bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical solution of scattering states for Hulthén potentials
Authors: Chen Chang-Yuan  , Lu Fa-Lin  , Sun Dong-Sheng  ,   盐城师范学院物理系，盐城 224002
Published: December 2020

In this paper, using the exponential function transformation, the radial Schrdinger equation with the Hulthén potential is transformed into a hypergeometricdifferential equation under the condition that an effective approximation as 1/r2≈λ2e-λr/(1-e-λr)2 is used for the centrifugal term in the case of any l-states. The exact solution of s-wave scattering state and the approximate analytical solution of non-s-wave scattering states for the Schrdinger equation with the Hulthén potential are presented. The normalized wave functions expressed in terms of hypergeometric functions of scattering states on the “k/2π scale" and the calculation formula of phase shifts are given. The physical meaning of the approximate analytical solution is discussed.
Generalized projective synchronization of two four-dimensional chaotic systems
Authors: Min Fu-Hong  , Wang Zhi-Quan  ,   (1)南京理工大学自动化系，南京 210094; (2)南京理工大学自动化系，南京 210094;南京师范大学电气与自动化工程学院，南京 210042
Published: December 2020

In this paper, the generalized projective synchronization has been observed in the coupled four_dimensional chaotic systems. The different nonlinear feedback controllers are designed by an active control method for synchronization of two chaotic systems with the same or different structures. The proposed technique allows us to arbitrarily direct the scaling factor to a desired value. Numerical simulation is provided to show the effectiveness of the theoretical analysis.
A new method to recognize determinism in time series
Authors: Wu Yan-Dong  , Xie Hong-Bo  ,   (1)淮阴工学院计算科学系，淮安 223001; (2)江苏大学生物医学工程系，镇江 212013
Published: December 2020

Compared with singular value decomposition, symplectic geometry spectrum is a measure preserving and nonlinear transform. So, it is more suitable for nonlinear dynamics system analysis. A new method to detect determinism in time series based on symplectic geometry spectrum (SGS) is proposed in the present work. Chaos and stochastic process could be recognized by applying the non_parameter Mann_Whitney on the SGS of original data and its surrogate data. The method is first tested on stochastic processes, the Lorenz, Rossler, Mackey_Glass and high dimensional coupling equations. Then it is applied to two data sets of Santa Fe to test its effect on experimental data. Finally, the robust ness of the method is tested on the time series with different data length and different levels of additive noise.
Investigation on the cascade synchronization system based on the optoelectronic negative feedback chaotic lasers
Authors: Liao Jian-Fei  , Xia Guang-Qiong  , Wu Jia-Gui  , Xu Li  , Wu Zheng-Mao  ,   西南大学物理学院，重庆 400715
Published: December 2020

A novel chaotic repeater system based on the cascade synchronization in optoelectronic negative feedback chaotic lasers is proposed. The synchronization characteristics and the influence of the parameter mismatch on the synchronization have been investigated. The results show that complete synchronization can be realized with suitable system parameters, and the internal parameter mismatch of the lasers have influence on the synchronization quality. But the system has greater robustness to parameter mismatch compared with the cascade synchronization based on the optical feedback.
A theoretical study on double differential cross sections for electron impact ionization of helium at low energies
Authors: Zhang Sui-Meng  , Wu Xing-Ju  , Sun Rui  , Yang Huan  , Gao Kuang  , Zhou Jun  ,   (1)安徽师范大学物理与电子信息学院，芜湖 241000; (2)安徽皖西学院数理系原子与分子物理研究所，六安 237012; (3)安徽皖西学院数理系原子与分子物理研究所，六安 237012；安徽师范大学物理与电子信息学院，芜湖 241000
Published: December 2020

In the present work we have studied the double differential cross sections for single ionization of a helium atom by electron impact at low energies. The double differential cross sections of the secondary ejected electron have been obtained by integrating the triple differential cross sections over the entire angular range of the primary scattered electron. The double differential cross sections for electron impact ionization of helium at incident energies of 26.3，28.3，30.3，32.5，34.3，36.5 and 40.7eV have been calculated in the BBK and DS3C model. The present DS3C results are compared with the absolute measurements，and reasonably good agreement has generally been found except for low incident energies (e.g.，26.3eV) and low ejected angles. In addition，the direct and exchange amplitudes are also considered. It has also been shown how the exchange effects contribute to the cross sections.
Correlation of emitted electrons in near threshold double ionization of helium by electron impact
Authors: Cao Shi-Ping  , Ma Xin-Wen  , Dorn A.  , Dürr M.  , Ullrich J.  ,   (1)Max-Planck-Institute for Nuclear Physics,Saupfercheckweg 1,Heidelberg,Germany 69117; (2)中国科学院近代物理研究所,兰州 730000; (3)中国科学院近代物理研究所,兰州 730000；中国科学院研究生院,北京 100049
Published: December 2020

We have performed an experiment on near threshold double ionization of helium by 106eV electron impact with an improved reaction microscope. In this experiment the momenta of three particles after ionization were measured, and the information on correlation of emitted electrons was obtained. Detailed descriptions of the experimental setup and the methods of reconstruction of electron momentum were given. We focused on the analysis of momentum and energy distributions and the angular correlation of the emitted electrons. The experimental results were compared with Wannier's prediction, and it was found that the experimental results showed some characteristic features predicted by Wannier theory.
Effect of vacuum-induced coherence in a four-level atomic system via quantum interference
Authors: Chen Jun  , Liu Zheng-Dong  , Zheng Jun  , Fang Hui-Juan  ,   (1)南昌大学近代物理研究所，南昌 330031; (2)南昌大学近代物理研究所，南昌 330031;广东工业大学实验中心,广州 510090; (3)南昌大学近代物理研究所，南昌 330031;南昌大学纳米技术工程研究中心，南昌 330047; (4)南昌大学纳米技术工程研究中心，南昌 330047
Published: December 2020

In this paper，we report the effects of vacuum-induced coherence in a laser-driven four-level atom consisting of three near-degenerate upper levels having an additional coherence term due to interaction with the vacuum of the radiation field. We show that such coherence preserves the electromagnetically induced transparency and optical bistability phenomena. The dynamical behavior of the population distribution via vacuum-induced coherence was also analyzed numerically.
Effect of pump laser intensity on optically pumped D2O gas terahertz laser
Authors: He Zhi-Hong  , Yao Jian-Quan  , Shi Hua-Feng  , Huang Xiao  , Luo Xi-Zhang  , Jiang Shao-Ji  , Li Jian-Rong  , Wang Peng  ,   (1)天津大学精密仪器与光电子工程学院激光与光电子研究所，教育部光电信息技术科学重点实验室，天津 300072; (2)天津大学精密仪器与光电子工程学院激光与光电子研究所，教育部光电信息技术科学重点实验室，天津 300072；中山大学光电材料与技术国家重点实验室，广州 510275; (3)中山大学光电材料与技术国家重点实验室，广州 510275
Published: December 2020

Based on the semi-classical theory，the pulsed-laser pumped D2O gas tera-Hz laser was theoretically analyzed，the relation between the intensity of pumping laser and the output tera-Hz laser light was studied and numerically calculated. According to the result of calculation，the intensity of the output tera-Hz laser light increased approximately linearly with that of the input laser in a certain range，but gradually decreased because of the bottleneck effect when the intensity of the input laser exceeded a fixed value，and for given gas pressure，cavity length and operating temperature，an optimal intensity of pumping laser exists. A frequency tuning range of the output signal occurred when the intensity of the input laser was strong enough.
Investigation of the output characteristics of extremely short external cavity semiconductor laser using the ray tracing method
Authors: Wu Jia-Gui  , Wu Zheng-Mao  , Xia Guang-Qiong  ,   西南大学物理学院，重庆 400715
Published: December 2020

Based on the ray tracing method，the implicit expression of the output spectrum of the extremely short external cavity semiconductor laser (ESECSL) has been deduced for the first time. As a result，the output spectrum and P-I characteristic of ESECSL have been investigated. The results show that: when the length of external cavity changes by an amount of the order of wavelength，the P-I characteristic of ESECSL will change obviously. The lasing wavelength of ESECSL will hop periodically in the range of 10nm with the variation of the length of external cavity. Especially，the hopping range of the lasing wavelength will reach the maximum for the external cavity length varying within the range of 40—70μm. The simulations are well in accordance with the experimental reports.
Study on the property of the second harmonic in the nearfield of a Bessel ultrasonic field based on the Fourier-Bessel series
Authors: Du Hong-Wei  , Peng Hu  , Jiang Zhao-Hui  , Feng Huan-Qing  ,   中国科学技术大学电子科学与技术系，合肥 230027
Published: December 2020

A new method based on the Fourier-Bessel series is applied in KZK equation to calculate the second harmonic component of a zero-order Bessel ultrasonic field in viscous medium. An analytical solution of a series form is obtained and a new conclusion is drawn. Assuming the source sound pressure to be J0(α0r)，the second harmonic sound pressure has a radial distribution of J20(α0r) function profile in the near field. This conclusion explains the experimental results reported in literature appropriately and indicates that the second harmonic field has different radial distributions in the near and far field，thus solves the problem of radial distribution of the second harmonic in the nearfield of Bessel ultrasonic field. Moreover，the conclusion implies that the second harmonic field has similar limited diffraction property as the fundamental. A numerical computation and simulation example is given subsequently.
Power law of horizontal convection at high Rayleigh numbers
Authors: Sun Liang  , Sun Yi-Feng  , Ma Dong-Jun  , Sun De-Jun  ,   (1)中国科学技术大学地球与空间科学学院,合肥 230026；中国科学院大气物理研究所LASG国家重点实验室,北京 100029; (2)中国科学技术大学力学和机械工程系,合肥 230027; (3)中国科学院研究生院生物运动力学实验室,北京 100049
Published: December 2020

The horizontal convection at high Rayleigh number (Ra) in a rectangle cavity with aspect ratio of 1∶10 is numerically simulated. The horizontal convection is an important model to understand the ocean circulation and the power laws of the flow are the most concerned. According to the results within the regime of 104Ra11, three continuous regimes are obtained: the linear regime (104Ra6), the transition regime (106Ra8) and the 1/5-power law regime (108Ra11). For the flow strength, a 1/3-power law of Ra is fitted when Ra is not high enough (107Ra8). However, a 1/5-power law is obtained when Ra is high enough (108Ra11). The 1/5-power law confirms the analysis of Rossby and implies that 1/3-power law of Ra for Nusselt number by Siggers et al. is an over estimation.
Size-induced enhancement of bulk modulus and transition pressure of nanocrystalline Ge
Authors: Wang Hui  , Liu Jin-Fang  , He Yan  , Chen Wei  , Wang Ying  , Gerward L.  , Jiang Jian-Zhong  ,   (1)丹麦技术大学物理系，DK-2800 Lyngby/Denmark; (2)浙江大学材料科学与工程学系新结构材料实验室,杭州 310027
Published: December 2020

In situ energy dispersive X-ray diffraction measurements with synchrotron radiation source have been performed on nanocrystalline Ge with particle sizes 13, 49 and 100 nm by using diamond anvil cell. Whereas the percentage volume collapse at the transition is almost constant, the values of the bulk modulus and transition pressure increase with decreasing particle size. Models are suggested to describe the grain-size dependences of bulk modulus and transition pressure. The trend of the predicted results is consistent with the experimental results while the absolute values are still different from experimental ones.
Dependence of electronic-transport sensitivity on the coupling between single molecule and atomic-chain electrode
Authors: Wang Li-Guang  , Chen Lei  , Yu Ding-Wen  , Li Yong  , Terence K. S. W.  ,   (1)江南大学理学院，无锡 214122; (2)新加坡南洋理工大学电气与电子工程学院，新加坡 639798
Published: December 2020

The electronic transport sensitivity depending on the coupling interface between a phenalenyl molecule and atomic chain lead in three-electrode single-molecular device is theoretically modeled and studied using self-consistent tight-binding method. Electronic transmission probabilities are obtained by changing the hopping integral on the interface. The result shows that the electron transmission probability lowers as the coupling strength becomes weak. Not only the transmission probability shows high peaks, but also the transmission energy bands become wider as the coupling strength increases. A novel property of the symmetrical three-electrode phenalenyl molecule device acting as a good plus-minus energy switch without source is discovered.
Localized interface phonon polaritons in two coupled semi-infinite superlattices
Authors: Gong Zhi-Qiang  , He Meng-Dong  ,   中南林业科技大学理学院，株洲 412006
Published: December 2020

Using a transfer matrix method, we study the characteristics of the localized interface phonon polariton modes in two coupled superlattices (SLs) with a defect layer. Comparing different structure defects of SL where the dielectric characteristics of defect layers are different, we find that there are certain differences in the distribution and number of the localized interface phonon polariton modes in the Reststrahlen regions ［ωTO，ωLO］ and there are different characteristics for anti-symmetric modes in the above structures. The structuraly defective SL of which the dielectric constant of defect layer is independent of frequency was emphatically investigated. We found that the localized interface phonon polariton modes in such structure are sensitive to the thicknesses and order of the constituent layers, the thickness of the defect layer as well as the transverse wavenumber q∥.
An in situ method for characterizing the kinetics of the oxidation process of copper thin films via sheet resistance
Authors: Luo Yu-Feng  , Zhong Cheng  , Zhang Li  , Yan Xue-Jian  , Li Jin  , Jiang Yi-Ming  ,   复旦大学材料科学系,上海 200433
Published: December 2020

In this paper, a new in situ method was developed for characterizing the kinetics of the oxidation process of copper thin films by using sheet resistance. Copper thin films were prepared on glass substrate by vacuum deposition. The oxidation kinetics of the copper thin films was studied via sheet resistance which increased during the process. The results suggested that this new method can be applied to the characterization of the reaction kinetics of copper thin film.
Propagation of Bessel-correlated partially coherent hollow beams in the turbulent atmosphere
Authors: Wang Tao  , Pu Ji-Xiong  ,   华侨大学电子科学与技术系,泉州 362021
Published: December 2020

Based on the extended Huygens-Fresnel principle, the propagation formulas for Bessel-correlated partially coherent hollow beams in a turbulent atmosphere has been derived, then the propagation properties of such beams in the turbulent atmosphere have been investigated in great detail. The results indicate that the turbulent atmosphere, the spatial coherence and the beam width play important roles in the beam propagation.
The existence of two types of generalized synchronization of nonlinear systems
Authors: Guo Liu-Xiao  , Xu Zhen-Yuan  ,   (1)江南大学理学院信息与计算科学系，无锡  214122; (2)江南大学理学院信息与计算科学系，无锡  214122；江南大学信息与工程学院，无锡  214122
Published: December 2020

The existence of two types of generalized synchronization of chaotic nonlinear systems is studied. When the modified system collapses to a stable equilibrium or periodic oscillation, the existence of generalized synchronization can be converted to the problem of compression fixed point under certain conditions. Strict theoretical proofs are given to the exponential attractive property of generalized synchronization manifold. Numerical simulations illustrate the correctness of the present theory.
Symbolic time series characterization and block entropy analysis of DC-DC converters
Authors: Wang Xue-Mei  , Zhang Bo  , Qiu Dong-Yuan  , Chen Liang-Gang  ,   (1)华南理工大学电力学院,广州  510640; (2)华南理工大学电力学院,广州  510640；湖南工业大学电气与信息工程学院，株洲  412008
Published: December 2020

A method based on symbolic time series and entropy theory is proposed to analyse the nonlinear behaviours of DC-DC converters. Firstly, the nonlinear continuous system is described by a discrete time series, which is then transferred to a symbol series composed of simple characters; and the series' block entropy is calculated by means of informatics methodology; consequently, a new quantifiable statistical index is obtained. This study takes a one-order voltage feedback DCM and a two-order current feedback CCM Boost converter as examples, and the results illustrate that the coarse-grained statistical method of block entropy, which can quantify the period-doubling and chaos behaviours in DC-DC converters and precisely confirm the appearance of chaos, is a simple and practical analysis method which has not been used in DC-DC converters yet.
Prediction of the chaotic time series from parameter-varying systems using artificial neural networks
Authors: Wang Yong-Sheng  , Sun Jin  , Wang Chang-Jin  , Fan Hong-Da  ,   海军航空工程学院兵器科学与技术系，烟台  264001
Published: December 2020

Prediction of the chaotic time series generated by the complex parameter-varying systems is researched in this paper. The parameter-varying Logistic system is constructed firstly, and the properties of this kind of system are analyzed. These systems, whose parameter values change with time, do not have attractor shape invariable with time evolution because of their continually changing dynamical property. Combining the Takens' embedding theorem and the artificial neural networks (ANN) theory, we interprete the feasible reason that ANN method can be used to predict the chaos systems with the invariable attractor shape, and then discuss the potential problem that will be met when using ANN to predict the parameter-varying system. Experiments of forecasting the chaotic time series from parameter-varying Ikeda system using neural networks have been performed. The previous theoretical analyses are validated by the experiment results. The results also show that if only simply increasing the training data, the neural networks' predicting generalization ability may be reduced, the generalized predicting result on the parameter-varying system is especially seriously affected by the selected training data set. So prediction of the parameter-varying systems must be well resolved before the chaotic time series prediction can be made practical.
Multi-scale recurrence quantification analysis of the dynamic characteristics of two phase flow pattern
Authors: Dong Fang  , Jin Ning-De  , Zong Yan-Bo  , Wang Zhen-Ya  ,   (1)天津大学电气与自动化工程学院，天津  300072; (2)天津大学电气与自动化工程学院，天津  300072；河北大学质量技术监督学院，保定  071051
Published: December 2020

Based on the conductance fluctuating signals of the gas/liquid two phase flow measured in a vertical upward pipe, the multi_scale recurrence quantification analysis method is used to study the dynamic characteristics of gas/liquid two phase typical flow patterns. The results show that the low frequency bubble and churn flow patterns take on more developed line texture structure along the diagonal direction of the chaotic recurrence plot, which indicates that the low frequency bubble and churn flow have deterministic motion behavior. However, with increasing motion frequency of bubble and churn flow, the chaotic recurrence characteristics become worse and the motion tends to random gradually. For the slug flow, the intermittent rectangular massive texture appears on chaotic recurrence plot, which indicates that the intermittent motion characteristics of the liquid plug and gas plug appear in the high frequency band, whereas bubble flow motion in slug flow pattern appears in the low frequency band, and with increasing motion frequency of bubble flow, the bubble flow loses the deterministic behavior gradually. It is shown that multi-scale and nonlinear analysis based on conductance fluctuating signals is an efficient approach to understanding and characterizing the dynamic characteristics of gas/liquid two phase flow patterns.
Error mechanism of light source for synchrotron radiation computed tomography technique
Authors: Wang Min  , Cen Yu-Wan  , Hu Xiao-Fang  , Yu Xiao-Liu  , Zhu Pei-Ping  ,   (1)安徽工业大学机械工程学院，马鞍山  243002; (2)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  230026; (3)中国科学院高能物理研究所同步辐射室，北京  100049
Published: December 2020

Based on the unique advantages of synchrotron radiation X-ray with high resolution and collimation，and the advantage of nondestructive observation of computed-tomography technique，synchrotron radiation computed tomography technique is widely used in many fields. In this paper，the errors caused by light source such as unevenness，supersaturation and super penetration are studied for synchrotron radiation computed tomography technique，and its three basic error forms are given. Numerical simulation results confirm this analysis.
Stabilizing the silicon fullerene Si24 by La and Gd encapsulation
Authors: Wang Xiao-Qiu  , Wang Bao-Lin  ,   (1)淮阴师范学院物理系，淮安  223001; (2)淮阴师范学院物理系，淮安  223001；淮阴工学院物理系，淮安  223003
Published: December 2020

Using gradient-corrected spinpolarized density-functional theory (DFT) for electronic structure calculations，we study the fullerene of silicon Si24 with Th and D2d symmetries in the neutral state stabilized by lanthanum and gadolinium encapsulation. The electronic and magnetic properties of La@Si24 and Gd@Si24 are calculated using spin unrestricted DFT. The higher spin magnetic moment is achieved for Gd@Si24 and the magnetic moment of La@Si24 is completely quenched. These results could possibly lead to new phases and derivatives of silicon.
Electronic structure and conductance of fullerene C20
Authors: Zhang Hong-Yu  , Wang Li-Guang  , Zhang Xiu-Mei  , Yu Ding-Wen  , Li Yong  ,   (1)江南大学理学院，无锡  214122; (2)江南大学理学院，无锡  214122；南京大学固体微结构物理国家重点实验室，南京  210093; (3)清华大学国家摩擦重点实验室微纳分室，北京  100084
Published: December 2020

The electronic structure and electronic conductance of C20 molecule bridged between two Au electrodes are studied by the first principles based on the density functional theory and the nonequilibrium Greens function. The three transmission systems based on C20 molecules are modeled，and the transmission spectra and the molecular orbital distributions are obtained. The reasons why the electronic structure and the electronic transmission are formed are discussed. The results show that the electrons are transported through the C20 bridge on the molecular shell. When one K or one Si atom is inlaid inside C20，the conductivities indicate that the electrons can transfer partly inside the C20 molecule，but most electrons ave transported on the C20 fullerene shell.
Analysis of the transmittance of modified Savart polariscope in the static large field of view polarization interference imaging spectrometer
Authors: Du Juan  , Zhang Chun-Min  , Zhao Bao-Chang  , Sun Yao  ,   (1)西安交通大学理学院，西安  710049; (2)中国科学院西安光学精密机械研究所空间光学研究室，西安  710119
Published: December 2020

The principle of beam splitting of modified Savart polariscope in the static large field of view polarization interference imaging spectrometer(SLPIIS) is described. The reflection and refraction in every uniaxial of modified Savart polariscope are analyzed， with the incident plane coincident or perpendicular to the principle section of the left plate，based on the electromagnetic boundary conditions. Formulas for the transmittance of the modified Savart polariscope are given as functions of wavelength of the incident light，angle and thickness of the half-wave plate，which are analyzed through computer simulation with different half-wave plates. It is proved that the modified Savart polariscope has the advantages of having both large field of view and high flux，and can be used as high performance lateral shearing beam splitter in SLPIIS. This theoretical study will provide guidance for the experimental study of new polarization interference imaging spectrometer.
Design and fabrication of gold transmission phase gratings for soft X-rays
Authors: Qiu Ke-Qiang  , Xu Xiang-Dong  , Liu Ying  , Hong Yi-Lin  , Fu Shao-Jun  ,   中国科学技术大学国家同步辐射实验室，合肥  230029
Published: December 2020

The diffraction efficiency of a gold transmission phase grating is simulated as a function of the depth of grooves and the duty cycle on the basis of the scalar diffraction theories. It is shown that the +1 order diffraction efficiency of a transmission phase grating with appropriate groove depth and duty cycle can beup to 21.9% of the incident light，whereas it is no greater than 10% for a conventional amplitude-mode transmission grating. Transmission gratings with area of 20mm×5mm，period of 1μm，duty cycle of 0.55 and 200nm thick gold bars supported by a membrane of 300nm thick polyimide have been fabricated by combining holographic lithography and electroplating. Its diffraction efficiency has been measured in national synchrotron radiation laboratory，and the maximum efficiency in +1 order is about 16% at λ=7.425nm.
Application of laser-induced breakdown spectroscopy in analyzing microelements in three kinds of fruit samples
Authors: Zhang Da-Cheng  , Ma Xin-Wen  , Zhu Xiao-Long  , Li Bin  , Zu Kai-Ling  ,   (1)中国科学院近代物理研究所,兰州  730000; (2)中国科学院近代物理研究所,兰州  730000；中国科学院研究生院,北京  100049
Published: December 2020

It is a relatively new task to apply the laser-induced breakdown spectrosopy(LIBS) to plant samples. To apply LIBS technique in the field related to foodstuff safety, we have done primary experiments using three kinds of fruit samples prepared by vacuum freeze-dried technique using the technique of discriminated LIBS spectra. The relative contents of six trace elements Ca, Na, K, Fe, Al and Mg in the samples were analyzed. By comparison we found that in apple samples the relative content of Na is the highest and the relative content of Ca is the lowest, and the contents of K, Fe, Mn, Mg are different for different fruit samples. Experiment results showed that LIBS technique is a valid means for measuring and comparing the content of trace elements in plant samples.
Theoretical investigation on the characteristics of transmission spectra of the two-cavity Fabry-Perot structure based on fiber gratings for single-frequency fiber laser
Authors: Xu Ou  , Lu Shao-Hua  , Jian Shui-Sheng  ,   北京交通大学光波技术研究所,全光网络与现代通信网教育部重点实验室，北京  100044
Published: December 2020

The characteristics of transmission spectra of the all-fiber two-cavity Fabry-Perot (F-P) configuration based on fiber Bragg gratings (FBG) are theoretically analyzed and modeled. The explicit expression of the transmission coefficient for two-cavity F-P structures is derived. When the single resonant transmission peak is produced at the central wavelength in FBG stop band, the general conditions for the lengths of two cavities and reflectivities of FBGs are presented. Based on the theoretical analysis, the transmission spectra of symmetric and asymmetric two-cavity F-P structures are simulated, and the simulation results are discussed and explained qualitatively. The design guidelines of the device, including the choices of cavity length, grating length and index modulation depth， are put forword. The results show that, when the increasing of the cavity length of a single-cavity F-P structure results in multiple resonant peaks in the stop band, the two-cavity F-P structures of the same length can suppress the secondary resonant peaks and keep the main peak unaffected without degrading the performance through appropriately designing the cavity lengths and FBGs.
Whispering-gallery modes based on evanescent field in cylindrical micro-cavity
Authors: Yang Rui  , Yu Wen-Hua  , Bao Yang  , Zhang Yuan-Xian  , Pu Xiao-Yun  ,   云南大学物理科学技术学院，昆明  650091
Published: December 2020

We present the observation of whispering-gallery modes (WGMs) in cylindrical micro-cavity coupled to a fiber taper based on evanescent field with a coupling efficiency of about 10%. All the WGMs spectra of cylindrical micro-cavities with four different diameters are precisely indexed by an explicit asymptotic formula with the positions and separation as parameters. By introducing the parameter “mode field radius" of WGMs, the mode separations calculated by mode field radius agree well with the experimental results. And by determining the difference between experimental resonant wavelengths and the theoretically assigned ones, the dispersive curve of quartz fiber is corrected over the spectrum range of 1295—1320nm and the precision of refractive index determination is as high as 10-5.
Investigation on the dispersion characteristics of a uniform plasma grating
Authors: Yu Lu-Le  , Sheng Zheng-Ming  , Zhang Jie  ,   (1)中国科学院物理研究所光物理重点实验室，北京  100190; (2)中国科学院物理研究所光物理重点实验室，北京  100190；上海交通大学物理系，上海  200240
Published: December 2020

Recently, the plasma Bragg gratings induced by two intersecting laser pulses has been predicted theoretically. The dispersion relation of uniform plasma gratings under the oblique incidence of a light wave is investigated with the transfer-matrix method and the coupled-mode theory. Both approaches show that such plasma gratings exhibit a photonic band gap, near which strong dispersion appears. The photonic band gap has different polarization characteristics when the light wave is obliquely incident on the plasma grating. With the increase of the incident angle, the band gap for an S-polarized wave increases gradually, while that for a P-polarized wave decreases first rapidly, then vanishes when it approaches the Brewster angle, and finally becomes wide with the further increase of the incident angle. Since the plasma grating has an ultrabroad photonic band gap and can support an ultrahigh damage threshold of incident light waves, it has the potential to be a novel photonic device to manipulate extremely intense laser pulses.
Structure and magnetic properties of the pseudobinary solid solution TbGa1-xGex(0≤x≤0.4)
Authors: Zhang Ji-Ye  , Luo Jun  , Liang Jing-Kui  , Ji Li-Na  , Liu Yan-Hui  , Li Jing-Bo  , Rao Guang-Hui  ,   中国科学院物理研究所北京凝聚态物理国家实验室，北京  100190
Published: December 2020

Polycrystalline samples of TbGa1-xGex(x≤0.4) have been prepared by arc-melting. X-ray powder diffraction reveals that all the samples crystallize in a single phase of CrB-type structure and space group Cmcm. The lattice constants of the compounds decrease linearly with the increasing Ge content. The compounds form a solid solution in the Ge content range of 0≤x≤0.4. The asymptotic Curie points and the effective paramagnetic moments of the compounds have been determined by thermomagnetic measurements. The ordering temperatures were derived from ac susceptibility data. The XRD patterns at various temperatures reveal that there is no structure phase transition in the samples with x=0.2 and 0.3 in the temperature range of 113—273K.
Structure and photoluminescence of Zn2GeO4 polycrystalline films prepared by radio-frequency magnetron sputtering
Authors: Wang Zhen-Ning  , Jiang Mei-Fu  , Ning Zhao-Yuan  , Zhu Li  ,   苏州大学物理科学与技术学院,苏州  215006
Published: December 2020

Films were deposited on Si substrates at different temperatures by RF magnetron sputtering and subsequently annealed in vacuum at 800℃. Well crystallized films were prepared successfully. The influences of substrate temperature on the structure, the componsition and the morphology of Zn2GeO4films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and atom force microscope. The results show that Zn2GeO4 films grow with (220) preferred orientation with the increase of substrate temperature above 400℃, and the substrate temperature between 500 and 600℃ is suitable for GeO2 crystalline growth. XPS spectra show that the films contain four chemical compositions of Zn2GeO4, GeO2, Ge and ZnO. Besides, with the increase of substrates temperature, the size of crystal grains increases, and the surface of films is smooth and continuous. The green emission consisting of two peaks centered at 530 and 550nm, which is attributed to luminescence centers of Ge2+ substituting Zn2+ at different sites.
Linear and nonlinear optical properties of CdSe quantumn dots
Authors: Zhu Bao-Hua  , Wang Fang-Fang  , Zhang Kun  , Ma Guo-Hong  , Gu Yu-Zong  , Guo Li-Jun  , Qian Shi-Xiong  ,   (1)复旦大学物理系，上海  200433; (2)河南大学光学与光电子技术研究所，开封  475004; (3)河南大学光学与光电子技术研究所，开封  475004；南京林业大学信息学院，南京  210037; (4)上海大学理学院，上海  200444
Published: December 2020

On the basis of measurement and theoretical analysis, the linear and nonlinear optical properties of the CdSe quantumn dots with different nanoparticle sizes were investigated. The relation between the nanoparticle size and the absorption peak of CdSe quantumn dots was characterized by UV-VIS-NIR spectroscopy, and the dependence of third-order nonlinear susceptibility of quantumn dots on nanoparticle size was investigated by picosecond Z-scan technique with different excitation wavelengths (532nm and 1064nm,resp.). The analysis of optical properties of the films was carried out using the theory of localized field enhancement. The experimental and theoretical results showed the dependence of third-order nonlinear susceptibilities χ(3) on the CdSe nanoparticle size. With CdSe nanoparticle size around 4.3nm and the excitation wavelength of 532nm, which was close to the resonance, the third-order nonlinear susceptibility χ(3) showed a maximum value of 2.0×10-11 esu.
Preparation and properties of GeC thin films deposited by reactive RF magnetron sputtering
Authors: Li Yang-Ping  , Liu Zheng-Tang  , Liu Wen-Ting  , Yan Feng  , Chen Jing  ,   西北工业大学材料学院，西安  710072
Published: December 2020

GeC thin films were deposited on ZnS substrates with reactive RF magnetron sputtering, and the influences of the processing parameters on sputtering of the Ge target and IR transmission properties of the GeC films were studied. At low substrate temperatures, the GeC film contained H atoms in forms of CH2，CH3 and Ge-CH3 groups, which caused IR absorption, whereas the absorption decreased obviously at elevated substrate temperatures. Target-substrate distance, RF power, Ar:CH4 gas flow ratio and total gas pressure had great impacts on the poisoning and sputtering of the Ge target, but their impacts on the IR absorption of the GeC film was small. When the Ge target was poisoned greatly, adhesion of the GeC film was inferior, with the weakening of the target poisoning, adhesion of the GeC film increased. Hydrogen-free GeC film with excellent adhesion was prepared on ZnS substrate under optimized parameters, and its refractive index was about 1.78. The C content in the GeC film was larger than the Ge content, and C and Ge formed mainly C—Ge bonds. GeC/GaP antireflective and protective film system was prepared on ZnS substrate, giving good antireflective effect.
Up-conversion mechanisms of Yb-Er co-doped Al2O3 film and its temperature characteristics
Authors: Li Cheng-Ren  , Ming Cheng-Guo  , Li Shu-Feng  , Ding Jian-Hua  , Wang Bao-Cheng  , Zhang Li  ,   (1)大连理工大学物理与光电工程学院，大连  116024; (2)辽宁师范大学物理与电子技术学院，大连  116029
Published: December 2020

Yb-Er co_doped Al2O3 film was prepared on SiO2/Si substrate using a medium frequency magnetron sputtering system, and the concentrations of dopant Er and Yb ions were 0.3% and 3.6%, respectively. The up-conversion mechanisms of Er3+ photoluminescence at 529 and 549nm were discussed. The fluorescence intensity ratio of the green up-conversion spectra were measured in the temperature range of 291.8—573.3K, and the temperature characteristics were fitted as R=5.37exp(-738/T). At the temperature of 366K, the sensitivity has the maximum value of 0.0039 K-1. The results show that the Yb∶Er∶Al2O3 film is a suitable material for minitype, high-sensitivity and high-temperature optical sensors.
Scattering from a diffuse target in the slant atmospheric turbulence
Authors: Wei Hong-Yan  , Wu Zhen-Sen  , Peng Hui  ,   西安电子科技大学理学院，西安  710071
Published: December 2020

Based on the extended Huygens-Fresnel principle and ITU-R atmospheric turbulence model (the altitude-dependent model proposed by International Telecommunication Union-Recommendation in 2001), the treatment includes the effect of the atmospheric turbulence both on the laser beam as it propagates to the target and on the scattered field as it propagates back to the receiver. The covariance function and variance of the scattering intensity are derived considering the fluctuations of the log-amplitude and phase, and the numerical results are presented. The influences of wavelength, receiver altitude and propagation distance on the covariance function and normalized variance of the scattering are discussed.
Time offset measurement algorithm based on bispectrum for pulsar integrated pulse profiles
Authors: Xie Zhen-Hua  , Xu Lu-Ping  , Ni Guang-Ren  ,   (1)西安电子科技大学电子工程学院，西安  710071; (2)中国科学院国家授时中心，西安  710600
Published: December 2020

In order to improve time offset measurement precision of pulsar integrated pulse profile and enhance the capability of noise suppression, a time offset measurement algorithm based on bispectrum for pulsar integrated pulse profile was proposed. Theoretically, bispectrum can completely suppress the additive Gaussian white noise, and the time offset in the third-order cumulants will result in phase rotation in the bispectrum. Time offset measurement algorithm based on bispectrum can be deduced by contrasting self-bispectrum and cross-bispectrum and solving the extremum formula. The results of experiments show that time offset measurement algorithm based on bispectrum can suppress the additive Gaussian white noise, and its precision is higher than that based on power spectrum proposed by Taylor.
Variational iteration method for solving the equatorial sea-air oscillator model for global climate
Authors: Mo Jia-Qi  , Lin Wan-Tao  ,   (1)安徽师范大学，芜湖  241000；上海高校计算科学院E-研究院SJTU研究所，上海  200240；湖州师范学院，湖州  313000; (2)大气科学和地球流体力学数值模拟国家重点实验室，中国科学院大气物理研究所，北京  100029
Published: December 2020

A three dimentional equation for the equatoral sea-air oscillator Kelvin wave is considered. By using the variational iteration method，the approximate solution of the corresponding model is studied. The variational iteration method is an analytic method，the obtained solution can be used in further analytical operations.
Conformal symmetry and Hojman conserved quantity of Lagrange system
Authors: Liu Chang  , Mei Feng-Xiang  , Guo Yong-Xin  ,   (1)北京理工大学理学院力学系，北京  100081; (2)辽宁大学物理学院，沈阳  110036; (3)辽宁大学物理学院，沈阳  110036；北京理工大学理学院力学系，北京  100081
Published: December 2020

In this paper the conformal invariance under special infinitesimal transformations of Lagrange systems is studied. The necessary and sufficient conditions for the conformal invariance under infinitesimal transformations which is Lie symmetric at the same time are given. Finally we get the Hojman conserved quantities of the conformal invariance.
Control of beam halo-chaos by the number of ions in small fixed regions
Authors: Yang Cui-Yun  , Weng Jia-Qiang  , Liu Hai-Ying  , Liu Ping  , Tang Guo-Ning  , Fang Jin-Qing  ,   (1)电子科技大学中山学院电子工程系,中山  528402; (2)广西师范大学物理与电子工程学院,桂林  541004; (3)桂林师范高等专科学校物理与信息技术系,桂林  541002; (4)中国原子能科学研究院,北京  102413
Published: December 2020

Exploiting the information provided by the number of ions in some fixed regions outside the matched radius boundary, the simulation of controlling the beam halo-chaos of a high intensity ion beam has been studied by applying the logarithm-function controller. Control results show that the halo-chaos and its regeneration can be eliminated effectively for five different initial distributions, respectively. The controlling method is easy to realize in experiment because it only needs to probe the control information in small and fixed regions.
Response of Duffing one-sided constraint oscillator to combined deterministic harmonic and random excitation
Authors: Rong Hai-Wu  , Wang Xiang-Dong  , Xu Wei  , Fang Tong  ,   (1)佛山大学数学系，佛山  528000; (2)西北工业大学应用数学系，西安  710072
Published: December 2020

The resonance of single-degree-of-freedom nonlinear impact oscillator to combined deterministic and random excitation is investigated. The method of harmonic balance, perturbation method and the method of stochastic averaging are used to determine the response of the system. The theoretical analyses are verified by numerical results. Theoretical analyses and numerical simulations show that when the intensity of the random excitation increases, the nontrivial steady state solution may change form a limit cycle to a diffused limit cycle. Under some conditions the system may have two steady state responses, one is a non-impact response, the other an impact response.
Sub-100 fs high power Yb-doped single polarization large-mode-area photonic crystal fiber laser amplifier
Authors: Liu Bo-Wen  , Hu Ming-Lie  , Song You-Jian  , Chai Lu  , Wang Qing-Yue  ,   天津大学精密仪器与光电子工程学院，光电信息技术科学教育部重点实验室，天津  300072
Published: December 2020

An ytterbium-doped single polarization large-mode-area photonic crystal fiber laser amplifier is demonstrated, which can deliver average power of 16 W at a repetition rate of 50 MHz, corresponding to 320 nJ pulse energy. The length of the fiber is 3.5 m, and the pulse could be shorter since the spectrum is further broadened due to the SPM. The pulse duration is compressed to 85 fs after passing through a grating pair. The oscillator and amplifier of the system are composed of the same single polarization large-mode-area photonic crystal fiber, resulting in better environmental stability and compactness.
Frequency-tunable all-optical clock division using semiconductor laser subjected to external optical injection
Authors: Niu Sheng-Xiao  , Zhang Ming-Jiang  , An Yi  , He Hu-Cheng  , Li Jing-Xia  , Wang Yun-Cai  ,   太原理工大学理学院物理系，太原  030024
Published: December 2020

All-optical time division was obtained in the frequency range from 9.0GHz to 19.8GHz. Nonlinear dynamics of a Fabry-Perot laser diode subjected to external optical injection is applied for all-optical clock division. The research results indicate that semiconductor laser subjected to external light injection performs period-one oscillation. We obtain the clock division of the signal pulses when the second harmonic frequency of the period-one oscillation approaches the repetition rate of the signal pulse, and the second harmonic and the fundamental frequency of the period-one oscillation were locked by the signal pulses simultaneously. Numerical simulation was performed on the all-optical time division with signal pulse injection using the rate equation of the semiconductor laser. The simulation result is in good agreement with the experiment. Phase noise level of the divided clock is observed to be smaller than -90 dBc/Hz over a frequency detuning range of 1.5GHz by changing the repetition rate of signal pulses under the fixed wavelength detuning value and input signal pulse power.
The numerical emulation of linear characteristics of optical pulse propagation in microring coupled-resonator optical waveguides
Authors: Tian He  , Zhang Yun-Dong  , Wang Hao  , Qiu Wei  , Wang Nan  , Yuan Ping  ,   哈尔滨工业大学光电子技术研究所可调谐激光技术国家级重点实验室，哈尔滨  150080
Published: December 2020

The general expression of dispersion relation of microring coupled-resonator optical waveguides was obtained using transfer matrix method. Based on the dispersion relation the linear characteristics of optical pulse propagation in microring coupled-resonator optical waveguides was discussed with respect to the bandwidth, group velocity, dispersion and linear phase shift. These characteristics are important for applications of coupled-resonator optical waveguides in optical communications or as optical sensors.
Electrowetting in double-walled carbon nanotubes: molecular dynamics simulations
Authors: Wang Lei  , Zhang Zhong-Qiang  , Zhang Hong-Wu  ,   大连理工大学运载工程与力学学部，工程力学系，工业装备结构分析国家重点实验室，大连  116024
Published: December 2020

On the basis of the atomistic simulations of electrowetting of single-walled carbon nanotubes by mercury, the electrowettings in double-walled carbon nanotubes are studied. Classical molecular dynamics simulations in conjunction with a macroscopic electrocapillarity model are carried out to clarify the effect of inner tube’s size on electrowetting. Results show that there is a great difference between electrowetting in single-walled and double-walled carbon nanotubes. The inner tube plays a key role in the electrowetting of double-walled carbon nanotube. Very different phenomenon occurs when the size of the inner tube is changed.
Study on electronic structure and transport properties of graphene nanoribbons with single vacancy defects
Authors: Ouyang Fang-Ping  , Wang Huan-You  , Li Ming-Jun  , Xiao Jin  , Xu Hui  ,   (1)中南大学物理科学与技术学院，长沙  410083; (2)中南大学物理科学与技术学院，长沙  410083；湘南学院物理系,郴州  423000
Published: December 2020

Based on first-principles electronic structure and transport calculations, we have studied electronic structure and transport properties of graphene nanoribbons with single vacancy defects. It is shown that introduction of the single vacancy defects leads to a flat band belt at the Fermi energy level for graphene nanoribbons and the semiconductor-metal transition in zigzag semiconducting graphene nanoribbons, which is useful in the energy-band engineering. Armchair graphene nanoribbons with odd width are metallic with good electric conduction while armchair graphene nanoribbons with even width have metallic band structures with character of the group IV semiconductor. Single vacancy defects weakens the conduction of armchair graphene nanoribbons with odd width while obviously strengthens the conduction of armchair graphene nanoribbons with even width.
Enhanced mid-infrared transmission in heavily doped n-type semiconductor film based on surface plasmons
Authors: Hua Lei  , Song Guo-Feng  , Guo Bao-Shan  , Wang Wei-Min  , Zhang Yu  ,   中国科学院半导体研究所，北京  100083
Published: December 2020

Transmission of electromagnetic wave in a heavily doped n-type GaAs film is studied theoretically. From the calculations, an extraordinary transmission of p-polarized waves through the film with subwavelength grooves on both surfaces at mid-infrared frequencies is found. This extraordinary transmission is attributed to the coupling of the surface-plasmon polariton modes and waveguide modes. By selecting a set of groove parameters, the transmission is optimized to a maximum. Furthermore, the transmission can be tuned by dopant concentrations. As the dopant concentration increases, the peak position shifts to higher frequency but the peak value decreases.
Spin-tunneling time and transport in a ferromagnetic/semiconductor/ferromagnetic heterojunction with a δ tunnel barrier
Authors: Du Jian  , Zhang Peng  , Liu Ji-Hong  , Li Jin-Liang  , Li Yu-Xian  ,   (1)河北师范大学物理科学与信息工程学院，石家庄  050016; (2)河北师范大学物理科学与信息工程学院，石家庄  050016；承德民族师范高等专科学校物理系，承德  067000
Published: December 2020

We study the characteristics of the spin-tunneling time and the transmission coefficient in a ferromagnetic/semiconductor/ ferromagnetic heterojunction with a δ tunnel barrier. The effects of the quantum size and Rashba spin-orbit coupling are discussed. It is shown that the existence of the tunnel barrier will reduee the magnitude of the transmission coefficient and the variation of the barrier strength will change the phase of the transmission coefficient. The oscillation frequency of the transmission coefficient increases with the increasing of the Rashba spin-orbit coupling. When the spin-dependent electron tunnels through the heterojunction, the tunneling time becomes longer with the length of the semiconductor increasing. The Rashba spin-orbit coupling also affects the spin-tunneling time.
Dispersion relation model of valence band in strained Si
Authors: Song Jian-Jun  , Zhang He-Ming  , Dai Xian-Ying  , Hu Hui-Yong  , Xuan Rong-Xi  ,   西安电子科技大学微电子学院，宽禁带半导体材料与器件教育部重点实验室，西安  710071
Published: December 2020

There has been much interest lately in the strained Si CMOS technology used for carrier mobility enhancement. The dispersion relation of valence band in strained Si is the theoretical basis for understanding and enhancing hole mobility. With in the frame of K.P theory, the dispersion relation is derived by taking strained Hamiltonian perturbation into account. The corresponding model obtained can be applied to calculate the valence band structure and hole effective mass along arbitrarily K wavevector direction in strained Si grown on arbitrarily oriented relaxed Si1－xGex(0≤x≤0.6) substrates, and hence is valuable as reference for the design of devices.