Abstract:Terahertz (THz) communication is being considered as a potential solution to mitigate the demand for high bandwidth. The characteristic of THz band is relatively different from present wireless channel and imposes technical challenges in the design and development of communication systems. Due to the high path loss in THz band, wireless THz communication can be used for relatively short distances. Even, for a distance of few meters (>5 m), the absorption coefficient is very high and hence the performance of the system is poor. The use of multiple antennas for wireless communication systems has gained overwhelming interest during the last two decades. Multiple Input Multiple Output (MIMO) Spatial diversity technique has been exploited in this paper to improve the performance in terahertz band. The results show that the Bit Error Rate (BER) is considerably improved for short distance (<5 m) with MIMO. However, as the distance increases, the improvement in the error performance is not significant even with increase in the order of diversity. This is because, as distance increases, in some frequency bands the signal gets absorbed by water vapor and results in poor transmission. Adaptive modulation scheme is implemented to avoid these error prone frequencies. Adaptive modulation with receiver diversity is proposed in this work and has improved the BER performance of the channel for distance greater than 5 m.

Abstract:Eu2 -doped GaN (GaN:Eu2 ) nanofibers were synthesized by a facile approach that combined electrospinning and ammonification techniques. SEM and TEM images revealed that the nanofibers consist of GaN nanoparticles with uniform size. XRD result showed that the GaN:Eu2 sample predominantly exhibited the hexagonal phase of GaN (h-GaN) and the average grain size was evaluated to be 7.3 nm. Further Raman characterization showed that two extra GaN Raman shifts with the peaks of 252 and 422 cm-1 were observed. As was expected, characteristic strong blue emission from Eu2 ions doped in GaN matrix was observed at 407 nm in the photoluminescence spectrum.

Abstract:A high-integration detector which consists of a patch antenna, a matching circuit, schottky diodes (SBD) and lenses has been developed. The integration of detectors is increased obviously comparing with that of separated detectors by integrating antennas, matching circuits and SBD on a chip in SMIC 130 mm. To improve the directivity of the antenna on chip, the nylon lens with air cave was designed and optimized. The air cave in lens not only provides space for assembling but also reduces the size of lens. It was calculated through testing that the antenna gain at 220 GHz is 22 dB, in which the contribution of lens is about 20 dB. The tested responsivity of the detector can achieve 130-150 V/W and the noise equivalent power (NEP) is estimated to be 400~460 pW/Hz.

Abstract:A slow-wave structure (SWS) composed of a grating inside a rectangular waveguide is adopted as the circuit of the backward wave oscillator (BWO) in terahertz regime in this paper. Its dispersion curves and interaction impedance are presented by an analytical method and three-dimensional (3-D) electromagnetic software. The results by analysis and simulation agree well. By optimization, a BWO with the SWS at a central frequency 340GHz is fully verified by 3-D particle-in-cell (PIC) code. The BWO is demonstrated more than 100mW output power with very low current density and 30GHz tuning bandwidth.

Abstract:In this investigation, the coupling losses caused by Fresnel reflection, core misalignment between single mode fiber (SMF) and HC-PCF are analyzed. A novel solution proposed from this research will reduce the coupling losses by using a T-type tube as a connector. Meanwhile, the theoretically calculated optimized gaps are at 15 μm in SMF-HCPCF direction and 25 μm in HCPCF-SMF direction. Thus, an experiment has been carried out, and the results of the practical gap in the above mentioned two directions have also been obtained. Furthermore, compared with detection by traditional methods, the proposed new detection method with PCF can remarkably enhance the Raman spectroscopy signal. Finally, the prospect of using the combination of HC-PCF and Raman spectroscopy in gas-cell detection has been demonstrated by using oxygen and nitrogen.

Abstract:Combined with the fundamental theorems of thermodynamics and the heat radiation theory, Pennes bioheat equation is improved, which can describe the thermal process in tissue subject to heat stimulation of moxibustion more vividly. Applying the Green function method, we derive the analytical solution of the equation and establish a straightforward way to quantitatively interpret the temperature behavior of living tissues, such as healthy tissue, tumor tissue, non-acupoint tissue and acupoint tissue, as a result of moxibustion. The concept of temperature attenuation coefficient (TAC) is proposed to measure the energy absorption at different depth of tissue. The coherence between the simulation and experiment about surface temperature demonstrates the flexibility and availability of the solution. The oscillation energy flow has a mild stimulus to the biological tissues, which is an advantageous physical exciter for organization to achieve its good functions. Our results reveal that the heat with high frequency is mainly absorbed by the surface layer, while that of low frequency can deeply penetrate into the living biological parts. Significantly, the diseases can be treated by moxibustion heat through the role of deep penetration.

Abstract:Mirrored aperture synthesis (MAS) has been proposed to utilize a few antennas to provide high spatial resolution for Earth remote sensing. But the sensitivity of MAS is not completely analyzed. For this problem, the characteristic of the noise in 2-D MAS is derived. Further, both the sensitivity of 1-D and 2-D MAS are analyzed. Numerical simulations are carried out to evaluate the sensitivity of a MAS system, and comparisons between the sensitivity of MAS and traditional aperture synthesis are made.

Abstract:Terahertz focal plane imaging technology has many advantages such as high image resolution, short time period, simple system and small size, and it has wide application prospect in security and industrial inspection. Because the sensitivity of the terahertz focal plane detectors is still low, most of them can only adopt the active imaging mode, and there is no more acceptable testable performance evaluation parameter and model for THz active imaging system, it is difficult to provide the theoretical basis and method for its system design guide. Based on the characteristics of terahertz source and focal plane detector, the minimum resolvable contrast matched filter model of terahertz active imaging system is established by considering the influence of target - background characteristic, atmospheric attenuation and device attenuation. The MRC model is validated by combining the literature examples and the experimental results of the actual terahertz focal plane active imaging system. The results show that the measured value and the calculated value are basically the same, and the error is within the reasonable range, which shows the validity of the model.

Abstract:In this paper, the γ-irradiation effect on InAs / GaSb II superlattice long-wave detectors was studied. The detector has a good anti-radiation performance under the irradiation of ₆₀Co γ-rays as the current-voltage (I-V) characteristics of the devices did not change significantly with the increase of the irradiation dose. And compared with the value before irradiation, the reduction rate of the zero-bias resistance was only 3.4% under the irradiation dose of 100Krad (Si). By combining the real-time I-V curves at different irradiation doses and the evolution of the dark current with time after the irradiation, the damage and the corresponding mechanism of the γ-irradiation were analyzed. At zero bias as well as small reverse bias, the current is obviously increased after irradiation. The radiation damage is dominated by the transient ionization effect, and the device performance can be recovered in a short time. While at large reverse bias, the main dark current mechanism is the direct tunneling current, leading to a decreased dark current with the increase of the irradiation dose. The time of the damage recovery is significantly longer than the ionization damage, and an annealing may be required.

Abstract:The medium wave infrared channel (MWIR) has the characters of high precision on-orbit calibration and reflectance computation insensitive to the top of atmospheric (TOA) temperature, which make it a suitable reference standard for reflectance validation between bands. The glint area on the sea surface has the characters of relatively high reflectivity, high frequency and uniform surface performance, which make it a suitable test site for on-orbit validation of satellite sensors. Based on the two starting points, this paper first built up the reflectance relationship between MWIR and solar reflectance bands based on Fresnel’s law, then used VIIRS (Visible Infrared Imaging Radiometer) mid-infrared band (3.697μm) as reference standard to validate the four solar reflectance bands (0.672、0.862、1.238 and 1.602μm) on sea surface sun glint regions, and finally analyzed the uncertainties of this validation model. The results show that the uncertainties of the four solar reflectance bands are 3.8%、3.9%、4.1%、4.1%, respectively. Therefore, the model proposed in this paper can be used for optical inter band cross validation.

Abstract:Particles in the atmosphere change the polarization state of light by scattering and absorption, and analyzing and measuring the polarization information of the light can provide a wealth of important information about the composition of the particulate matter. Soot is the main absorptive particulate matter in the visible light range. Light scattering and absorption in atmosphere can change optical polarization properties. Analysis and Measurement on interaction of polarized light with atmospheric particulates can provide important information to evaluate the atmospheric composition and conditions. In this paper, it was proposed a polarization character focusing on the evaluation of soot content in the air, based on our polarized photon scattering simulation program. The simulation results demonstrate that the polarization parameter at a specific scattering angle can identify the soot particles from the other air pollutants and corresponding experiments classify the preliminary study. Compared with non-polarization optical measurement, polarization characterization can not only be improved from the current non-polarization scattering instrument, but enhance the contrast of distinguishing different type particles and optimize the detection setup.

Abstract:We have studied two different kinds of terahertz first-order distributed feedback quantum cascade lasers (THz-DFB-QCL), both of which are based on a metal-metal waveguide. In the convenient edge-emitting laser structure, single mode emission is not obtainable due to a high reflectivity and a random phase of the reflected wave caused by the cleaved facet. To realize stable single-mode emission, we have demonstrated for the first time THz-DFB-QCLs in which THz wave is extracted via a diffraction grating. Our simulations illustrate that an optimized diffraction grating will give rise to a diffraction efficiency of about 70%, and a reflectivity less than 1%. It will also result in a laser beam pattern with a low divergence angle of 10×50°. Such a low reflectivity will keep the mode oscillation inside the DFB grating not disturbed, which is crucial to realize stable single-mode emission. Experimentally, by utilizing a diffraction grating to extract THz wave, we have realized THz-DFB-QCLs with stable single-mode emission near 2.58 THz and the side-mode-suppression-ratio is about 23dB. The measured laser beam pattern is in good agreement with the calculations. Most importantly, due to the good diffraction efficiency and beam directionality, the diffraction grating based THz-DFB-QCL significantly improves the output power compared with the edge-emitting counterpart.

Abstract:Discrete spatial under-sampling effect of the detector array has a great impact on the imaging results, so the quantitative method of the under-sampling effects is a crucial issue for the performance evaluation of an electro-optical imaging system. Considering the human visual characteristics, a target-characteristics-based equivalent blur model for under-sampled imaging systems is proposed. The introduction into the model of the tolerance of the under-sampling system to the spurious response and the effective frequency spectrum makes the newly proposed model more accurate in the prediction of the target discrimination performance of an under-sampled imaging system.

Abstract:This paper proposes an automatic registration method for optical and Synthetic Aperture Radar (SAR) images based on geometric structural properties. In the proposed method, the phase congruency feature with photometric invariance is first introduced for image feature extraction, and then both the magnitude and orientation information of phase congruency are used to build a geometric structural feature descriptor named HOPC (Histogram of Orientated Phase Congruency). A similarity metric named HOPCn is defined for image matching by using the Euclidean distance of the descriptors. This similarity metric can capture the geometric structural similarity between images, and has been tested using 4 pairs of optical and SAR images. Experimental results show that HOPCn is robust to non-linear radiometric differences, and outperforms the state-of-the-art similarity metrics such as correlation coefficient and mutual information. Moreover, this paper also design an automatic registration method based on HOPCn. Experimental results demonstrate the effectiveness and robustness of the proposed method.

Abstract:We proposed an system of optical time domain reflectometer with double repetition rates based on the single photon detector with InGaAs/InP avalanche photodiode. Two arrays of laser pulses with slight different repetition rates were injected into the fiber to monitor the fiber broken point. A fast single photon detector was adopted for high sensitivity in reflected pulses detection. What’s more, the measuring time was reduced. By adjusting the difference of the repetition rates, not only the mearsuring range of the system could be extended ,but also the measurement accuracy could be changed.

Abstract:In the way of pursing large width and high resolution imaging, ground imaging distortion is an important factor that needs to be eliminated, therefore, a zoom scanning combine with adjustable slit diaphragm imaging method was proposed in this paper. The corresponding control formula of zoom scanning and slit were deduced. Results show that, under appropriate controlling, this method could effectively reduce the ground distortion brought by the increase of the scanning angle and can maintain the ground resolution to be unchanged (same as the resolution under sub-satellite point) during a wide scan imaging process. Besides, a zoom swing scanning imaging system was designed to verify the feasibility of our method in large width and high resolution imaging applications. This is of great significance for the development of large width and high resolution imaging observation.

Abstract:The ordered three-dimensional photonic crystals with infrared photonic band gap was prepared from 3.87 μm polystyrene (PS) microspheres by vertical substrate self-assembly method. It is found that the microspheres exhibit the highest order and least defect when the ratio of ethanol to water in the suspension is 2:8 (V%). With increasing the concentration of microspheres in the suspension, the number of stacking layers and the thickness of the photonic crystals were improved. Then the reflection and radiation properties of the photonic crystals with different ordering degree in the infrared band were characterized. The results reveal that higher ordering degree and larger ordered area of the microspheres lead to higher reflectivity and lower emissivity of the photonic crystals, thereby effectively inhibiting the infrared radiation of the aim surface.

Abstract:As a new kind of optical imaging technology, polarimetric imaging can efficiently increase the detection dimension of the information by detecting the polarization properties of the optical wave, this is useful for obtaining the target information comprehensively and accurately. Firstly, the method of polarization imaging detecting is introduced and the typical polarization imaging systems are reviewed in this paper. Then, based on Stokes Vector, a simultaneous, real-time, division of aperture chromatic polarimetric imaging camera with full-polarization-state detection is introduced in detail. Finally, the experimental results of full polarimetric imaging and polarimetric dehazing imaging using this camera are demonstrated. The experimental results indicate that the polarimetric imaging technology of full polarization states simultaneous detecting has obvious advantages on developing the detecting distance and acquiring the detail features, so it can provide important supplement for modern optical imaging system.

Abstract:Gaussian decomposition is the most commonly used methods for waveform analysis, which is a key post-processing step for the applications of space-borne LiDAR data. However, it usually fails to detect the overlapping pulses of large-footprint waveform data. Therefore, a Gaussian progressive decomposition method based on wavelet transform was proposed in this study to address this issue and applied to Ice, Cloud, and land Elevation Satellite / Geoscience Laser Altimeter System (ICESat/GLAS) data. The new proposed method mainly consists of three key steps. First, the wavelet transform was adopted to detect the target features and estimate the component feature parameters, then the Gaussian model was established to optimize the feature parameters. Second, a new component was added if the fitting accuracy didn’t meet the requirements. Finally, waveform decomposition based on wavelet transform was completed until no more new components were added. Additionally, a comparison experiment between the new proposed method and the Gaussian decomposition method based on inflection point was also conducted to verify the reliability of the new proposed algorithm. Experiment results indicated that our new proposed algorithm can detect twice targets as many as the method based on inflection point, and effectively decompose the targets from overlapping waveforms due to high fitting accuracy of above 98%.

Abstract:Organic thin-film semiconductor devices have important research and application value in the fields of microelectronics and optoelectronics. The film quality is one of the key factors affecting the device performance such as the uniformity of film spatial distribution. This parameter was studied by analyzing the reflectance difference maps of pentacene thin film grown on an anisotropic substrate which were measured by reflectance difference microscopy. The results demonstrate the capability of reflectance difference microscopy to study the processing of thin film growth.

Abstract:A novel hybrid surface plasmon waveguide structure is proposed, It is based on metal ridge-triangular semiconductors, the numerical simulation and analysis of the waveguide structure are carried out based on the finite element method.Also, the electric field distribution, transmission length, normalized mode field area as well as quality factor of the structure are considered here. Finally, the results show that: at the operating wavelength of 1550 nm, by optimizing the parameters, its effective mode field area is up to 0.00193, the transmission length is 37.7um, and the quality factor is 4853, besides,the structure has lower loss.Compared with the metal plate hybrid waveguide structure, in this paper, the design of the structure has a greater quality factor and stronger light field limiting ability, what's more, the waveguide comprehensive performed better. This kind of waveguide structure has a wide application prospect in the fields of micro-nano photonics, optoelectronic communication and optical information storage.

Abstract:Polarization is a kind of transmit modality of light, and we can understand detect information from the other one dimensionality by polarization information. Polarization imaging contains rich target parameters including spectrum, radiant intensity, polarization state, space geometry, etc in which can improve the target detection and recognition ability. Based on the bidirectional reflectance distribution function model, the paper establishes Infrared radiation transmission equation of object surface, and we deduce the mathematical model with respect to a lot of factors of the degree of polarization. Aim at the infection of circumstance factors, a lot of experiment of the Infrared polarization and the Infrared hyper-spectral polarization imaging about different material and standard blackbody were developed. The result show that the infrared degree of polarization of blackbody is not relate to wave length, and the method of infrared polarization quantitative analysis is put forward that is based on the infrared polarization characteristics of standard blackbody.

Abstract:This paper focuses on quantitative detection performance for point target of single-sampling and over-sampling systems and presents an imaging chain simulation model based on the sampling model of sub-pixel, which depicts detection for targets with various heights and sizes under given resolution conditions. Single-sampling and over-sampling with the same IFOV, over-sampling of two times IFOV were taken into account. Performance of the three sampling systems was compared and analyzed from the following four aspects: target signal’s acquisition capability, background signal and clutter level, detectability and measurement characteristics. Results are listed as follows: over-sampling of the same IFOV is conductive to the acquisition of the target signal and has better detectability, while that of two times IFOV suppresses target signal and goes against detecting target with low SCR; over-sampling has inhibitory effect on background signal and clutter; over-sampling collects apparently superfluous radiation intensity and the error has to be corrected.

Abstract:A “Two Times Thermal Irradiance and Four Times Measuring Method” for measuring the emissivity of the object was proposed. According to the instrument developed independently, the method and design has the advantage to measure the irradiance of the thermal irradiance which is exactly the same as that which is irradiated to the measured object. The method not only improve the measurement accuracy, but also can be designed as a small size portable emissivity tester. Designing of 1000w / m2 or more strong heat radiation source, the signal to noise ratio in equipment is increased substantially. In order to compensate for the warming of the measured target under the strong heat radiation source, the universal expression of solving the emissivity in the non-isothermal system and a "Process Method" for compensating warming were proposed, which solved the bottleneck problem caused by the temperature change in the non-temperature system. The comparison of the three measurement results of the emissivity measurement method shows that the method proposed in this paper is superior to the other two methods.

Abstract:GaAs/AlxGa1-xAs 2DEG samples are prepared by MBE. In the sample preparation process, by changing the Al component, the spacer layer thickness, contrast body doping and delta doping two methods, samples are analyzed by the Hall test in the 300K. It obtains the GaAs/ AlxGa1-xAs 2DEG channel structure with mobility is 7.205E3cm2/VS at room temperature, carrier concentration is 1.787E12/cm3. The THz response rate of GaAs-based HEMT structures with different channel widths at 300K and 77K temperatures is calculated by using Mathematica software. It provides a reference for the research and preparation of HEMT THz detectors.

Abstract:The Geostationary Interferometric Infrared Sounder (GIIRS) on board FY-4A is a Michelson interferometer infrared sounder. The interferogram is sampled at discrete points. The zero path difference (ZPD), which is the peak of the interferogram, is not sampled. This effectively shifts the interferogram and adds a linear phase to the spectrum. A linear regression on the residual phase of the calibrated spectrum will reveal the shift. This method has been used in the interferogram signal processing of the GIIRS, and has abstained the better results.

Abstract:Based on dual-disperser coded aperture snapshot spectralimaging（DD-CASSI）system, method using multiple sample image (MultiFrame-DD-CASSI ) was put forward, so that sampling rate was increased,and a new math model was put forward, realized spectral compression in3-D data cube. The system makes full use of spectra’s coherence, and0.99 spectral correlation fitting and 40db image peak signal noise were achieved with 32 frames sample image.