bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of stability of the equilibrium state of periodic motion in a nonlinear relative-rotation system
Authors: Zhao Wu  , Liu Bin  , Shi Pei-Ming  , Jiang Jin-Shui  ,   (1)燕山大学信息工程学院，秦皇岛  066004; (2)中国第一重型机械集团公司设计研究院,大连  116600
Published: December 2020

For solving stability of motion in a nonlinear relative rotation shafting, a sort of periodic variable coefficient linear ordinary differential equations was studied. Movement stabilization criterion of nonlinear relative rotation system was obtained by transferring the fundamental matrix of the solution of the ordinary differential equation to Jordan canonical. Using the Lyapunov function method, the stabile balance position of relative rotation motion of driving system in a variety of mechanical equipments was studied, and the analytic expression of the stable region was obtained. The method supplies theoretical laws, similarity analog criterion and technique means of selecting working parameter of stable working interval of a type of mechanical driving systems. The result of the research can be used for analysis and evaluation of the torsional vibration stability of the main driving system of heavy and complex rotary machines.
The criterion of instability for a weakly interacting Fermi gas
Authors: Yuan Du-Qi  ,   宝鸡文理学院物理系，宝鸡  721007
Published: December 2020

Using the equation of free energy for a weakly interacting Fermi gas, the stability of a weakly interacting Fermi gas in the absence of external potential is studied by means of thermodynamics. The instability arising from the weakly attractive interacting of a Fermi gas is pointed out. The particle density criterion and the temperature criterion of instability for the imperfect Fermi gas with weakly attractive interaction are given, and the dependance of the critical density of particles on the temperature and the mass of particle and the attractive interaction is discussed.
A novel approach for Chua’s circuit design and its hardware implementation
Authors: Li Ya  , Yu Si-Min  , Dai Qing-Yun  , Liu Ming-Hua  , Liu Qing  ,   (1)广东工业大学信息工程学院，广州  510090; (2)广东工业大学信息工程学院，广州  510090；井冈山学院物理系，吉安  343009; (3)广东工业大学自动化学院，广州  510090; (4)湖南涉外经济学院信息与电子工程系，长沙  410205
Published: December 2020

A novel circuit design approach for Chua's non-dimension state equation is proposed in this paper. First, variable-scale reduction, differential to integral conversion and time yardstick transformation are made on the Chua's non-dimension state equation. Then each module circuit based on the state equation is designed and linked with the other circuits by corresponding relationships between state variables. The circuit consists of inverted adder, integrator and inverter, and has symmetric structure. Compared with the other existing chaotic circuits, the circuit has three main characters: (1) It proposes a circuit modularization design, giving a more general design principle for a family of chaos circuits which and can be applied to circuit design of other non-dimensional state equations. (2) The circuit parameters are independent and adjustable by using inverted adder, and convenient for circuit implementation. (3) The chaotic signal spectrum can be regulated by adjusting integral resistors or capacitances, convenient for practical applications. According to this method, a novel Chua's circuit which can generate three scrolls using polynomial is designed, and corresponding hardware experiments are performed. The computer simulations are in good agreement with hardware experiment results. This confirms the feasibility of our method.
A new chaotic system and analysis of its properties
Authors: Wang Jie-Zhi  , Chen Zeng-Qiang  , Yuan Zhu-Zhi  ,   南开大学自动化系，天津  300071
Published: December 2020

This paper reports a new three-dimensional continuous autonomous chaotic system, which is different from the Lorenz, Chen and Lü systems. The new system contains two quadratic cross-product terms and four system parameters. Basic dynamic properties of the new system are studied by means of theoretical analysis, numerical simulation, Lyapunov exponent spectrum, bifurcation diagrams and Poincaré section diagrams. The different dynamic behaviors of the new system are analyzed when each system parameter is changed.
An improved two-lane traffic flow lattice model
Authors: Tang Tie-Qiao  , Huang Hai-Jun  , Xue Yu  ,   (1)北京航空航天大学经济管理学院，北京  100083; (2)北京航空航天大学经济管理学院，北京  100083;北京航空航天大学汽车工程系，北京  100083; (3)广西大学物理系，南宁  530004
Published: December 2020

An improved two-lane traffic flow lattice model is proposed. The model introduces a new function to govern the flow shift between two lanes, and then eliminates the flaws of vehicle backward movement which may appear in existing lattice models. The sufficient and necessary conditions for keeping the model’s linear stability are derived. Numerical simulations which correctly reproduce the lane changing behavior induced by small disturbances are presented.
Intelligent decision-making in a two-route traffic flow model
Authors: Fu Chuan-Ji  , Wang Bing-Hong  , Yin Chuan-Yang  , Gao Kun  ,   中国科学技术大学近代物理系，非线性科学中心，合肥  230026
Published: December 2020

Intelligent decision-making based on the information feedback in a two-route traffic flow model is studied. Compared to the mechanical decision-making which induces an oscillation and low efficiency of system, intelligent decision-making will improveme the efficiency. Our results suggest that one should not only devote to obtaining optimal information feedback, but also make an intelligent decision based on information feedback at hand.
Numerical study on the aggregation of magnetic particles with power law interactions
Authors: Xu Xiao-Jun  , Wei Gao-Yao  , Cai Ping-Gen  , Jin Jin-Sheng  , Xia A-Gen  , Ye Gao-Xiang  ,   (1)浙江大学物理系,杭州  310027; (2)浙江工业大学应用物理系,杭州  310014
Published: December 2020

We introduce in the diffusion-limited aggregation model an internal degree of freedom, i.e., a spin taking two states (up and down) with power-law Ising interaction. The fractal aggregation of magnetic particles with different ranges of interaction is investigated by Monte Carlo simulation. The simulation shows that for the antiferromagnetic coupling, the spins of the particles in the aggregates tend to be oriented alternately. For the ferromagnetic coupling, however, the spin orientation distribution of the aggregates depends on the interaction range: for the short-range interaction, domains with different sizes are observed in the aggregates, i.e., the aggregates exhibit ferromagnetic structure; for the long-range interaction, during the earlier stage of the growth process, the aggregates exhibit approximately antiferromagnetic structure, then, in subsequent growth of the outer part of the aggregates, the spin states of all particles are similar. The morphology and magnetization of the magnetic fractal aggregates as well as their evolutions with different ranges of interaction are also studied.
A weighted scale-free network model with large-scale tunable clustering
Authors: Pan Zao-Feng  , Wang Xiao-Fan  ,   上海交通大学自动化系,上海  200240
Published: December 2020

Based on the weighted scale-free network model proposed by Barrat, Barthélemy and Vespignani (BBV), we propose a generalized BBV (GBBV) model with large-scale tunable clustering coefficient. Theoretical analysis and numerical simulations show that the GBBV model retains many properties of the BBV model, such as power-law distributions of node degree, node strength and edge weight. However, the GBBV model overcomes the drawback of the BBV model that the clustering coefficient can only be tuned in a small interval, and therefore the GBBV model can be used for modeling networks with large clustering coefficients.
Analysis of contrast error mechanism for synchrotron radiation computed-tomography technique
Authors: Wang Min  , Hu Xiao-Fang  , Wu Xiao-Ping  ,   中国科学技术大学中国科学院材料力学行为和设计重点实验室,合肥  230027
Published: December 2020

Based on the unique advantages of high intensity, high resolution and good collimation of synchrotron radiation X-ray, the nondestructive synchrotron radiation computed-tomography technique is widely used in many fields. In this paper, the contrast error of this technique is studied, and four basic error-forms are discussed. The numerical simulation results confirmed the analysis.
Analysis of the focus error characteristic in high density optical disk driver
Authors: Shen Quan-Hong  , Pei Jing  , Xu Duan-Yi  , Ma Jian-She  , Qi Guo-Sheng  , Li Li-Hua  ,   清华大学精密仪器与机械学系，光盘国家工程研究中心，北京  100084
Published: December 2020

High density digital video disc (HD-DVD) is one of the high density optical data storage technologies to meet the demand of high definition TV. The knife-edge method for focus error detection in HD-DVD driver is proposed in this paper. The calculation model for optical intensity distribution on photo detector under different defocusing amount is deduced on the basis of Fresnel formula and scalar diffraction theory.The S curve obtained theoretically showing how the focus error intensity varies with defocusing amount is in agreement with the experimental one for HD-DVD driver,which validates the calculation model.Furthermore, the focusing noise caused by pit-modulation in HD-DVD driver is analyzed and indicated to be less than 4.5%. It is concluded that a satisfactory focus range of linearity is realized in HD-DVD driver with knife-edge method which has high sensitivity and low focusing noise.
Investigation on all-optical logic AND and NOR gates based on the same structure
Authors: Zhao Chan  , Zhang Xin-Liang  , Dong Jian-Ji  , Huang De-Xiu  ,   华中科技大学光电子科学与工程学院，武汉  430074
Published: December 2020

A novel scheme for all-optical logic AND and NOR gates is proposed based on the same structure, and the principle of operation is the cross-gain modulation in cascaded single-port-coupled semiconductor optical amplifiers (SOAs). By using the dynamic models of single-port-coupled SOA, two kinds of logic operations are demonstrated successfully at 20Gb/s. A good agreement is shown between the numerical simulation and the experimental results.
Active synchronization of two independent femtosecond and picosecond lasers and sum frequency generation of two laser pulses
Authors: Wang Peng  , Zhao Huan  , Wang Zhao-Hua  , Li De-Hua  , Wei Zhi-Yi  ,   中国科学院物理研究所，北京  100080
Published: December 2020

The scheme for synchronizing Ti:sapphire femtosecond laser and Nd:YVO4 picosecond laser is discribed. Sub-ps jitter is obtained, based on which broad-band femtosecond blue-light laser of 460nm is generated through mixing two laser pulses in the BBO crystal. The technique not only shows a general way of synchronizing lasers of completely different wavelength and pulse width, but also demonstrates a new scheme for generating ultra-short laser with new wavelength through nonlinear frequency mixing.
First-principle calculations on the geometry and relaxation structure of anatase TiO2(101) surface
Authors: Ma Xin-Guo  , Tang Chao-Qun  , Huang Jin-Qiu  , Hu Lian-Feng  , Xue Xia  , Zhou Wen-Bin  ,   华中科技大学物理系,武汉  430074
Published: December 2020

First-principle calculations based on the plane-wave pseudopotential method have been used to study the surface energy and structure of anatase TiO2(101) surface.There are six different structures of the anatase TiO2(101) crystal surface because different atoms are terminated on the surface layers. The calculation result shows that anatase TiO2(101) crystal surface structure which the outermost and second layer respectively terminated by twofold coordinated oxygen atoms and fivefold coordinated titanium atoms is much more stable than the other five structures. By investigating the effect of variable vacuum layer thickness and slab thickness on the surface energy and surface atomic displacements, we find that slab thicknesses of at least 12 atom layers and vacuum layer thickness of more 0.4nm are sufficient to converge the surface energy to within 0.01 J/m2. At last, we obtained the result that the twofold coordinated oxygen atoms have an inward relaxation of 0.0012nm, and fivefold coordinated titanium atoms have an outward relaxation of 0.0155nm,while the length of Ti—O bonds and quantity of electric charge of titanium and oxygen atoms are changed, making the structure more stable.
Influence of interaction between Cu adatoms on the hopping diffusion on Cu(001) surface
Authors: Wang Yong-Liang  , Zhang Chao  , Tang Xin  , Zhang Qing-Yu  ,   大连理工大学三束材料改性国家重点实验室，大连  116023
Published: December 2020

Based on the atomic interaction potential with the embedded atom, molecular dynamics simulation was used to study the variation of Cu(001) surface caused by a Cu adatom and the hopping barriers of another Cu adatom in its vicinity. The results show that the Cu adatom may distort the positions of Cu atoms in the substrate to the extent of 2 lattice constants and the influence is as deep as 10 layers. Due to the interaction of the stress field between two adatoms, the hopping diffusion barriers of the adatoms are decreased and the adatoms are more active in diffusion than a single adatom. By comparing the difference of hopping barriers to and fro along the same diffusion path, the migrating behavior of the adatoms can be divided into two kinds of diffusion, depending on the distance between the two adatoms. If they are at a distance longer than the effective distance of the atomic interaction potentials, the diffusion of adatoms is affected only by the interaction of the stress field between two adatoms. If they are at a distance shorter than the effective distance of the atomic interaction potentials, the two adatoms should be considered as an ad-dimer in different states.
Study of ZnO film growth by reactive magnetron sputtering using plasma emission spectra
Authors: Li Yong  , Sun Cheng-Wei  , Liu Zhi-Wen  , Zhang Qing-Yu  ,   大连理工大学三束材料改性国家重点实验室，大连  116023
Published: December 2020

Using on-line measurement of plasma emission spectra during reactive magnetron sputtering, the growth of ZnO films was studied with the variation of O2 flow and deposition temperature, ranging from room temperature to 750℃. With the structural characterization and measurement of optical properties, we revealed the role of growth temperature and O2 flow in the growth of ZnO film. The results showed that O2 flow was important in determining the sputtering yield of Zn target. When the flow ratio of O2 to Ar+O2 (R)>0.75%, the sputtering yield of Zn decreased linearly with increasing O2 flow. When R was in the 10%—50% range, the concentration of oxygen varied slowly, which may be useful for the control of film growth. The intensity of emission spectrum of atomic Zn at 481.3 nm varied with increasing deposition temperature T. When T550℃, the intensity increased sharply with increasing deposition temperature. By controlling the deposition temperature, a high-quality film with the composition close to stoichiometric ZnO was fabricated on Si(001) substrate at 750℃ and ultraviolet photoluminescence was detected at room temperature.
The effect of distribution of holes in the momentum-space on the photoresponse of p-type quantum well infrared photodetector
Authors: Zhou Xu-Chang  , Chen Xiao-Shuang  , Zhen Hong-Lou  , Lu Wei  ,   中国科学院上海技术物理研究所红外物理国家重点实验室，上海  200083
Published: December 2020

The electronic structure and photoresponse of p-type quantum well infrared photodetector (QWIP) are calculated by self-consistent method. The effect of distribution of holes in the momentum-space on the photoresponse of the device is studied. The calculation results show that the contribution of holes to the photocurrent depends on the distribution of holes in the momentum-space, so the density of holes and the temperature influence the photoresponse of the p-type QWIP. The theoretical results agree well in the change of photoresponse of device with doping concentration and temperature in the experiment.
Valence band photoemission of Sm fullerides
Authors: Wang Xiao-Xiong  , Li Hong-Nian  , Qian Hai-Jie  , Su Run  , Zhong Jun  , Hong Cai-Hao  , Wang Jia-Ou  ,   (1)浙江大学物理系，杭州  310027; (2)中国科学院高能物理研究所，北京  100049
Published: December 2020

Valence band structure of Sm-intercalated C60 thin films is researched with ultraviolet photoelectron spectroscopy and synchrotron-radiation photoemission spectroscopy. Most valence electrons of Sm transfer to C60，and the bonding nature is mainly ionic. No Fermi edge is observed for all stoichiometries. Thus the superconducting Sm fulleride has semiconducting property at room temperature. Density of states near the Fermi level is obtained for single phase of Sm2.75C60. Photoemission of the solid solution phase differs apparently from that of Sm2.75C60. SmxC60 (2.752.75C60 and Sm6C60, which indicates that another phase exists or Sm doping proceeds smoothly through the LUMO+1 band. The interfaces between different phases are unstable above 130 ℃.
Study of deposition of super thin Fe film on NiO(001) substrate
Authors: Wang Li-Jin  , Teng Jiao  , Yu Guang-Hua  ,   北京科技大学材料物理与化学系，北京  100083
Published: December 2020

One to ten Fe monatomic layers (ML) with wedge-shape were deposited on the NiO(001) substrate by molecular beam epitaxy (MBE) and pulsed laser deposition (PLD), respectively. The analysis in situ of surface magneto-optic Kerr effect indicates that the Fe layer gives rise to an about 2ML thick magnetic dead layer at the interface of Fe/NiO by MBE deposition. The magnetic dead layer is about 3ML for the method of PLD. X-ray photoelectron spectroscopy indicates that both ways of deposition can lead to interfacial chemical reactions.
Intense blue upconversion fluorescence of Tm3+/Yb3+-codoped bismuth tellurite glasses
Authors: Yang Dian-Lai  , Hou Yan-Yan  , Zhao Xin  , Liu Gui-Shan  , Lin Hai  , Liu Ke  , Edwin Yue-Bun Pun  ,   (1)大连轻工业学院化工与材料学院，大连  116034; (2)香港城市大学电子工程系，香港九龙
Published: December 2020

In this paper, Tm3+/Yb3+-codoped bismuth tellurite glasses with high refractive index have been synthesized. The refractive index of Tm3+/Yb3+-codoped bismuth tellurite glasses were measured by Metricon 2010 prism coupler at two wavelengths, and the values n1=2.0365 at 632.8nm and n2=1.9795 at 1550nm were obtained. The absorption spectra, fluorescence spectra and infrared transmittance spectra of this glass were measured and analyzed. Based on Judd-Ofelt theory, and intensity parameters Ωt(t=2，4 and 6) were obtained to be 3.90×10-20, 2.03×10-20 and 9.03×10-21cm2, respectively. Then the radiative transition probabilities, radiative lifetimes and fluorescence branching ratio were calculated. Intense blue three-photon upconversion fluorescence and near-infrared two-photon upconversion fluorescence were investigated under the excitation of 980nm diode laser at room temperature. Wide infrared transmission window, high refractive index and strong blue three-photon upconversion emission of Tm3+ indicate that Tm3+/Yb3+-codoped LKBBT glasses are promising upconversion optical and laser materials.
Optical properties and cooperative luminescence of Yb-doped borate-silicate glasses
Authors: Li Shan-Feng  , Miao Zhuang  , Peng Yang  , Zhang Qing-Yu  ,   大连理工大学三束材料改性国家重点实验室，大连  116023
Published: December 2020

Yb-doped borate-silicate glasses with various Yb2O3 concentrations were fabricated by means of high-temperature solid-state reaction. The absorption and the photoluminescence, as well as the Raman spectra, were measured and analyzed. The absorption and emission cross-section around 980nm is calculated based on the absorption measurement. The dependence of radiative lifetime of Yb3+-2F5/2 on Yb2O3 concentration is also presented. The relationship between up-conversion photon and the infrared emission, together with the assistant phonon, is described according to the up-conversion photoluminescence and Raman spectra analysis.
Photoluminescence of GaAs(110) quantum wells modulated by surface acoustic waves
Authors: Yang Guang  , P. V. Santos  ,   (1)Paul-Drude固体电子学研究所,德国柏林  D-10117; (2)华中科技大学光电子科学与工程学院,武汉  430074;Paul-Drude固体电子学研究所,德国柏林  D-10117
Published: December 2020

We studied the low temperature (15K) photoluminescence properties of un-doped GaAs(110) quantum wells modulated by surface acoustic waves (SAW) by photoluminescence (PL) spectroscopy technique. Under the influence of the SAW, the decreasing of PL intensity and the splitting of the PL lines were observed. The magnitude of the splitting can be up to 10meV when the power applied to the transducers is 20dBm. Furthermore, the spin injection in GaAs(110) quantum wells generated by circular polarization light under the influence of SAW was also discussed.
Multiple-state storage capability of nitrogen-doped Ge2Sb2Te5 film for phase change memory
Authors: Lai Yun-Feng  , Feng Jie  , Qiao Bao-Wei  , Ling Yun  , Lin Yin-Yin  , Tang Ting-Ao  , Cai Bing-Chu  , Chen Bang-Ming  ,   (1)Silicon Storage Technology,Inc.,Sunnyvale  94086,USA; (2)复旦大学专用集成电路和系统国家重点实验室，上海  200433; (3)上海交通大学微米/纳米加工技术国家重点实验室，薄膜与微细技术教育部重点实验室，上海  200030
Published: December 2020

Nitrogen-doped Ge2Sb2Te5 (N-GST) film for phase change memory was prepared by reactive sputtering. Testing results show that doped nitrogen combines with Ge to form GeN, which not only restrains crystal grain growth but also increases the crystallization temperature and phase transformation temperature of Ge2Sb2Te5 (GST). Phase change memory (PCM) with N-GST can realize three-state storage in one PCM cell by using the resistivity difference between the amorphous state, the face centered cubic phase and the hexagonal phase of GST.
Uniqueness and stability of solution to the linear transient eddy current electromagnetic field problem for determining solution
Authors: Xie Li  , Lei Yin-Zhao  ,   北京航空航天大学自动化科学与电气工程学院，北京  100083
Published: December 2020

The linear transient eddy current electromagnetic field problem for determining solution is characterized by replacing the interface condition of the tangential component of the electric field intensity by the interface condition of the normal component of the magnetic flux density, and ignoring the displacement current in the constraint equations. In is a fundamental theoretical problem whether the solution to the irregular problem for determining solution in unique and stable. In this paper, we introduce a scalar potential function in the nonconducting region,and prove the existence of an auxiliary function which is important to the problem. After deriving the energy estimate inequality, the uniqueness and stability of the solution to the linear transient eddy current electromagnetic field problem for determining solution are proved. The results of the paper can provide theoretical basis for analyzing and calculating the linear transient eddy current electromagnetic field problem. As an application example, we present the analytical solution to the eddy current problem that a single-turn coil driven by solitary pulse current is arranged coaxially with a spherical conductor.
A new molecular model for main-chain liquid crystalline polymers based on molecular dynamics simulations
Authors: He Lan  , Shen Yun-Wen  , K. L. Yung  , Xu Yan  ,   (1)西北工业大学机电学院，西安  710072; (2)香港理工大学工业系统工程系，香港 九龙红
Published: December 2020

This paper has derived a new molecular model for simulating semi-rigid main-chain LCPs (liquid crystalline polymers) based on the traditional GB (Gay-Berne)/LJ (Lennard-Jones) model, named Solo-LJ-SP-GB model. A single LJ unit and two nonlinear springs have been firstly used to describe the flexible spacers between GB units in the LCPs. Using the current model, the simulation time is less than 10% of that spent by using the traditional GB/LJ model, when simulating the semi-flexible main-chain LCP of 169 molecular chains with 6 flexible spacers between neighboring GB units, which greatly enhances the computational efficiency. Through using the current model to study the phase behaviors of semi-flexible main-chain LCPs, the odd-even effects of thermodynamic properties depending on the number of flexible spacers and the phase transition from isotropic to liquid crystalline have been observed, which agrees well with the existing experimental data and the simulation results of the traditional model. It is shown that the new model enables to describe the structural properties of semi-rigid main-chain LCPs accurately.
Mass analyzed threshold ionization spectra of ethyl bromide
Authors: Tang Bi-Feng  , Xiong Ping-Fan  , Zhang Xiu  , Zhang Bing  ,   (1)孝感学院物理系,孝感  432100; (2)孝感学院物理系,孝感  432100;中国科学院武汉物理与数学研究所,武汉  430071; (3)中国科学院武汉物理与数学研究所,武汉  430071
Published: December 2020

Using one-color two-photon (1C2P) scheme, high-resolution mass analyzed threshold ionization MATI spectra of ethyl bromide have been recorded. Accurate values for the adiabatic ionization energy have been determined to be 83097±3 cm-1 and 85452±3 cm-1 for the X1 2E1/2 and X2 2E1/2 states of the cation， respectively, giving a splitting of 2355±6 cm-1. The ionic vibrational frequencies were also obtained, and the values were in agreement with high accuracy with the literature data. The spectra showed extensive excited vibrational structure as a result of wave packet evolving on the potential energy surface of the dissociative state in the time interval between the absorption of the two photons. The vibrational calibration was done based on the known vibrational frequencies of the neutral ethyl bromide. The spectrum was found to exhibit mainly vibrational modes involving the dissociation of the molecule, including some non-totally symmetric modes.
Plasma effect on the Kα group emission of He-like neon
Authors: Zhang Li  , Li Xiang-Dong  , Jiang Xin-Ge  ,   (1)伊犁师范学院物理与电子信息学院,伊宁  835000; (2)中国科学院上海光学精密机械研究所,强场激光物理国家重点实验室,上海  201800; (3)中国科学院上海光学精密机械研究所,强场激光物理国家重点实验室,上海  201800;中国科学院研究生院,北京  100049
Published: December 2020

The spectra shifts for the intercombination line (1s2p(3P1)→1s2) and the resonance line (1s2p(1P1) →1s2) of He-like neon, which are the two electronic dipole transitions in the Ｋα group emissions, are studied under dense plasma conditions by using the self-consistent field ion sphere model. The results show the two electronic dipole transitions red shift nearly linealy with the increase of plasma electron density. Moreover, the red-shift energy becomes more sensitive to the plasma electron density when the plasma electron temperature is lower. It is worthy to note that the energy discrepancy between these two spectral lines is equal to the exchange energy of state 1s2p(3P1). So, it is the first time that the exchange energy varying with plasma environment is observed both qualitatively and quantitatively. This result may be useful to dense plasma diagnosis in connection with variation of the relative position and the spectral fine structure splitting in high density plasmas.
Analysis of Cr atom trajectory and focusing deposition in the standing wave field
Authors: Zheng Chun-Lan  , Li Tong-Bao  , Ma Yan  , Ma Shan-Shan  , Zhang Bao-Wu  ,   同济大学物理系,上海  200092
Published: December 2020

The laser-focused atomic deposition is a new way to build the nano transfer standard of high reliability adequate for application. Based on the semi-classical model, this paper starts from the motion equation of chromium atom in the laser standing wave field to get the trajectory of the atoms in the standing wave field by analytical simulation. The effects on focal line features are discussed as a result of the angular collimation, velocity spread in the atomic beam and the spherical aberration. The effects from different deposition positions are also discussed. This paper also gives a sample of the grating structure nanofabricated by laser focusing of Cr atoms.
Effects of spin multiplicity on atomic structure of titanium trimer
Authors: Chang Zhi-Wen  , Wang Qing-Lin  , Luo You-Hua  ,   (1)河南大学理论物理研究所,开封  475001; (2)华东理工大学理学院，上海  200237；河南大学理论物理研究所,开封  475001; (3)昆明冶金高等专科学校，昆明  650033
Published: December 2020

Atomic structures of titanium trimer have been obtained at different spin multiplicities by means of density functional theory (DFT) method. Also, vibrational frequencies of corresponding atomic structures were calculated. The results indicate that effects of spin multiplicity on atomic structure of titanium trimer are remarkable, especially for bond distances and vibrational frequencies. After taking account of spin multiplicities, the ground state of titanium trimer is a septet.
The second-order moment representation of nonparaxial vectorial Laguerre-Gaussian beams
Authors: Kang Xiao-Ping  , Lü Bai-Da  ,   (1)四川大学激光物理与化学研究所,成都  610064; (2)四川大学激光物理与化学研究所,成都  610064;琼州大学物理系，五指山  572200
Published: December 2020

Based on the nonparaxial vectorial moment theory of light beam propagation proposed by Porras, the characteristic parameters, such as the beam width, far-field divergence angle and M2 factor of nonparaxial vectorial Laguerre-Gaussian (LG) beams with initial circular polarization, are derived and expressed in terms of a series sum. The nonparaxial vectorial Gaussian beam is treated as a special case of our result. It is shown that the second-order-moment based beam width propagates according to the hyperbolic law, and for w0/λ→0 (w0-waist width,λ-wavelength) the far-field divergence angle θ approaches 90°, which is larger than 63.435° predicated by the nonparaxial scalar theory. The M2 factor of nonparaxial vectorial LG beams depends not only on the mode index p, but also on the w0/λ. Finally, comparison between the propagation of nonparaxial vectorial LG beams and that of nonparaxial scalar LG beams indicates that the far-field divergence angle is greatly influenced by the vectorial effect when w0/λ is relatively small. The problem which results from θ→90° and the applicability of the nonparaxial vectorial moment theory as well as the possible method for solving the problem are discussed.
Modulation instability of near frequency propagation regime in polarization-maintaining fibers
Authors: Jia Wei-Guo  , Shi Pei-Ming  , Yang Xing-Yu  , Zhang Jun-Ping  , Fan Guo-Liang  ,   内蒙古大学物理系，呼和浩特  010021
Published: December 2020

The coherently coupled nonlinear Schrdinger (NLS) equation of the propagation of a light pulse in a fiber has been utilized. We have studied modulation instability of linearly polarized lights with near frequency not only in anomalous dispersion regime but also in normal dispersion regime in polarization-maintaining fibers, when the polarization direction along the two birefringence axes are orthogonal and the intensities along the two birefringence axes are equal. The results show that modulation instability can be produced both in anomalous and normal dispersion regimes. The input pulses have obviously different gain spectra when input power regime is different in normal dispersion regime. Furthermore, the gain spectra are different for different wave lengths (or different frequencies) when the power of input pulse is kept constant.
Near-field optical property of multi-layer dielectric gratings for pulse compressor
Authors: Liu Shi-Jie  , Shen Jian  , Shen Zi-Cai  , Kong Wei-Jin  , Wei Chao-Yang  , Jin Yun-Xia  , Shao Jian-Da  , Fan Zheng-Xiu  ,   (1)中国科学院上海光学精密机械研究所，上海  201800; (2)中国科学院上海光学精密机械研究所，上海  201800;中国科学院研究生院，北京  100049
Published: December 2020

Multi-layer dielectric gratings for pulse compressor in high-energy laser system must provide high diffraction efficiency. In addition, its laser induced damage property is critical for the system. Nonuniform optical near-field distribution of multi-layer dielectric gratings is one of the important factors to limit its laser induced damage threshold. Electric field distributions in the grating region and multi-layer film region are analyzed by using Fourier modal method. Effects of grating structure on peak magnitude of electric field in grating ridge are analyzed when the top layer material is HfO2 and SiO2, respectively. The results show that there exists an optimum top layer thickness, at which the peak magnitude of electric field within grating ridge is a minimum. And the peak electric field in the grating ridge can be reduced by designing top gratings with high aspect ratio structure when top layer thickness is increasing. Finally, the peak electric field in the grating ridge can also be reduced when the multi-layer dielectric grating is used at big incident angle.
Pulsed digital holographic recording of ultra-fast process of the femto-second order
Authors: Wang Xiao-Lei  , Wang Yi  , Zhai Hong-Chen  , Zhu Xiao-Nong  , Mu Guo-Guang  ,   南开大学现代光学研究所，光电信息技术科学教育部重点实验室，天津  300071
Published: December 2020

In this paper, we report a pulsed digital micro-holography system for recording ultra-fast process of the order of femto-second. Two sub-pulse-train generators can be adjusted independently for generating reference beams with different spatial angles and object beams of the same angle, respectively, and the time delay between the sub-pulses can be adjusted from pico-senconds to femto-seconds. In the experiment, the ultra-fast dynamic process of air ionization induced by a femto-second laser pulse is recorded by the holographic recording system through spatially angular multiplexing, and both of the digitally reconstructed images in intensity and phase are obtained, which show the dynamic process of formation and propagation of the plasma with a time resolution of the order of femto-second.
Physical realization of single qubit gate using laser-two-level-atom system
Authors: Chen Ming-Lun  , Wang Shun-Jin  ,   (1)四川大学物理系，成都  610064; (2)四川大学物理系，成都  610064;兰州重离子加速器国家实验室核理论中心,兰州  730000
Published: December 2020

The time dependent Schrdinger Equation of a laser-two-level-atom system has been solved by algebraic dynamics method. The exact analytical solution is obtained, and the single qubit logical gate can be realized through adjusting the amplitude and frequency of the single mode laser field as well as strength of the short pulse laser field.
A highly stable differential phase shift key distribution QKD system
Authors: Li Ming-Ming  , Wang Fa-Qiang  , Lu Yi-Qun  , Zhao Feng  , Chen Xia  , Liang Rui-Sheng  , Liu Song-Hao  ,   华南师范大学信息光电子科技学院光子信息技术广东省高校重点实验室,广州  510631
Published: December 2020

We propose and demonstrate an improved differential phase shift key distribution scheme. Alice uses a pulsed laser source and two cascaded fiber loops to get coherent pulses, then modulates them randomly under differential phase shift scheme, which compensates for the random polarization mode dispersion and phase shift. An interferometer made up of two Faraday mirrors is employed to detect single photon under gate mode. In one-way transmission, QKD is free from Trojan attack. Our experiment at setup can work stably for a long time (at least 24h) with an error ratio of 3%. The stable scheme is efficient, economical and favorable for practical application.
Theory of surface thermal lens signal in optical coating with cw modulated top-hat beam excitation
Authors: Chen Xiao-Xiao  , Li Bin-Cheng  , Yang Ya-Pei  ,   (1)电子科技大学光电信息学院，成都  610054; (2)电子科技大学光电信息学院，成都  610054;中国科学院光电技术研究所，成都  610209; (3)中国科学院光电技术研究所，成都  610209
Published: December 2020

The theoretical model based on the Fresnel diffraction integral is developed to describe the surface thermal lens (STL) signal excited by a cw modulated top-hat beam. The three-dimensional profile of temperature rise, the radial profile of the surface displacement and the diffraction signal of the probe beam obtained with both top-hat and Gaussian beam excitations are compared by numerical calculation. The dependence of the surface thermal lens amplitude on the experimental parameters are discussed. Numerical results show that the top-hat beam STL instrument is more sensitive than the Gaussian beam STL instrument, with a maximum sensitivity enhancement factor of approximately 2.
Clad-pumped Er3+/Yb3+-codoped short pulse fiber laser with high average power output exceeding 2W
Authors: Liu Yan-Ge  , Zhang Chun-Shu  , Sun Ting-Ting  , Lu Yun-Fei  , Wang Zhi  , Yuan Shu-Zhong  , Kai Gui-Yun  , Dong Xiao-Yi  ,   南开大学现代光学研究所，天津  300071
Published: December 2020

A clad-pumped short pulse Er3+/Yb3+-codoped fiber laser based on master oscillator and power amplifier (MOPA) structure, integrating the performances of broad-band tunable wavelength, uniform output power spectrum, high repetition rate and high average power to together, is proposed and demonstrated. Combining the cavity parameter optimization of the fiber master oscillator and power fiber amplifier with gain saturation characteristic of erbium-doped fiber, we achieved a lasing output with uniform output power and continuously tunable wavelength in the range from 1535 to 1530nm (i.e. 35nm band width). The maximum output power fluctuation is no more than 0.5 dBm, the average power is about 2 W, pulse repetition rate is greater than 10 GHz and pulse width is less than 30 ps in the whole tunable wavelength band width. Furthermore, the laser has advantages of good performance, simple all-fiber structure and convenient operation.
Observation of spatial solitons in nematic liquid crystals
Authors: Zhan Kai-Yun  , Pei Yan-Bo  , Hou Chun-Feng  ,   (1)哈尔滨工业大学物理系，哈尔滨  150001; (2)哈尔滨工业大学物理系，哈尔滨  150001;中国石油大学(华东)物理科学与技术学院，东营  257061
Published: December 2020

Using He-Ne laser, semiconductor laser，and Ar+ laser as the light sources, we observed the self-focusing phenomena of light wave at low power and the forming of spatial solitons in nematic liquid crystal. The spatial solitons with a length over five millimeters and multiple-mode spatial optical solitons were viewed. Furthermore, the forming conditions and characteristics of these solitons were also discussed.
Effect of different laser polarization direction on high order harmonic generation of nitrogen molecule——A simulation via TDDFT
Authors: Cui Lei  , Gu Bin  , Teng Yu-Yong  , Hu Yong-Jin  , Zhao Jiang  , Zeng Xiang-Hua  ,   (1)北京师范大学低能核物理研究所，北京市辐射中心，北京  100875; (2)扬州大学物理科学与技术学院,复杂性科学中心,扬州  225002
Published: December 2020

The high order harmonic generation (HHG) of nitrogen molecule irradiated by ultra-intense femto-second pulsed laser is simulated by the time dependent density functional theory (TDDFT) method with the general gradient approximation of the exchange-correlation energy. The effect of different laser polarization direction on HHG is discussed. The results indicate that the HHG spectrum of N2 has similar characteristics as the typical atom HHG spectrum. With the increase of the angle θ　between laser polarization direction and molecular axis, the spectral intensity of HHG decreases, which is in agreement with the experimental result by J.Itatanl published in Nature.
Small amplitude travelling wave solitons in biased photorefractive crystal
Authors: Chen Shou-Man  , Shi Shun-Xiang  , Dong Hong-Zhou  ,   (1)西安电子科技大学技术物理学院,西安  710071; (2)西安电子科技大学技术物理学院,西安  710071;安康师范专科学校物理系,安康  725000
Published: December 2020

The positive and negative travelling wave solitons are predicted in photorefractive crystal biased by positive electric field in the low intensity regime. The amplitude and width of these solitons do not vary, showing the bright soliton properties, whereas the propagation properties of these solitons differ from previously observed steady-state photorefractive spatial solitons. These travelling wave solitons move on a straight line trajectory. The deflecting angle can be controlled by adjusting the parameter of the system.
Theoretical study on ultrafast response of semiconductor optical amplifier
Authors: Jiang Zhong  , Zhang Xin-Liang  , Huang De-Xiu  ,   华中科技大学武汉光电国家实验室(筹)和光电子科学与工程学院，武汉  430074
Published: December 2020

We proposed a novel method to analyze the propagation of sub-picosecond optical pulses through semiconductor optical amplifiers(SOA), fully considering spectral dispersion of ultrashort pulses. A reasonable model is established via sampling the pulses simultaneously in time domain and frequency domain. Based on the established model, we observed an evident shift of the pulse spectrum, which agrees well with the experiment results in literature. Further, the relationship is discussed respectively between the value of shift and several external conditions, including wavelength, energy, width of the pulse, length of SOA and injected current. Gain suppression induced by ultrafast nonlinearities including carrier heating, spectral hole burning and two-photon absorption is described in detail, employing two-beam configuration. The simulated results give good guidance to the improvement of ultrafast dynamic characteristics of SOAs.
Motion modes of granular particles in a vibrating narrow tube
Authors: Jiang Ze-Hui  , Wang Yun-Ying  , Wu Jing  ,   哈尔滨工业大学物理系，哈尔滨  150001
Published: December 2020

Experiments are performed to investigate the motion modes of granular particles contained in a vibrating narrow tube. It is found that the motion modes strongly depend on the bed thickness and vibration acceleration. Experiments show that in a container with small lateral size, convection rolls and arching of the particles can be confined. For the bed with sufficient thickness, a condensed state of particles always exists in the lower part of the bed, even when strong vibration is applied. Once a condensed state is formed, subharmonic bifurcations of the impact of granular particles at the container bottom can be observed. Experiments reveal that the bifurcation points are independent on the bed thickness. For shallow beds, the particles may be in condensed states or in convections, depending on the particle size.For spherical particles with a narrow size distribution, an ordered packing of the particles is observed. The packing consists of a concentric array of cylindrical “shells" of particles.In the “shell”, the particles are arrayed hexagonally.
The effect of the granule velocity on the dilute-dense flow transition in granular system
Authors: Huang De-Cai  , Sun Gang  , Hou Mei-Ying  , Lu Kun-Quan  ,   中国科学院物理研究所北京凝聚态物理国家实验室，北京  100080
Published: December 2020

The effect of granule velocity on the dilute-dense flow transition in granular system is studied both experimentally and by numerical simulations. Our experiments show that high granule velocity above the exit results in a decrease of critical exit size in dilute-dense flow transition if the inflow rate is fixed. When the granular flow becomes the dense flow, the effect of the granule velocity is counteracted by a high density region above the exit, and the outflow rate is almost irrelative with the granule velocity. Similar results are also obtained by molecular dynamics simulations for corresponding two-dimensional systems. With simulation calculations, the space distributions of the density and speed are also obtained. The distributions show that the density and the thickness of the granule accumulation above the exit vary with the incoming granule velocity, and the variation plays a key role in determining the final granular flow state.
Initial dynamic behavior of nano-void growth in single-crystal copper under shock loading along 〈111〉 direction
Authors: Deng Xiao-Liang  , Zhu Wen-Jun  , He Hong-Liang  , Wu Deng-Xue  , Jing Fu-Qian  ,   (1)四川大学物理科学与技术学院，成都  610064; (2)中国工程物理研究院流体物理研究所冲击波物理与爆轰物理重点实验室，绵阳  621900; (3)中国工程物理研究院流体物理研究所冲击波物理与爆轰物理重点实验室，绵阳  621900;四川大学物理科学与技术学院，成都  610064
Published: December 2020

Initial stage of nano-void growth in single crystal copper under shock loading along direction has been investigated by using molecular dynamics (MD) simulation. The results show the void growth rate, represented by iucrease of equivalent radius of void vs time, keeps constant under certain shock strength. Two kinds of dislocation mechanisms of single void growth have been observed. When shock strength is lower than a critical value, dislocations nucleate and move outward only in the area around two vertices of the void along the shock direction and the void only grows along shock direction. When shock strength exceeds the critical value, dislocations nucleate and move outward not just in the above area but also in the equator perpendicular to the shock direction, and the void grows both along the shock direction and its normal. By examining the displacement history of atoms around the void surface, we find that the radial velocities of the vertices along and perpendicular to the shock direction almost keep constant during the tensile process. Based on constant radial velocities of vertices, we have derived a model of void growth which explains the constant void growth rate well.
Investigation on the broadening of band gap of wurtzite ZnO by Mg-doping
Authors: Jin Xi-Lian  , Lou Shi-Yun  , Kong De-Guo  , Li Yun-Cai  , Du Zu-Liang  ,   河南大学特种功能材料重点实验室，开封  475001
Published: December 2020

The electronic structure of pure and Mg-doped wurtzite ZnO has been investigated by using first-principles ultrasoft pseudopotential method in the generalized gradient approximation. The calculation indicates that the band gap of ZnO broadens with increasing Mg-doping concentrations. Our work shows that the bottom of conduction band is determined by the Zn 4s electron states which can shift to a higher energy due to Mg-doping.
First-principles calculations on the superconductivity and magnetism of doping MgCNi3
Authors: Zhang Jia-Hong  , Ma Rong  , Liu Su  , Liu Mei  ,   东南大学物理系，南京  210096
Published: December 2020

We use the first-principles method to calculate the electronic band structures of MgCNi3. The calculated results show that the hybridization between C 2p and Ni 3d electron orbits leads to the planar characteristic of Ni 3d band. The Fermi level is located on the right slope of the van Hove singularity (vHs) peak. The high density of states (DOS) at the Fermi level with vHs and large magnetic fluctuations near the ferromagnetic phase transition point are the important factors for the superconductivity of MgCNi3. We study the variance of superconductivity and magnetism for three types of substitute doping in MgCNi3, and find that the electron doping moves the Fermi level to the lower DOS side, and transforms MgCNi3 to paramagneticm phase without superconductivity. The inter-metal compounds with the same valence electrons doping change the shape of Fermi surface, resulting from the hybridization between atoms. The decrease of the DOS decreases their superconductivity. The hole doping enhances the DOS at the Fermi level on the peak of vHs, but the large magnetic exchange interactions induce the ferromagnetic order, and the superconductivity disappears abruptly.
Transverse acoustic phonon excitation of two-dimensional Heisenberg ferromagnetic system
Authors: Cheng Tai-Min  , Xianyu Ze  ,   (1)东北大学理学院，沈阳  110004; (2)沈阳化工学院数理系，沈阳  110142
Published: December 2020

A magnon-phonon interaction model is developed on the basis of two-dimensional square Heisenberg ferromagnetic system. The transverse acoustic phonon excitation is studied through Matsubara Green function theory, and the transverse acoustic phonon dispersion curve is calculated at the main symmetric point and on the symmetric line in the first Brillouin zone. It's found that on the line Σ in first Brillouin zone, there is hardening for the transverse acoustic phonon in the smaller wave vector zone (point Γ near kxa＜0.2), but there is softening for the transverse acoustic phonon in the softening zone (0.25＜kxa＜0.7), there is hardening for the transverse acoustic phonon at point M near (0.75＜kxa). On the line Δ, there is no phonon softening and hardening for transverse acoustic phonon. On the line Z, there is softening for transverse acoustic phonon in smaller wave vector zone (point X near kxa＜0.65), but there is hardening for the transverse acoustic phonon at the point M nearby. The influences of different parameters on the transverse acoustic phonon excitation are also illustrated. It's found that the coupling of the magnon-phonon coupling and the spin wave stiffness are the main factors affecting the transverse acoustic phonon softening.