Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335
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Abstract:ZnMn codoped BaTiO3 films were fabricated on Si (100) and LNO/Si (100) substrates by a solgel procedure. In order to study the effects of different doping levels on the microstructure and ferroelectric phase of BaTiO3 thin films, BTO films doped with Zn and Mn, respectively, were also investigated. Both the characterization of Xray diffraction (XRD) and atomic force microscope (AFM) indicate uniform and dense films with average grain size under 30 nm. By comparisons of the optical constant refractive index and extinction coefficient of BaTiO3 films in the wavelength from 400 nm to 700 nm, it was obtained that there is a change in the optical band gap due to the different amount of Zn and Mn added. Furthermore, a better defined PE loop with a remnant polarization of 11.26 μC/cm2 shows that Zn and Mn dopanting play an essential role in ferroelectric improvement.
Abstract:To achieve relatively high frame rates with relatively low costs, a Tshaped terahertz imaging system with beamscanning function is presented. The system employs two orthogonally oriented copolarized scanning fanbeam antennas arranged in a Tshaped configuration. Both transmitting and receiving antennas consist of a pyramid horn feed, a fixed elliptical mainreflector to generate thin fan beam, and a rotating subreflector to realize beam scanning function, all of which are embedded between two parallel metal plates. In this paper, specific design details of such a system were discussed, especially for the systematic method proposed to design a fanbeam scanning antenna with high performance. In addition, some experimental imaging results were shown, which demonstrated the capability of the system.
Abstract:An atmospheric transmittance model for molecular oxygen absorption band near 762 nm is expressed by a polynomial including temperature and pressure. The polynomial coefficients are expressed as another power series of cosine of incident angle. Similarly, a mean atmospheric transmittance model is also given. Numerical tests indicate that under vast majority of circumstances the fitting errors (RMS) of the atmospheric transmittance model and those of the mean atmospheric transmittance model are less than 0.0001 and 0.0005, and their maximal errors are less than 0.0005 and 0.003, respectively. Both models were applied to the study on remote sounding of atmospheric pressure profile from space. In addition, a correction method is given for the interval error of atmospheric transmittance.
Abstract:Thermal effect on phase masks in wavefrontcoded athermalized imaging systems is analyzed. Several wellknown oddsymmetric phase functions at different temperature are derived. The properties of phase functions suffering from thermal effect are presented. The performances of the phase functions are evaluated with and without considering thermal effect by numerical simulation. The results show that the similarity of outoffocus MTFs and recoverability of blurred encoding images of the wavefrontcoded athermalized system are degraded severely by the thermal effect.
Abstract:The response of photoconductive HgCdTe detectors to the irradiation of CW bandoff laser was studied. It was found that there is a point of inflexion, T0, on the temperature dependence of the voltage response of the detector. The voltage response increases with temperature for temperature of the detector T＜T0, and decreases with temperature for T＞T0. Two time scales are found to be due to the two thermally resistive bonding layers. The inflection temperature is determined by the impurity concentration. For temperature T＜T0, the temperature dependence of the voltage response depends on the variation of mobility of the carrier , whereas T＞T0, thermally generated carriers contribute to the voltage response.
Abstract:Ultrahigh vacuum scanning tunneling microscopy（STM） and spectroscopy （STS）were used to characterize Hg1-xCdxTe grown by liquidphase epitaxy (LPE) method. The sample was etched with 3% Brominemethanol in 2.5 minutes. The STM images display submicrometersized pit structures with depths ranging from a few tens to a few hundreds nanometers. The scanning tunneling spectra show a larger apparent gap than the energy band gap of the bulk material due to the tipinduced band bending effect. In contrast, the scanning tunneling spectra of the pits show a finite slope through zero volt, implying the contribution of high density of band gap states which blur out the band gap information.
Abstract:The imperfects in the wafer structure of high power 1060 nm diode laser, which prevents the improvement of laser power, was analyzed. Base on the analyzing results, the quantum well and the waveguide form were optimized. The relationship between waveguide width and laser power was simulated. According to the distribution of various modes, the position of quantum well was optimized and an asymmetric wide waveguide structure was designed. The calculation results of confinement factor for various modes show that the optimized asymmetric waveguide structure could increase the loss of high order modes while decrease the confinement factor of fundamental mode.
Abstract:The electronic structure and properties of zinc blende InSb codoped with Ga and N have been investigated by means of the density functional theory based on firstprinciples pseudo potential calculations. It is found that single species of N or Ga doping has a small effect on the band gap of InSb. With Ga and N codoped into InSb, its band gap is changed remarkably with the increase of codoping level of Ga/N.
Abstract:The total noises of focal plane array sensors, readout circuit and their coupling noise were theoretically analyzed. The temperature and integral time dependence of the noise were measured and analyzed for large perimeterarearatio of extended wavelength InGaAs FPA (38×500 μm2). The experimental results show that in certain conditions, FPA noise is not proportional to the square root of integral time. The relationship between FPA noise and dark current at different temperature were studied. Results show that the noises mainly come from 1/f noise and the current noise at the input stage of readout circuit.
Abstract:Unusual spectral lines of the 43 vibration state transitions of DF molecules and the 32 vibration state transitions of HF molecules have been observed in the DF/HF lasers operated with cold pumping reaction. Several typical spectrums were given, and the gain coefficients of these fundamental spectral lines of the high vibration state were calculated. Experimental results and theoretical calculations have shown that the kinetics process of these lines can not be explained by the cold pumping reaction only. The fluorine atom recombination and hot pumping reaction subsequently may be the main factors. The influences of hot pumping reaction and chain pumping reaction on the emission spectrum, gain and gain zone length of DF/HF lasers operated with the cold pumping reaction were discussed.
Abstract:Timing system was used to measure the timeofflight(TOF) of laser pulse in light detection and ranging(LIDAR). Performance of a LIDAR system is directly influenced by the properties of the timing system. A timetodigital converter(TDC) based on FPGA was designed for photoncounting LIDAR. By integrating the delay line interpolation into FPGA, the designed TDC could measure the TOF with fine accuracy and resolution. The performance of the TDC and its application in photoncounting LIDAR were analyzed and studied experimentally. Eventtiming of 9 channels was implemented with this TDC, with a resolution of 29 ps and a timingaccuracy of 37 ps. Using a LIDAR system equipped with the TDC, threedimensional imaging can be realized with time accuracy of 421 ps and 6.3 cm resolution in space.
Abstract:Integrate imaging technology, spectrum technology and microscope, a novel molecular hyperspectral imaging (MHSI) system based on AOTF (acoustooptic tunable filters) was presented. The system was used to capture hyperspectral images of rat retinal sections selected from three groups: normal(N), diabetic(D), and EPOtreated(E0). By processing hyperspectral images data of 30 samples, single band images and the pseudocolor images of N、D、E0 group are gained. Typical spectra curves of the ONL cells of N、D、E0 are extracted. By analyzing these images, descending order of the ONL thickness is N、E0、D. The experimental results cite that the ONL thickness of E0 group will be increased after EPO treated. By analyzing these spectrums, transmission intensity of D group is generally higher than that of N group in the spectral field from 550 nm to 1000nm and transmission intensity of E0 group is in the middle of D and N. By analyzing spectrum relations, results show the spectral signature of the E0 group was more similar to that of N than that of D to N. The above results suggest EPO may prevent cell apoptosis and has protective effect on rat DR at a certain level. MHSI system may probably provide a potential approach to researching pathogenesis、causes of blindness and drug efficacy of DR in future.
Abstract:A new type of symmetrical metalcladding optical waveguide structures is proposed. The guiding layer that supports the oscillating field is submillimeter scale and severs as the sample room. The waterbased Fe3O4 magnetic fluid with a volume fraction of 0.15% is injected into the sample room. The ultrahigh order modes are excited by a 860 nm laser beam on the structure with small incident angle (＜5). Owing to the strong concentration of the magnetic field, the sensitivity of the ultrahighorder modes is very high. The rise and fall time of magnetic fluid is 2 ms when 10 mT magnetic field is applied.
Abstract:An inverse synthetic aperture radar (ISAR) imaging method based on motion compensation of a moving target was presented. The concept of radar imaging was applied to the process of moving target detection with low signal to noise ratio(SNR). The lateral and radial velocity of the target can be acquired by means of imaging processing. The location of the moving target and estimation of its crosssectional area could be fulfilled using the multibaseline image interferometric method. The geometric model for imaging moving target was established. A method for the compensation of signals from channels of multi antenna time division multiplexing (TDM) receiver was proposed. The unambiguous angle orientation based on multibaseline phase unwrapping was presented. The influence of the image SNR on interferometric orientation accuracy was analyzed. The validity of the proposed method was testified by both simulation and an example of its application.
Abstract:A fast CayleyMenger determinantbased endmember extraction algorithm for hyperspectral unmixing was proposed. The algorithm is to find the simplex enclosing the hyperspectral data with minimum volume. It improves current simplexbased algorithms in several aspects. The introduction of CayleyMenger determinant makes it easy to use features of Hermite matrix to accelerate the searching process and gives a stable result finally. Moreover, a dimensionality reduction transform is not necessary in this algorithm, which will avoid the loss of useful information during the dimensionality reduction. The experimental results on synthetic and real hyperspectral dataset demonstrated that the proposed algorithm is a fast and accurate algorithm for the hyperspectral unmixing.
Abstract:Estimating the content of soil organic matter (SOM) using hyperspectral remote sensing is an inevitable requirement for precision agriculture. In this study, averages of spectral reflectance and first derivative of 791 sample pieces were measured in the visible and nearinfrared (350~2500 nm) bands, which belong to five different soil types from four provinces, including phaeozem in Heilongjiang, alluvial soil in Henan, paddy soil in Sichuan and Zhejiang, purple soil in Sichuan and Zhejiang, and seashore saline soil in Zhejiang. The correlation coefficients between organic matter content and spectral reflectance were calculated, while the characteristic spectral bands mentioned in precedent researches were summarized. The results show that 600~800nm can be used as common characteristic bands of these different types of soils from different regions in the study, which is important for building the universal model for soil organic matter with alternative parameters. Another conclusion is that above 2% in SOM is not necessary for predicting SOM.
Abstract:active andA new semiempirical model is presented for soil moisture content retrieval, using ENVISAT ASAR and LANDSATTM data collaboratively. Firstly, a back propagation(BP) neural network algorithm(GA) is introduced, and a genetic algorithm is applied to optimize the weights of the node of BP neural network. Then the TM bands (TM3, TM4, TM6) and ASAR data(VV, VH, VH/VV) are taken as the input of the GABP neural network, and the output corresponds to the ground soil moisture. The partial field measurements of soil moisture are used as training samples to train the network and to achieve the map of soil moisture distribution. The field measurements are used to test the validity of the BP neural network algorithm and effectiveness of the active and passive remote sensing cooperative inversion. The comparison between the inversion using single data set(TM or ASAR), and the cooperative inversion of active and passive remote sensing data demonstrates that the new algorithm is more effective, and shows considerable potential in soil moisture retrieval by integrating active and passive remote sensing data. passive remote sensing; GABP neural network; soil moisture; inversion
Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335