bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary target design for integrated direct-drive fast ignition experiments on Shenguang-II upgrade facility
Authors: Tian Chao  , Shan Lian-Qiang  , Zhou Wei-Min  , Gao Zhe  , Gu Yu-Qiu  , Zhang Bao-Han  ,   Science and Technology on Plasma Physics Laboratory, Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China;,   Department of Engineering Physics, Tsinghua University, Beijing 100084, China
Published: December 2020

The laser energy will be increased substantially when the Shenguang-II laser facility upgrade is completed and the petawatt picosecond laser beam will be equipped at the same time. For the fast ignition approach, direct-drive implosions have some advantages over indirect-drive ones, such as higher energy efficiency and lower mixing of cone material into fuel. Based on Shenguang-II upgraded laser facility, integrated direct-drive fast ignition experiments will be carried out and it will contribute to the further understanding of the relevant physics such as integrated coupling efficiency. The radiation hydrodynamic code Multi1D is used to design fast-ignition targets, and the optimized target parameters are achieved. The optimized target has a relatively thick wall (35 μm) and 420 μm-outer-radius CH shell, which are consistent with the scaling laws in target design. The deposition in the optimization target of the hot electrons generated by the picosecond petawatt pulse is also calculated according to the hot electrons scaling relation. The results show that the achieved areal density is high enough to stop the hot electrons.
Gasified singlewire almunum Z-pinch load formed by fast rising current
Authors: Wu Jian  , Li Xing-Wen  , Li Yang  , Yang Ze-Feng  , Shi Zong-Qian  , Jia Shen-Li  , Qiu Ai-Ci  ,   State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049, China;,   State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an 710024, China
Published: December 2020

In order to suppress the core-corona structures commonly observed in the single-wire exploding stage of wire array Z-pinch, the laser probe diagnostic is analyzed, and the exploding characteristics of aluminum wire under negative-polarity and fast-rising current pulses (90-170 A/ns) are investigated using a picosecond laser probe. The aluminum wire with a diameter of 15 μ m and a length of 2 cm, has a peak resistive voltage of 35-50 kV and a resistivity of 30-40 μΩ·cm before the voltage collapsed. The ohmic energy deposited in the load is 1.5-2.5 eV/atom at the voltage peak time, and 2.5-4.0 eV/atom at the time when the Joule heating power drops off to half of its maximum value. A faster rising current would lead to an increase of the energy deposition rate, and enhance the breakdown voltage. In most shots, nearly all the aluminum atoms near the electrodes are in the gaseous state, and liquid drops or clusters existing at the central part of the wire. While in some shots, the load is exploded into a gaseous state homogeneously along the axis. At about 127 ns after the laser peak, 70% of the initial mass is located within a diameter of 1 mm, and all the mass is within a diameter of 2 mm.
Electronic theoretical model of static and dynamic strength of steels
Authors: Wang Yun-Fei  , Li Yun-Kai  , Sun Chuan  , Zhu Ling-Bo  , Miao Yong  , Chen Xue-Bing  ,   School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China;,   National Key Laboratory of Science and Technology on Materials Under Shock and Impact, Beijing 100081, China
Published: December 2020

Valence electron structure has an intrinsical influence on the physical properties of material. On the basis of empirical electron theory of solids and molecules, combining with dynamic mechanical process of calculating steel, we constructe a new model for calculating static and dynamic strengths of steel. The static (dynamic) strengths of multi-composition steel, predicted by the proposed model, accord well with the experimental values. It is the first time to introduce the valence electron structure into the model for predicting dynamic properties.
Structural transformation of liquid water under shock compression condition
Authors: Wang Wen-Peng  , Liu Fu-Sheng  , Zhang Ning-Chao  ,   Institute of High Pressure and High Temperature Physics, Southwest Jiaotong University, Chengdu 610031, China
Published: December 2020

Using shock wave loading and real time optical transmission measurements, the transmission spectra of liquid water compressed between the quartz windows under pressures in a range of 1-1.6 GPa are obtained. A discontinuity of liquid water at nearly 0.9 GPa during the shock is observed. Combining the phase diagram of water with calculation results, it is suggested that the discontinuity of liquid water is due to a possible phase transition from low density water to high density water under the experimental conditions. The method can also be used to study other transparent molecular liquids in shock compression experiments.
First-principles study of the lattice dynamics, dielectric and piezoelectric response in BaTiO3/SrTiO3 (1：1) superlattice
Authors: Wang Jiang-Duo  , Dai Jian-Qing  , Song Yu-Min  , Zhang Hu  , Niu Zhi-Hui  ,   School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China
Published: December 2020

The crystal structure, spontaneous polarization, contributions of electrons and phonons to the dielectric and piezoelectric responses of BaTiO3/SrTiO3 (1:1) 10-atom superlattice are calculated using first-principles. We explore the ground structure from the highest P4/mmm phase by successively freezing the unstable polar modes. We find that the ground structure possesses the Cm symmetry. The contributions of phonons to dielectric and piezoelectric tensor coming from individual atoms and individual modes are explored. Detailed analysis shows that the ε22 and e26 are mainly due to the A“phonons with ωλ=197 and 146 cm-1, while the A” phonons with ωλ=97 cm-1 also make relatively large contributions. The ε33 and e33 are mainly due to the A' phonons with ωλ=189 and 139 cm-1. The ε11 and e11 are mainly due to the A' phonons with ωλ=246 cm-1. On the other hand, the O and Ti atoms make great contributions to the lattice dielectric and piezoelectric responses.
Resonance mode of an equilateral triangle with triangle notch
Authors: Zhang Zhi-Dong  , Gao Si-Min  , Wang Hui  , Wang Hong-Yan  ,   School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, China
Published: December 2020

A symmetrically breaking nanostructure, equilateral triangle with triangle notch, is designed. The extinction spectrum and surface electric field distribution on the structure surface are investigated by the discrete dipole approximation method. The results show that a Fano resonance line-shape occurs in the extinction spectrum, which results from the interference between the bonding and antibonding hybridized plasmon resonance. The effects of the structural parameters of the symmetrically breaking nanostructure on resonance mode are also studied.
The reflectivity and ohmic contact resistivity of Ni/Ag/Ti/Au in contact with p-GaN
Authors: Huang Ya-Ping  , Yun Feng  , Ding Wen  , Wang Yue  , Wang Hong  , Zhao Yu-Kun  , Zhang Ye  , Guo Mao-Feng  , Hou Xun  , Liu Shuo  ,   Shaanxi Provincial Key Laboratory of Photonics and Information Technology, Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049, China;,   Solid State Lighting Engineering Research Center, Xi'an Jiangtong University, Xi'an 710049, China;,   Shaanxi Supernova Lighting Technology Co. Ltd, Xi'an 710077, China
Published: December 2020

The ohmic reflectivity of Ni/Ag/Ti/Au in contact with p-GaN is studied. It is found that under different thickness values of Ni, different annealing temperatures and different annealing atmospheres, the performances of Ni/Ag/Ti/Au electrode are greatly changed. The contact resistivity is measured using the transmission line model. The reflectivity of the electrode is investigated by using a spectrophotometer. The results reveal that the thinner the Ni metal layer, the higher its reflectivity is, in addition, the thickness value of Ni metal has a little influence on contact resistivity. There appears an abrupt decrease in reflectivity of electrode after annealing at a temperature higher than 400 ℃. It is noticed that the reflectivity decreases more sharply after annealing in oxygen atmosphere than in nitrogen atmosphere. However, annealing in oxygen atmosphere is more helpful to reduce the contact resistivity. The comprehensive evaluations of the contact resistivity and reflectivity indicate that the better performances of Ni (1 nm)/Ag/Ti/Au electrode after rapid annealing in oxygen atmosphere at 400 ℃ are achieved: its contact resistance reaches 5.5× 10-3 Ω·cm2 and reflectivity rises up to 85% at 450 nm. Light emitting diode (LED) of vertical structure is fabricated with an optimal electrode. The LED under an injection current of 350 mA can achieve the following working parameters: the working voltage is 3.2 V, the optical output power is 270 mW, and the electro-optical conversion efficiency is 24%.
Plasmon excitation in C60 fullerene dimers
Authors: Yin Hai-Feng  , Zhang Hong  , Yue Li  ,   College of Physics and Electronic Engineering, Kaili University, Kaili 556011, China;,   College of Physical Science and Technology, Sichuan University, Chengdu 610065, China
Published: December 2020

Plasmon resonances in C60 fullerene dimers are investigated using time-dependent density functional theory. Owing to larger separation between molecules, there exist capacitive coupling plasmon modes in fullerene dimers. With the decrease of the gap distance, low-energy capacitive coupling plasmon modes show red shift. When the gap distance further decreases, because of the electrons tunneling across the dimer junction, plasmon resonance modes of C60 fullerene dimers are significantly modified, and the charge transfer plasmon modes occur. C60 fullerene dimer is different from metallic nanostructures dimmer. As the gap distance is again reduced, the charge transfer plasmon modes are not blue-shifted, but they are further red-shifted. In the range of the visible spectrum, C60 fullerene dimmers have strong absorption peaks.
Internal quantum efficiency of InGaN/GaN multiple quantum well
Authors: Wang Xue-Song  , Ji Zi-Wu  , Wang Hui-Ning  , Xu Ming-Sheng  , Xu Xian-Gang  , Lü Yuan-Jie  , Feng Zhi-Hong  ,   School of Physics, Shandong University, Jinan 250100, China;,   State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China;,   National Key Laboratory of Application Specific Integrated Circuit (ASIC), Hebei Semiconductor Research Institute, Shijiazhuang 050051, China
Published: December 2020

The InGaN/GaN multiple quantum wells are grown on a (0001)-oriented sapphire by using metalorganic chemical vapor deposition. Dependences of the photoluminescence (PL) peak energy and PL efficiency on injected carrier density and temperature are studied. The results show that the temperature-dependent behavior of the peak energy is in the manner of decrease-increase-decrease (S-shaped), and the maximum of the PL efficiency is observed at about 50 K. The former is attributed to the potential inhomogeneity and local characteristics of the carrier recombination in the InGaN matrix. The latter indicates that the traditional method that the internal quantum efficiency (IQE) is considered to be 100% at low temperature, should be corrected. Furthermore, it is found that the IQE depends on not only temperature but also injected carrier density. Based on the above discussion, an improved method of setting the IQE, i.e., measuring the dependence of PL efficiency is proposed.
Phase-field crystal method investigated the dislocation annihilation and grain boundary migration in grain shrink process
Authors: Li Shang-Jie  , Chen Zheng  , Yun Jiang-Juan  , Zhang Jing  ,   State Key Laboratory of Solidification Processing, Northwest Ploytechnical University, Xi'an 710072, China
Published: December 2020

The phase-field crystal method is used to analysis the dislocation annihilation and grain boundary migration mechanism in the grain shrink process of the circular grain which has three different misorientations from the matrix grain. Results show that when the misorientation between the circular grain and the matrix grain is 17°, the structure of grain boundary is composed of dislocations whose cores is so near that can not find a single dislocation. This grain boundary can not be explained by the dislocation model. However the circular grain area decreases linearly with time, which is in good agreement with the classical boundary migration theory. When the misorientation is 4°, the grain boundary structure is composed of discrete dislocations. Dislocations climb along the radial dierction and the grain rotation occurs for the circular grain to adjust the space of dislocations in the process of circular grain shrinkage. Reactions may take place with the dislocatins becoming closer. For the misorientation of 10°, portion of the grain boundary is composed of discrete dislocations and portion of dislocations with cores overlapped. Dislocations climb along the radial direction and tangential motion occurs at the same time in the grain shrinkage process. The coupled motion lead to the dislocations becoming close and reacting with each other.
Preparation of SiON film by plasma enhanced chemical vapor deposition and passivation on Si
Authors: He Su-Ming  , Dai Shan-Shan  , Luo Xiang-Dong  , Zhang Bo  , Wang Jin-Bin  ,   Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, Xiangtan University, Xiangtan 411105, China;,   National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China;,   Jiangsu Key Laboratory of Asic Design, Nantong University, Nantong 226019, China
Published: December 2020

The influences of technological condition on thickness and refractive index of the SiON films preprared by plasma enhanced chemical vapor deposition and the influence of SiON/SiNx stacked film on passivation performance on P-type silicon wafer are investigatied. The results show that the refractive index of SiON film varies from 1.48 to 2.1 and thickness varies from 30-60 nm by changing the gas flow of NH3 and the gas flow ratio of N2O/SiH4. The pressure and RF power mainly affect the thickness of the film. The greater the pressure, the higher the RF power, the faster the deposition rate is and the thicker the film is. The influences of temperature on the film thickness and refractive index can be ignored. The passivation shows that the passivation performance of P-type silicon film after annealing SiON/SiNx stacked films with a gas flow ratio of N2O/SiH4 20 and 30 in the absence and the presence of NH3, is best, which the implied voltages and the lifetimes of minority carriers are 652 mV, 56.7 μs and 649 mV, 50.8 μs, respectively. The passivation effect of SiON/SiNx stacked film is superior to that of the reference SiNx film.
The reliability analysis of using the volume averaging method to simulate the solidification process in a ingot
Authors: Li Ri  , Wang Jian  , Zhou Li-Ming  , Pan Hong  ,   Key Laboratory of Materials Processing and Control Engineering, Hebei University of Technology, Tianjin 300130, China
Published: December 2020

Adopting the Euler and the volume averaging methods, a three-phase mathematical model with parent melt as the primary phase, columnar dendrites and equiaxed grains as two different secondary phases is developed, and the coupled macroscopic mass, momentum, energy and species conservation equations are obtained separately. Taking the Al-4.7 wt% Cu binary alloy ingots for example, the flow field, temperature field, solute field, columnar-to-equiaxed-transition and grain sedimentation in two-dimension are simulated, and the simulated result of ingot and macrosegregation result are compared with their experimental values. The simulation results of temperature field, flow field and structure are basically consistent with the theoretical results, but the result of solute field shows that the simulated values is lower than the measured value on the edge, this is because the model does not take the shrinkage and forced convection into account, and the inner results is higher than the results on edge. The shrinkage and inverse segregation therefore should not be neglected. This model are still necessarily improved. Besides, based on the analysis of simulation results, the advantages and the disadvantages of the volume averaging method to simulate the solidification in a ingot are evaluated.
Analysis of a 94 GHz, TE6,2 Denisov laucher
Authors: Zhang Tian-Zhong  , Yu Sheng  , Niu Xin-Jian  , Li Hong-Fu  , Li Hao  ,   Terahertz Science and Technology Research Center, University of Electronics Science and Technology of China, Chengdu 610054, China
Published: December 2020

The launcher is an important component of the gyrotron builded-in quasi optical convertor. The propagate characteristics of high order modes in volume waveguide are analyzed in this paper based on geometric optical theory. The waveguide coupling equations and the corresponding coupling coefficients of the modes in the perturbation waveguide are derived based on the mode coupling theory. The power distribution in the perturbation waveguide and the field on the wall are analyzed by the numerical calculation code which is written in MATLAB language. The 3D simulation software can be used to verity the numerical result. As an example, a Denisov launcher of 94 GHz, TE6,2 is designed, and the numerical simulation result shows that the conversion efficiency is more than 98%, The hot-test experimental results show that the profile of output field is well consistent with the numerical result.
Mechanism of multiple bit upsets induced by localized latch-up effect in 90 nm complementary metal semiconductor static random-access memory
Authors: Chen Rui  , Yu Yong-Tao  , Shangguan Shi-Peng  , Feng Guo-Qiang  , Han Jian-Wei  ,   National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

By using the pulsed laser single effect facility, the single event upset and latch-up phenomenon are studied, and the bitmap of 90 nm complementary metal oxide semiconductor (CMOS) static random-access memory (SRAM) is mapped. It is shown that many multiple bit upsets occur and pulsed supply current of 20 mA amplitude is monitored. Based on the technology computer aided design (TCAD), it is found that the localized latch-up in CMOS SRAM is the main reason for the single event multiple bit upsets. Finally, by analyzing the results of the pulsed laser experiment and TCAD, it is found that the P/N well potential collapse is the key physical mechanism responsible for the spreading of the single event latch-up effect in 90 nm CMOS SRAM.
Two types of nanoscale nonlinear memristor models and their series-parallel circuits
Authors: Dong Zhe-Kang  , Duan Shu-Kai  , Hu Xiao-Fang  , Wang Li-Dan  ,   School of Electronic and Information Engineering, Southwest University, Chongqing 400715, China;,   Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong, China
Published: December 2020

The memristor is a novel kind of electronic device with dynamic variable resistance that is dependent on the past history of the input current or voltage. As the fourth fundamental circuit element, the memristor captures a number of unique properties that have been found to possess attractive potentials in some promising fields such as nonvolatile memory, nonlinear circuit and system, and neuromorphic system. Additionally, compared with a circuit of single memristor, series-parallel circuit of memristors possesses more abundant device characteristics which arouses increasingly extensive interest from numerous researchers. In this paper, the mathematical closed-form charge-governed and flux-governed HP memristor nonlinear models are presented with constructive procedures. In particular, these models are more realistic by taking into account the nonlinear dopant drift effect nearby the terminals and the boundary conditions, and by adding a simple and effective window function. Furthermore, based on the internal parameters and threshold of the memristor respectively, the theoretical derivation and numerical analysis of the memristor-based series-parallel connection circuits have been made comprehensively. For obtaining the characteristics of the memristor-based combinational circuits intuitively, a graphical user interface is designed based on Matlab software, which is beneficial to displaying the properties of the memristive system clearly. The results in the present paper may provide theoretical reference and reliable experimental basis for the further development of the memristor-based combinational circuits.
A method of fast-neutron imaging with energy threshold based on an imaging plate
Authors: Zhang Fa-Qiang  , Qi Jian-Min  , Zhang Jian-Hua  , Li Lin-Bo  , Chen Ding-Yang  , Xie Hong-Wei  , Yang Jian-Lun  , Chen Jin-Chuan  ,   Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

A method of fast-neutron imaging with energy threshold is presented in this paper, which is based on an imaging plate covered with a metal foil and a hydrogen-rich foil in order to reduce the contribution from the neutrons with a lower energy such as the scattering neutrons from samples. The method is capable of effectively reducing the relative sensitivity of the imaging detector to neutrons with energies in a certain energy range. The 14 MeV neutron imaging structure with an energy threshold is designed, and it includes a TR imaging plate covered with an about 150 m Pb foil and a 500 m polyethylene foil. The calculated results show that for the present structure its sensitivity to the neutrons with smaller than 8 MeV is reduced by 30% less than that to the neutrons with 14 MeV. The fast-neutron radiography is validated experimentally on a DT neutron generator (K400). The results indicate that the neutron imaging structure with an energy threshold is available to remove the edge enhancement effect introduced by scattering neutrons from samples.
Detection of small space debris impact induced flash and its application
Authors: Li Hong-Wei  , Han Jian-Wei  , Wu Feng-Shi  , Cai Ming-Hui  , Zhang Zhen-Long  ,   Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

In the research of space debris impact induced discharge the measurements of the density and temperature of the impact plasma are very important and difficult. Spectrum analysis is the best method of measuring the density and temperature of hypervelocity impact induced plasma. This method has been successfully used for detecting the density of the plasma produced by hypervelocity particles with diameters larger than 1 mm. In this paper, we present a method of detecting the light flash that is produced by the hypervelocity impact of 200 μm particles which is the foundation for the spectrum analysis method. The characteristics of the light flash of the impact and the impact induced discharge are also discussed.
Time irreversibility analysis of converter based on symbolic dynamics
Authors: Xu Hong-Mei  , Jin Yong-Gao  , Jin Jing-Xuan  ,   College of Engineeing, Yanbian University, Yanji 133002, China
Published: December 2020

A new method based on symbobic dynamics and relative entropy theory is proposed to examine the nonlinear behaviours of converters. Firstly, the discrete numerical sequence is obtained from iteration map, which is then transferred to a symbol-time series according to the topological conjugation, and the relative entropy is calculated by means of forward and backward probabilities. This paper takes a first one-order voltage feedback DCM Boost converter as an example, and the result shows that the relative entropy, which can measure quantitatively the distance apart from equilibrium when converter lies in a chaotic state, is a new and quantified nonlinear dynamic behaviours which has not been used in converters yet.
The VMI study on branching ratio decay from Eu 6p1/28s autoionizing state
Authors: Liang Hong-Rui  , Shen Li  , Jing Hua  , Dai Chang-Jian  ,   School of Science, Tianjin University of Technology, Tianjin 300384, China;,   Key Laboratory of Display Materials and Photoelectric Devices, Ministry of Education, Tianjin 300384, China
Published: December 2020

A velocity-map-imaging (VMI) method is employed to investigate systematically the dynamical process of ejected electrons from autoionizing states of the Eu atom for the first time as far as we know. An atom is excited stepwise from the 4f76s6s8 S7/2 ground state to the 4f76s8s8 P7/2 Rydberg state via the 4f76s6p6 P5/2 intermediate state, then further excited to the 4f76p1/2(J=3)8s and 4f76p1/2(J=4)8s autoionizing states using the three-step isolated-core excitation method. According to the excitation pathways and selection rules, the value of total angular momentum of the autoionizing state can be calculated. The energy conservation and angular momentum parity conservation would enable us to determine the final states during the autoionizing process. The ejected electron, which decays from the autoionizing process, can be focused and imaged by the electron lens and the kinetic energy of it is resolved by the position sensitive detector. By combining velocity-map-imaging method with the mathematical transformation, the ejected electron energy distribution can be obtained, also the branching ratio is confirmed. Simultaneously, by tuning the wavelength of the third laser, the characteristic of the branching ratio following the variation of the photon energy, and the possibility of the population inversion have been discussed.
Extraction of nonlinear characteristics from eddy current magnetic field of Al-alloy weld and their classification
Authors: Gao Peng  , Wang Chao  , Zhi Ya  , Li Yang  , Wang Li-Bin  , Cong Zheng  ,   School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China
Published: December 2020

GMR (giant magneto resistance) sensor can be used to measure the eddy current magnetic field of the Al-alloy weld. The nonlinear time series analysis method is introduced to study the signals from the eddy current magnetic field of the weld in three different states, which include good, lack of penetration, and clustered blowhole weld. Several nonlinear characteristic parameters, such as Lyapunov exponent and correlation dimension etc., are extracted. The results show that the eddy current magnetic field of the Al-alloy weld has distinguished chaotic features. Analysis of the Lempel-Ziv complexity and approximate entropy for different signals leads to the conclusion that these two complex measures are sensitive to the eddy current magnetic field of the weld zone. Through these methods, nonlinear characteristics of eddy current magnetic field of the weld can be obtained for identifying and classifying the type of the weld, which will serve as an efficient supplementary diagnostic tool to reveal different patterns of the welds.
Simulation analysis of the depth of field characteristic of negative refraction flat lens
Authors: Zhu Xing-Fu  , Liang Bin-Ming  , Zhan Sheng-Gao  , Chen Jia-Bi  , Zhuang Song-Lin  ,   College of Optics and Electronics Information Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
Published: December 2020

In virtue of wave-front coding theory, a computer simulation analysis of the depth of field extension of negative refraction flat lens is carried out. The depth of field extension can be achieved by 6.7 times in the slab, when its index is -1, through computer simulation. When the refractive index of the tablet is slightly offset, taking -0.99 for example, 6.9 times of the depth of field extension can be achieved after the introduction of the calibration lens.
Firstorder quantum phase transition in the two-mode Dicke model
Authors: Yu Li-Xian  , Liang Qi-Feng  , Wang Li-Rong  , Zhu Shi-Qun  ,   School of Physical Science and Technology, Soochow University, Suzhou 215006, China;,   Department of Physics, Shaoxing University, Shaoxing 312000, China;,   Laser Spectroscopy Laboratory, Shanxi University, Taiyuan 030006, China
Published: December 2020

The multi-mode Dicke model, which describes many atoms interacting with the multi-mode photons, has attracted much attention; it not only exhibits rich quantum phases, but also has an important application in quantum information. In this paper, we explore the ground-state properties of the two-mode Dicke model by the Holstein-Primakoff transformation and Boson expansion method, and theoretically predict a new first-order quantum phase transition. In the experiment, this quantum phase transition could be detected by measuring the mean-photon number or the atom population.
780 W narrow linewidth all fiber laser
Authors: Zhang Li-Ming  , Zhou Shou-Huan  , Zhao Hong  , Zhang Kun  , Hao Jin-Ping  , Zhang Da-Yong  , Zhu Chen  , Li Yao  , Wang Xiong-Fei  , Zhang Hao-Bin  ,   Science and Technology on Solid-state Laser Laboratory, Beijing 100015, China
Published: December 2020

High-power narrow linewidth fiber lasers are extensively applied in coherent detection and power-spectrum beam combination etc. The suppressing method of stimulated Brillouin scattering is analyzed. And the theory of sinusoidal phase modulation is analyzed also. A single frequency laser is broadened to become a 2.9 GHz linewidth seed by sinusoidal phase modulation technology. The power of the seed is then boosted from 50 mW to 780 W through a three-stage power amplifiber configuration. Central wavelength and linewidth of the laser are 1064.34 nm and 2.9 GHz respectively, with an optical-optical efficiency being 79%. And the beam quality is Mx2 =1.44 and My2 =1.43. The output powers before and after phase modulation are compared with each other. And the reason why output power increases is analyzed. The stimulated Brillouin scattering threshold is promoted by added longitudinal mode. Finally, the output power is promoted after phase modulation, so that the output power of this laser is only limited by the pump power. If the pump power is increased, the higher output power of narrow linewidth fiber laser will be achieved.
A Nd：YAG regenerative amplifier seeded by 1064 nm picosecond fiber
Authors: Lian Fu-Qiang  , Fan Zhong-Wei  , Bai Zhen-Ao  , Yu Jin  , Lin Wei-Ran  , Zhang Xiao-Lei  , Liu Di  , Zhao Tian-Zhuo  ,   The Academy of Opto-electronics, Beijing 100094, China;,   University of Chinese Academy of Science, Beijing 100049, China;,   Beijing GK Laser Technology Co., Ltd, Beijing 100190, China;,   Hi-Tech Optoelectronics Co., Ltd, Beijing 102206, China
Published: December 2020

The picosecond pulse from 1064 nm Yb-doped all-fiber mode-locked laser is amplified by Nd: YAG regenerative amplifier. Research is focused on the influence of Yb-doped all-fiber mode-locked laser on the efficiency of energy extraction of Nd: YAG regeneration amplifier. In order to increase the efficiency of energy extraction, spectral oscillatory fringe is decreased by means of restricting the self-phase modulation of Yb-doped all-fiber mode-locked laser. The Nd:YAG regenerative amplifier produces stable pulse energy of 1.3 mJ at a repetition rate of 1 kHz, which is seeded by a Yb-doped all-fiber mode-locked laser, with a low energy of 3.2 nJ, center wavelength of 1064.1 nm, 3 dB bandwidth of 0.35 nm 11 ps duration.
Photonic crystal fibers with high nonlinearity, large birefringence and multiple zero dispersion-wavelength
Authors: Wang Er-Lei  , Jiang Hai-Ming  , Xie Kang  , Zhang Xiu-Xia  ,   School of Instrument Science and Opto-electronics Engineering, HeFei University of Technology, Hefei 230009, China;,   School of Electronics and Information Engineering, Beifang University of Nationalities, Yinchuan 750021, China
Published: December 2020

A novel kind of total internal reflection photonic crystal fiber (TIR-PCF) with highly nonlinear, large birefringence and multiple zero-dispersion wavelengths is designed. Characteristics such as birefringence, effective mode areas, nonlinearity and dispersion are investigated by finite element method (FEM). Numerical results demonstrate that the birefringence is 2.54×10-2 at the wavelength of 1.55 μm, and high nonlinear coefficients (50.22 W-1·km-1 and 54.61 W-1·km-1 in X, Y polarization directions respectively) are obtained by setting the appropriate structure parameters. In addition, two zero-dispersion wavelength points appear in the infrared band, one of which emerges near the wavelength of 1.55 μm. The design provides a new structure for large birefringence, highly nonlinear and photonic crystal fiber with multiple zero-dispersion wavelengths, and it could be widely used in polarization control, nonlinear optics, dispersion management and super-continuum generation.
Modeling the bidirectional reflectance distribution function of seawater with spilt oil
Authors: Sun Lan-Jun  , Tian Zhao-Shuo  , Ren Xiu-Yun  , Zhang Yan-Chao  , Fu Shi-You  ,   Information Optoelectronics Research Institute, Harbin Institute of Technology at Weihai, Weihai 264209, China
Published: December 2020

Study on the bidirectional reflectance distribution function (BRDF) of seawater with spilt oil will provide a theoretical basis for detection of oil film on sea surface and oil emulsion in sea water, which will be of great significance for protection of marine environment and marine ecological balance. In this paper a model of BRDF for oil-polluted seawater has been developed by applying Monte Carlo method and Mie scattering theory. The BRDFs of clean seawater, oil-covered seawater, and oil-emulsion seawater are investigated at wavelengths of 532 nm and 355 nm. Simulation results of different film thicknesses and oil emulsion concentrations are presented. Results show that the BRDF is rather sensitive to the degree of pollution in seawater. The presence of oil film or oil emulsion will cause a decrease of the BRDF. At the same angles of observation, the BRDF value of seawater decreases with the increase of oil film thickness and oil emulsion concentration. Oil spill detecting and monitoring can potentially be achieved using BRDF data from optical sensors.
Selective-area growth of GaAs and GaAs/InxGa1-xAs/GaAs nanowires by MOCVD
Authors: Cui Jian-Gong  , Zhang Xia  , Yan Xin  , Li Jun-Shuai  , Huang Yong-Qing  , Ren Xiao-Min  ,   State Key Laboratory of Information Photonics & Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876, China
Published: December 2020

We have investigated the catalyst-free selective-area growth of GaAs and GaAs/InxGa1-xAs/GaAs (0x3. GaAs nanowire length would become longer by reducing the mask opening size. Thus we can form the GaAs nanowire uniform arrays with appropriate length and width by controling growth conditions and mask opening size. Then the photoluminescence measurement of GaAs/InxGa1-xAs/GaAs (0x<1) core-shell nanowires is carried out.
Amorphizing and mechanical properties of co-sputtered Al-Zr alloy films
Authors: Ma Bing-Yang  , Zhang An-Ming  , Shang Hai-Long  , Sun Shi-Yang  , Li Ge-Yang  ,   State Key Laboratory of Metal Matrix Composites, Shanghai JiaoTong University, Shanghai 200240, China
Published: December 2020

In order to reveal the reason why mechanical properties of alloy films increase continuously after amorphizing, a series of Al-Zr alloy films with different Zr contents are prepared by magnetron co-sputtering of Al and Zr targets. The microstructure and mechanical properties of the films are characterized through a number of techniques, including X-ray energy dispersive spectroscopy, X-ray diffraction, transmission electron microscopy, and nanoindentation. Results show that the films with low Zr content form highly supersaturated solid solutions due to high dispersibility of vapor particles and non-equilibrium growth of the film in co-sputtering process. The film grains are refined to nanoscale particles due to dramatic lattice distortion and the film hardness increases rapidly. As Zr content increases, the film hardness increases continuously because of the increase of Al-Zr chemical bonds after amorphizing, and reaches a high value of 9.8 GPa at 33.3 at.% Zr. The research results reveal the effect of the Al-Zr chemical bonds on mechanical properties in amorphous films
Calculation of electron transport in GaAs nanoscale junctions using first-principles
Authors: Liu Fu-Ti  , Cheng Yan  , Chen Xiang-Rong  , Cheng Xiao-Hong  ,   College of Physics and Electronic Engineering, Yibin university, Yibin 644007, China;,   College of Physical Science and Technology, Sichuan University, Chengdu 610064, China;,   Computational Physics Key Laboratory of Sichuan Province of Yibin university, Yibin 644007, China
Published: December 2020

Electron transport properties of GaAs cluster, which is sandwiched between two semi-infinite Au(100)-3×3 electrodes in four different anchoring configurations (top-top, top-hollow, hollow-top, hollow-hollow), is investigated using the combination of density functional theory and non-equilibrium Green's function method. We optimize the geometry of junctions at different distances, simulate the breaking process of Au-GaAs-Au junctions, calculate the cohesion energy and conductance of the junctions as functions of distance dz, and obtain the most stable structure when the distances are set at 1.389 nm, 1.145 nm, 1.145 nm, 0.861 nm, respectively. For stable structures, the Ga-As bond lengths of the junctions is 0.222 nm, 0.235 nm, 0.227 nm, 0.235 nm, respectively. The equilibrium conductances are 2.33 G0, 1.20 G0, 1.90 G0, 1.69 G0,respectively. All junctions have large conductance. In the range of voltage from -1.2–1.2 V, the I-V curve of the junctions shows linear characteristics.
Time domain theory of the electronic transport property of semiconductors measured by means of square-wave-modulated free carrier absorption technique
Authors: Zhang Xi-Ren  , Gao Chun-Ming  ,   School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

A time-domain model for the square-wave-modulated free carrier absorption (MFCA) is developed in measuring the electronic transport properties (the carrier lifetime, the carrier diffusivity, and the front surface recombination velocity) of semiconductor wafers. The dependences of time-domain MFCA signals on the electronic transport properties at different modulation frequencies are investigated by computer simulation. It is found that there are the high sensitivities of MFCA signal to the individual transport parameter. Furthermore, compared with the results by frequency-domain MFCA, in time-domain MFCA measuring ranges the transport properties can be improved.
Spin-torque critical current tuned by stress
Authors: Guo Zi-Zheng  , Deng Hai-Dong  , Huang Jia-Sheng  , Xiong Wan-Jie  , Xu Chu-Dong  ,   Department of Applied Physics, College of Science, South China Agricultural University, Guangzhou 510642, China
Published: December 2020

Excessive spin-torque critical current has long been a problem received much attention. In this paper, we suggest that by introducing the out-of-plane stress or the stress anisotropy field, the out-of-plane demagnetizing field can be compensated effectively, and in this way the spin-torque critical current can be reduced. Specifically, the four-component distributed spin-circuit model is used to calculate the polarization current which is transferred from the polarizer to the detector (free layer).The properties of magnetization switching in the free layer of the lateral spin valve are studied under the influence of stress by using the Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation. Results show that, if the stress direction is appropriately selected, the out-of-plane demagnetizing field can be effectively compensated, thereby the spin torque critical current can be significantly reduced. Furthermore, as the stress is increased and the demagnetizing field is reduced, the magnetization reversal time is greatly reduced.
Ordered subset image reconstruction studied by means of total variation minimization and fast first-order method in low dose computed tomograhpy
Authors: Mao Bao-Lin  , Chen Xiao-Zhao  , Xiao Da-Yu  , Fan Sheng-Yu  , Teng Yue-Yang  , Kang Yan  ,   Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang 110819, China;,   Key Laboratory of Medical Image Computing of Ministry of Education, Northeastern University, Shenyang 110819, China
Published: December 2020

Low-dose computed tomography(CT) has an advantage to reduce X-rays that are harmful to the body. This paper considers the issue of reconstructing high-quality low-dose CT images from incomplete projection data. Generally, this can be done by statistical image reconstruction methods. However, the huge number of iterations of the statistical reconstruction algorithms leads to long computing time, making them difficult to be of practical value. To solve this problem, we propose a method to alleviate the issue by using total variation minimization and fast first-order method for the ordered subsets. We use Split Bregman alternating direction method to solve the optimization problem. Then, the projection onto convex sets method is used to speed up the convergence rate of the iterative method. Numerical experiments show that the relative reconstruction error of the proposed method can decrease faster than the first-order method of ordered subsets with the same iterative number.
Traffic state prediction based on competence region
Authors: Liu Qing-Chao  , Lu Jian  , Chen Shu-Yan  ,   Jiangsu Key Laboratory of Urban ITS, Southeast University, Nanjing 210096, China;,   Jiangsu Province Collaboratire Innovation Center of Modern Urban Traffic Technologies, Nanjing 210096, China
Published: December 2020

Traffic state prediction is a key basis of traffic flow guidance system and traffic information publishing system. This paper presents a new method of forecasting the traffic state of unban expressway based on competence region. This method can predict the traffic state grade of road based on the distance between the sample data and the traffic state cluster center by creating a competence region of neural network classifier. And this method can effectively integrate the temporal and spatial features together without considering the correlation between the different features, and thus it has a strong adaptability. The experimental results show that this traffic state prediction method can reduce the prediction error and improve the equality coefficients compared with the classical algorithms. The prediction method used in this paper is effective and accurate for forecasting traffic state based on the competence region.
Geometrical statistical channel model and performance investigation for multi-antenna systems in wireless communications
Authors: Zhou Jie  , Jiang Hao  , Hisakazu Kikuchi  , Shao Gen-Fu  ,   Laboratory of Meteorological Observation and Information Processing, Nanjing University of Information Science and Technology, Nanjing 210044, China;,   Department Of Electronic and Electrical Engineering, Niigata University, 950-2181, Japan;,   Department Of Automation, Hangzhou University of Electronic Science and Technology, Hangzhou 310018, China
Published: December 2020

For testing an adaptive array algorithm in cellular communications, we develop a geometry based statistical channel model that provides the statistics of angle-of-arrival and doppler spectra of the multi-path components, into which introduced are the new concepts of effective scatterers and reflection probability. This channel model is suitable for describing the outdoor and indoor propagation environments, which is applied to the performance of multiple input multiple output (MIMO) system. A comparison between our theoretical calculations and customary results shows that the analysis is correct and applicable to microcell environments, which can promote the research of the statistical channel models and provide accurate and flexible channel models for the MIMO multi-antenna systems.
Simulation of frequency discrimination for spaceborne Doppler wind lidar (I)：Study on the retrieval of atmospheric wind speed for Mie channel based on Fizeau interferometer
Authors: Zhang Ri-Wei  , Sun Xue-Jin  , Yan Wei  , Liu Lei  , Li Yan  , Zhao Jian  , Yan Wan-Xiang  , Li Hao-Ran  ,   College of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China;,   Northwest Institute of Nuclear Technology, Xi'an 710024, China
Published: December 2020

System structure of spaceborne Doppler wind lidar is investigated. Simulation system of frequency discrimination is built based on Fizeau interferometer. The wind retrieval algorithm of Mie channel is simulated and studied. The horizontal line-of-sight (HLOS) wind error is analysed using the simulated result of the radiosonde dataset. The result shows that the wind speed of lower troposphere can be retrieved in Mie channel based on Fizeau interferometer. The average values of HLOS wind error deviation and standard deviation in lower troposphere are less than 1 m·s-1 and 2 m·s-1, respectively. Distributions of aerosol and cloud have an influence on wind error for spaceborne Doppler wind lidar, and the maximum wind deviation will increase twice.
Highly birefringent ZrF4-BaF2-LaF3-AlF3-NaF photonic quasi-crystal fiber with twin grapefruits holes
Authors: Su Wei  , Lou Shu-Qin  , Zou Hui  , Han Bo-Lin  ,   School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

A novel design of highly birefringent photonic quasi-crystal fiber based on ZrF4-BaF2-LaF3-AlF3-NaF glass with twin grapefruit air holes near the core and twofold symmetry is proposed. The basic unit is composed of one square and its neighboring regular triangle. Using the finite element method, the birefringence and confinement loss are investigated simultaneously by changing the pitch of air holes and sizes of air holes. Numerical results show that the fiber maintains single mode operation in a wide wavelength range from 1.8 μm to 2.2 μm, and the birefringence is on the order of 10-2, two orders of magnitude larger than that of the conventional polarization-maintaining fibers, which is largest (around 2 μm) ever reported to our knowledge and the same order of magnitude as that obtained by fiber using elliptic air holes But this designed fiber is easy to fabricate compared with the fibers using elliptic air holes.
Generation of narrowband triphoton frequency-entangled states via cold-atom ensembles
Authors: Liu Rui  , Yu Ya-Fei  , Zhang Zhi-Ming  ,   Laboratory of Nanophotonic Functional Materials and Devices (SIPSE), Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006, China
Published: December 2020

We propose a scheme for the generation of narrowband triphoton frequency-entangled states. This scheme uses the four-wave mixing and the electromagnetically induced transparency in two cold-atom ensembles. By using the second-order perturbation theory, some relevant calculations are performed. By analyzing the coincidence-counting rate, we study the correlation and nonclassical properties of these states, and find that they have a similar feature to that of the discrete-variable W state, and can show the antibunching effect.