bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical study of TCE Ne-like Ge 19.6nm X-ray laser
Authors: Qiao Xiu-Mei  , Zhang Guo-Ping  ,   北京应用物理与计算数学研究所,北京 100088
Published: December 2020

Strongly amplified X-ray laser observed in the recent transient collisional excitation (TCE) experiments pumped by a single short pulse suggests that with the help of low level prepulse producing lowly ionized preplasma it is also possible to obtain high gain in the TCE scheme. The TCE Ne-like Ge 19.6nm X-ray laser pumped by low level prepulse were studid with our code series. Time evolution of plasma status shows that the position of peak gain drifts outward and the gain region is widened as time goes on, which is similar to the QSS scheme.
A new Schottky barrier structure of GaN-based ultraviolet photodetector
Authors: Zhou Mei  , Zuo Shu-Hua  , Zhao De-Gang  ,   (1)中国科学院半导体研究所集成光电子学国家重点实验室，北京 100083; (2)中国农业大学理学院应用物理系，北京 100083
Published: December 2020

A new GaN-based ultraviolet photodetector with Schottky barrior structure is proposed. Comparied with the conventional i-GaN/n+-GaN structure，there is an additional thin n-AlGaN cap layer on the i-GaN in the new structure. The simulation result demonstrates that the new structure leads to an increased quantum efficiency in GaN photodetection，since the negative effect of surface states on the photodetector is reduced in the new structure. In addition，it is suggested that the performance of device with the new structure could be further improved by employing an even thinner AlGaN cap layer with higher carrier concentration.
A study of back contacts of CdTe thin film solar cells
Authors: He Jian-Xiong  , Zheng Jia-Gui  , Li Wei  , Feng Liang-Huan  , Cai Wei  , Cai Ya-Ping  , Zhang Jing-Quan  , Li Bing  , Lei Zhi  , Wu Li-Li  , Wang Wen-Wu  ,   四川大学材料科学与工程学院，成都 610064
Published: December 2020

We have prepared polycrystalline CdTe thin films by close-spaced sublimation，then the film surface was been etched by nitric-phosphoric acid. After etching，the grain boundaries of CdTe thin films are broadened and it could be seen clearly that the surface became polished and more smooth, when observed by scanning electron microscope (SEM). After NP etching，highly conductive Te-rich layer is formed on the surface of CdTe thin film，as detected by X-ray diffraction (XRD). Four types of back-contact layers, including Cu, Cu/ZnTe：Cu, ZnTe：Cu and ZnTe/ZnTe：Cu were deposited respectively on the etched CdTe thin film，and the influences on the solar cells performance were compared. Our studies showed that the performance of CdTe solar cells with ZnTe/ZnTe：Cu complex back-contact layer was better than those with other back-contact layers，and the highest conversion efficiency of 13.38% has been obtained for CdTe polycrystalline thin film solar cells of 0.5cm2 size.
Reproducing kernel particle method with complex variables for elasticity
Authors: Chen Li  , Cheng Yu-Min  ,   (1)上海大学上海市应用数学和力学研究所，上海  200072; (2)上海大学上海市应用数学和力学研究所，上海  200072；长安大学理学院工程力学系，西安  710064
Published: December 2020

The reproducing kernel particle method with complex variables is developed in this paper. The advantages of the developed method is that the correction function of a 2-D problem is formed with 1-D basis function. Then，we apply the method to two-dimensional elasticity，and the application to two-dimensional elasticity is presented, and the corresponding formulae are obtained. Compared with the conventional reproducing kernel particle method，the reproducing kernel particle with complex variables developed in this paper has greater precision and computational efficiency. Some examples given in this paper demonstrated the efficiency of the present method.
The stress characteristics of metal nanowires: an atomistic simulation study
Authors: Wen Yu-Hua  , Shao Gui-Fang  , Zhu Zi-Zhong  ,   (1)兰州理工大学，甘肃省有色金属新材料国家重点实验室,兰州  730050；厦门大学物理系,厦门大学理论物理与天体物理研究所,厦门  361005; (2)厦门大学物理系,厦门大学理论物理与天体物理研究所,厦门  361005; (3)厦门大学物理系,厦门大学理论物理与天体物理研究所,厦门  361005；重庆工学院计算机学院,重庆  400050
Published: December 2020

In this paper, we have used molecular statics calculations with the quantum corrected Sutten-Chen type many-body force field to study the stress distribution characteristic of nickel nanowires with ［100］, ［110］ and ［111］ crystallographic orientations in equilibrium state. The simulated results show that tensile stress on the surface of the nanowires causes them to contract along the length. It can be seen that the stress is tensile in surface region while compressive in core region. With the increasing of diameter, the average stress in core region is compressive and strongly decreased to approach to zero, while the surface tensile stress first increases, and then tends to a non-zero constant. The contraction ratio of length, and average stress in core and surface are always largest for ［100］ nanowire and smallest for ［111］ nanowire.
Pressure control model for transport of liquid mercury in carbon nanotubes
Authors: Zhang Zhong-Qiang  , Zhang Hong-Wu  , Wang Lei  , Zheng Yong-Gang  , Wang Jin-Bao  ,   大连理工大学工程力学系，工业装备结构分析国家重点实验室，大连  116024
Published: December 2020

Carbon nanotubes have a significant application in nanotechnology as nanopipes conveying fluids. In this paper, a pressure control model for transport of liquid mercury through carbon nanotubes using classical molecular dynamics simulations in conjunction with an atomistic model is presented. Wetting of single-walled carbon nanotubes by mercury occurs above a threshold pressure of liquid mercury. The liquid mercury can be transported through carbon nanotubes with the continuous increase of its internal pressure. Also, we show that single-walled carbon nanotubes can transport liquid mercury discontinuously when a periodical pressure is applied on the liquid.
Preparation and characteristics of p-type ZnO by treated gaseous ammonia annealing
Authors: Tang Li-Dan  , Zhang Yue  ,   (1)北京科技大学材料物理与化学系，北京  100083; (2)北京科技大学材料物理与化学系，北京  100083；北京科技大学新金属材料国家重点实验室，北京  100083
Published: December 2020

The p-type ZnO：Al films deposited by RF/DC magnetron sputtering at room temperature were treated by gaseous ammonia annealing. The characteristics were examined by XRD, FESEM and Hall measurement. The results showed that the films crystallized in the wurzite phase with a preferential orientation along the c-axis and the surfaces are smooth and dense without visible pores and defects over the film, and the grain size was about 40—60nm at the annealing temperature of 700℃. The Hall measurement showed p-type conduction with the high carrier concentration of 8346×1018 cm-3 and low resistivity of 25014 Ω·cm when the annealing temperature was 700℃.
Properties of white organic electroluminescent device with double light-emitting layers based upon different hosts
Authors: Wu Xiao-Ming  , Hua Yu-Lin  , Yin Shou-Gen  , Zhang Guo-Hui  , Hui Juan-Li  , Zhang Li-Juan  , Wang Yu  ,   天津理工大学材料物理研究所,天津  300384；天津市光电显示材料与器件重点实验室,天津  300384；显示材料与光电器件教育部重点实验室，天津  300384
Published: December 2020

A novel phosphorescent white organic light-emitting device (WOLED) with configuration of ITO/NPB/CBP:TBPe:rubrene/BAlq:Ir(piq)2(acac)/BAlq/Alq3/Mg:Ag was fabricated successfully, where the phosphorescent dye Ir(piq)2(acac) was doped into BAlq (electron transport material) as the red emitting layer, and fluorescent dye TBPe and together with rubrene was doped into CBP (ambipolar conductivity material) as the blue and orange emitting layer, respectively. The emitting layers were sandwiched between the undoped NPB and BALq layers. We also discussed how to achieve the bright pure white light with high stability through optimizing the doping concentration of each dopant and employing the balanced charges distribution for the introduction of the heterojunctions between the different hosts in detail. This device turns on at the driving voltage of 42 V. It presents a maximum external quantum efficiency and brightness of 15% and 15000 cd/m2, respectively. The Commission Internationale de l'Eclairage (CIE) coordinates varies from (0368, 0389) at 10 V to (0314, 0327) at 15 V, and the best point is located at (0334, 0339) at 13 V. With the good EL performance，this kind of WOLED are particular suited for working as the backlight in LCD in combination with color filters to achieve the full color display.
Study of nucleation of void-induced phase transformation under shock compression
Authors: Shao Jian-Li  , Wang Pei  , Qin Cheng-Sen  , Zhou Hong-Qiang  ,   北京应用物理与计算数学研究所，北京  100088
Published: December 2020

Molecular dynamics simulations have been used to study the nucleation and growth of void-induced phase transformation of single crystal Fe under shock-wave loading along the ［001］ direction and effects of initial temperature on the process. It was found that: 1) phase transformation nucleates firstly on the (110) and (110) planes around the void and grows along the ［110］,［110］ and ［110］,［110］ directions, respectively, and then grow along 〈111〉 directions of the (110) and (110) planes, and ultimately “V" shaped grains form; 2) under the same shock compression, grains at initial temperature 300 K are smaller than those at 60 K, and at the same time, many embryos appear around the grains. These phenomena indicate that void-induced phase transformation nucleates and grows along certain directions, and increasing the initial temperature can diversify the action. Finally, we calculate the statictics of pressure-volume tensor and energy distributions, and give a preliminary analysis of the nucleation and growth of phase transformation.
Neuron excitability changes induced by low-power laser irradiation
Authors: Qiao Xiao-Yan  , Li Gang  , Dong You-Er  , He Bing-Jun  ,   (1)南开大学生命科学学院，天津  300071; (2)山西大学物理电子工程学院，太原  030006; (3)山西大学物理电子工程学院，太原  030006；天津大学精密仪器与光电子工程学院，天津  300072; (4)天津大学精密仪器与光电子工程学院，天津  300072
Published: December 2020

The change in excitability induced by low-power laser was investigated for freshly dissociated rat hippocampal CA3 pyramidal neuron using the whole-cell patch clamp technique. The experimental results indicate that the activation potential of Na+ channel shifted towards a more negative potential, the peak amplitude of INa increased in a voltage-dependent and reversible manner, the steady-state activation curve and inactivation curve of INa were significantly shifted, the half-activation voltage and the half-inactivation voltage respectively changed from (-4414±528)mV to (-5655±614)mV(n=8,Pn=8, P+ channel, further affect the depolarizing and firing of action potential, and finally be involved in adjusting the excitability of neurons.
Polarization properties of partially coherent flat-topped light beams diffracted through a regular polygonal aperture
Authors: Fu Wen-Yu  , Ma Shu-Yi  ,   (1)陇东学院物理系与电子工程学院，庆阳  745000; (2)西北师范大学物理与电子工程学院，兰州  730070
Published: December 2020

Based on the beam coherence-polarization matrix and the propagation law, the polarization properties of partially coherent flat-topped light beams diffracted through a regular polygonal aperture are studied systematically. The expression for the degree of polarization of partially coherent flat-topped light beams is derived. And according to that, the expression for the degree of polarization of Gaussian Schell-model beams and the propagation of partially coherent flat-topped light beams in the free space are obtained. It is shown that the polarization properties of partially coherent flat-topped light beams diffracted through a rectangular aperture depends on the truncation parameter, spatial coherence parameters, diffraction angle, propagation distance and the order of flat-topped light beams.
Stability of equilibrium state of a kind of nonlinear relative rotation dynamic system and associated harmonic approximate solution
Authors: Meng Zong  , Liu Bin  ,   燕山大学电气工程学院, 秦皇岛  066004
Published: December 2020

The nonlinear dynamic equation with two masses in relative rotation is established, which contains a kind of generalized nonlinear elastic force. Using variable gradient method, the Lyapunov function is gotten, and the stability of the relative rotation nonlinear autonomous system is studied. The approximate solution of the associated harmonic response of the relative rotation nonlinear non-autonomous system under two forcing excitations of different frequencies is obtained by the method of perturbation.
Performance of various quantum-key-distribution systems using 1.55 μm up-conversion single-photon detector
Authors: Jiao Rong-Zhen  , Feng Chen-Xu  , Ma Hai-Qiang  ,   北京邮电大学理学院，北京  100876
Published: December 2020

The performance of various quantum-key-distribution (QKD) systems is analyzed using 1.55 μm up-conversion single-photon detector. The dependence of quantum efficiency and dark count rate change on the pump power was also discussed. The comparison is based on the secure communication rate as a function of distance for three QKD protocols: the Bennett-Brassard 1984, the Bennett-Brassard-Mermin 1992, and the coherent differential-phase-shift keying protocols. We show that the up-conversion detector allows for higher communication rate and longer communication distance than the commonly used InGaAs/InP APD for all three QKD protocols, and the properties of quantum key distribution system can be greatly improved by this detector.
An encryption approach to chaos synchronization communications by using CPRNG
Authors: Li Wei  , Hao Jian-Hong  , Qi Bing  ,   华北电力大学电气与电子工程学院，北京  102206
Published: December 2020

A data encryption approach to chaos synchronization communications by using a novel chaos-based pseudo-random number generator (CPRNG) is proposed. Chaotic sequence generated by the drive system is turned into encryption keys in CPRNG and the data can be alternately encrypted according to byte by using the keys. The advantages of the cryptosystem are its higher level of security and synchronization, and it is easily implemented by software.
Study on the fractional-order Liu chaotic system with circuit experiment and its control
Authors: Chen Xiang-Rong  , Liu Chong-Xin  , Wang Fa-Qiang  , Li Yong-Xun  ,   西安交通大学电气工程学院，电力设备电气绝缘国家重点实验室，西安  710049
Published: December 2020

In this paper, applying frequency domain techniques based on Bode diagram, fractional-order Liu chaotic system is studied. An electronic circuit unit of tree shape is designed to realize the fractional-order chaotic Liu system. Circuit experiment of 2.7-order Liu system, as well as simulation results of fractional-order Liu chaotic system with α=0.8—0.1 in step size of 0.1， verify the circuit unit's effectiveness, and prove that chaos actually exists in the fractional-order Liu chaotic system with order as low as 0.3. A simple, but effective linear feedback controller is designed to realize the chaotic control of fractional-order Liu chaotic system.
The influence of molecular ground state wave function on high-order harmonic generation from N2 molecules in intense laser fields
Authors: Guo Zhong-Hua  , Zhou Xiao-Xin  ,   (1)西北师范大学物理与电子信息工程学院，兰州  730070; (2)西北师范大学物理与电子信息工程学院，兰州  730070;兰州城市学院培黎工程技术学院，兰州  730070
Published: December 2020

Vector polarization mode switch mechanism of the vertical-cavity surface-emitting laser with anisotropic optical injection is numerically investigated. The results are as follows:First, when the injection current is near the threshold current, the polariz
Optical bistability performance of laser-diode end-pumped Tm, Ho: YLF laser
Authors: Zhang Xin-Lu  , Wang Yue-Zhu  , Li Li  , Ju You-Lun  ,   (1)哈尔滨工程大学理学院, 哈尔滨  150001; (2)哈尔滨工业大学光电技术研究所可调谐激光国家重点实验室,哈尔滨  150001
Published: December 2020

The bistable output of a 792 nm laser-diode end pumped continuous wave Tm, Ho: YLF laser is reported for the first time. When the temperature of the Tm, Ho: YLF crystal is 283 K, the width of bistable section is 100 mW, and the jump power at the turning point is 15 mW. The influence of crystal temperature on the bistable performance of 2 μm laser is studied in the experiment. The width of bistable section was reduced from 100 mW to 60 mW and the jump power at the turning point reduced from 15mW to 6 mW respectively, when the temperature of laser crystal is increased from 283 K to 298 K. The bistable output in the continuous wave Tm, Ho: YLF laser comes from the co-effect of the energy transfer upconversion, excited state absoption and lower level reabsorption of 2 μm laser light.
A method to measure the Brillouin linewidth of SBS medium using mixture media
Authors: Hasi Wu-Li-Ji  , Liu Shu-Jie  , Lü Zhi-Wei  , Yin Guo-He  , Teng Yun-Peng  , He Wei-Ming  , Zhao Xiao-Yan  ,   哈尔滨工业大学可调谐激光技术国家级重点实验室，哈尔滨  150001
Published: December 2020

In order to measure the Brillouin linewidth of SBS medium, a method using mixture media in two-cell stimulated Brillouin scattering (SBS) system is proposed, which uses the medium to be measured as amplifier medium and the mixture media as generator medium. The profile of gain coefficient versus the difference of Brillouin frequency shift is fitted with Lorentzian curve. The width at half-maximum of this curve is the Brillouin linewidth. In the experiment, using Nd:YAG Q-switched laser system and CCl4/C6H6 mixture, we measured the Brillouin linewidth of SBS media tetrachloroethylene (C2Cl4), hexachlorobutadiene (C4Cl6), acetone (C3H6O) and n-hexane (C6H14). The results show that the measured values are close to those calculated or published by other authors.
Investigation on frequency-detuning induced optical chaos synchronization switching
Authors: Qiu Xin  , Xia Guang-Qiong  , Wu Jia-Gui  , Wu Zheng-Mao  ,   西南大学物理学院,重庆  400715
Published: December 2020

A theoretical model characterizing a reported experiment on optical chaos synchronization switching is presented. Based on the model, the characteristics of optical chaos synchronization switching have been numerically simulated for different feedback strength and injection strength. The results show that: for a fixed feedback strength, both on-off switching ratio and width of the chaos switching will vary with the change of injection strength. When the injection strength equals to the feedback strength, the on-off switching ratio will reach a maximum. Furthermore, when the feedback strength and the injection strength are increased synchronously, both the on-off switching ratio and the width of the chaos switching will increase monotonicly.
Polarization beam splitter for self-collimated beams in photonic crystals
Authors: Shen Xiao-Peng  , Han Kui  , Li Hai-Peng  , Shen Yi-Feng  , Wang Zi-Yu  ,   中国矿业大学理学院物理系，徐州  221008
Published: December 2020

We present the design and simulation of an ultra-compact high-efficiency polarization beam splitter (PBS) based on self-collimation effect and photonic crystal band gap in two dimensional photonic crystals. The splitting properties of the PBS have been numerically studied using the finite difference time domain (FDTD) method. It was shown that a 90° separating angle and efficiency of greater than 85% for TE- and TM- modes over a wide frequency range 0.268—0.278(c/a) can be obtained. The size of PBS is only 9 μm×9 μm at optical communication wavelength λ＝1.55 μm. These features of the proposed PBS make it a promising candidate in optical communications application.
Short-pulsed explosive field emission and plasma expansion of carbon nanotube cathodes
Authors: Liao Qing-Liang  , Zhang Yue  , Huang Yun-Hua  , Qi Jun-Jie  , Gao Zhan-Jun  , Xia Lian-Sheng  , Zhang Huang  ,   (1)北京科技大学材料物理与化学系，北京  100083; (2)北京科技大学材料物理与化学系，北京  100083；北京科技大学新金属材料国家重点实验室，北京  100083; (3)中国工程物理研究院流体物理研究所，绵阳  621900
Published: December 2020

A large area cold cathode based on carbon nanotube films has been successfully fabricated. Investigation of the explosive field emission properties of the carbon nanotube cathode in a double-pulse mode was carried out and a high emission current density of 245 A/cm2 was obtained. The turn-on time of the CNT cathode is about 40 ns. The time- and space-resolution of the electron beam emitted from the cathode was investigated. The formation of the cathode plasma layer was proved and the plasma expanded at a velocity of ～8.17 cm/μs toward the anode. The plasma has big influences on the intensity and distribution of electron beams. The formation of cathode plasma had no preferential position and the local enhancement of electron beams was random. This carbon nanotube cathode appears to be suitable for high-power microwave device applications.
Diagnostic study on the electron density distribution of microwave plasma jet in local vacuum environment
Authors: Yang Juan  , Xu Ying-Qiao  , Zhu Liang-Ming  ,   西北工业大学航天学院，西安  710072
Published: December 2020

In order to diagnose the electron density of microwave plasma jet confined by solid boundary walls, the emission/Langmuir probe was applied to measure the plasma space potential and current and voltage property when the probe is charged by heating and scanning power supply separately. According to the plasma space potential, saturated current on the current-voltage characteristics of plasma can be distinguished, which can be used to estimate the number density of electrons in the plasma. The results show that the magnitude of electron density ranges from 8.8×1014 to 7.53×1016/m3, the electron density on the centerline of jet decreases linearly off the nozzle exit plane, but it has approximately parabolic distribution along the plasma jet direction when leaving the centerline. Increasing mass flow rate at constant power and increasing power at constant mass flow rate will increase electron density.
Integral of differential equations of three-particle Toda lattice
Authors: He Guang  , Mei Feng-Xiang  ,   (1)北京理工大学理学院，北京  100081; (2)北京理工大学宇航科学技术学院，北京  100081
Published: December 2020

The differential equations of three-particle Toda lattice are a Hamiltonian system. The integrals of the equations can be obtained by using the Noether theory and the Poisson theory.
First-principles calculations on the structures of Wn (n=3—27) clusters
Authors: Lin Qiu-Bao  , Li Ren-Quan  , Wen Yu-Hua  , Zhu Zi-Zhong  ,   (1)集美大学理学院，厦门  361021；厦门大学物理系，厦门  361005; (2)厦门大学物理系，厦门  361005
Published: December 2020

The structural properties of Wn　clusters (n=3—27) has been studied by employing the first-principles calculations based on the density functional theory. The most stable structures of clusters (n=3—7) with global energy minimum and optimized structures of clusters (n=8—27) with local energy minimum are determined. Based on the jellium model, the electronic configuration 1s21p61d102s21f142p63s23p62d104s22f143d101g181h223f14 is proposed which can explain well the electronic magic numbers and the relative stabilities of W clusters. The binding energy, the first and second differences of binding energies and the HOMO-LUMO gaps versus the number of atoms in the cluster are also analyzed, showing that W clusters become metallic very quickly with the increase of cluster size. This may also imply a quick change of bonding characters in the W clusters.
Influence of fused interface on the optical and thermal characteristics of vertical cavity lasers
Authors: He Guo-Rong  , Zheng Wan-Hua  , Qu Hong-Wei  , Yang Guo-Hua  , Wang Qing  , Cao Yu-Lian  , Chen Liang-Hui  ,   中国科学院半导体研究所，北京  100083
Published: December 2020

From the effective absorption coefficient of bonded interface and the relationship of interface to reflectivity at cavity mode for double bonded vertical cavity laser, it can be seen that bonded interfaces should be positioned at the null of standing wave distribution, and the thickness of interface should be less than 20 nm. Using the finite elements method, the temperature contour map of laser can be calculated. Results showed that the influence of thin interface to thermal characteristics of VCSELs is slight, while thick interface will lead to temperature increase of active region. SEM images demonstrate that hydrophobic bonding is suitable for the fabrication of the device, while hydrophilic bonding interface is unfavorable to optical and thermal properties of devices with interface thickness larger than 40 nm.
The influence of impurities on segregation of the (110) surface of O/RhxPt1-x alloy system
Authors: Zhang Hui  , Zhang Guo-Ying  , He Jun-Qi  , Wang Dan  , Yang Shuang  ,   (1)沈阳师范大学实验中心，沈阳  110034; (2)沈阳师范大学实验中心，沈阳  110034;哈尔滨工业大学，哈尔滨  150001
Published: December 2020

The atomic cluster models of (110) surface of RhxPt1-x disordered binary alloy were constructed under the condition that there is interaction between adsorption and segregation. The coverage of O is 0.5. Also，the models that may have an impact on the alloy debased with Cu，Ni and W were set up by computer respectively. It followed that impurities replaced every Rh which should be the nearest neighbor of O. The environment sensitive inlaid energy (EESE) and the electronic structure of the alloy surface doped with Cu，Ni and W was calculated by recursion method. The results of EESE show that, the influence of Ni，Cu and W on Rh-Pt alloy are all to reverse the segregation of the alloy surface. Furthermore，Ni is the most effective imupurity，and then Cu and W. Doped with impurities Cu，Ni and W，the covalent interaction between Rh and O is reduced，which reverses the surface segregation，so Pt segregates on the surface.
A novel white organic electroluminescent device with both phosphorescent and fluorescent dopants
Authors: Zhang Li-Juan  , Hua Yu-Lin  , Wu Xiao-Ming  , Zhang Guo-Hui  , Wang Yu  , Yin Shou-Gen  ,   天津理工大学材料物理研究所，天津  300384；天津市光电显示材料与器件重点试验室，天津  300384；显示材料与光电器件教育部重点实验室，天津  300384
Published: December 2020

A double-layer white organic electroluminescent device was fabricated by using hole transporting material NPB doped with phosphoresecent dye Ir(piq)2(acac) as red emitting layer and CBP doped with fluorescent dye TBPe as blue emitting layer. The configuration of this device was ITO/NPB/NPB：Ir(piq)2(acac)/CBP/CBP：TBPe/BCP/Alq3/Mg：Ag/Ag in which Alq3，NPB(undoped)，CBP(undoped) and BCP films functioned as electron transporting layer，hole transporting layer and exciton blocking layer，respectively. White emission was be successfully achieved from the device with good EL performance by adjusting the thicknessess of light-emitting layers and the proportion of the dopants (TBPe，Ir(piq)2(acac)). With a low turn-on voltage of 4.8V，it shows a maximum luminance of 7500cd/m2 and external quantum efficiency of 1.24% at the driving voltage of 9V. Pure white light with Commission Internationale de l'Eclairage (CIE) coordinates of(0.33 0.30)was obtained at an applied voltage of 15V.
A study of applicability of light emitting diodes in differential optical absorption spectroscopy measurements
Authors: Li Su-Wen  , Xie Pin-Hua  , Liu Wen-Qing  , Si Fu-Qi  , Li Ang  , Peng Fu-Min  ,   中国科学院环境光学与技术重点实验室，中国科学院合肥物质科学研究院，合肥  230031
Published: December 2020

The applicability and application of modern light emitting diodes (LEDs) as active source in differential optical absorption spectroscopy (DOAS) was discussed in this paper. The radiative properties of LEDs and spectral shape，spectral range，spectral stability were analyzed. When temperature was not constant，the Fabry Perot etalon structures of LEDs would interfered with the DOAS evaluation. If they were treated as a kind of ‘component' of atmosphere and retrieved with other atmospheric components together，their effect on the measurements could be restricted to a minimum. The experimental results showed that LEDs can be used successfully as light sources in active DOAS to measure NO2 in the atmosphere. The correlation of the NO2 concentration measured by the LEDs-DOAS and the xenon arc light DOAS was 0.99. The detection limits of 1.1×10-9 were obtained for the path length of a 0.7km in the atmosphere.
The new method of modeling horizontal error functions in variational assimilation with orthogonal wavelet
Authors: Cao Xiao-Qun  , Huang Si-Xun  , Du Hua-Dong  ,   (1)解放军理工大学气象学院，南京  211101; (2)解放军理工大学气象学院，南京  211101；国防科技大学，长沙  410073
Published: December 2020

Background error covariance is an important part of variational data assimilation system，which is used to spread the observation information to other grid points and vertical levels of the model. In order to model the inhomogeneity and anisotropy in horizontal error functions of raw background error covariance，a new method is proposed to model horizontal error functions based on orthogonal wavelet transforms. The results of experiments show that the new method successfully modeled the heterogeneity and anisotropy included in the local correlation functions and depicted the structure and feature of raw covariance correctly.
Differential equations of motion for constrained systems with respect to three kinds of nonholonomic variations
Authors: Zhao Zhe  , Guo Yong-Xin  , Liu Chang  , Liu Shi-Xing  ,   (1)北京理工大学理学院，北京  100081; (2)辽宁大学物理学院，沈阳  110036; (3)沈阳药科大学基础学院，沈阳  110016
Published: December 2020

Based on an analysis of three kinds of non-equivalent nonholonomic variations，i-e-，the Suslovs variation，Hlders variation and vakonomic variation， the method of Lagrange multipliers and stationary action principle are utilized to discuss the differential equations of motion for nonlinear nonholonomic constrained systems with respect to the three kinds of variations- The condition for the three kinds of equations to be equivalent is investigated- The equations for affine nonholonomic constrained systems are also obtained as special cases of the general nonholonomic systems- Two examples are given to illustrated the validity of the result-
A scheme for remote state preparation with low classical communication cost
Authors: Tao Yuan  , Pan Wei  , Luo Bin  ,   西南交通大学信息科学与技术学院，成都  610031
Published: December 2020

We propose a new remote state preparation process- After the sender measures her particles，adopting the new process，the receiver can greatly reduce the classical communication cost- With a partial entangled three-particle Greenberger-Horne-Zeilinger (GHZ) state and a partial entangled two-particle state as the quantum channel，we present a scheme for preparing remotely a three-particle GHZ state- Taking this scheme as an example， we show how to use this process in detail and present the application range of this process- Analysis shows: only one classical bit is required for remote preparation of the three-particle GHZ state by using this process-
The entanglement character of two entangled atoms in multiphoton Tavis-Cummings model
Authors: Zhang Ying-Jie  , Zhou Yuan  , Xia Yun-Jie  ,   曲阜师范大学物理工程学院，曲阜  273165
Published: December 2020

We investigated the entanglement time evolution of two entangled two-level atoms. The two atoms can undergo multiphoton transition when they interact resonantly with a single-mode field in the coherent state. The results show that the two-atom entangled state evolves periodicity. The influence of the two-atom initial state，the dipole-dipole coupling intensity between two atoms，the parameter of the coherent state and the number of the transitional photons on the entanglement degree of two atoms are revealed. When the initial state is a maximum entangled state，the state of the two entangled atoms will forever stay in this maximum entangled state. So this kind of entanglement state can be used for quantum information storage.
Investigation of the bifurcation of stochastic van der Pol system
Authors: Li Gao-Jie  , Xu Wei  , Wang Liang  , Feng Jin-Qian  ,   西北工业大学应用数学系，西安  710072
Published: December 2020

The Chebyshev polynomial approximation is used to investigate the stochastic bifurcation of van der Pol system with two-sided barriers. The numerical results show that there is not only diverse phenomena of period-doubing bifurcation in the system，but also exist, the grazing bifurcation which is unique for the non-smooth system. The grazing bifurcation is investigated emphatically， and the influence of the random factor on the grazing bifurcation in the stochastic non-smooth dynamics system is analyzed. It is shown that the Chebyshev polynomial approximation is a valid method for the investigation of non-smooth systems.
Localization of the relative positions of two atoms in the presence of optical feedback
Authors: Cheng Gui-Ping  , Zheng Jun  , Deng Wen-Wu  , Li Gao-Xiang  ,   华中师范大学物理科学与技术学院,武汉  430079
Published: December 2020

We have investigated the localization of the two atoms passing through a standing wave in an optical cavity by measuring the field quadrature. It was found that the localization of the two atoms can be better preserved in the absence of the damping of cavity. If the damping of cavity is taken into account, the compromise of atomic-position localization resulting from the damping of cavity can be decreased by feeding back into the cavity part of the output signal.
Photoluminescence spectrum of monocrystalline Si implanted by nitrogen cluster ions
Authors: Miao Jing-Wei  , Wang Pei-Lu  , Zhu Zhou-Sen  , Yuan Xue-Dong  , Wang Hu  , Yang Chao-Wen  , Shi Mian-Gong  , Miao Lei  , Sun Wei-Li  , Zhang Jing  , Liao Xue-Hua  ,   (1)四川大学原子核科学技术研究所,辐射物理及技术教育部重点实验室, 成都  610064; (2)四川师范大学物理与电子工程学院,成都  610066
Published: December 2020

The structure of surface layer of monocrystalline Si by implanting nitrogen cluster ions N+10 was transformed directly the nanocrystalline, which led to the change in optical properties of monocrystalline Si. Excited by the ultraviolet light of 250—320nm, the sample showed a clear luminescence band of 330—500nm and an extra intensive spectral peak with good monochromaticity around 360nm. The intensity of the peak were 5 times high as the intensity of the substrate or N+ implantation samples and 1.5 times high at the N+2 implantation samples, respectively. It was also found there were two other stable luminescence bands around 730nm in the visible region and around 830nm in the infrared region, respectively. The preliminary study indicated that an excellent photoluminescence material was formed in the implanted layer.
The spatial distribution of optical field in random media with different filling densities of the same material particles
Authors: Wang Hui-Qin  , Liu Zheng-Dong  , Wang Bing  ,   (1)南昌大学材料科学与工程学院,南昌  330031；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; (2)南昌大学材料科学与工程学院,南昌  330031；南昌大学物理实验中心,南昌  330031; (3)南昌大学近代物理研究所,南昌  330031
Published: December 2020

The problem of light localization in two-dimensional random media with different filling densities of the same material particles is studied by use of the finite difference time domain method. Based on the experimental parameters of random media, the spatial distributions of optical field in the media with different filling densities of scattering particles are simulated. Results show that when the scattering mean free path is close to the wavelength， the optical fields are localized obviously in the random media. And with the particle filling density increasing, the localization becomes stronger. So with the same pump beam, it is easier to achieve laser radiation for random media with higher filling densities of scattering particles. The results agree with the experiments qualitatively.
Measurement and characterization of temporal femtosecond speckle
Authors: Liu Wen-Jun  , Cao Wu-Gang  , Guo Jin-Xin  , Liu Hai-Lei  , Qu Shi-Liang  ,   哈尔滨工业大学(威海)光电科学系,威海  264209
Published: December 2020

Temporal femtosecond laser speckles are investigated both theoretically and experimentally. It is theoretically predicted that the temporal femtosecond speckles is generated when a coherent femtosecond pulse propagates through a random media. Temporal speckles on femtosecond scale are observed experimentally. These temporal femtosecond speckles are a direct result of random interference between scattered waves. Statistical characteristics of temporal speckles are discussed, and experimental results are presented.
Cystal end temperature distribution under different pumping light in solid state laser
Authors: Yang Yong-Ming  , Xu Qi-Ming  , Guo Zhen  ,   (1)西安电子科技大学技术物理学院，西安  710071; (2)西安建筑科技大学材料学院，西安  710055; (3)西安建筑科技大学理学院，西安  710055
Published: December 2020

In order to study how different pumping light profiles affect the crystal end temperature field, a classification creterion is suggested, according to which the pumping light can be classified as column light, Gaussian light and plane top light. The end temperature under different pumping power and different pumping light focus diameter are studied.It was found that the end temperature is the highest under the column pumping light, intermediate plane top pumping light and lowesl under Gaussian pumping light when the pumping light has the same power and the same focus diameter.It shows that the pumping light profile can seriously affect the crystal end temperature field. Finally the effect of the thermal effect caused by the end temperature was studied, which was found to affect the laser quality seriously. When the equivalent curvature radius of the thermal lens changes from 85 to 150mm, the far field walk-off angle and waist diameter become larger and larger and the laser works unsteadily.
Experimental research of small-scale self-focusing of ultrashort pulse with spatial modulation
Authors: Feng Ze-Hu  , Fu Xi-Quan  , Zhang Li-Fu  , Xu Hui-Wen  , Wen Shuang-Chun  ,   湖南大学计算机与通信学院，长沙  410082
Published: December 2020

The dynamic process of the small-scale self-focusing of ultrashort laser pulse is experimentally investigated. By using tabletop femtosecond laser, the pulse which is spatially modulated by the crossed-fiber diffraction passes through the carbon bisulfide. With different input power, the small-scale self-focusing of the pulse was obtained. By analyzing the contrast of the beam, we find that the small-scale self-focusing does not increase all along with the increasing of input power, but some new growth points appear in different places. They compete with each other, and finally lead to multiple splitting. The experimental results confirmed the numerical simulation.
Research on the optimum thickness of metallic thin film utilized to excite surface plasmon resonance
Authors: Wu Ying-Cai  , Gu Zheng-Tian  ,   (1)广东海洋大学信息学院，湛江  524088；上海理工大学理学院，上海  200093; (2)上海理工大学理学院，上海  200093
Published: December 2020

The optimum thickness of metallic thin film utilized to support the surface plasmon resonance (SPR) has been investigated, based on the characteristics of electromagnetic field energy distributing in the film and its compound permittivity. It was shown that the optimum film thickness is related to the wavelength of exciting light and the refractive index (RI) of the metallic thin film. In this paper, a mathematical expression has been established to describe their relationship, and verified in the experiment. Our theoretical analysis is also consistent with previous experimental results. When the SPR sensor is employed in angular interrogation, in order to obtain highest sensitivity, the optimum thickness of metallic thin film can be deduced from the wavelength of the exciting light and the imaginary part of the film RI, or be obtained with the center wavelength of the exciting light and imaginary part of RI when the sensor is utilized in wavelength interrogation.
Investigation of lithiation/delithiation mechanism in lithium-tin alloys for anode materials
Authors: Hou Xian-Hua  , Hu She-Jun  , Li Wei-Shan  , Zhao Ling-Zhi  , Yu Hong-Wen  , Tan Chun-Lin  ,   (1)华南师范大学化学与环境学院，广州  510006; (2)华南师范大学物理与电信工程学院，广州  510006; (3)华南师范大学物理与电信工程学院，广州  510006；五邑大学数理系,江门  529020
Published: December 2020

An ab initio method with the first-principles plane-wave pseudopotentials based on the density functional theory has been used to calculate the physical character and electrochemical performance of various alloy phases in Li-Sn alloy. The results show that Li5Sn2 alloy phase, with relatively small volume expansion ratio and large reversible capacity, is an ideal alloy electrode phase. On the other hand, many kinds of tin thin film electrodes were fabricated by direct current and radio frequency magnetic sputtering on copper foil collector as anode materials for lithium-ion batteries. The values of calculated Li intercalated potential using the CASTEP program are well consistent with the experimental values.
Implementation and application of cellular neural networks based on single electron device
Authors: Feng Chao-Wen  , Cai Li  , Li Qin  ,   空军工程大学理学院，西安  710051
Published: December 2020

This paper realizes cellular neural networks using the characteristic of negative differential resistance of hybrid single electron transistor and complementary metallic oxide semiconductor field effect transistor structure. The main building blocks consisting of cell core circuit, A and B template circuits are designed. Then a cellular neural network (CNN) is built and its application in image processing is studied. The computer simulation shows that the designed circuits are suitable for CNN implementation owing to its simple structure, low power dissipation and fast response. It could be used to form CNN of various scales so as to further increase the density of integrated circuits.
A new method to reduce the dark current of GaN based Schottky barrier ultraviolet photodetector
Authors: Zhou Mei  , Chang Qing-Ying  , Zhao De-Gang  ,   (1)中国科学院半导体研究所集成光电子学国家重点实验室，北京  100083; (2)中国农业大学应用物理系，北京  100083
Published: December 2020

A new method to reduce the dark current of GaN based Schottky barrier ultraviolet photodetector is proposed. In comparision with conventional i-GaN/n＋-GaN structure, an additional thin p-GaN cap layer is introduced on the i-GaN(n--GaN) in the new structure. The simulation results showed that the additional layer makes the dark current to decrease in the photodetector due to the increase of the Schottky barrier height. The effects of thickness and carrier concentration of p-GaN layer on the dark current of the photodetector were also studied. It is suggested that the dark current of the new structure device could be better reduced by employing p-GaN with higher carrier concentration as the cap layer.
A periodic coupled quantum well transport
Authors: Wang Hai-Xia  , Yin Wen  ,   (1)山西大学理论物理研究所，太原  030006; (2)山西大学理论物理研究所，太原  030006；中国科学院物理研究所，北京  100080
Published: December 2020

Using the method developed by Gurvitz S.A for solving Shrodinger equations and numerical calculation, we investigate the driving frequency dependence of the current of periodic coupled quantum wells.The results indicate that the stable current increases with the driving frequency on condition of the driving frequency being smaller than the energy difference between wells. Otherwise, the stable current will decrease with increasing driving frequency. Therefore,the current of the system can be controlled by the driving frequency.
The effects of the Breit interaction on electron impact excitation cross sections of the 1s2s3S1 metastable level of He-like ions
Authors: Yang Ning-Xuan  , Jiang Jun  , Xie Lu-You  , Dong Chen-Zhong  ,   (1)西北师范大学物理与电子工程学院，兰州  730070; (2)西北师范大学物理与电子工程学院，兰州  730070；兰州重离子加速器国家实验室原子核理论研究中心，兰州  730000
Published: December 2020

The electron impact excitation(EIE) cross sections of He atom and He-like Fe24+, Xe52+ and U90+ ions from the metastable 1s2s3S1 to all of 1snl(n=2,3; l=s,p,d) states are calculated systematically by using the fully relativistic distorted-wave (RDWB) program developed by our group recently. The effects of the Breit interaction on the EIE cross sections of He-like isoelectronic sequences ions at different energies of incident electrons is studied, and some important conclusions are summarized, which can be extended to other highly charged ions. Also, comparison of the present calculations for 1s2s3S1→1s2p3P and 1s2s3S1→1s3s3S1 with the available experimental results gave good agreement.
The transformation of ultra-cold Rydberg atom to plasma
Authors: Zhao Jian-Ming  , Zhang Lin-Jie  , Li Chang-Yong  , Jia Suo-Tang  ,   量子光学与光量子器件国家重点实验室,山西大学物理电子工程学院，太原  030006
Published: December 2020

Ultra-cold Rydberg atoms are obtained using three-photon excitation in the Cs magneto-optical trap(MOT), and the signals of the plasma are measured through changing the interaction time. The spontaneous evolution and the ionization mechanism are investigated.
Relation of harmonic radiative energy and laser phase in high-order harmonic generation
Authors: Ge Yu-Cheng  ,   北京大学物理学院和核物理与核技术国家重点实验室，北京  100871
Published: December 2020

The behavior of an atom in strong laser field and the dynamic process of high-order harmonic generation (HHG) are analyzed with the quantum theory and saddle-point method. Within a laser optical cycle of a long duration laser, the relations between the radiative energy and the laser phase of HHG show a Gaussian-like distribution which peaks at 7180°. A parameterized formula is deduced to calculate the high harmonic emission duration and the bandwidth of the HHG energy-phase distribution. The peak position, maximum and the bandwidth of a selected energy-phase distribution pulse depend on the laser parameters. Calculations show that a pure single (double) energy-phase distribution pulse(s) can be generated by a 3-cycle laser with a carrier-envelope phase of 175° (105°). A single symmetric energy-phase distribution pulse peaks at the carrier phase of 5386° and spans 5334°. The double energy-phase distribution pulses separated by 17533° have the same height. They peak at -3151° and 14381°, and span 7219° and 7334°, respectively. These results may be useful for researches of ultra-short X-ray generation, pulse separation, measurement and its application.
A new synthesis method for synthesizing on-axis flat-topped beams by using a defocusing telescope system
Authors: Zhao Bao-Yin  , Lü Bai-Da  ,   四川大学激光物理与化学研究所，成都  610064
Published: December 2020

A new method for synthesizing on-axis flat-topped beams by using a defocusing telescope system is proposed, where the flat-topped multi-Gaussian beam is chosen as the ideal beam. Within the framework of the paraxial approximation and based on the Collins diffraction integral formula, the analytical expressions for the on-axis field and incident field are derived and analyzed physically. The effect of beam order N, flat-top length parameter L, position of the flat-top centre zc and central longitudinal spatial frequency Sc on the on-axis intensity distribution is illustrated by numerical examples. A comparison of our results with the method for simulating the ideal beam by use of the rectangular function shows the advantages of our method.
Ultrafast internal conversion and vibrational relaxation in singlet excited-state all-trans-β-carotene as revealed by femtosecond time-resolved stimulated Raman spectroscopy
Authors: Zhao Xiao-Hui  , Ma Fei  , Wu Yi-Shi  , Ai Xi-Cheng  , Zhang Jian-Ping  ,   (1)北京分子科学国家实验室,中国科学院化学研究所分子动态与稳态结构国家重点实验室,北京  100080；河北大学物理科学与技术学院,保定  071002；中国人民大学理学院化学系,北京  100872; (2)北京分子科学国家实验室,中国科学院化学研究所分子动态与稳态结构国家重点实验室,北京  100080；中国人民大学理学院化学系,北京  100872; (3)中国人民大学理学院化学系,北京  100872
Published: December 2020

A femtosecond time-resolved stimulated Raman scattering (FSRS) apparatus was built, and was used to study the ultrafast internal conversion and vibrational relaxation processes between the singlet excited states of all-trans-β-carotene in solution. The FSRS apparatus, constructed on the basis of a three-pulse pump-probe scheme, achieved a time resolution of 150fs, a spectral resolution of 23.7cm-1, and a detection spectral window of 300—4000cm-1. The FSRS results are interpreted in terms of a serial internal-conversion scheme between the low-lying singlet excited states, i.e. S2→SX→S1→S0. Spectral dynamics analysis and kinetics analysis proved that the intra-molecular vibrational relaxation in the S1 state proceeds on a time scale of 0.3—0.6ps, while the ‘hot’ S1 state decays with a time constant similar to the lifetime of this state (～11ps). Furthermore, the time scale of intra-molecular vibrational relaxation and vibrational cooling processes in the S0 state are shown to be ～0.3 and ～15ps, respectively. These results are useful for a deeper insight into the light-harvesting function of carotenoids in photosynthetic organisms.