrum using the emissivity normalized method and discussed the feasibility of recognizing objects using ground object thermal infrared spectra. The results show that the emissivity normalized method based on thermal multispectral data can invert object temperature and emissivity spectrum efficiently. It means that inversion of emissivity spectra can be effectively applied in feature recognition, especially for different soil properties.

Abstract:Performance of the matching method which directly using SIFT feature points needs to be improved. This paper proposed an improved SIFT matching method which firstly uses the scale ratio histogram of the matched feature points to estimate the approximate scale ratio k of the image pair, then increases the base scale up to k times and extracts featur points points again for the higher resolution image, finally performs feature matching again to obtain the result. The experiment results show that, compared with the existing improved SIFT matching methods with scale difference, performance is improved significantly for structured image pairs.

Abstract:This paper presents a study of Smith-Purcell (SP) radiation properties with the particle-in-cell (PIC) simulation. The model supposes one-dimension (1D) dielectric cylindrical photonic crystal driven by a single electron bunch and a train of periodic bunches, respectively. The results show that the radiation from a single electron bunch is enhanced by increasing the dielectric constant and layers of the photonic crystal. The terahertz (THz) coherent SP radiation is obtained by exciting the photonic crystal with periodic electron bunches. The coherent radiation strength is improved by choosing proper operating parameters.

Abstract:In order to obtain precise attitude calculation for FY-2 in regional observation, the model of FY-2 full disk infrared images is established. The key parameters for FY-2 attitude calculation resolved from the model is validated. In the regional observation, distance-based algorithm is presented, and the results meet the requirements of precision.

Abstract:Atmosphere profiles obtained from atmosphere radiation measurement (ARM) were used to correct the AMSR-E data of the same time and site. Comparison between MVIs computed by the brightness temperatures before and after atmosphere correction proved the reasonability of the atmosphere correction. Atmosphere correction was applied to the AMSR-E data for a selected day with atmosphere data obtained from MODIS and MLS. The results showed the algorithm developed in this paper was reliable.

Abstract:The SST operational retrieval algorithm has been derived and validated for FY-3A. Using long time series of in-situ measurements data and coincide/collocated FY-3A VIRR sensor data collected in the Bohai Sea and northern Yellow Sea, we proposed a split-window algorithm suitable for FY-3A VIRR SST retrieval. Validation against independent data shows the mean deviation between satellite and matchup in-situ measurements was 0.78 ℃ with a RMSE of 0.93.

Abstract:The Closely Spaced Objects (CSOs) unity is treated as an extended target with a random vector and a random matrix to respectively represent the kinematic states of the centroid and the extension state. Then the Gaussian inverse Wishart implementation of extended-target PHD filter is utilized to track CSOs under clutter and miss detection. New recursive expressions are given for the ill modeling of the original GIW-PHD filter. Consequentially, multiple (shape) models can be easily incorporated with the modified GIW-PHD filter to handle extension changes caused by splitting and merging of CSOs. The effectiveness of the proposed method is demonstrated by simulations. Simulation results show that the proposed method not only improves the estimation precision of the states, but also more sensitive to the extension changes of CSOs compared with the original GIW-PHD filter.