Abstract:A sub-10 μmInGaAs (IGA) focal plane array (FPA) , with cut-off wavelength of 2.6 μm has been developed.The pixel pitch is reduced significantly comparing with that of reported extended wavelength IGA FPAs.To verify the feasibility of technology, the performance of sub-10 μm IGA FPA was tested and compared with 30 μm pixel pitch IGA FPA, which was fabricated from the same epitaxial material.The sub-10 μm IGA FPA exhibits high performances in terms of dark current (0.45 nA @VR= 10 mV) and R0A (14.7 Ω·cm2) at room temperature.Its quantum efficiency can reach 63%.The comparable performances to 30 μm pixel pitch IGA FPA illustrate that the sub-10 μm IGA FPA fulfils the needs of large formats (> 1K × 1K) and high densities in extended wavelength IGA detectors.

Abstract:GaSb-based DBR lasers with high-order Bragg gratings are fabricated without complex process.The16 th-order and 24 th-order Bragg gratings are fabricated with double-trench ridge waveguide by using standard contact optical lithography respectively.The 16 th-order Bragg grating laser achieves single longitudinal mode continuouswave (CW) operation at room temperature with side mode suppression ratio (SMSR) as high as 17.5 d B.The maximum single mode continuous-wave output power is more than 10 mW at room temperature.The laser shows a very excellent wavelength stability against injection current.The single spatial mode operation is maintained in the entire injection current range.The 24 th-order Bragg grating laser even shows a side mode suppression ratio up to22.5 d B at room temperature.The emission wavelength is around 2.0 μm.

Abstract:To improve terahertz (THz) radiation intensity, the dipole antenna arrays with THz chokes on a thin LT-GaAs film are designed.The output radiation of the proposed linear array can be linearly enhanced by increasing the number of elements, while the average matching efficiency is changed insignificantly.The AC component flowing into the coplanar strip line (CPS) is limited by THz chokes which leads to a more stable resonant frequency, and the average matching efficiency is twice that of an array without chokes.We find the staggered array has a narrower emission spectrum than the gridding one due to the coupling of adjacent elements in the vertical direction.By designing the array on a polyimide lens instead of a silicon lens, a high input resistance can be obtained, and the total efficiency is raised from 25% to 35%.

Abstract:A hybrid dual wedge plasmonic (HDWP) waveguide consisting of two dielectric wedges and a diamond metal wire was proposed.The coupling between dielectric wedge waveguide mode and long-rang surface plasmon polariton mode results in both lowpropagation loss and ultra-deep-subwavelength confinement.The HDWP waveguide achieves a normalized mode area of 2.9 × 10-3with a moderate propagation length of 532 μm or a propagation length of 3028 μm with a normalized mode area of 6.2 × 10-3.The impacts of possible fabrication imperfections on the mode properties are studied.The results indicate that the HDWP waveguide is quite tolerant to fabrication errors.

Abstract:Current studies on the relationship between carrier concentration in nano-scale semiconductor structure and its local conductance is mainly on parameters fitting.For above connection, existing models rely on artificial fitting parameters such as ideal factor.For above reason, derivation of carrier concentration though measured local conductance can not be done.In this work, we present a scheme to obtain the carrier concentration in narrowquantum wells (QWs) .Cross-sectional scanning spreading resistance microscopy (SSRM) provides unparalleled spatial resolution (< 10 nm, Capable of characterizing single QW layer) in electrical characterization.High-resolution local conductance has been measured by SSRMon molecular beam epitaxy-grown GaAs/AlGaAs QWs cleaved surface (110) .Based on our experimental set-up, a model which describes conductance by the only argument, i.e.carrier concentration has been built.Using the model, our implementation derived carrier concentration from SSRMmeasured local conductance in GaAs/AlGaAs QWs (doping level:1016/cm3-1018/cm3) .Relative errors of the results are within 30%.

Abstract:A SOI-based 25-channel AWG with 200 GHz channel spacing is demonstrated.The minimum distance between the input waveguides (Δxi) /output waveguides (Δxo) /arrayed waveguides (d) is optimized respectively.Then the boundary structures between the free propagation regions (FPRs) and the arrayed waveguides (W2/L2/L3) are optimized in detail.The experiment results showthat the insertion loss of the AWG is 5 ～ 7 d B, and the crosstalk of it is 13 ～ 15 dB.Compared with our previous work, the performance of AWG in this paper has been improved greatly, and further methods to improve the performances of insertion loss and crosstalk have been proposed as well.

Abstract:In order to achieve lowcontact resistances of InAs/AlSb heterostructures with the undoped In As cap layer, Pd/Ti/Pt/Au alloyed ohmic contact has been investigated.The contact resistance Rcis evaluated by using transmission-line-model (TLM) measurements.A minimum of 0.128 Ω·mm has been obtained by using the optimal rapid thermal annealing (RTA) with the condition at temperature of 275 ℃ and annealing time of 20 s.The measurement from transmission electron microscopy (TEM) demonstrates that the Pd atoms diffuses into the semiconductor, which is beneficial to the formation of a high-quality ohmic contact during the rapid thermal annealing.This study shows that the contact resistance Rcis reduced significantly after Pd/Ti/Pt/Au alloyed ohmic contact, which is suitable for its application in InAs/AlSb heterostructures.

Abstract:This paper presents an improved small-signal model and a W-band monolithic low noise amplifier (LNA) using 100 nm InAlAs/InGaAs/InP-based high electron mobility transistors (HEMT) technology.For improving the fitting accuracy of S-parameters in low frequency, the small-signal model takes into account differential resistances of gate-to-source and gate-to-drain diodes, which modeled by resistances Rfsand Rfd.A W-band LNA monolithic millimeter-wave integrated circuit (MMIC) has been designed and fabricated based on this model to verify the feasibility of this model.The amplifier is measured on-wafer with a small-signal peak gain of 14.4 d B at 92.5 GHz and 3-dB bandwidth from 85 to 110 GHz.In addition, the MMIC also exhibits an excellent noise characteristic with the noise figure of 4.1 dB and the associate gain of 13.8 d B at 88 GHz.This MMIC amplifier shows wider 3-dB bandwidth and higher per-stage gain than others results at the similar band.

Abstract:An approach for determination of small-signal equivalent circuit model elements for InP HBT is presented in this paper.The skin effect of the feedlines is taken into account in the proposed model.This method combines the analytical approach and empirical optimization procedure.The intrinsic elements determined by a conventional analytical parameter transformation technique are described as function of extrinsic resistances.An excellent fit between measured and simulated S-parameters in the frequency range of 2 ～ 110 GHz is obtained for InP HBT.

Abstract:The characteristics and mechanism of set/reset process in high-k based resistive random-access memory devices were studied.A great fluctuation in set/reset voltages was observed in the NbAlO single-layer RRAMdevices.However, it shows highly uniform and reproducible switching cycles in Al2O3/NbAlO/Al2O3 nanolaminate stack structures.Based on the electric-filed modulating effect, we proposed a unified resistive switching model to simulate the set and reset operations, and the switch parameters dispersion due to the great randomness of the conductive spots formation or annihilation was discussed for a single-layer RRAM.When an ultra-thin Al2O3 films was embedded in NbAlO-based RRAMdevices, there is an obvious improvement in the stabilization of the set/reset switching voltages.It can be explained that the electric-field distribution is rearranged and locally controlled in the stack structure, therefore the conductive filament bridges and ruptures appear in the thin buffer layer.

Abstract:In0.83Ga0.17As layers were grown on InP substrate with InAlAs metamorphic buffers by gas source molecular beam epitaxy.The characteristics of In GaAs and InAlAs layers grown with different temperature schemes were investigated by high resolution X-ray diffraction reciprocal space maps, atomic force microscopy, photoluminescence and Hall-effect measurements.Results showthat a higher growth temperature gradient of the InAlAs metamorphic buffers leads to a broader (004) reflection peak.The tilt angle between the epilayer and the substrate increases as well.The surface of the buffer layer becomes rougher.It indicates that the material defects increase and lattice relaxation becomes insufficient.In0.83Ga0.17As layers were grown on the InAlAs metamorphic buffer with a fixed growth temperature gradient.A higher growth temperature leads to a moderate full width at half maximum along the Qxdirection of the (004) reflection, a stronger photoluminescence at 77 K, but a rougher surface of In0.83Ga0.17As.This indicates that the material defects can be suppressed at higher growth temperatures.

Abstract:The influence of temperature, humidity and pressure on the measurement of exhaust gas CO concentration after pretreatment is analyzed.An on-line correction algorithm with multi-environment factors of neural network for the vehicle exhaust CO detection has been proposed.First, the exhaust gas sample data has been trained offline to build the BP neural network model, and then the real-time measured temperature, humidity, pressure and decimal absorption value of the samples have been put into the model for its online correction.Then the corrected CO concentration has been achieved, so the measurement error of the NDIR sensor caused by environmental changes has been solved.Through the prototype experiment, the simulation experiment and the comparison with SEMTECH-EcoStar, the maximum relative deviation of the CO with the concentration from 0 to 0.2% is 4.8%when the temperature range is from 30 to 50℃, relative humidity is from 25 to 40%, the pressure is from 95 to 115 k Pa.The experiments have been carried out in the vehicle field to get the correction factor between 0.8 and 1, which verifies the necessity and reliability of the method and provided effective technical support for the detection of the CO concentration of the high-temperature exhaust gas from motor vehicles.

Abstract:A modified folded groove waveguide called folded double ridge groove waveguide (FDRGW) is put forward for developing broadband high-power terahertz (THz) travelling-wave tube (TWT) .A newtransmission waveguide which is appropriate for this newkind of SWS as input and output energy coupler is proposed.It can be found from the high frequency characteristic simulation results that the folded double ridge waveguide SWS can increase the average interaction impedance and extend its operating bandwidth.In addition, the particle-in-cell (PIC) simulation results reveal that with the beam voltage of 27.4 kV and the beam current of 0.25 A, the average output power of the newfolded double ridge groove waveguide TWT can reach 65.8 W and the corresponding gain is 27.21 dB at the center frequency 340 GHz.Therefore, the folded double ridge groove waveguide TWT could be used as wide-band and high-power terahertz radiation source.

Abstract:A terahertz quasi-optical detector has been presented, which is mainly composed of a GaAs antenna-coupled Schottky diode chip and a highly resistive silicon lens.In order to reduce the ohmic loss, the standard terahertz Schottky diode fabrication process has been improved by forming the antenna patterns on the semi-insulating GaAs layer.Experimental responsivity and DSB conversion loss of the quasi-optical detector are 1 360 ～ 1 650 V/W and10.6 ～ 12.5 dB at 335 ～ 350 GHz range, respectively.The noise equivalent power (NEP) is estimated to be 1.65～ 2 pW/Hz1/2.Imaging experiments based on this quasi-optical detector have been carried out in both direct-and heterodyne-detection modes, successfully demonstrating its potential in terahertz imaging applications.

Abstract:The nanomembrane with embedded asymmetric coupled QWs by chemical etching was rolledup into a three-dimensional tube structure via a strain-engineering route, it is found that there are two different modes of its optical properties and the modes can be expressed as two different strain release:uni-axial strain release and bi-axial strain release by the PL spectra obtained from microtubes with different diameters.In order to study the internal relationship between the strain state and the objective factors that affect the strain state, experimentally we used different concentration of HF acid etching solution to corrode the corresponding sacrificial layer of the nanomembrane which is rolled-up into a three-dimensional tube structure.Besides, the PL spectra of microtubes showthat the uni-axial strain release and bi-axial strain release of microtubes are not only related to the influence of substrate, but also to the initial state of microtube and they can be transformed into each other under a certain condition.

Abstract:Correlation between surface defects on Liquid Phase Epitaxial (LPE) growth of HgCdTe films and Te-rich precipitates in CdZnTe substrates were studied.Results shown that three kinds of surface defects of LPE growth of HgCdTe film are as follows:surface crater defects, pinhole-like defects and concave pits, which related to the Te-rich precipitates in CdZnTe substrates.Substrate remelting process during LPE growth of HgCdTe film can reduced these defects.There was the negative correlation between the depth of the remelting layer and the matching of the surface defects and the Te-rich precipitates.The remelting of substrate surface layers during the LPE process affect the number and morphologies of HgCdTe surface defects, as well as the depth and the morphologies of the Te-rich precipitates.

Abstract:Aiming at the design and application of the interband cascade structure in long wavelength detection, E-k relation and energy band information of multi-quantum-well relaxation region were calculated by using two-band model under the envelope-function approach and transfer matrix method.The structure of relaxation region was specially optimized.On the premise of the tunneling process of photon-generated carriers in relaxation region, the electric field of absorption region was reduced to suppress generation-recombination current and tunneling current, and to improve the electrical performance of device.The quantum efficiency of prepared double-stage interband cascade photodetector was up to 20% at 10.5 μm, which proved that the relaxation region and tunneling region had well transport of photoexcited carriers.The 50% cutoff wavelength of the device was 11.5 μm at 80 K, which was the longest wavelength infrared detector of interband cascade structure at 80 K.

Abstract:A large-area high-performance near-infrared absorber based on plasmonic nanostructures is introduced, fabricated and experimentally characterized.The periodic plasmonic nanostructures are prepared by self-assembled template, a charming low-cost technology for making large-area samples.Experimental results showthat the absorbance can be as high as 99%.The spectral position of the absorption peak is experimentally demonstrated to be tuned by the geometric dimensions.The physical origin of the absorption effect is theoretically explained as well.

Abstract:In marine target detection, a target could be lost by a mid-infrared detector if it's located in sun glint area.Aiming at this problem, a real-time mid-infrared polarization imaging system employing a Wollaston Prism was designed which utilized the polarization characteristics of sun glint.The Wollaston Prism enabled beam separation into ordinary and extraordinary rays which vibrate at two orthogonally polarized directions, and two images were acquired on the same detector plane with light focused by an imaging lens.Degree of polarization of the target scene could be calculated and assist to detect marine targets.It enables effective sun glint suppression and marine targets detection.

Abstract:In this study, a simulated foliar spectral dataset based on the empirical PROSPECT model was generated according to variations of chlorophyll content (Cab) , carotenoid content (Car) , and leaf water content (LWC) .The spectra data were then resampled to a gradient of spectral resolutions and conducted a CWA analysis.The analysis of the spectral resolution impact on retrieving the plant biophysical and biochemical parameters was then performed.The results showed that: (1) CWA can be used to successfully extract sensitive features and to establish retrieving models of parameters including Cab, Car and LWC with high accuracy. (2) With decline of spectral resolution, the number of sensitive features, their correlation, and retrieving accuracy tend to decrease.However, the decline amplitude and the inflection point of the decline curves are all different, which reflected the different impact of the spectral resolution different for different parameters. (3) A significant difference on the sensitivity of spectral resolution was found among different plant biophysical and biochemical parameters, with the LWC appeared to be the most insensitive, followed by Cab, and Car.Based on this result, in retrieving Car, Cab and LWC with CWA, a reasonable result is expected only if the spectral resolution is no lower than 8 nm, 32 nm and 64 nm, respectively.The present study provides a basic understanding in selection of hyperspectral sensors for retrieving and monitoring of plant biophysical and biochemical parameters with the CWA method.

Abstract:In consideration of the phase difference between the reflected electromagnetic wave and incident electromagnetic wave in the input waveguide of the filter, operational performances for different design conditions are analyzed by the coupled mode theory (CMT) , then the filter structure based on photonic crystal 1 × 3 cavity is optimized.The characteristics of the filter are studied by using the FDTD method.Average peak wavelength normalized transmission of the 96 pass-bands obtained by adjusting locations of the tuning rods below1 × 3 cavity is up to 89.6%.Average spacing between adjacent peak wavelengths is 1.25 nm.Average band width of the filter and average quality factor of the cavity are 1.19 nm and 1 350.2, repectively.Tunable ranges of the dropping peak wavelengthes are between 1 534.04 nm and 1 653.16 nm.The results showthat the filer has the characteristics of high normalized transmission, narrowband width, and stable wavelength signal dropping intensity etc.This structure has potential value in the designs of dense wavelength division demultiplexing (DWDDM) system, optical sensing device, and dense optical path integration etc.

Abstract:The slices of fresh porcine tissue was investigated by exploiting our home-built photoconductive microprobe-based THz near-field imaging system.The results showthat the muscle region and adipose region in the porcine tissue can be clearly discriminated in THz near-field images with a good contrast, far better than the images of the samples imaged by using the conventional terahertz time domain spectroscopy.The work demonstrated here indicates that the photoconductive microprobe-based THz near-field microscopy is feasible for the detection of biological samples and is very promising to be used in biomedical detections.

Abstract:In order to obtain macroscopic and quantitative porosity data in outcrop rapidly, a newHyperspectrum based porosity estimation method was proposed in this paper.Sandstone samples were collected from field outcrop and measured for porosity data, whose influence factors were analyzed with rock thin section.After the preprocessing on the spectral data of rock samples, the spectral response mechanism of porosity was preliminarily explored.Considering the high dimensionality of spectral bands and the multiple correlation between bands, the porosity estimation models were constructed using the partial least squares method.The important bands in the model were indicated by the variable importance in the projection.The results showthat:sandstone porosity can be indirectly retrieved based on the correlation between interstitial fillings and porosity and the spectral characteristics of interstitial fillings;sandstone porosity shows good spectral response; reflectance has the ability to estimate porosity quantitatively (porosity estimation model based on full wavelengths:R2= 0.72, RMSE = 2.28, RPD =1.94) ; the important bands help to reduce the independent variable dimension and find the porositysensitive spectral response.This study lays the foundation for porosity characterization in the outcrop based on hyperspectral images.

Abstract:In order to improve the performance of traditional staggered double vane (SDV) traveling wave tube (TWT) , a newkind of step-type staggered double vane (SSDV) slowwave structure (SWS) is proposed, and a newtype of input/output coupling structure is designed based on this novel SWS.Moreover, a W band sheet electron beam SSDV SWS TWT is designed in this work.The calculation results showthat the SSDV SWS TWT has a higher interaction impedance, so that it can achieve a higher saturated gain and higher interaction efficiency in a less interaction circuit length.In the frequency range of 90 ～ 100 GHz, the interaction impedance of SSDV SWS is greater than 4 Ω, which is higher than the traditional SDV SWS.The reflect ratio (S11) of high frequency structure of W band sheet electron beam TWT is less than -15 dB.Moreover, the saturated input power of the traveling wave tube is only about 0.7 W, and the maximum output power can be about 800 W, the corresponding efficiency is more than 7.8%, and the gain is more than 30.6 dB.

Abstract:Tropical cyclone (TCs) rapid intensification (RI) often results in large forecast errors and it is among the most significant challenges facing operational TCs forecasting centers.In this study, Hato (2017) and Vicente (2012) were selected that have the most significant features happened in the South China Sea in the past 20 years.Based on Fengyun-2 (FY-2) geostationary meteorological satellite high-temporal resolution data, an algorithm for characterizing the cloud in TCs vertical motion signal was developed, which was combinated with vertical wind shear and inner dynamic information.And the authors investigate the interaction between the cloud vertical motion and RI.The results showthat the process of RI like the seesaw, with the convection intensity increased and decreased, better organized TCs internal structure was proved TC intensity change with the maximum value of the cloud vertical motion gathered in the core area of the typhoon.The continuous increase of cloud ascending motion within 0 ～ 50 km was the most significant contribution to RI, and sudden changes had happened within1 ～ 2 h.The findings corroborate previous RI study results while providing additional insights into internal structure in TC, also it provides references for TC monitoring and future study work.