bluuebunny/crossref_metadata_2025 huggingface dataset:
Theory and simulation of laser pulse trapping and amplifying in the interaction with a thin foil and a solid target
Authors: Zou De-Bin  , Zhuo Hong-Bin  , Shao Fu-Qiu  , Yin Yan  , Ma Yan-Yun  , Tian Cheng-Lin  , Xu Han  , Ouyang Jian-Ming  , Xie Xiang-Yun  , Chen De-Peng  ,   college of Science, National University of Defense Technology, Changsha 410073, China;,   college of Computer, National University of Defense Technology, Changsha 410073, China
Published: December 2020

In this paper we suggest a simple structure consisting of a thin foil and a solid target with specified gap width to achieve the laser-field amplification, and study the trapping process of a single pulse. Both the theoretical and simulation results show that the EM fields are trapped as standing waves between two layers of enhanced electron density. The laser energy can be accumulated like the accumulation of charges in capacitor, a stably trap is reached after several oscillations. The compressing and the expanding of the electron layer, generated by the incident light pressure, the trapped light pressure and the charge electrostatic fields, are the direct reason for the energy oscillations.
A three-dimensional particle-in-cell/Monte Carlo computer simulation based on negative hydrogen ion source
Authors: Yang Chao  , Liu Da-Gang  , Wang Xiao-Ming  , Liu La-Qun  , Wang Xue-Qiong  , Liu Sheng-Gang  ,   University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

Based on the analysis of the plasma physics mechanism in negative hydrogen ion source, the particle-in-cell algorithm is studied and optimized and a high efficient storage method of particles is designed. Using the Monte Carlo collision model, considering the plasma potential and coulomb collisions between charged particles, the full three-dimensional particle-in-cell/ Monte Carlo algorithm (PIC/MCC) is developed. With the magnetic charge model, using the FDTD method, the line cusp magnetic field is calculated. With the negative hydrogen ion source JT-60U and considering the main reactions in the negative hydrogen ion source, the full three-dimensional PIC/MCC simulation algorithm is verified by simulation.
Investigation of proton irradiation damage in BaTiO3 thin film by computer simulation
Authors: Zhu Yong  , Li Bao-Hua  , Xie Guo-Feng  ,   Faculty of Materials, Optoelectronics and Physics, Xiangtan University, Xiangtan 411105, China
Published: December 2020

BaTiO3 is a kind of perovskite ferroelectric which has the advantages of ferroelectric property, piezoelectric property and radiation resistance. BaTiO3 thin films and devices have important applications in strong irradiation environment. The structure damage, especially the oxygen vacancy has a crucial influence on the response of ferroelectric under radiation. Molecular dynamics is used to simulate the formation process and the recovery process of defects in BaTiO3 under the impact of primary knock-on atom (PKA). The results show that the initial motion direction and energy of PKA have significant effects on the number of defects, and the averaged threshold displacement energies of Ba, O and Ti atom are 69 eV, 51 eV and 123 eV respectively. The calculated displacement energy is obviously larger than default value (25 eV) in SRIM code. Furthermore the SRIM code is used to simulate the proton irradiation damage in BaTiO3 thin film. The results show that the number of vacancy increases with the increase of proton energy, but the increase rate decreases, and the number of vacancy decreases obviously with the increase of incidence angle when it is more than 60°.
Amending the ferromagnetic properties of Ga0.94Mn0.06As films by He+ irradiation
Authors: Ding Bin-Feng  , Xiang Feng-Hua  , Wang Li-Ming  , Wang Hong-Tao  ,   Department of Physics and Electronic Information, Langfang Teachers College, Langfang 065000, China
Published: December 2020

Ion irradiation of semiconductors is a well understood method to tune the carrier concentration in a controlled manner. We show that the ferromagnetism in Ga0.94Mn0.06As films, known to be hole-mediated, can be modified by He ion irradiation. The coercivity can be increased by more than three times. The magnetization, Curie temperature and the saturation field along the out-of-plane hard axis all decrease as the fluence increases. The electrical and structural characterization of the irradiated Ga0.94Mn0.06As layers indicates that the controlled amending of magnetism results from a compensation of holes by generated electrical defects and not from a structural modification.
Optical properties of N-doped Cu2O films and relevant analysis with first-principles calculations
Authors: Pu Chun-Ying  , Li Hong-Jing  , Tang Xin  , Zhang Qing-Yu  ,   Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, School of Physics and Opto-electronic Technology, Dalian University of Technology, Dalian 116024, China;,   College of Materials Science and Engineering, Guilin University of Technology, Guilin 541004, China
Published: December 2020

N-doped Cu2O films are deposited at different temperatures by sputtering a CuO target in the mixture of Ar and N2. By the analysis of transmission spectra, it is found that the N-doped Cu2O films are changed into a direct allowed band-gap semiconductor and the optical band gap energy is enlarged to 2.52±0.03 eV for the films deposited at different temperatures. The first-principles calculations indicate that the energy band gap increase by 25%, which is in good agreement with the experimental result. The change from a direct forbidden band-gap transition to a direct allowed band-gap transition can be attributed to the occupation of 2p electrons of N at the top of valence band in the N-doped Cu2O film.
First principles investigation of interaction between interstitials H atom and Nb metal
Authors: Rao Jian-Ping  , Ouyang Chu-Ying  , Lei Min-Sheng  , Jiang Feng-Yi  ,   Institute of Materials Sciences and Engineering, Nanchang University, Nanchang 330029, China;,   Department of Physics, Jiangxi Normal University, Nanchang 330022, China
Published: December 2020

Understanding of the interaction between Nb and interstitial H is helpful for using Nb metallic membrane as H2 purification selective membrane. By first-principles calculations, the site occupation of H in the interstitials of the bcc Nb lattice is studied, and the relation between the site energy and the size of the interstitial is discussed. The interaction between interstitial H and Nb lattice is analyzed and the influence of the electronic structure on the interaction is discussed. The results show that in addition to the influence of the interstitial size on the H solution energy, strong bonding interaction between H-1s and Nb-3d is another important reason for the low H solution energy in Nb lattice. The H diffusion coefficient in Nb metal is evaluated and results show that it is approximately 7.8× 10-9 m2/s at 500 ℃, Which is in agreement with experimental observation.
Research of electronic and magnetic properties on gold doped zigzag graphene nanoribbons
Authors: Hu Xiao-Hui  , Xu Jun-Min  , Sun Li-Tao  ,   SEU-FEI Nano-Pico Center, Key Lab of MEMS of Ministry of Education, Southeast University, Nanjing 210096, China
Published: December 2020

Using first principle based on the density functional theory, we have studied the the electronic and magnetic properties of zigzag graphene nanoribbons (ZGNRs) doped by gold atoms in divacancy. Our calculations show that edge site is the most stable doping site for gold atom, and the magnetism of ZGNRs is inhibited by the introduction of impurities. However, in the case of large enough doping ratio, the magnetic moment of doped edge restores anomalously. The band structure characteristic of gold doped ZGNRs is sensitive to doping ratio. As the doping ratio increases, Au doped ZGNRs show semiconducting, half-metallic and metallic properties, respectively. Our calculations prove that gold atoms doped ZGNRs could modulate the magnetic and band structure character, guiding the follow-up experiments, and promoting the application of graphene in spintronics.
One-shadow-mask ultralow-voltage indium-tin-oxide thin-film transistors on paper substrates
Authors: Mao Yan-Kai  , Jiang Jie  , Zhou Bin  , Dou Wei  ,   Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082, China
Published: December 2020

A new kind of electric-double-layer indium-tin-oxide (ITO) thin-film transistor (TFT) is fabricated on a paper substrate by one-shadow-mask process. The channel layer can be simultaneously self-assembled between ITO source/drain electrodes by only one shadow mask during RF magnetron sputtering deposition at room temperature. Base on this, we choose microporous SiO2 with electric double layer effect as a gate dielectric, and successfully develop the ultralow-voltage oxide TFT on a paper substrate. The TFT exhibits a good performance with an ultralow operation voltage of 1.5 V, a field-effect mobility of 20.1 cm2/Vs , a subthreshold swing of 188mV/decade, and a large on-off ratio of 5× 105. The full-room-temperature oxide TFT on the paper substrate by one-shadow-mask process shows a lot of advantages, such as low operation voltage, simple device process, low cost, etc. Such a TFT is very promising for the application of low-power and portable electronic products in the future.
Effect of surface plasmon polariton of Ag nanoparticles on the photoluminescence property of up-conversion materials
Authors: Tong Jian-Bo  , Huang Qian  , Zhang Xiao-Dan  , Zhang Cun-Shan  , Zhao Ying  ,   Institute of Photo Electronics thin Film Devices and Technique of Nankai University, Key Laboratory of Photo Electronics Thin Film Devices and Technique of Tianjin, Key Laboratory of Opto Electronic Information Science and Technology, Ministry of Education, Tianjin 300071, China;,   School of Information Engineering. Hebei University of Technology, Tianjin 300071, China;,   State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310027, China
Published: December 2020

Silver nanoparticles are added into Yb3+ and Er3+ co-doped NaYF4 up-conversion materials using co-sintering process. Changes in diffraction intensity and surface morphology are inspected by X-ray diffraction and scanning electron microscope measurement, respectively. The optical absorption and Photoluminescence spectra are measured using UV/visible spectrophotometer and photoluminescence measurements. By optimizing the quantity of Ag nanoparticles, we obtain obvious enhancements of the photoluminescence intensities of Yb3+ and Er3+ co-doped NaYF4 materials, which shows a 28% enhancement in 300—800 nm wavelength range and a 55% enhancement at 544 nm. Different mechanisms are proposed for light quenching and surface plasmon enhanced absorption with Ag nanoparticles adjustment.
The effect of substrate on terahertz transmission properties through metal subwavelength dual-ring structure
Authors: Liu Jian-Feng  , Zhou Qing-Li  , Shi Yu-Lei  , Li Lei  , Zhao Dong-Mei  , Zhang Cun-Lin  ,   Beijing Key Laboratory for Terahertz Spectroscopy and Imaging, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal University, Beijing 100048, China
Published: December 2020

Terahertz waves through a split-ring resonator (SRR) can induce the resonant absorption, and this can be explained by using the theory of LC resonant circuit and the model of half wave resonance. However, in the dual-ring structure without the split gap, we still observe the resonant absorption in the THz frequency range. By analyzing the phenomenon, we think that it can be explained by using a the model of half wave resonance. Furthermore, it is found that if the structure is fabricated on quartz crystal substrate, we can obtain the angle-dependent terahertz waveforms using terahertz time-domain spectroscopy (TDS) when the sample is rotated in plane, as well as the frequency domain spectra. But this phenomenon does not exist in the silicon-based structure, which may be attributed to the birefringence effect of the quartz crystal substrate on the subwavelength metal dual-ring structure. The main purpose of this article is to explain the physical process of the effect.
Study on 3D von Neumann equation with anisotropy for convex grains
Authors: Wang Hao  , Liu Guo-Quan  , Luan Jun-Hua  ,   School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China;,   State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
Published: December 2020

Understanding the laws of grain growth in three dimensions is one of the classic problems of materials science. By considering the anisotropy in real polycrystalline structure and the relationship between the integral of surface mean curvature and the mean caliper diameter of a convex individual grain, three-dimensional von Neumann equation for accurate grain growth rate is studied. The result shows that accurate grain growth rate of a convex grain is related to the grain mean caliper diameter, the sum of the length of grain edges and the corresponding dihedral exterior angles. This result is verified by Kelvin tetrakaidecahedron and the only five convex regular polyhedra.
Genetic algorithm with regularization method to retrieve ocean atmosphere duct
Authors: He Ran  , Huang Si-Xun  , Zhou Chen-Teng  , Jiang Zhu-Hui  ,   Institute of Meteorology, PLA University of Science and Technology, Nanjing 211101, China
Published: December 2020

Due to the fact that regularization method can overcome the ill-posed characteristic and obviously suppress noise and errors propagation in practical inverse problem, a new algorithm (genetic algorithm with regularization method) is proposed, combining fitness function of genetic algorithm with regularization term to retrieve ocean duct parameter. Simulation experiments show that retrieval accuracy of the new algorithm is better than that of traditional genetic algorithm. When the noise errors are less than 10%, the noise-immune performance is better. Finally, the inversion result from airborne radar clutter local date of sea surface in the Wallops island is compared with real refractivity profile, pointing out the efficiency of algorithm. The new method provides a new consideration for inverse research of ocean atmosphere duct.
The fault-tolerance study of QCA adder based on probability model
Authors: Huang Hong-Tu  , Cai Li  , Yang Xiao-Kuo  , Liu Bao-Jun  , Li Zheng-Cao  ,   College of Science, Air Force Engineering University, Xi'an 710051, China
Published: December 2020

The probability models of 2 different quantum cellular automaton (QCA) adders are based on the theory of probabilistic transfer matrix and circuit partition. The effect of individual component on the overall fault-tolerance is fully analyzed at the same level. The simulation shows that the effect of the wire is minor when the success probability is low, while the overall fault-tolerance rises sharply once the success probability is high. And the inverter is considered to be a major factor that affects the overall fault-tolerance in the variation range of parameter. Frobenbius norm of the overall error probabilistic transfer matrix is employed to study the fault-tolerance difference. The result shows that the overall fault-tolerance of QCA adder consisting of 5-input majority is superior to the other. Such fault-tolerance analyses should be used for a better characterization of QCA circuit design and fault-tolerance improvement.
Calculating far field of an arbitrarily oriented electric dipole located above layered half space using reciprocity theorem
Authors: Ge De-Biao  , Wei Bing  ,   Department of Physics Xidian University, Xi'an 710071 China
Published: December 2020

Based on the reciprocity theorem, the far field formulation of an arbitrarily oriented electric dipole located at the interface of the layered half space is deduced. Then, considering the optical path difference between directed wave and reflected wave, the formula of the electric dipole located above the interface of the layered half space is discussed. The TE and the TM reflection coefficients of the layered half space can be calculated by the propagation matrix method or the continued fraction method. The presente method, in which the deduction process possesses concise physics concept, is suitable for calculating the radiated field of an electric dipole when the observation point is away from the interface. The numerical results show that using our method the far radiation field of an arbitrarily oriented electric dipole located above the interface of layered half space can be guickly analyzed.
Synchronization for fractional order hyperchaotic Chen system and fractional order hyperchaotic Rssler system with different structure
Authors: Li Dong  , Deng Liang-Ming  , Du Yong-Xia  , Yang Yuan-Yuan  ,   College of Mathematics and Statistics, Chongqing University, Chongqing 400030, China;,   College of Physics Science, Chongqing University, Chongqing 400030 China
Published: December 2020

There is larger key space in fractional order hyperchaotic systems (FOHS), however, the FOHS with different structures are more common in the field of secret communication. Therefore, it is important to study the synchronization method of the system. In this paper, the synchronization between two different FOHS is investigated. i.e., the Chen FOHS and the Rssler FOHs. Based on the fractional order stability theory, two different controllers are designed for synchronizing the drive system and the response system. When the parameters are known in advance, active control synchronization is adopted, the method is simple without constructing any special function. When the parameters are fully unknown, a adaptive control law and a parameter update rule are introduced. Numerical simulations are presented to verify the effectiveness and the feasibility of the synchronization scheme.
Research on the photocatalysis synergistic effect of Mo-X(B, C, N, O, F) codoped TiO2
Authors: Liang Pei  , Wang Le  , Xiong Si-Yu  , Dong Qian-Min  , Li Xiao-Yan  ,   China Jiliang University, Hangzhou 310018, China
Published: December 2020

The plane-wave ultrasoft pesudopotentials based on the density functional theory is used to study the formation energy, the electronic structure and the optical properties of molybdenum and different nonmetallic elements codoped anatase TiO2, where the nonmetallic elements are boron, carbon, nitrogen, oxygen and fluorine. Firstly, we calculate the total densities of states and the band structures of different kinds of codoping TiO2, and analyse the codoping modulation effect on band gap by using the energy band theory. Furthermore, we analyse the synergistic effects on stability and catalysis of TiO2 caused by codoping. And then the state of each atom's bond effect is obtained by analysing the total density map. Finally, we come to the conclusion that molybdenum-carbon codoping structure is superior to others on modulating the photocatalysis of TiO2 in visible light. Our theoretical research will be instructive and meaningful for photocatalysis area of TiO2 in the future.
The study of dynamical potentials of highly excited vibrational states of HOCl
Authors: Wang Ai-Xing  , Liu Yi-Bao  , Fang Chao  ,   Engineering Research Center of Nuclear Technology Application, East China Institute of Technology, Ministry of Education, Nanchang 330013, China;,   College of Nuclear Engineering Technology, East China Institute of Technology, Nanchang 330013, China;,   Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China;,   Department of Physics, Tsinghua University, Beijing 100084, China
Published: December 2020

The dynamical potentials of highly excited vibrational states of HOCl in the bending and OCl stretching coordinates with anharmonicity and Fermi coupling are studied. The result shows that HO stretching vibration mode has significantly different effects on OCl stretching mode and HOCl bending mode under different polyad numbers. The dynamical potentials and the corresponding phase space trajectories are studied in the case that the polyad number is 24 and it is found that the quantal vibrational energy levels could be classified by the fixed points of dynamical potentials and the quantum environments could be identified by the numerical values of action integrals.
Design and analysis of double incidence metamaterials composed of mushroom-shaped structure
Authors: Zhang Hong-Xin  , Li Shan  , Zhang Jin-Ling  , Liu Wen  , Lü Ying-Hua  ,   School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China
Published: December 2020

An ultra-wide band metamaterial may be achieved via the design of some structures. A metamaterial unit supporting two-dimensional (2D) incident electromagnetic (EM) wave is proposed based on the mushroom type-structures, which has an ultra-wide band with seamlessly combined band of right-handed and left-handed pass-bands. This unit is designed by setting two reverse symmetrical mushroom-shaped strips on each side of the dielectric substrate respectively, and the electric resonance and the magnetic resonance could be excited simultaneously. With CST software, the right-handed and left-handed properties are analyzed and verified by means of spectrum analysis, effective parameters of permittivity, permeability and index of refraction extracted from S parameters, and equivalent magnetic resonance circuits. The results show that the structure can present left-handed properties with 1 GHz left-handed pass-band in X waveband, either EM wave is incident in the direction perpendicular or parallel to the plane of the substrate. When the EM wave is incident in the direction perpendicular to the substrate, the right-handed and the left-handed pass-bands appear at 7.2 GHz9.3 GHz and 9.3 GHz11 GHz respectively; while when the EM wave is incident in the direction parallel to the substrate, the right-handed and the left-handed pass-bands appear at 7.0 GH9.0 GHz and 9.0 GHz10 GHz respectively. It also shows that the zero indexes of refraction occur at 9.3 GHz and 9.0 GHz in the tow instances above. So that a plus-zero-negative metamaterial is constructed and a 2D incident balanced-structure with an ultra-wide band of 3 GHz is achieved.
Study on optimal size of repeater insertion with ununiform temperature distribution
Authors: Wang Zeng  , Dong Gang  , Yang Yin-Tang  , Li Jian-Wei  ,   College of Pysics Sicence, Qingdao University, Qingdao 266071, China;,   Microelectronics Institute, Xidian University, Xi'an 710071, China
Published: December 2020

Based on the influence of nonuniform temperature distribution on interconnect delay, an analytical model to estimate the optimal size of repeaters inserting RC interconnect is presented in this paper. In the proposed analytical model the temperature distribution is taken into account and a temperature correction factor is introduced to modify the repeater size and obtain the optimal interconnect delay. Adopting parameters of 90 nm and 65 nm process technology, the proposed model is compared with the model without considering the temperature distribution. Results show that the new model is more accurate and saves the repeater insertion area with maximum values of 15.6% and 36.7% in 90 nm and 65 nm technology, respectively.
Design and optimization of left-handed materials with specific frequency bands
Authors: Gao Ren-Jing  , Wang Guo-Ming  , Liu Shu-Tian  , Tang Zhen-An  ,   Faculty of Vehicle Engineering and Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024, China;,   Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian 116024, China
Published: December 2020

In this paper, a design optimization method for left-handed materials with specific frequency bands is proposed. A microstructure of the left-handed material is constructed based on the transmission line theory, and the properties of this material are simulated numerically with the S-parameter retrieval method and analyzed with equivalent transmission line model. The effects of the size parameters of the microstructure on the left-handed characters are analyzed. The analysis results verify that this structure does exhibit left-handed characteristics with appropriately sized microstructure. Then the mathematical model of the microstructure with maximized frequency band-width and lower loss at given frequencies is proposed, and examples are given. The design result confirms that the optimized model is applicable and accurate.
Study on influence of oxide aperture shape on modal characteristics of VCSELs
Authors: Liu Fa  , Xu Chen  , Zhao Zhen-Bo  , Zhou Kang  , Xie Yi-Yang  , Mao Ming-Ming  , Wei Si-Min  , Cao Tian  , Sheng Guang-Di  ,   Key Laboratory of Opto-Electronics Technology (Beijing University of Technology), Ministry of Education, Beijing 100124, China
Published: December 2020

The effects of oxide aperture shape whose size is small, on the mode characteristics of external cavity oxide-confined photonic crystal vertical cavity surface emitting laser (VCSEL) is studied extensively based on the finite-difference time-domain algorithm. A new three-dimensional model of optical field in photonic crystal VCSEL is built and the influence of the variation in aperture shape on the characteristics of far-field and spectrum is pointed out. It is found that the modal characteristics of PhC-VCSEL are influenced by the shape of oxide aperture, the influence on spectrum feature is more apparent. It can be explained from the distribution of modal field by the fact that the symmetrical characteristic of prismatic oxide aperture is not identical to that of high-order mode. But the influence is less apparent while the depth of photonic crystal hole is deeper. The reason for this matter is illustrated. The results can be used to guide the fabrication of external cavity oxide-confined photonic crystal VCSELs.
Effect of Doppler broadening on the vacuum induced coherence-dependent probe field absorption in Y-type four-level system
Authors: Jia Ke-Ning  , Liang Ying  , Liu Zhong-Bo  , Tong Dian-Min  , Fan Xi-Jun  ,   College of Physics and Electronics, Shandong Normal University, Jinan 250014, China;,   School of Physics, Shandong University, Jinan 250100, China
Published: December 2020

Using the numerical result, the influence of the Doppler broadening on the vacuum induced coherence (VIC) related probe field absorption is discussed. It is shown that if there exists no Doppler broadening, only when VIC is absent can the electromagnetically induced transparency (EIT) phenomenon occur; VIC leads the probe field absorption to vary obviously and the gain to appear; in both cases with and without VIC, the absorption curve has a double-peak structure which is symmetrical about the probe detuning. If there exists the Doppler broadening, in both cases with and without VIC, EIT phenomenon can always occur; VIC still leads the probe field absorption to vary obviously and the gain to appear; no matter whether the VIC is present. The probe field absorption has the following characteristics: the absorption curve no longer has symmetry about the probe field detuning and changes gradually from the double-peak structure to the single-peak structure with Doppler broadening width (D) increasing; the probe field absorption does not monotonically increase or decrease with D increasing; the probe field absorption, when the probe and driving fields propagate along the opposite directions, is smaller than that when the probe and driving fields propagate along the same directions.
Theoretical study of linewidth enhancement factor of InGaAs/GaAs strained quantum well lasers
Authors: Zhang Fan  , Li Lin  , Ma Xiao-Hui  , Li Zhan-Guo  , Sui Qing-Xue  , Gao Xin  , Qu Yi  , Bo Bao-Xue  , Liu Guo-Jun  ,   National Key Laboratory of High Power Semiconductor Lasers, Changchun University of Science and Technology, Changchun 130022, China;,   The Changchun Regional Office of the Armored Forces Representative Bureau, the Equipment Headquarters of the P.L.A., Changchun 130103, China
Published: December 2020

A simple model of calculating the linewidth enhancement factor ( factor) is presented by introducing the correlative theory and its conversion formula of the factor in detail. The contributions of interband transition, free carrier absorption and band gap narrowing to the factor are taken into account. Carrier concentration and differential gain dependence of photon energy are obtained from the gain curves for different carrier concentrations. The gain curves and the factor of InGaAs/GaAs quantum well are simulated, separately, and the results accord well with those reported in the literature. Subsequently discussed are two important parameters of InGaAs/GaAs quantum well laser containing quantum well width and In mole fraction. The results show that the increase of two parameters leads the factor to increase.
Coherent beam combination of two high power double clad fiber lasers by using an all-fiber Michelson cavity
Authors: Zhu Ya-Dong  , Xiao Hu  , Wang Xiao-Lin  , Ma Yan-Xing  , Zhou Pu  ,   College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Michelson cavity technique provides an effective solution for coherent beam combination. In this paper, coherent beam combination of two fiber lasers by using an all-fiber Michelson cavity technique is demonstrated, and 11.75 W coherent output power with a coherent combination efficiency of 95.76% is obtained. The influences of the relation of coherent combination efficiency to laser cavity length difference, and the pump symmetry on coherent combination efficiency are studied experimentally. Experimental results show that the coherent combination efficiency is highly sensitive to the influence of laser cavity length difference, that the difference in combinination efficiency, induced by laser cavity length difference, can be as large as 18%, and that there is an optimal cavity length difference. The maximal influence of pump symmetry on coherent combination efficiency is within 2%, which can be neglected.
Four-wavelength multiplexer/demultiplexer based on photonic crystal resonant coupling
Authors: Zhang Jia  , Xu Xu-Ming  , He Ling-Juan  , Yu Tian-Bao  , Guo Hao  ,   Department of Physics, Nanchang University, Nanchang 330031, China;,   State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

Resonant cavities are used widely in the field of integrated optics due to their excellent frequency-selective properties. Based on the characteristics of resonant coupling between two photonic crystal ring resonators, four cavities with different sizes and waveguides, the demultiplexing of four wavelengths, i.e. 1310 nm, 1550 nm, 1600 nm and 1650 nm is realized. The numerical results obtained by the finite-difference time-domain method show that the output efficiency of the four wavelengths can be higher than 90% only by modulating the radii of the border rods of output waveguides. The presented device that has not only a compact size with 12 μ m× 17μm but also a high output efficiency, may have potential application in the future optical communication field.
Multilevel fast multipole boundary element method for 3D acoustic problems and its applications
Authors: Wu Hai-Jun  , Jiang Wei-Kang  , Lu Wen-Bo  ,   State Key Laboratory of Machinery System and Vibration, Shanghai Jiao Tong University, Shanghai 200240, China
Published: December 2020

It is suitable to solve the acoustic problems by using the fast multipole boundary element method (FMBEM), since the FMBEM can accelerate the matrix-vector multiplication dramatically by reducing the CPU time and memory of conventional boundary element method to O(N log2N) and O(N) respectively. We propose a 3D acoustic FMBEM based on Burton-Miller formulation in this paper. A new adaptive algorithm is applied to the diagonal form FMBEM, and a new proposed analytical moment formulation is used in the moment computation. Both of them further improve the efficiency of FMBEM. Acoustic scattering of soft sphere at resonant frequency is investigated to validate the accuracy of solution using Burton-Miller formulation. Comparisons of solution to the multi-radiating spheres problem with the one solved by Bapat's program demonstrate the accuracy and the efficiency of our algorithm in solving large-scale acoustic problems. In the end, we use our algorithm to analyze the inner sound filed of a car and dolphin acoustic scattering.
Orthogonal wavelet transform weighted multi-modulus blind equalization algorithm based on quantum particle swarm optimization
Authors: Guo Ye-Cai  , Hu Ling-Ling  , Ding Rui  ,   College of Electronic and Information Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China;,   School of Electrical and Information Engineering, Anhui University of Science and Technology, Huainan 232001, China
Published: December 2020

When constant modulus blind equalization algorithm (CMA) is used to equalize high-order QAM signals, there occur the defects of the slow convergence rate and big steady mean square error. In order to overcome these disadvantages, orthogonal wavelet transform weighted multi-modulus blind equalization algorithm based on the quantum particle swarm optimization (QPSO-WTWMMA) is proposed. In this proposed algorithm, quantum particle swarm optimization algorithm and orthogonal wavelet transform are combined into weighted multi-modulus blind equalization algorithm (WMMA) according to the feature of higher-order QAM signal constellations. Accordingly, the equalizer weight vector can be optimized by QPSO algorithm, the autocorrelation of the input signals can be reduced via using orthogonal wavelet transform, and WMMA is used to choose appropriate error models to match QAM constellations. The theoretical analyses and the computer simulations in underwater acoustic channels indicate that the proposed algorithm can obtain the fastest convergence rate and the smallest steady mean square error in equalizing high-order QAM signals. So, the proposed algorithm has important reference value for the underwater acoustic communications.
Propagation theory for bi-static long-range bottom reverberation in shallow water waveguide
Authors: Gao Bo  , Yang Shi-E  , Piao Sheng-Chun  ,   Science and Technology on Underwater Acoustic Laboratory, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Bi-static long-range bottom reverberation in shallow water is investigated, and the impulse response function is derived using the linear theory of sound channel. For the case of almost layered medium, the adiabatic mode solution is introduced for the derivation of transfer function. The reverberation intensity is calculated for the range-dependent waveguide, and then both the intensities and the decaying rules are compared with their corresponding counterparts in different wedged sea areas. It is shown that the propagation effect on intensity of distant bottom reverberation can not be neglected for the bi-static active sonar in shallow water waveguide.
Study on static pressure of fiber cable spool based on distributed fiber Bragg grating sensing technology
Authors: Ma Cheng-Ju  , Ren Li-Yong  , Tang Feng  , Qu En-Shi  , Xu Jin-Tao  , Liang Quan  , Wang Jian  , Han Xu  ,   State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences,Xi'an 710119, China;,   School of Science, Xi'an Shiyou University, Xi'an 710065, China;,   Xi'an Institute of Modern Control Technology, Xi'an 710065, China
Published: December 2020

Based on the theoretical analysis of the static pressure distribution of fiber cable layer in an optical fiber cable spool, we establish a theoretical model of the force in the cable winding system. Simulations indicate that with the increase of the twining layers, the pressure of every layer in the spool increases very quickly at the beginning and mildly then. The static pressure of fiber cable layers in the spool on cable winding device is sensed by use of distributed fiber Bragg gratings (FBG). The quantitative relationship between the variation of FBG center wavelength and the system pressure is given theoretically. It is shown experimentally that with the increase of the twining layers, the variation pace of FBG center wavelength in every layer is very quick at the beginning and gentle then. Theoretical simulations coincide with experimental results very well. This technology provides us a real-time method to monitor the pressure of the fiber cable layer in the cable winding process.
Simulation study on the dynamic mechanisms of nucleation during the initial stage of supercooled liquid potassium
Authors: Liu Li-Xia  , Hou Zhao-Yang  , Liu Rang-Su  ,   Department of Mathematics, Xidian University, Xi'an 710071, China;,   Department of Applied Physics, Chang'an University, Xi'an 710064, China;,   School of Physics and Microelectronics Science, Hunan University, Changsha 410082, China
Published: December 2020

The solidification process of liquid metal potassium is simulated by using the molecular dynamics method. According to the evolution properties of average atomic energy in system, bonding type and clustering type among atoms, and the dynamic parameters of mean-square displacement and non-Gaussian parameter, the dynamic mechanisms in initial nucleation of supercooled liquid potassium are deeply studied. It is found that the supercooled liquid region can be divided into two different stages according to the evolutions of thermodynamic, dynamic and structural properties of supercooled liquid. And the potential crystallization nuclei appear in the lower temperature region of supercooled liquid. It is also found that the potential crystallization nuclei are formed with the disaggregations of icosahedron clusters during the -relaxation regime, and the critical size of nucleus is about 300 atoms.
Surface microstructure and stress characteristics in pure titanium after high-current pulsed electron beam irradiation
Authors: Li Yan  , Cai Jie  , Lü Peng  , Zou Yang  , Wan Ming-Zhen  , Peng Dong-Jin  , Gu Qian-Qian  , Guan Qing-Feng  ,   College of Material Science and Engineering, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

The specimens of polycrystalline pure titanium are irradiated by high-current pulsed electron beam (HCPEB). Surface microstructures and defects induced by HCPEB irradiation are investigated by using X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy technique. The XRD results show that the high value of stress (GPa order) is introduced into the irradiated surface layer, and the characteristics of preferential orientations (100), (102) and (103) are present after HCPEB treatment. The surface microstructure observations indicate that martensitic transformation occurs in the irradiated surface and a large number of plate martensite structures are formed in the irradiated surface. Moreover, strong plastic deformation is triggered by HCPEB treatment. After one pulse, (100) type slip bands are formed in the interior of grain, which leads to the increase of dislocation density. After multi- pulses, deformation microstructures change significantly, and the number of deformation twins increases evidently. The formation of these deformation structures produces a significant effect both on the evolution of surface textures and on grain refinement, which improves the mechanical performance of irradiated surface. It is suggested that HCPEB technique is an effective approach to surface hardening for pure titanium.
Fabrication of In-Al codoped ZnO nanobunches photodetectors
Authors: Yuan Ze  , Gao Hong  , Xu Ling-Ling  , Chen Ting-Ting  , Lang Ying  ,   Department of Physics, School of Physics and Electronic Engineering, Harbin Normal University, Key Laboratory of Semiconductor Nano Composite Materials, Ministry of Education, Harbin 150025, China
Published: December 2020

High-density In-Al codoped ZnO (In, Al, ZnO) nanobunches are synthesized by using chemical vapor deposition method, which can be used to fabricate In, Al, ZnO nanobunches photodetectors. The ZnO nanobunches each have a hexagonal wurtzite structure. It is found that the average length of the nanobunches is ～5 m. The photoconduction mechanism and a series of photoelectric characteristics are studied including I-V characteristic measured in dark and UV illumination, responsivity and response time. The results indicate the presence of an internal gain mechanism. The response time is less than 0.5 s and decay time is about 23 s, so the fabricated device can indeed be used for light detection.
Effects of 3 MeV proton irradiations on AlGaN/GaN high electron mobility transistors
Authors: Lü Ling  , Zhang Jin-Cheng  , Li Liang  , Ma Xiao-Hua  , Cao Yan-Rong  , Hao Yue  ,   School of Microelectronics, Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, Xidian University, Xi'an 710071, China
Published: December 2020

AlGaN/GaN high electron mobility transistors (HEMT) are exposed to 3 MeV protons irradiation. The drain saturation current decreases 20% and the maximum transconductance decreases 5% at a fluence of 1× 1015 protons/cm2. As fluence increases, the thread voltage is shifted toward more positive values. After proton irradiation, the gate leakage current increases. The degradation caused by 1.8 MeV proton is significantly higher than by 3 MeV proton irradiation at the same fluence. The radiation damage area and the density of vacancies at a given depth are obtained from software SRIM. As the energy of the incident proton increases, the non-ionizing energy transferred to the crystal lattice decreases. It is concluded that vacancies introduced by proton irradiation may be the primary reason for the degradations of electrical characteristics of AlGaN/GaN HEMT.
Non-classical eigen state and the persistent current in one-dimensional mesoscopic ring with the electron-two-phonon interaction
Authors: Luo Zhi-Hua  , Liang Guo-Dong  ,   Department of Physics, Guangdong University of Education, Guangzhou 510303, China;,   Department of Optoelectronic Enginecring, Jinan University, Guangzhou 510632, China
Published: December 2020

For the one-dimensional mesoscopic ring with the ferromagnetic texture, to restrain the quantum fluctuations caused by the electron-one-phonon interaction, the non-classical correlation effects are used in our research to solve this puzzling problem, i.e. 1) the hopping electron-displaced phonon state correlation; 2) the process correlation between the phonon squeezed state, and the one-phonon coherent state, originating from the squeezed coherent state of phonon; 3) the renormalization of the phonon displacement. It is found that due to the electron-two phonon interaction, the squeezing effect of phonon is enhanced significantly. Because of the effect of the electron-displaced phonon correlation the non-classical eigen state energy declines significantly and the amplitude of the persistent current increases substantially. Particularly the process correlation between the squeezed phonon state and the one-phonon coherent state is by far the most important contribution to these non-classical effects. First of all, this effect more greatly increases the squeezing effect of phonon field in contrast to the ideal squeezed state. As a result, it will restrain effectively the Debye-Waller effect (factor wph) with wph wph(0). Furthermore, when we combine the effective renormalization of the phonon displacement with the effect of process correlation between the phonon squeezed state and the one-phonon coherent state, the phonon squeezing effect will increases substantially, at the same time, the D-W effect decreased more substantially (wph wph(0), thereby weakening the quantum fluctuation to a bigger degree. With these results, the non-classical eigen energy (En) is much lowered (En En(0)), while the amplitude of eigen persistent current is increased most significantly (In In(0)).
Experimental and theoretical studies on the influence of unintentionally doped carbon on magnetic properties in ZnMnO:N
Authors: Wu Kong-Ping  , Gu Shu-Lin  , Zhu Shun-Ming  , Huang You-Rui  , Zhou Meng-Ran  ,   School of Electrical and Information Engineering, Anhui University of Science and Technology, Huainan 232001, China;,   School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
Published: December 2020

Mn-N co-doped ZnO film on sapphire substrate is fabricated by metal-organic chemical vapor deposition method with changing the acceptor-doped source and importing the hydrogen and increasing the pressure to suppress carbon (C) approach gradually. X-ray diffraction displays the strong C-axis orientation. Raman sepectrum is employed to analyze vibration modes related to C elements. Hall measurements on the samples by van der Pauw method reveal the transition from n-type to p-type after suppression of C, which is possible due to the complex of (CN)O acting as a shallow donor. The first principles simulation calculation for Mn and N codoped ZnO crystals has been perfermed, and the total density of states reveals the strong p-d interaction and magnetic moment existing in the Mn and N codoped ZnO. The introduction of the complex of (CN)O, causes the p-d interaction to disappear and the magnetic moment to reduce even disappear. Therefore, the formation of magnetic bound polaron of Mn 3d electronics and N 2p local bound electronic determines the magnetic interaction effect, which can be explained from the theoretical predication on the Mn 3d and N 2p ferromagnetic (hole) coupling on the ferromagnetism.
Investigation of tangent bifurcation in voltage mode controlled DCM boost converters
Authors: Xie Ling-Ling  , Gong Ren-Xi  , Zhuo Hao-Ze  , Ma Xian-Hua  ,   College of Electrical Engineering, Guangxi University, Nanning 530004, China
Published: December 2020

The voltage mode controlled boost converters contain plenty of bifurcation phenomena. Tangent bifurcation is one of these phenomena. The investigation of the tangent bifurcation in voltage mode controlled boost converters operating in discontinuous conduction mode (DCM) is performed. The third iterative map is derived according to the first iterative map. Based on the tangent bifurcation theorem, the conditions of producing the tangential bifurcation in the DCM boost converters are deduced mathematically. The computer simulations are performed to capture the effects of some chosen parameters on the tangent bifurcation behavior of the system. The results show that the variation of the feedback factor leads to tangent bifurcation and intermittent chaos phenomena. Experimental results show that the system does exhibit tangent bifurcation under the particular operating conditions, thus validating the theoretical analysis and the simulation results.
A subwavelength antenna array design for time reversal communication
Authors: Zhang Zhi-Min  , Wang Bing-Zhong  , Ge Guang-Ding  ,   Institute of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, China;,   School of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000, China
Published: December 2020

Based on the super-resolution property of time reversal electromagnetic wave far-field focusing, a subwavelength antenna array is proposed. The elements of the array are etched into those that have microstructures, placed at an interval of λ/20 apart from one another, and have independent channels. Compared with the subwavelength antenna arrays, each of which is composed of other microstructure elements, the array, whose radiation property of individual antennae is similar to others, shows better super-resolution characteristic of far-field focusing. Therefore, an effective wireless terminal antenna array is provided for the high-speed and high-quality multiple-antenna communication using the time reversal technology.