bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Bragg periods per grating period on performance of Bragg concave diffraction grating
Authors: Du Bing-Zheng  , Zhu Jing-Ping  , Mao Yu-Zheng  , Liu Hong  , Wang Kai  , Hou Xun  ,   Shaanxi Key Laboratory of Information Photonic Technique, Key Laboratory for Physical Electronics and Devices of the Ministry of Education, School of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

Concave diffraction gratings (CDGs) have the advantages of being compact, time reliability, cost effective, and channel spacing accuracy. These devices can be used in the wavelength division multiplexing (WDM) systems and micro-spectrometer devices. However, comparing with arrayed waveguides gratings (AWGs), the development of traditional CDGs is far from satisfactory. Because the traditional CDGs need deeply etched facets and perfect grating profiles to reduce the insertion losses, which will increase the difficulty in etching process. In order to solve this problem, Bragg reflectors based CDGs (Bragg-CDGs) are proposed. This structure can greatly reduce the insertion loss, and reduce the difficulty in etching process. The performance of the Bragg-CDG is determined by both the reflection condition of the Bragg reflectors and the diffraction condition of the CDG. With the Bragg reflection condition determined, the diffraction condition of Bragg-CDG will have a major influence on the performance of device. For successive strips based Bragg-CDG, the number of Bragg periods per diffraction grating period is an important parameter of Bragg-CDG. The diffraction condition of concave gratings is closely related to this parameter. This parameter has an effect on the performance of Bragg-CDG, specially termed resolution, the free spectrum range, and the diffraction efficiency. The effect of the number of Bragg periods per diffraction grating period on the Bragg diffraction grating is studied by theoretical analysis. In addition, four Bragg-CDGs with different numbers of Bragg periods are studied using the finite-difference time domain method. The results show that with sizes of diffraction gratings fixed, the resolution of Bragg-CDG does not have a significant improvement by changing the number of Bragg periods per diffraction grating period; the total number of diffraction orders is proportional to the number of Bragg periods per diffraction grating period. The Bragg-CDG with a single Bragg period per grating period has a maximum diffraction efficiency, since it has the minimal number of diffraction orders; in addition, with the increase of the number of Bragg periods per diffraction grating period, the free spectrum range of the main diffraction order gradually decreases. This research can contribute to the development of the demultiplexer with the low insertion loss, the high resolution, and the wide operating waveband.
Quantization of plasmon in two-dimensional square quantum dot system
Authors: Wu Reng-Lai  , Xiao Shi-Fa  , Xue Hong-Jie  , Quan Jun  ,   College of Physics Science and Technology, Lingnan Normal University, Zhanjiang 524048, China;,   School of Electronic Engineering, Xi'an Aviation University, Xi'an 710077, China
Published: December 2020

Plasmon in quantum dot system is one of the most notable research topics in the field of optoelectronics. With the development of nanotechnology, plasmon in nano-structure has received considerable attention due to its potential applications in future natural science areas. To better understand the quantum effect and the properties of plasmon, in this paper we use the linear response theory and the tight-binding approximation to investigate the collective response of charge in a twodimensional square quantum dot system. The results show that when the frequency of the external field equals the frequency of the plasmon, there are strong charge collective oscillations in the quantum dot system, accompanied by great energy absorption and near-field enhancement. Owing to the quantization of plasmon, the collective charge oscillations in a two-dimensional square quantum dot system are found at different frequencies. The number of quantum modes of plasmon increases with the size and electron number of square quantum dots increasing, this behaviour of quantum mode of plasmon is similar to the one of phonon. The reasons for this behaviour are as follows. First, with the increase of quantum dot size, there are more energy levels around the fermi energy, and the electrons can jump from more energy levels to the outside of fermi circle, so there are more collective excitation frequencies (i.e., more quantum modes of plasmon) in a larger size system. Second, with the increase of electron number in quantum dots, there are more energy levels occupied by electrons, so there are more quantum modes of plasmon too. Furthermore, the size dependence of plasmon shows that with the increase of quantum dot size, the frequency interval between two neighbouring modes of plasmon is smaller, and the discrete modes of plasmon will gradually display quasi-continuous characteristic and transform gradually into the classical continuous modes of plasmon, and the frequency spectrum of plasmon turns into the classical dispersion relation. Such a characteristic is in accord with Bohr's correspondence principle, implying that the quantum plasmon and classical plasmon are gradually unified in a macroscopic size. The dependence of plasmon on the size and electron number of quantum dots also show that with the increase of the quantum dot size, the frequencies of the plasmon is red-shifted and the excitation intensity of the plasmon increases; with the increase of the electron number in quantum dot, the frequency of the plasmon is blue-shifted and the excitation intensity of the plasmon increases.
Deterministic interface states in photonic crystal with graphene-allotrope-like complex unit cells
Authors: Jia Zi-Yuan  , Yang Yu-Ting  , Ji Li-Yu  , Hang Zhi-Hong  ,   College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China
Published: December 2020

Topological insulators have aroused much research interest in condensed matter physics in recent years. Topological protected edge states can propagate unidirectionally and backscattering free along the boundaries of the topological insulators' which will be important for future electronic devices for its immunity to defects. Topology is dependent only on the symmetry of lattice of the system rather than its specific wave form. Thus, based on the analogy between electronics and photons, photonic topological insulator has also been demonstrated both theoretically and experimentally. Graphene, composed of a monolayer of carbon atoms in honeycomb lattice, exhibits unusual properties due to its intriguing band diagram. Many types of graphene allotropes have been proposed theoretically. However, due to fabrication difficulties, most of graphene allotropes are unavailable. Here, we propose to study two dimensional (2D) photonic crystal (PC) with complex lattices, similar to that of graphene allotrope. The complex PC structure provides more degrees of freedom in manipulating its symmetry.Interface states can also exist in the interface region between two PCs, if they have different topological properties. Without any surface decoration, deterministic interface states can be created when bulk photonic band inversion can be induced and are demonstrated theoretically and experimentally in 2D PCs with square lattice. By controlling the parameters of PCs, their bulk photonic band properties are engineered and topological phase transition occurs. By inverting the bulk photonic band properties, interface states exist in the common band gaps for two PC systems in the gapped region. Similarly, we proceed to complex honeycomb lattice of PCs. By lowering its original C6v symmetry to C3v, C3, C2v and even C2 symmetry, the degeneracies of valley Dirac dispersion at the corners of Brillouin zone are lifted. Photonic band inversion occurs in all four symmetries and the deterministic interface states are numerically realized in the interface region between two PCs. Unidirectional propagation of interface state immune to backscattering along the interface channels is demonstrated if a source with proper optical vortex index is utilized. Due to its easy fabrication, PC is a perfect platform to explore the topological properties of complex lattice and these acquired topological optical states can be of benefit to the control the propagation of light in the photonic waveguide.
Acoustic focusing lens with near-zero refractive index based on coiling-up space structure
Authors: Sun Hong-Xiang  , Fang Xin  , Ge Yong  , Ren Xu-Dong  , Yuan Shou-Qi  ,   Research Center of Fluid Machinery Engineering and Technology, Faculty of Science, Jiangsu University, Zhenjiang 212013, China;,   State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

An acoustic focusing lens based on a coiling-up space structure with near-zero refractive index is studied. According to the direction selection mechanism for acoustic waves in a near-zero refractive index material, we adopt the coiling-up space structure as a basic unit for arrangement, and design a geometric structure with specific incident and outgoing interfaces which is used to manipulate the outgoing direction of transmitted wave. Thus, the focusing effects for plane acoustic wave and cylindrical acoustic wave are realized. Besides, the influences of rigid scatterers inside the lens on the focusing performance are also discussed in detail. Moreover, the shape and direction of the acoustic waveform can be manipulated accurately by changing the outgoing interface of the lens with the near-zero refractive index. The results show that the lens with a single and two circular surfaces could realize the focusing effects of the plane and cylindrical acoustic waves, respectively, and the rigid scatterers inside the lens have no effects on the focusing performance. In addition, the cylindrical acoustic wave could be transformed into the plane acoustic wave through the lens with the circular incident surface and the plane exit surface, and the inclined angle of the exit surface could be used to manipulate the propagation direction of the plane wave. The simulation results between the lenses composed of the coiling-up space structure and the effective medium are in good agreement with each other. This type of lens has the advantages of single cell structure, high focusing performance, and high robustness. This work provides theoretical guidance and experimental reference for designing a novel acoustic focusing lens with the near-zero refractive index, and offers a new idea for studying the manipulation of the acoustic waveforms.
Detector characterization and electron effect for laser-driven high energy X-ray imaging
Authors: Zhang Tian-Kui  , Yu Ming-Hai  , Dong Ke-Gong  , Wu Yu-Chi  , Yang Jing  , Chen Jia  , Lu Feng  , Li Gang  , Zhu Bin  , Tan Fang  , Wang Shao-Yi  , Yan Yong-Hong  , Gu Yu-Qiu  ,   Science and Technology on Plasma Physics Laboratory, Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China;,   IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240, China
Published: December 2020

High energy X-ray sources based on laser-wakefield accelerated electron beams have several important advantages, including high photon energy and small source size, and have many important applications such as high resolution radiography in non-destructive testing. Firstly, the thickness of electron converter is optimized with the targets Ta, W and Pb each with an optimal thickness of 2 mm. We calibrate the intrinsic spatial resolution of CsI needle-like scintillation screen, bismuth germanium oxide (BGO) scintillation array and DRZ scintillation screen with an X-ray tube. And the spatial resolution of CsI needle-like scintillation screen is as high as 8.7 lp/mm. The energy deposition responses of these three detectors to high X-ray are also simulated. Experiments show that the features of a two-layer object can be resolved up to an area density of 33.0 g/cm2 by using the high X-ray source generated by injecting laser-wakefield accelerated electron beam into a Ta convertor target. Experiment that compares X-ray radiography, mixed radiography of X-ray and electron, and electron radiography, is also carried out. Since low X-ray yield and low detection efficiency are two serious problems in high energy X-ray radiography based on laser-wakefield accelerated electron beams, we propose and prove a method of improving image signal intensity greatly at the cost of image contrast by adopting the mixed radiography of X-ray and electron.
Effects of Sr doping on electronic and thermoelectrical transport properties of CaMnO3 based oxide
Authors: Zhang Fei-Peng  , Zhang Jing-Wen  , Zhang Jiu-Xing  , Yang Xin-Yu  , Lu Qing-Mei  , Zhang Xin  ,   Henan Provincial Engineering Laboratory of Building-Photovoltaics, Institute of Sciences, Henan University of Urban Construction, Pingdingshan 467036, China;,   Anhui Provincial Key Laboratory of Advanced Functional Materials and Devices, College of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China;,   National Key Laboratory of Advanced Functional Materials, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
Published: December 2020

The electronic and the electrical properties of the Sr doped CaMnO3 oxide for Ca site are studied by the density funtional theory calculation method. The Sr doped CaMnO3 oxide bulk samples are prepared by the citrate acid sol-gel method as well as the ceramic preparation method, and the thermoelectric transport properties are analyzed. The results show that the Sr doped CaMnO3 oxide still has the indirect band gap yet with the band gap energy slightly decreasing from 0.756 eV to 0.711 eV. The effective mass of carrier near Fermi level is modified and the carrier density near Fermi level is also increased. The ability to release electrons of Sr is stronger than that of the Ca, and the Sr acts as n-type donor doping specy within the CaMnO3 compound. The electrical resistivity values remarkably decrease for the Sr doped CaMnO3 oxide materials. The Seebeck coefficient increases slightly to a certain extent compared with that of the intrinsic CaMnO3. The resistivity values for the Ca1-xSrxMnO3 (x=0.06, 0.12) samples at 373 K decrease to 25% and 21% of the un-doped intrinsic CaMnO3 sample, respectively. The Seebeck coefficients for the Ca1-xSrxMnO3 (x=0.06, 0.12) samples at 373 K increase to as high as 112.9% and 111.1% of the Seebeck coefficient for un-doped intrinsic sample, respectively. The thermoelectric performance is effectively enhanced by Sr doping for the CaMnO3 oxide material.
Magnetotransport property of negative band gap HgCdTe bulk material
Authors: Shen Dan-Ping  , Zhang Xiao-Dong  , Sun Yan  , Kang Ting-Ting  , Dai Ning  , Chu Jun-Hao  , Yu Guo-Lin  ,   Science College, Donghua University, Shanghai 201620, China;,   State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
Published: December 2020

In recent years, spintronic devices have attracted more and more attention because of their good characteristics. The spin-orbit coupling of HgCdTe is one of the most important parts in the study of narrow gap semiconductors. The magneotransport properties of the Hg0.9Cd0.1Te bulk material with an inverted band structure have been hardly reported so far. The spin-orbit coupling strength of HgCdTe is closely related to the band gap. The strength of the spin-orbit coupling increases with the width of the band gap decreasing. Thus, Hg0.9Cd0.1Te should have strong spin-orbit coupling. Meanwhile it should be one of the most suitable materials to fabricate spintronic devices. The main propose of our experiments is to prove this inference. Inside the sample, Rashba spin-orbit interaction (SOI) strongly influences the spin-splitting due to the lack of structural inversion symmetry. In other words, Rashba SOI is the main part of the zero field spin splitting △0. The band structure of Hg1-xCdxTe can be precisely tuned by changing the composition of Cd which keeps an inverted band order when 0 x Γ8 band lying below the Γ6 band (or equivalently a positive band gap) when x0.165. In this paper, the p-type HgCdTe bulk material with Cd component of 0.1 is grown by single crystal. Anodic oxidation is used to induce an inversion layer on the HgCdTe bulk, and indium is used to facilitate Ohmic contacts. The magnetoresistance is measured in the van der Pauw configuration, and the magnetic field is applied perpendicularly to the film. All measurements are carried out in an Oxford Instruments He cryogenic system. At 1.5 K and zero gate voltage, the carrier density n is 1.3×1016 m-2. Clear Shubnikov-de Haas (SdH) oscillation in ρxx and quantum Hall plateaus of Rxy are observed in the Hg0.9Cd0.1Te bulk material with an inverted band structure is investigated in magnetotransport experiment. This indicates that our sample is a good transistor. Fast Fourier transformation is used to deduce the zero-field spin-splitting △0 which is about 26.55 meV. By studying the beating patterns in SdH oscillations we find that the effective g-factor is about-11.54. Both the large zero field spin splitting and the negative effective g-factor suggest that Hg0.9Cd0.1Te has really strong spin-orbit coupling. The investigation of SOI in Hg0.9Cd0.1Te can increase our knowledge of Hg-based narrow-gap semiconductors and benefit the field of spintronics.
Stimulated-emission based spectral domain optical coherence tomography for molecular contrast imaging
Authors: Hu Zhe-Hao  , Shangguan Zi-Wei  , Qiu Jian-Rong  , Yang Shan-Shan  , Bao Wen  , Shen Yi  , Li Peng  , Ding Zhi-Hua  ,   College of Optical Science and Engineering, State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
Published: December 2020

Due to unnoticeable changes in complex refractive index of tissue under varied pathological and physiological states, the traditional optical coherence tomography (OCT) is deficient in molecular characterization. In this paper, the stimulated-emission based optical coherence tomography is proposed, which provides both molecular contrast and scattering contrast OCT imaging simultaneously. Based on the established ultra-high resolution spectral domain OCT system, a pump-probe spectral domain OCT system with a single wide-bandwidth light source is developed through an added modulated pump beam via spectrum splitting. In addition, the theory about the stimulated-emission signal and the image formulation under the modulated pump beam is presented. The coherent detection of the transient stimulated emission is realized by the developed pump-probe spectral domain OCT system. With the stimulated-emission OCT signal and the traditional OCT signal obtained at the same time, molecular contrast OCT images of the samples consisting of nitride powder are reconstructed successfully.
Thermal nonequilibrium detonation model of solid explosive
Authors: Li Shi-Yao  , Yu Ming  ,   Graduate School of China Academy of Engineering Physics, Beijing 100088, China;,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: December 2020

A thermal nonequilibrium reactive flow model is proposed to deal with the detonation dynamics of solid explosive. For the detonation in solid explosive, the solid-phase reactant and gas-phase product in the chemically reactive mixture zone do not have molecular collisions as in the case of gaseous detonation, so the solid-phase reactant and gas-phase product can arrive at a mechanical equilibrium but cannot reach a thermal equilibrium when the detonation happens. The main properties of the present detonation model are as follows. The Euler equations for chemical mixture and the mass conservation equation for solid-phase reactant are used to express the chemically reactive flows in solid explosive detonation as a traditional way, and an additional set of governing equations of the species physical variables for solidphase reactant is derived to give an expression to the thermal nonequilibrium between the solid-phase reactant and gas-phase product. The chemical mixture within a control volume is defined as a collection of species which possess distinct internal energy or temperature, and the same pressure and velocity. For the explosive detonation, the species include solid-phase reactant and gas-phase product. Based on the mixing rule that every species can preserve the conservation of its internal energy in the reactive mixture zone, the evolution equation of internal energy for solid-phase reactant may be obtained, meanwhile, based on the property of mechanical equilibrium in the reactive mixture zone, the total volume fraction is equal to one, and the equation of state of every species, the evolution equation of volume fraction for solid-phase reactant and the evolution equation of pressure for chemical mixture can be derived. Thus, the theoretical model of solid explosive detonation includes the conservation equation of mass, momentum, total energy and the evolution equation of pressure for the chemical mixture, and the conservation equation of mass and the evolution equation of internal energy and volume fraction for the solid-phase reactant. The partially differential equations of the detonation model are numerically solved by a finite volume scheme with two-order spatiotemporal precision, through using a wave propagation algorithm by means of Strang splitting operator. The validation of the proposed detonation model is checked by the propagation of planar one-dimensional detonation, the propagation of cylindrically divergent detonation and the interaction between two cylindrically divergent detonations, and the typical examples demonstrate that the proposed theoretical model of solid explosive detonation is reasonable.
Optical property of X-two ring structure
Authors: Pan Ting-Ting  , Cao Wen  , Deng Cai-Song  , Wang Ming  , Xia Wei  , Hao Hui  ,   Key Laboratory on Opto-Electronic Technology of Jiangsu Province, School of Physics Science and Technology, Nanjing Normal University, Nanjing 210023, China
Published: December 2020

In this paper, the metal periodic array structure of X-two ring based on the principle of Fano resonance is proposed, which is composed of two concentric rings around the center X. The optical properties of the structure are investigated by using the finite difference time domain method. According to the simulated transmission spectra, electric field distribution and charge distribution, when linearly polarized light is incident to the metal surface, Fano resonance can be excited and the interaction between resonance modes can be produced in the structure of X-two ring, which can make resonance valleys generated at different positions. Fano resonance is mainly formed by the coherent interference between a bright mode with the larger radiation broadening and a dark mode with the weak radiation broadening, thus the structural resonance valley of X-two ring based on Fano resonance is strongly dependent on the relative parameters of the structure (the arm length of X, the distance between the inner ring and outer ring, the width of the inner ring and outer ring, the period, the number of ring, and the angle of X). In other words, over the wavelength range of 450 nm to 3000 nm, the intensity and position of the structural resonance valley are adjustable as the change of the relative geometric parameters of the structure. In addition, due to weak radiation damping and strong local electromagnetic field enhancement of Fano resonance, the resonance frequency and line type can significantly shift with the change of the environmental refractive index. Therefore, the further analysis of the variation of the structural resonance valley under the conditions of different refractive indices can be concluded that the structure of X-two ring has a higher sensitivity to the refractive index of surrounding environment, up to 1300 nm/RIU. The above results show that the structure of X-two ring not only is simple, economical, compact and efficient, but also has great potential applications in refractive index sensors and some photonic devices.
Principle analysis of snapshot Mueller matrix imaging polarimeter using birefringent crystal
Authors: Cao Qi-Zhi  , Yuan Chang-An  , Hu Bao-Qing  , Ren Wen-Yi  , Zhao Yin-Jun  , Zhang Jing  , Li Jian-Ying  , Deng Ting  , Mingwu Jin  ,   College of Physics and Electronic Engineering, Guangxi Teachers Education University, Nanning 530023, China;,   Key Laboratory of Environment Change and Resources Use in Beibu Gulf, Ministry of Education and Guangxi Key Laboratory of Earth Surface Processes and Intelligent Simulation, Guangxi Teachers Education University, Nanning 530023, China;,   School of Science Northwest A & F University, Yangling 712100, China;,   Department of Physics, University of Texas at Arlington, Arlington, TX 76019, USA;,   Department of Electrical and Computer Engineering, University of Delaware, Newark, DE 19716, USA
Published: December 2020

Conventional Muller matrix imaging polarimeter (MMIP) with several rotating elements suffers mechanical complexity, vibration noise, heat generation, and other unwanted problems. To overcome those shortcomings, we present a snapshot Muller matrix imaging polarimeter (SMMIP) using a birefringent crystal with high extinction ratio. The snapshot imaging polarimeter allows a single image to be used to measure the polarization of a scene without electronic control units or moving mechanical components. This new polarimeter combines the technique of Muller matrix spectropolarimetry with a snapshot imaging polarimeter through using modified Savart polariscope (MSP-SMMIP). It contains both a generator and an analyzer module. Spatial polarization fringes are localized on a sample by incorporating modified Savart polariscope into a polarization generator module. These fringes modulate the Mueller matrix components of the sample, which are subsequently isolated with modified Savart polariscope in an analyzer module, and the analyzer and the imaging lens combine with 16 beams to create interference, resulting in spatial modulation on the two-dimensional CCD camera. Expressions for interference intensities, optical system analysis, theory of calibration and method of reconstruction are presented. Finally, the numerical simulation is used to demonstrate theoretical analysis and the feasibility of MSP-SMMIP. The layout is very easy to calibrate and the reference target is only a linear polarizer at 22.5°. Moreover, the remarkable advantages of the proposed instrument, compared with conventional Muller matrix imaging polarimeter, are that it is also simple, compact, snapshotted, and static (no moving parts). Therefore we believe that the proposed snapshot imaging polarimeter will be very useful in many applications, such as biomedical imaging and remote sensing.
Development of quantum voltage noise source chip for precision measurement of Boltzmann constant
Authors: Wang Lan-Ruo  , Zhong Yuan  , Li Jin-Jin  , Qu Ji-Feng  , Zhong Qing  , Cao Wen-Hui  , Wang Xue-Shen  , Zhou Zhi-Qiang  , Fu Kai  , Shi Yong  ,   Department of Electricial Engineering, Tsinghua University, Beijing 100089, China;,   National Institute of Metrology, Beijing 100029, China;,   Key Laboratory of the Electrical Quantum Standard of AQSIQ, Beijing 100029, China
Published: December 2020

The Johnson noise thermometer is used to precisely measure Boltzmann constant by comparing the thermal noise caused by charge movement and the quantized voltage reference noise synthesized by the quantum voltage noise source (QVNS). The QVNS signal is synthesized based on quantized voltage pulses produced by two channels of superconducting Josephson junction arrays, which are designed for cross-correlation electronics. The Nb/NbxSi1-x/Nb Josephson junction is used as a core device of QVNS chip in this work for its non-hysteretic current-voltage (I-V) characteristics and conveniently adjustable barrier parameters.In this paper, we present the design consideration, fabrication process, and measurement results of the QVNS chip. The QVNS chip contains two Josephson junction arrays, each consists of four 6 μm×12 μm junctions and is embedded in a 50 Ω coplanar waveguide transmission line. The random noise in signals from the two driven channels is eliminated by cross-correlation, and then an accurate quantum noise is obtained. Test chips with different areas of Josephson junctions are also designed on the same mask, aiming at estimating the variation range of Ic. The typical fabrication process for voltage standard chips in our laboratory is used for preparing the QVNS chip.The sample is measured at 4.2 K. The DC I-V curve shows that the critical current Ic is 6.1 mA. The I-V characteristics of the junctions under 5 GHz microwave radiation are measured. For a series array of four junctions, a 41.44 μV one-stage Shapiro step is observed. Calculation shows that the error between the measurement and theoretical value of 41.36 μV is about 1.9‰, which means that the QVNS chip performs well under microwave radiation and can be used for synthesizing the AC quantum voltage reference noise.A single-frequency 100 kHz sinusoidal waveform is synthesized by the QVNS chip under pulse driven signal. A spectrum of the synthesized sinusoidal waveform shows a single peak, which means that the digital pulse signal is perfectly filtered by Josephson junction arrays and the synthesized signals possess quantum accuracy. The results indicate that our chip has good dynamic response and works well in synthesizing a single-frequency AC quantum voltage signal. This work can provide core devices for the noise thermometry system and support the precise measurement of Boltzmann constant as well as redefinition of Kelvin in future. As a next step, the design and package will be further improved, and the probe module will be optimized to reduce the measurement uncertainty.
Density functional theory of InCn+(n=110) clusters
Authors: Zhang Chen-Jun  , Wang Yang-Li  , Chen Chao-Kang  ,   College of Science, Xi'an Aeronautical University, Xi'an 710077, China;,   College of Science, Enigeering University of CAPF, Xi'an 710086, China
Published: December 2020

Small indium-doped carbon clusters InCn+(n=110) are systematically studied by the density functional theory at the B3 LYP/LANL2 DZ level. The computed properties include equilibrium geometries, electronic energies, vibrational frequencies, dipole moments and rotational constants for individual species. The calculation results show that the open-chain linear isomers with the indium atom bound to the end of the carbon chain are the most stable geometry in all cases. There must exist a cyclic or fan structure in the metastable or the third stable structure of cluster. The bigger the size of the cluster, the more obvious the stability of the structure is. The electronic ground state is found to be alternately a triplet for even n and a singlet for odd n with the only exception of InC+. It is generally observed that the spin contamination is not serious for all electronic ground states because the s2 values are uniform and in general deviate slightly from the pure spin values, and the B3 LYP wave functions are nearly spin-pure. It is also found that in the lowest-energy linear structure, the InC bond is longer (from 2.319 to 2.850 ) than the corresponding CC bonds in a range from 1.268 to 1.360 . The CC distances can be assimilated to moderately strong double bonds underlying a clear bonding in the corresponding structures. In addition, we observe a clear alternation in CC distances. The CoddCeven distances are shorter than the CevenCodd ones which mainly results from the charge distribution and spin density. According to the calculation and analysis of the incremental binding energy and the second difference we can deduce an even-odd alternation in the cluster stability for the linear InCn+, with their n-odd members being more stable than the adjacent even-numbered ones. This parity effect also appears in the adiabatic ionization potential curves. The analysis of magnetic properties shows the even-odd alternation with n-even clusters presenting higher values of magnetic moment than n-odd ones. The study of the polarizability indicates that the average values of both the polarization tensors and the anisotropic invariants increase with the size of cluster increasing.
High-order delay detached-eddy simulations of cylindrical separated vortex/vortex induced noise based on transition model and acoustic analogy
Authors: Wang Guang-Xue  , Wang Sheng-Ye  , Ge Ming-Ming  , Deng Xiao-Gang  ,   College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China;,   School of Physics, Sun Yat-sen University, Guangzhou 510275, China
Published: December 2020

The numerical prediction of transition from laminar to turbulent flow has proven to be an arduous challenge to computational fluid dynamics (CFD). Few approaches can provide routine accurate results within the cost limitations of engineering applications. In the present paper described is the application of a -Re transition model in combination with the delay detached eddy simulation (DDES) and Ffowcs Williams and Hawkings (FW-H) acoustic analogy method to cylinder vortex/vortex induced noise at a subcritical Reynolds number. In the process of numerical simulation, a traditional DDES based on the full-turbulence model SST is carried out for comparison and a 7th-order weighted compact nonlinear scheme (WCNS-E8T7) is adopted to ensure that the physical models are not affected by numerical dissipation or dispersion. In the first case, single cylinder cross-flow at ReD =4.3104 and Ma=0.21, is considered as a benchmarking problem for validating turbulence models and aerodynamic noise prediction methods. Its aerodynamic coefficients, St, CL and CD at root-mean-square (rms) and averaged values are measured by Szepessy and Bearman, while an acoustic measurement was recently made at Ecole Centrale de Lyon. The traditional DDES only based on SST model (SST-DDES) delays the instability of the shear layer on the sides of the cylinder, which leads to the recirculation zone in mean flow to grow and the induced drag to increase. Moreover, the vortex shedding frequency predicted by SST-DDES is larger than the actual value, which makes the whole sound pressure level (SPL) spectrum move toward high frequency region. However, combining the -Re transition model, the DDES (called Tran-DDES in the present article) can give the results in good agreement with the experimental data. In the second case considered is an airfoil in the wake of the cylinder. The flow condition is similar to that in the first case and the experimental results are also obtained at Ecole Centrale de Lyon. The issue of SST-DDES in recirculation zone in mean flow is weakened, which relates to the interaction between the airfoil and cylinder wake, the prediction of mean flow by SST-DDES is similar to that by the Tran-DDES. But in terms of the rms values of turbulent fluctuation components and SPL, the predictions by Tran-DDES are still better than those by SST-DDES.
First-principles study of optical properties of germanium doped with phosphorus and bismuth
Authors: Huang Lei  , Liu Wen-Liang  , Deng Chao-Sheng  ,   School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, China
Published: December 2020

Using first-principles calculations based on density functional theory, we investigate the electronic structures and optical properties of germanium doped by phosphorus and bismuth with different concentrations. By analyzing the electronic structures and optical properties of the doped systems, we can theoretically analyze and predict the optical and electrical practical applications of N-doped germanium semiconductors. By analyzing and comparing the densities of electronic states before and after doped, we can draw some conclusions. The conclusions show that the Fermi level moves in the direction of conduction band after being doped. Although germanium is an indirect band gap luminescent material, the doped systems all become direct band gap luminescence. Doping more or less affects various optical properties in different energy ranges. In a low energy range, the dielectric function and refractive index of the doped systems are affected. When the doping concentration is 2.083%, the dielectric function and refractive index of the doped system both have a special change. And the absorption of the doped system is changed in the high energy. As the energy increases after the absorption peak, the absorption of the doped system drops faster. The reflectance of the doped system is affected in all the energy ranges. The reflectance of the doped system increases in medium energy. And the reflectance of the doped system is reduced in low energy and high energy range. However, when the doping concentration is 2.083% and the energy is less than 1.7 eV, the reflectance of the doped system is higher than that of the undoped system. The conductivity of the doped system forms two peaks, adding a peak in low energy. The additional peaks in the systems where the doping concentrations are 1.563% and 2.083% are obvious. The peak of the loss function increases after being doped. However, as the doping concentration increases, the increment of the loss function decreases. As the doping concentration increases, the peak is formed at a higher energy. The conclusions are of significance for guiding the optical applications of N-type doped germanium. According to the conclusions, we can adjust the doping concentration and energy range in the optical applications of N-doped germanium.
Memristor-based multi-scroll chaotic system and its pulse synchronization control
Authors: Yan Deng-Wei  , Wang Li-Dan  , Duan Shu-Kai  ,   Chongqing Key Laboratory of Nonlinear Circuits and Intelligent Information Processing, Chongqing 400715, China;,   School of Electronic and Information Engineering, Southwest University, Chongqing 400715, China
Published: December 2020

The memristor is a nonlinear element and intrinsically possesses memory function. When it works as nonlinear part of a chaotic system, the complexity and the randomness of signal will be enhanced. In this paper memristor is introduced into a three-dimensional chaotic system based on the augmented L system. The interesting and promising behaviors of complex single, double and four-scroll chaotic attractors generated only by varying a parameter have not been reported in memristive chaotic system and thus they deserve to be further investigated. It is also obvious that such a simple change of one parameter could be used to generate a variety of quite complex attractors. Therefore, as a nonlinear device the memristor plays an important role in this system. Firstly, some basic dynamical properties of the memristive chaotic system, including symmetry and in-variance, the existence of attractor, equilibrium, and stability are investigated in detail. By numerically simulating the power spectrum, Lyapunov exponent, Poincare map and bifurcation diagram, in this paper we verify that the proposed system has abundant dynamical behaviors. The sensitivities of system parameters to the chaotic behaviors are further explored by calculating, in detail, its Lyapunov exponent spectrum and bifurcation diagrams. The results of simulation and experiment are in good agreement, thereby proving the veracity of analysis. The memristive chaotic circuit is designed using the memristor, operational amplifier, analog multiplier and other conventional components. The circuit implementation of the memristive system is simulated using SPICE (simulation program with integrated circuit emphasis). The SPICE simulation results and the theoretical analysis are found to be in good agreement, and thus verifying that the system can produce chaos. Pulse synchronization has the following characteristics: low energy consumption, fast synchronization and easy-to-implement single-channel transmission. Therefore, it is more practical in chaotic secure communication. Subsequently the pulse chaos synchronization is realized from the perspective of the maximum Lyapunov exponent, and numerical simulations show the existence of new memristive chaotic system and the feasibility of pulse synchronization control, and also provide an experimental basis for further studying the applications of the memristive chaotic system in voice secure communication and information processing.
Influence of noice on tripartite quantum probe state
Authors: Zhao Jun-Long  , Zhang Yi-Dan  , Yang Ming  ,   School of Physics and Material Science, Anhui University, Hefei 230601, China
Published: December 2020

Quantum metrology is a subject of studying quantum measurement and quantum statistical deduction, and the precision of parameter estimation can be enhanced by quantum properties. In general, the process of parameter estimation includes four steps:preparation of probe state, parameterization process, measurement, and data processing. Of these four steps, the preparation of probe state is the most crucial. However, in practical applications, in the process of preparing quantum probe state, the probe system will couple to its environment, which will inevitably cause the quantum properties of the probe system to deteriorate, and thus reducing the precision of quantum parameter estimation. The dynamics of quantum Fisher information (QFI) for W state and Greenberger-Horne-Zeilinger (GHZ) state have been studied in decoherence channels. Because W state and GHZ state have different entanglement properties, the studies of the dynamics of QFI for the superposition of W state and GHZ state are of practical significance in quantum metrology field. In this paper, the dynamics of QFIs for the superposition of W state and GHZ state in three typical decoherence channels (depolarization channel, amplitude damping channel and phase damping channel) are studied. In the four steps of quantum parameter estimation, our major attention is paid to the first step (i.e., the preparation of probe state). For comparison, the QFIs of different probe states are studied, with the other three steps fixed, i.e., all the probe states will undergo the same parameterization, measurement and estimation process. The parameterization process involved here is a quantum spin operation (specified by the spin rotation direction), which is chosen to maximize the QFI of the probe state. The initial probe states under consideration are the superpositions of W state and GHZ state of three-particle and five-particle systems, and the QFI dynamics of those probe states are studied in the three different typical decoherence channels. By using the operator-sum (Kraus) representation of those three typical decoherence channels, the QFI dynamics of the probe state can be analytically derived in three different decoherence channels. The results show that in the depolarization channel, the maximum QFI of the probe state decreases with the decoherence evolving to zero in the end; in the amplitude damping channel, the QFI of the probe state decreases to the minimum with the decoherence evolution and then increases to the shot noise limit; in the phase damping channel, the QFI of the probe state decreases with the evolution of decoherence, but the final stable value is not zero. Further analyses show that W state component of the superposition plays a role in resisting phase damping and the GHZ state component plays a role in resisting amplitude damping. These results can help us to choose the optimal probe state for maximizing the estimation precision in practice.
Influence of surge movement in non-uniform water flow on performance of underwater quantum communication
Authors: Nie Min  , Pan Yue  , Yang Guang  , Sun Ai-Jing  , Yu Sai-Ya  , Zhang Mei-Ling  , Pei Chang-Xing  ,   School of Communication and Information Engineering, Xi'an University of Posts and Telecommunication, Xi'an 710121, China;,   School of Electronics and Information, Northwestern Polytechnical University, Xi'an 710072, China;,   State Key Laboratory of Integrated Service Networks, Xi'an University of Electronic Science and Technology, Xi'an 710071, China
Published: December 2020

Quantum communication is brand new way of communication in which quantum entanglement is used to transmit information. It is an interdisciplinary subject combining quantum informatics with modern communication theory. Motivated by the communication requirements for underwater sensor networks, submarines, etc., underwater optical communication has been developing rapidly in recent years due to the ideal information security of quantum communication. However, the research on the performance of underwater quantum communication in sea has not yet been fully developed because of a series of factors such as surge, salinity and seaweed and so on. In this paper, the influence of surge in non-uniform water flow on the underwater quantum communication is studied theoretically and experimentally. Firstly, a new Boussinesq equation with a given flow function is derived based on the horizontal and vertical wave velocity of the free surface to represent the free surface boundary conditions. On the other hand, In view of the nonlinear motion of movement, the complexity of change and the randomness of the distribution, the spectrum is used for numerically calculating the surge. The characteristics of wave motion are described by wave height, period and wavelength. Secondly, the influence of surge on the entanglement of underwater quantum channel is analyzed. It is proved that the wave height of surge and the change of the cycle affect quantum communication due to the destruction of the quantum coherence and the reduction in quantum entanglement degree. Thirdly, the influence of surge motion on the quantum channel capacity is studied. The influence of the relation between the wavelength and the transmission cycle on the quantum channel capacity is simulated. The relationship between the physical characteristics of surge wave and the capacity of depolarized channel is established. Fourthly, the influence of surge motion on error rate in quantum key distribution is studied. The simulation results show that when the sea surface wind speed changes in a range of 0-20.5 m/s, the propagation cycle is increased gradually. The channel entanglement is increased from 0.0012 to 0.8426, and the channel capacity is reduced from 0.8736 to 0.1024. In the key distribution process, the quantum bit error rate increases from 0.1651 to 0.4812. Therefore, in underwater quantum communication, the parameters of the system should be adjusted adaptively according to the varying degree of the surge movement.