bluuebunny/crossref_metadata_2025 huggingface dataset:
Bandwidth and gain of optical parametric chirped pulse amplification pumped by non-monochromatic light
Authors: Liu Hua-Gang  , Zhang Ruo-Bing  , Zhu Chen  , 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

Laser pulse was decomposed into components of different frequencies using Fourier transform, and the numerical calculation model was built up for coupled equations of optical parametric amplification pumped by non-monochromatic light. Effects of non-monochromatic light on small signal gain, large signal gain and gain bandwidth of optical parametric amplification were investigated. Though non-monochromatic pump light decreases the gain of optical parametric process, it can improve the gain bandwidth. The larger the bandwidth of the pump light, the wider the gain bandwidth. Reasons for parametric gain decrease and gain bandwidth improvement were analyzed with respect to the phase mismatch and the parametric bandwidth.
Design and analysis of the Z-pinch loads on the PTS facility
Authors: Ding Ning  , Zhang Yang  , Ning Cheng  , Shu Xiao-Jian  , Xiao De-Long  ,   北京应用物理与计算数学研究所，北京  100088
Published: December 2020

In this paper，a method for designing and optimizing the wire-array loads used on the PTS facility is presented. Both ZP-0D code (shell model) and MARED-1D code (MHD model) are used for the simulation. By comparing results from each code，the characteristics of the Z-pinch implosion plasma driven by the PTS facility are investigated，and the load parameters are optimized. It is found that，a 15nH concentrator inductance is efficient for PTS facility to work at load currents up to 10MA. And an optimized tungsten wire-array load is able to produce an X-ray radiation with peak power up to 100TW and a highest efficiency of conversion for the wall-plug power of about 10%. By further investigation and comparison with experimental data，we suppose that the PTS facility will have similar X-ray radiation productivity as the Saturn facility operating in the long-pulse mode.
Numerical simulation of microstructure evolution during directional solidification of Ti-45at.%Al alloy
Authors: Wang Kuang-Fei  , Guo Jing-Jie  , Mi Guo-Fa  , Li Bang-Sheng  , Fu Heng-Zhi  ,   (1)哈尔滨工业大学材料学院，哈尔滨  150001; (2)河南理工大学材料学院，焦作  454100
Published: December 2020

The microstructural evolution of Ti-45at.%Al alloy during directional solidification was simulated by applying a solute diffusion controlled solidification model，and the results have showed that under high thermal gradient the stable primary spacing can be adjusted by branching or competitive growth，irrelevant of the initial seed spacing. In addition，under a given pulling speed，increasing thermal gradient decreases primary cell/dendrite spacing，and under a given thermal gradient，increasing pulling velocity，we have observed a cell/dendrite transition region consisting of cells and dendrites，and which varies with the thermal gradient in a contradicting way，i.e. increasing the thermal gradient leading to the decrease of the range of the transition region. The simulated results agree reasonably well with experiment results.
An improved block cryptosystem based on iterating chaotic map
Authors: Xu Shu-Jiang  , Wang Ji-Zhi  ,   山东省计算中心，济南  250014
Published: December 2020

Recently，a large number of chaotic cryptosystems have been proposed，yet many of them have the drawbacks of lack of robustness and security. In this paper，we point out the weakness of a very recent block cipher algorithm which is based on the chaotic map and give the improved scheme of it. We provide the chosen plaintext attack to recover the permuted plaintext string. It is shown that the generation mechanism of binary sequences which depends on the key but not on the plaintext facilitates leakage of information and is vulnerable to attacks. Based on such a fact，we give the improved scheme to achieve higher security.
Effects of rare earth content on microstructure and magnetic properties of (Nd,Dy)-(Fe,Al)-B alloys
Authors: Li Xiu-Mei  , Liu Tao  , Guo Zhao-Hui  , Zhu Ming-Gang  , Li Wei  ,   钢铁研究总院功能材料研究所,北京  100081
Published: December 2020

The (Nd,Dy)-(Fe,Al)-B alloys with different rare earth (RE) contents were prepared using melt-spun and strip cast techniques, and the dependence of their microstructures and magnetic properties on RE contents were investigate. It is found that an appropriate RE in magnets is beneficial to the formation of (Nd,Dy)2Fe14B single phase and uniform distribution of the Nd-rich phase on grain boundaries. When the rare earth content of casting strip treated as main phase is close to the stoichiometric concentration, the coercivity and energy product of magnet are enhanced significantly. Moreover, heat treatment of casting strips can improve effectively the magnetic performance of final sintered magnets.
A universal algorithm for transforming chaotic sequences into uniform pseudo-random sequences
Authors: Sheng Li-Yuan  , Xiao Yan-Yu  , Sheng Zhe  ,   (1)Department of Applied Mathematics Science College，University of Western Ontario London，ON，Canada N6A 5B7; (2)中南大学数学与统计学院，长沙  410075; (3)中南大学物理科学与技术学院，长沙  410083
Published: December 2020

We present a universal algorithm for transforming chaotic sequences of either chaotic map systems or chaotic differential dynamic systems into uniform pseudo-random sequences. Theoretically，the algorithm is based on bit-operations represented by floating-point algorithm，not aiming at any definite physical chaotic systems. It has been proved that，any real random variable generally has a type of natural tendency of homogenization which exponentially increases bitwise with random variable. As a result，any real chaotic sequence can be completely transformed into the pseudo-random sequence having uniform identical independent distribution. Adopting logistic map，Hénon map and Lorenz system as examples to test the universal validity of the algorithm，respectively，the experiments demonstrate that the algorithm is correct. We can reasonably expect that the universally valid algorithm should become the technological basis of standardized modular design of chaotic pseudo-random sequence generator in hardware implementation.
First-principle study on electronic structure of BaTiO3 (001) surfaces
Authors: Ni Jian-Gang  , Liu Nuo  , Yang Guo-Lai  , Zhang Xi  ,   电子科技大学微电子与固体电子学院，成都  610054
Published: December 2020

Electronic structures of the (001) surface of cubic phase barium titanate have been calculated by using plane-wave pseudopotential method within the density functional theory. Geometry optimization indicates that the largest atomic relaxation occurs to metal atoms in surface layers where all atoms are displaced inward, and the interlayer distances vary alternately. Total energy calculation shows that the TiO2-terminated surface is unstable compared with that with BaO termination. One reason is that surface state of O-2p orbital observed in band structure of TiO2 termination helps the electron state shift towards higher energy region in both valence band and conduction band. Redistribution of electrons near surface region in TiO2 termination also provides evidence that intensity of covalent bonding between Ti and O atoms differs and hence TiO2 termination is more suitable for surface adsorption. In contrast, such difference was eliminated in BaO termination, accounting for its superiority in surface stability.
Scanning photoacoustic mammography with a focused transducer featuring extended focal zone
Authors: Xu Xiao-Hui  , Li Hui  ,   医学光电科学与技术教育部重点实验室，福州  350007；福建师范大学物理与光电信息科技学院，福州  350007
Published: December 2020

A focused transducer，featuring extended focal zone，is employed for scanning photoacoustic mammography.Using the transducer with extended focal zone，a large tissue sample can be imaged conveniently.Phantom experiments demonstrate that the location，size and optical energy deposition of absorbers can be imaged correctly.The depth and lateral resolution of image is 0.3mm and 2mm，respectively.And the transducer can be applied in conventional ultrasonic technology to achieve multimode diagnosis as well.Preliminary study shows that this method could be potential in early diagnosis of breast cancer.
Generalized synchronization of spatiotemporal chaos systems by phase compression
Authors: Jing Xiao-Dan  , Lü Ling  ,   (1)辽宁师范大学物理与电子技术学院,大连  116029; (2)辽宁师范大学物理与电子技术学院,大连  116029；辽宁工业大学数理科学系,锦州  121001
Published: December 2020

A phase compression scheme is proposed to achieve generalized synchronization for spatiotemporal chaos systems. The method is shown to be effective and practical by applying it to the numerical simulation of the Fitzhugh-Nagumo system, a kind of spatiotemporal chaos of reaction diffusion system. The effect of synchronization on the system is studied under bounded noise and the results show that the synchronization method has strong capability in anti-jamming. Generalized synchronization of two arbitrary spatiotemporal chaos systems can be realized by the method, which shows its universality in applications. The structure of the synchronous controller is simple and easy to use.
Analytical potential energy function for tritium water molecule T2O(X1A1)
Authors: Luo Wen-Lang  , Ruan Wen  , Zhang Li  , Xie An-Dong  , Zhu Zheng-He  ,   (1)井冈山大学数理学院，吉安  343009; (2)四川大学原子与分子物理研究所，成都  610065; (3)四川大学原子与分子物理研究所，成都  610065；井冈山大学数理学院，吉安  343009; (4)四川大学原子与分子物理研究所，成都  610065；井冈山大学信息科学学院，吉安  343009
Published: December 2020

The greatest difficulty in deriving the analytical potential energy function of T2O(X1A1) lies in its identity with that of H2O(X1A1) under the Born-Oppenheimer approximation. However, molecular potential energy function is actually a function of internal coordinates， such as bond length and bond angle which correlate with vibration energy, hence with vibration frequency, force constants and isotopic mass. Based on these relations, by using nuclear vibration, rotation, and translation energies to correct electronic energies, the force constants of T2O(X1A1) can be obtained, which represent the difference in masses of isotopes H and T. The calculations are reasonably consistent with reference values. After determining the dissociation limits and dissociation energy and all parameters of two-body terms of T2O(X1A1), the analytical potential energy function has finally been derived by using many-body expansion theory with due consideration of the isotopic effect. The potential energy contours correctly show the equilibrium structure of T2O(X1A1) and the characteristics of the reactions T+OT→T2O and O+T2→T2O. The results lay a sound basis for further researches on reactive collisions.
High frequency characteristics of a magnetically insulated transmission line oscillator oscillating in HEM11 mode
Authors: Wang Dong  , Chen Dai-Bing  , Fan Zhi-Kai  , Deng Jing-Kang  ,   (1)清华大学物理系，北京  100084; (2)清华大学物理系，北京  100084；中国工程物理研究院应用电子学研究所，绵阳  621900
Published: December 2020

Coaxial disk-loaded waveguide has been widely used in magnetically insulated transmission line oscillators (MILO). Although TM00 mode is assumed to be its main mode, the asymmetric mode might be excited by slight asymmetry of the structure, asymmetric emission of the beam, or both. So the research on asymmetric mode in coaxial disk-loaded waveguide is necessary. The general eigen equation with both symmetric and asymmetric modes in coaxial disk-loaded slow-wave structures is theoretically analyzed. Then, a HEM11 mode working MILO is designed and a tentative experiment is carried out to test its performance. Employing an electron beam of about 480 kV and 39 kA, HEM11 mode working MILO generates a high power microwave output of about 1.2 GW with 40 ns pulse duration at 1.98GHz. The power conversion efficiency is about 6.5% and the generated microwave mode is TE11 in the coaxial output region.
Quantum key distribution based on time coding and phase coding
Authors: Zhang Jing  , Wang Fa-Qiang  , Zhao Feng  , Lu Yi-Qun  , Liu Song-Hao  ,   华南师范大学信息光电子科技学院，光子信息技术实验室，广州  510006
Published: December 2020

A new quantum key distribution scheme is proposed to realize both phase coding and time coding based on two unbalanced Mach-Zehnder interferometers. The pulses which are discarded in the phase coding scheme can be coded in time coding, so the useful bit rate in the present scheme can be doubled. At the same time, the phase coding keys and the time coding keys are obtained. We can use one group of keys to communicate and the other one to guard against eavesdropping, or combine both of them to form new keys. This scheme has favorable application prospect.
High order dispersion effect of Ginzburg-Landau equation and its self-similar analytical solutions
Authors: Feng Jie  , Xu Wen-Cheng  , Liu Wei-Ci  , Li Shu-Xian  , Liu Song-Hao  ,   (1)华南师范大学光电子信息科技学院，光子信息技术实验室，广州  510006; (2)华南师范大学物理与电信工程学院，广州  510006
Published: December 2020

Using the methods based on the technique of self-similar analyzing, we find the parabolic asymptotic self-similar analytical solutions with third-order dispersion effect of constant coefficient Ginzburg-Landau equation which considers both the influence of high order dispersion and gain dispersion on the evolution of self-similar pulse. The self-similar amplitude function, phase function, strict linear chirp function and effective temporal pulse width are given in the paper. The results show that self-similar pulses still have linear chirp and remarkable third-order dispersion effect. And these theoretical results are consistent with numerical simulations.
An ultrasonic measurement model to predict the response from flat bottom hole for dual crystal contact probe
Authors: Zhao Xin-Yu  , Gang Tie  , Zhang Bi-Xing  ,   (1)哈尔滨工业大学现代焊接生产技术国家重点实验室，哈尔滨  150001; (2)中国科学院声学研究所，北京  100080
Published: December 2020

Dual crystal contact probes play an important role in many practical ultrasonic inspections, so it is essential to develop an ultrasonic measurement model in order to get a thorough understanding of the characteristics of this kind of transducers. By combining the multi-Gaussian beam model and the Kirchhoff approximation scattering model, a complete ultrasonic measurement model is provided to predict testing signals of a flat bottom hole for a dual crystal focused direct contact probe. By comparing with experimental results, the accuracy of predicted signals using this model has been verified.
Torsional buckling of a double-walled carbon nanotube under the action of coupled thermo-mechanical load
Authors: Yao Xiao-Hu  , Han Qiang  ,   华南理工大学土木与交通学院，广州  510640
Published: December 2020

Taking into account the effects of surrounding elastic medium and van der Waals forces between the inner and outer nanotubes and using the shell theory in continuum mechanics, the governing equation of carbon nanotube under the action of coupled thermo-mechanical load is established. Based on the model, an explicit formula for the critical load is derived in terms of the buckling modes of the shell and the parameters that indicate the effects of temperature change, surrounding elastic medium and the van der Waals force. Numerical simulation results show that at low and room temperature the critical load for infinitesimal buckling of a double-walled carbon nanotube increases as the value of temperature change increases, while at high temperature the critical load for infinitesimal buckling of a double-walled carbon nanotube decrease as the value of temperature change increases.
Influence of annealing oxygen pressure on the laser-induced thermoelectric voltage effect in YBa2Cu3O7-x thin films
Authors: Xiong Fei  , Zhang Hui  , Li Hong-Shan  , Zhang Peng-Xiang  , Jiang Zui-Min  ,   (1)复旦大学应用表面物理国家重点实验室，上海  200433; (2)昆明理工大学光电子新材料研究所，昆明  650051
Published: December 2020

The laser-induced thermoelectric voltage (LITV) signals were measured in the YBa2Cu3O7-x (YBCO) films annealed under different oxygen pressure. It was found that the detected LITV signals were enhanced 2—4 times with the increasing of annealing oxygen pressure. The effect can be explained by the dependence of thermoelectric anisotropy on the oxygen content in YBCO. When the films were illuminated by continuous lasers in the wavelength range of 473—808nm， the measured signals in the films annealed under 5000Pa oxygen pressure were larger than those in other films. Meanwhile， pulse ultraviolet laser illumination produced the largest signal in the films annealed under oxygen pressure of 105Pa. The response time of LITV signals was observed to become shorter with the increasing of annealing oxygen pressure， which was shown to have resulted from the increasing of thermal conductivity theoretically. The films annealed under 5000Pa oxygen pressure had the fastest response to the pulsed ultraviolet laser. The response time was 70ns and the rise time of 29ns was comparable to the duration of the applied laser pulse (about 28ns).
Effects of interfacial couplings on charge transport properties of DNA molecule
Authors: Meng Xian-Lan  , Gao Xu-Tuan  , Qu Zhen  , Kang Da-Wei  , Liu De-Sheng  , Xie Shi-Jie  ,   (1)山东大学物理学院，晶体材料国家重点实验室，济南  250100; (2)山东大学物理学院，晶体材料国家重点实验室，济南  250100；济宁学院物理系，曲阜  273155; (3)山东理工大学物理学院，淄博  255049
Published: December 2020

Using the three-dimensional tight-binding model and the matrix transfer method， effects of interfacial couplings on the charge transport properties of DNA molecule have been studied. The results indicate that when the interfacial couplings are ideal， both transmission coefficient and localization length of electrons are larger， the molecule shows higher conductivity， while the case is the contrary when the interfacial couplings are unideal. When the molecule and the metallic electrodes couple ideally， through voltage-current characteristic， it is found that the onset voltage of poly(dG)-poly(dC) DNA is lower than that for the poly(dA)-poly(dT) counterpart， and the current of the former is larger than that of the latter under the same bias voltage， so the conductivity of poly(dG)-poly(dC) DNA is higher than that of the poly(dA)-poly(dT) counterpart.
Determining the threshold of extreme events with detrended fluctuation analysis
Authors: Yang Ping  , Hou Wei  , Feng Guo-Lin  ,   (1)兰州大学大气科学学院，兰州  730000；中国科学院大气物理研究所东亚区域气候-环境重点实验室，北京  100029; (2)中国科学院大气物理研究所东亚区域气候-环境重点实验室，北京  100029；国家气候中心，中国气象局气候研究开放实验室，北京  100081
Published: December 2020

When the dynamic system is in the extreme states， or it is affected by an intensive disturbance， we will get an extreme event. The detrended fluctuation analysis (DFA) measures the long-term correlation of a system， so the extreme events has no effect on systems long-term correlation. Based on this idea， we determined the threshold of extreme events with detrended fluctuation analysis and the results testify its effectiveness. By this method， we analyzed the exreme events in Beijing for the temperature and rain. The results show that before the metaphase of the 1970s， the frequency and inensity of the extreme temperature events is mitigatory， and from 1970s to 1990s， there were very few extreme events. But from the metaphase of the 1990s to now， the extreme temperature events are frequent. The extreme low temperature event has a downtrend from the 1950s to now and never happened after 1978s. The frequency and intensity of extreme precipitations are periodic. The frequency and intensity were high in the metaphase of 1950s and 1960s, and were low in the remaining period. The transition occurred in the 1970s.
Energy and relativistic correction of the 1sns configuration in helium
Authors: Huang Shi-Zhong  , Ma Kun  , Wu Chang-Yi  , Ni Xiu-Bo  ,   安徽师范大学物理与电子信息学院，芜湖  241000
Published: December 2020

A Mathematica program is developed to calculate the energy and relativistic correction of helium-like atoms in 1sns configuration. A new set of trial functions for 1sns configuration in helium has been suggested. By virtue of the Rayleigh-Ritz variational method, the non-relativistic energies of 1sns configuration in helium (n=2—5) have been calculated, the relativistic corrections, which include mass correction, one- and two-body Darwin correction and spin-spin contact interaction, have been further calculated with the theory of perturbation. The calculated results are in good agreement with experimental data.
Grain-boundary effects on optical properties in SrTiO3 nanoparticles
Authors: Wu Xue-Wei  , Liu Xiao-Jun  ,   南京大学电子科学与工程系，近代声学教育部重点实验室，南京  210093
Published: December 2020

The size effects of SrTiO3 nanoparticles are investigated by Raman spectroscopy and UV-Visible absorption spectra with changing grain size in the range of 10—80 nm. It is found that the intensity for the first-order TO2 mode increases significantly as the grain size decreases from 80 to 10 nm. Such behavior suggests the presence of the micropolar regions on the grain boundary induced by the enhanced surface-defect dipoles. Moreover, the first-order TO2 and TO3 modes show red-shifts, indicating the increase of the Ti—O bond-length with decreasing grain size of SrTiO3 nanoparticles. The softening of the Raman mode is consistent with the lattice expansion investigated by XRD. In addition, the UV-Visible absorption spectra indicates the enhancement of absorption due to surface distortion states and hence the lattice expansion, which results in the increase of Eg-value.
Study on trapping force of focused optical field on the microsphere with the FDTD method
Authors: Yang Hao  , Feng Guo-Ying  , Zhu Qi-Hua  , Zhang Da-Yong  , Zhou Shou-Huan  ,   (1)四川大学电子信息学院，成都  610064; (2)四川大学电子信息学院，成都  610064；华北光电技术研究所，北京  100015; (3)四川大学电子信息学院，成都  610064；中国工程物理研究院激光聚变研究中心，绵阳  621900
Published: December 2020

The model of trapping force on microsphere based on the conservation of momentum are presented. Using 2-D FDTD algorithm, we calculated the effects of the wave length, waist of the Gaussian beam, the radius and refractive index of the microsphere on the trapping force. The results show that the microsphere located in a certain zone of focused laser optical electromagnetic fields will be trapped, and the trapping force deceases with the increase of the distance of the observed point away from the axis. When the refractive index of the surrounding medium is greater than that of the microsphere (such as an air bubble), it will be pushed out of the laser beam. The simulation results are in good aggrement with the experimental observation.
Slow wave propagation in metamaterial based nonradiative dielectric waveguides and its application
Authors: Yang Rui  , Xie Yong-Jun  , Wang Yuan-Yuan  , Fu Huan-Zhan  ,   西安电子科技大学天线与微波技术国家重点实验室,西安  710071
Published: December 2020

Different dispersion properties are imparted to nonradiative dielectric (NRD) waveguides by split ring resonator metamaterials. Both longitudinal-section magnetic and longitudinal-section electric modes are capable of propagating very slowly due to the metamaterial bianisotropic effects, and can even approach zero velocity. Enhanced energy flow in the considered structure is also demonstrated under certain conditions. Finally, miniaturization of NRD waveguide based on these unusual properties is proposed.
Propagation and localization of plane waves in two-dimensional homogeneous and isotropic random medium
Authors: Ding Rui  , Wang Zhi-Liang  , Hisanao Ogura  ,   复旦大学波散射与遥感信息教育部重点实验室，上海  200433
Published: December 2020

Propagation and localization of plane waves in two-dimensional homogeneous and isotropic random medium is studied. The approximate stochastic solution of the plane wave and the propagation behaviors are obtained by means of stochastic functional approach. The results verify the phenomenon of localization of waves in random medium. The agreements between the theory and the computer simulations are shown to be satisfactory in spite of the use of approximate theoretical formulas.
Investigation of the scattered field from a two-dimensional dielectric target above the planar surface with a Gaussian beam incidence
Authors: Wang Yun-Hua  , Zhang Yan-Min  , Guo Li-Xin  ,   (1)西安电子科技大学理学院，西安  710071; (2)中国海洋大学海洋遥感研究所，青岛  266003; (3)中国海洋大学物理系，青岛  266100
Published: December 2020

Differential scattering field of vertical incident Gaussian beam from a two-dimensional target near a plane interface is studied by means of a new hybrid method based on the reciprocity theorem (RT), the image theory (IT) and the method of moment (MoM). By application of IT, the plane interface is replaced by the virtual image of the actual target, and an equivalent model of the scattering problem is presented. In the equivalent model, the scattered field from the actual target and the virtual one are numerically calculated by employing MoM, and the rescattered coupling fields between the actual target and the virtual one are evaluated utilizing the combination of MoM and RT. The numerical results of these tests are presented and compared with previously published calculations for the same problems.
Analysis and simulation on propagation characteristics in waveguide filled with single-negative medium layers
Authors: Xiang Yang  , Qian Zu-Ping  , Liu Xian  , Bao Jun-Song  ,   (1)解放军理工大学通信工程学院，南京  210007; (2)解放军理工大学通信工程学院，南京  210007；总参第63研究所
Published: December 2020

The propagation characteristics of rectangular waveguide filled with two layers of single-negative medium are analyzed in this paper. The Drude-FDTD model is adapted to the application in three-dimension simulation program. Simulation results show that a subwavelength transmission mode exists in the waveguide. Based on the simulation results for different frequency and different medium parameter, energy propagation rule in this kind of waveguide is obtained. Especialy, the band width of microwave devices and antennas can be significantly widened with ENG-MNG filling method.
Light forces on moving atom in micro-cavity
Authors: Ding Cai-Ying  , Tan Lei  , Liu Li-Wei  , Xu Yan  ,   兰州大学理论物理研究所，兰州  730000
Published: December 2020

Optical forces on moving atom were investigated in micro-cavity using fully quantum theory. In terms of the models of moving atom interacting with micro-cavity field, using algebraic dynamics method, the Hamiltonian can be diagonalized by introducing a canonical transformation. The expression of evolution operator of the system and reduced density operators are calculated straightforwardly. Analytical expressions for the forces are obtained, and the forces are discussed for a traveling-wave field and a standing-wave field respectively.
Theoretical study of tunable terahertz radiation based on difference-frequency generation in GaSe and ZnGeP2 crystals
Authors: Liu Huan  , Xu De-Gang  , Yao Jian-Quan  ,   (1)天津大学精仪学院激光与光电子研究所，天津  300072; (2)天津大学精仪学院激光与光电子研究所，天津  300072；清华大学精密仪器与机械学系，北京  100084
Published: December 2020

Based on the theory of nonlinear optical frequency conversion, the phase-match angle, walk-off angle, acceptance angle and effective nonlinear coefficient of difference-frequency in GaSe and ZnGeP2 crystals are calculated under different phase-matched conditions. In the theoretical simulation, the experimental parameters which were reported to generate widely tunable terahertz waves by nonlinear optical difference-frequency method are adopted. The optimum phase-matched conditions corresponding to different terahertz wave bands are summarized through comparing the whole calculated results. The calculated results provide a sound and comprehensive theoretical basis for using optical difference-frequency method to generate tunable terahertz wave in the nonlinear crystals.
Domain structure inversion characterization of near stoichiometric lithium tantalate
Authors: Jia Bao-Shen  , Zhao Ye-Quan  , Zhang Xue-Feng  , Shen Yan  , He Yan-Lan  ,   (1)国防科技大学物理系，长沙  410073; (2)哈尔滨工业大学航天学院，哈尔滨  150001
Published: December 2020

Pure and MgO doped near stoichiometric lithium tantalate has been grown by adding flux method. The observation of the crystal wafers etched by hydrofluoric acid under metallographic microscope indicate that the domain structure of near stoichiometric lithium tantalate is hexagonal. Polarization experiments have been done by using the equipment made by ourselves. By using short-impulsed polarization electric field, several parameters, including the positive and negative direction coercive force field and polarization time were investigated. Polarization current and entirely reversed domain structure were obtained.
The defect modes in one-dimensional photonic crystal with multiple defects
Authors: Chen Xian-Feng  , Jiang Mei-Ping  , Shen Xiao-Ming  , Jin Yi  , Huang Zhen-Yi  ,   江苏工业学院数理学院，常州  213164
Published: December 2020

A one-dimensional photonic crystal containing multilayered half-wave defects is designed and the transmission spectrum is studied by using transfer matrix theory. Under the first-order approximation of Taylor expansion, the analytic expression for the defect mode frequency is derived, from which the coupling factor is deduced. Our results are fitted with the experimental results or numerical simulation, and can be used to describe the characteristics of the defect modes. The result is helpful for designing a multiple channel filter.
Design and characteristics of a near-elliptic inner cladding High birefringent polarization-stable photonic crystal fiber
Authors: Yan Feng-Ping  , Li Yi-Fan  , Wang Lin  , Gong Tao-Rong  , Liu Peng  , Liu Yang  , Tao Pei-Lin  , Qu Mei-Xia  , Jian Shui-Sheng  ,   全光网络与现代通信网教育部重点实验室，北京交通大学光波技术研究所，北京  100044
Published: December 2020

A new near-elliptic inner cladding (NEIC) structure of polarization-stable highly birefringent photonic crystal fiber (HB-PCF) is proposed and analyzed numerically by using the full-vector finite element method (FEM) under the condition of anisotropic perfectly matched layers. The result confirmed that the birefringence degradation of the proposed NEIC-PCF is less than 1.2×10-5 when the air hole diameter of the inner cladding along the short axis varies from 1.30μm to 1.18μm (varied by ～10%)，while the average birefringence is of the order of 10-3 at 1.55μm and the mode field diameters along long axis and short axis of the elliptic are 9.2μm and 2.4μm，respectively，which shows that the proposed PCF have excellent polarization stability.
Structural and magnetic properties of Ni1-xFex O thin films synthesized by pulsed laser deposition
Authors: Weng Wei-Xiang  , Yan Wen-Sheng  , Sun Zhi-Hu  , Yao Tao  , Guo Yu-Xian  , Wang Feng  , Wei Shi-Qiang  , Zhang Guo-Bin  , Xu Peng-Shou  ,   中国科学技术大学国家同步辐射实验室，合肥  230029
Published: December 2020

Pulsed laser deposition (PLD) method was used to fabricate Ni1-xFexO (x=0.02，0.05) dilute magnetic semiconductor thin films with room temperature ferromagnetism. For the Ni0.98Fe0.03O sample with a lower Fe content，the crystalline structures of the Ni1-xFexO films are of the NaCl type as determined by X-ray diffraction. For the Ni0.95Fe0.05O sample with a higher Fe content，some additional weak diffraction peaks corresponding to α-Fe2O3 phase can be observed. From the X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS)， it is shown that the doped Fe impurities in Ni0.98Fe0.02O are substitutionally incorporated into the NiO host and no secondary phases with room temperature ferromagnetism are found. These results show the intrinsic ferromagnetism of the Ni1-xFexO samples.
Preparation of anatase TiO2 nanotubes and their dye-sensitized solar cells
Authors: Zhang Yuan  , Zhao Ying  , Cai Ning  , Xiong Shao-Zhen  ,   南开大学光电子薄膜器件与技术研究所，天津  300071
Published: December 2020

TiO2 nanotubes were synthesized from commercial rutile powder by means of the hydrothermal method in alkaline solution at temperature of 150℃ for 48hours. The morphology and structure evolutions were characterized with SEM，TEM and X-ray diffraction. The TiO2 nanotubes mixed with Triton X-100 and acetyl acetone were screen-printed onto the glass substrate coated with a transparent conducting oxide (ITO，or tin-doped indium oxide)，then sintered at 450℃ for 30 minutes to form porous photoanode of dye-sensitized solar cells. A solar cell withactive area of 0.28cm2 was assembled with N719-coated nanotube-TiO2 electrode，Pt-coated ITO glass and iodide-based ionic liquid electrolyte. The J-V curve was measured using a standard solar simulator (AM1.5 spectrum，100mW/cm2)，and a photoelectric conversion efficiency of 2.17% was obtained.
Modeling the inter-molecular orientational correlation in orientational glassformers and the simulation analysis
Authors: Zhang Li-Li  , Zhang Jin-Lu  , Jiang Jian-Guo  , Zhou Heng-Wei  , Huang Yi-Neng  ,   (1)南京大学物理系固体微结构实验室，南京  210093; (2)伊犁师范学院物理与电子信息学院凝聚态物理与材料设计研究所，伊宁  835000; (3)伊犁师范学院物理与电子信息学院凝聚态物理与材料设计研究所，伊宁  835000；南京大学物理系固体微结构实验室，南京  210093
Published: December 2020

An effective bond model is proposed to describe the inter-molecule orientational correlation in orientational glassformers. The topological structures of the orientational correlation in the system are computer-smulated based upon the model. The results indicate that most of the bonding molecules appear in the form of molecular strings，and the phenomenon is explained using the probability theory. Furthermore，the simulated results are analyzed according to the string-model，and the rigourousness and feasibility of the model are discussed.
Photoluminescence and tail states of amorphous SnO2:(Cu，In) film
Authors: Zhang Zhi-Guo  ,   泉州师范学院理工学院，泉州  362000
Published: December 2020

The SnO2：(Cu，In) thin films are deposited on glass substrates by reaction evaporation. The photoluminecence(PL) of the films is researched. The films have amorphous structure. The transmittance is measured in the range 220—1100nm. The width of optical band gap is Eoptg=4.645eV. At room temperature，the photoluminescence is measured at different wavelengths，and continuous spectrum of photoluminescence is obtained in the range of 276—550nm. Especially，the density distributing in band tail states is determined by analyzing the emission spectrum.
Electronic properties of quantum wires in surface-acoustic-wave based single-electron transport devices
Authors: Li Hong  , Guo Hua-Zhong  , Lu Chuan  , Li Ling  , Gao Jie  ,   (1)四川大学物理科学与技术学院，成都  610064; (2)四川大学物理科学与技术学院，成都  610064；中国测试技术研究院，成都  610021; (3)四川师范大学物理与电子工程学院，成都  610068; (4)中国测试技术研究院，成都  610021
Published: December 2020

By fabricating a split gate on the surface of AlxGa1-xAs/GaAs heterostructure，we experimentally obtain a quasi-one-dimensional quantum wire. This structure could be used to implement single-electron transport driven by surface acoustic waves. Based on structures of conduction band and distribution of electrons in the fabricated quantum wires，the influence of quantum-wire widths on the confining potential of the electrons is also discussed. Especially，we numerically study how the linear electron concentration depends on the applied split-gate voltage. For the quantum wires fabricated，we find that the calculated pinch-off voltages agree well with the relevant experimental values measured at 0.3K.
Study of the characteristics of organic thin film transistors based on different active layers of pentacene and CuPc thin films
Authors: Yuan Guang-Cai  , Xu Zheng  , Zhao Su-Ling  , Zhang Fu-Jun  , Jiang Wei-Wei  , Huang Jin-Zhao  , Song Dan-Dan  , Zhu Hai-Na  , Huang Jin-Ying  , Xu Xu-Rong  ,   北京交通大学光电子技术研究所,北京  100044；北京交通大学发光与光信息技术教育部重点实验室,北京  100044
Published: December 2020

The surface morphology and crystallization of pentacene and CuPc films deposited on SiO2 substrate are characterized by X-ray diffraction (XRD) and scaning electron microscopy (SEM). It was observed that the pentacene film has island structure, the sizes of islands were about 100nm. The pentacene has clearer orientation than CuPc. We also studied organic thin film transistors (OTFTs) with different active layers of pentacene and CuPc, fabricated by shadow mask to investigate the characteristics of the device. The active layers pentacene and CuPc have the thickness of 40nm, the thickness of gate insulator layer SiO2 is 250nm and the ratio of width to length (W/L) of device channel is 20. We analyzed the property of devices by Keithley 2410 I-V. The results presented here show that OTFTs devices in which pentacene and CuPc are used as active layer exhibited the field-effect mobility (μEF) of 1.201cm2/V·s and 0.0694cm2/V·s, threshold voltage (Vth) of -20V and -15V, and (on/off) current radio of 104 and 105, respectively.
Band structure of strained Si/(111)Si1-xGex: a first principles investigation
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 a great interest in the strained Si CMOS technology lately, especially the modification of band structures which provides a theoretical basis for the design of the high-speed and high-performance devices and circuits. Calculations were performed on the band structures in strained Si/(111)Si1-xGex(0≤x≤0.4) by the first-principle pseudopotential approach of the plane wave based upon the density functional theory. It was found that the conduction band (CB) edge is characterized by the six valleys all the same, that valence band (VB) edge degeneracies are partially removed and that the electron mass in CB is unaltered under strain while the hole mass decreases along the ［100］ direction with increasing x. In addition, the fitted dependence of bandgap on x are in good agreement with KP theoretical calculation, from which the quantitative data supply valuable references to the devices design.
Study on electrical properties of n-GaN grown at low temperature by metal-organic vapor phase epitaxy
Authors: Wang Lai  , Zhang Xian-Peng  , Xi Guang-Yi  , Zhao Wei  , Li Hong-Tao  , Jiang Yang  , Han Yan-Jun  , Luo Yi  ,   集成光电子学国家重点实验室,清华信息科学与技术国家实验室，清华大学电子工程系，北京  100084
Published: December 2020

Electrical properties of n-GaN grown at 740℃ and 900℃ by metal-organic vapor phase epitaxy were studied in detail. According to the electrochemical capacitance-voltage measurement, it is helpful to reduce the background impurity concentration in unintendedly-doped n-GaN grown at low temperature using TEGa as Ga precursor rather than TMGa. The results of Hall effect measurement of heavily Si-doped n-GaN show that, as Si concentration increases, the electron concentration increases almost linearly, which exhibits the dopant band conducting effect, while the electron mobility decreases. Atomic force microscope and X-ray diffraction measurements show that the surface morphology and crystal quality of most samples were determined by growth temperature and Si doping level. The surface morphology of all samples had a visible change only when the doping level was much higher at the same growth temperature. On the other hand, after the samples were annealed in oxygen, the electron mobility of all the samples remained almost constant, but the electron concentration decreased when the Si concentration was larger than 6×1019 cm-3. This result indicates that in the heavily Si-doped n-GaN grown at low temperature, the annealing process could result in the formation of acceptors due to the replacement of N by Si atoms.
Numerical model of ITO /organic semiconductor/metal organic light emitting device
Authors: Hu Yue  , Rao Hai-Bo  , Li Jun-Fei  ,   电子科技大学光电信息学院，成都  610054
Published: December 2020

A numerical model of organic light emitting device (OLED) with metal/organic/metal structure was discussed on the basis of drift-diffusion equations in this paper. First，the influence of charges localized near the electrodes to the J-V curve was calculated and we got the same result of the literature. Second, the J-V curve of OLED with structure of ITO/PPV/Ca was simulated. In the simulation, the case of positive charge distribution localized near the anode was considered. The calculated J-V curve was in good agreement with the experiment. The charge creates an additional barrier and has a noted influence on the current density.
Four-wave-mixing process in secondary cores of a microstructured fiber
Authors: Ji Ling-Ling  , Lu Pei-Xiang  , Chen Wei  , Dai Neng-Li  , Zhang Ji-Huang  , Jiang Zuo-Wen  , Li Jin-Yan  , Li Wei  ,   (1)华中科技大学武汉光电国家实验室激光科学与技术研究部,武汉  430074; (2)华中科技大学武汉光电国家实验室激光科学与技术研究部,武汉  430074；武汉烽火通信科技股份有限公司,武汉  430074; (3)清华大学精密仪器与机械学系,北京  100084; (4)武汉烽火通信科技股份有限公司,武汉  430074
Published: December 2020

We report the generation of anti-Stokes emissions with wavelength 480—550nm in the secondary cores of a dual-core photonic crystal fiber from 800nm femto second laser pulses. The conversion efficiency is as high as 28%. The anti-Stokes frequency conversion of laser pulses has strong polarization dependence of the pump. The simulation of light propagation in the waveguide well explains the experimental results.
A fast algorithm for reflectivity calculation of micro/nano deep trench structures by corrected effective medium approximation
Authors: Liu Shi-Yuan  , Gu Hua-Yong  , Zhang Chuan-Wei  , Shen Hong-Wei  ,   (1)华中科技大学数字制造装备与技术国家重点实验室,武汉  430074; (2)武汉光电国家实验室光电材料与微纳制造研究部,武汉  430074
Published: December 2020

This paper proposes a fast algorithm for reflectivity calculation of micro/nano scale high-aspect-ratio deep trench structures by the novel method of corrected effective medium approximation (CEMA). Extensive comparative investigation on the infrared reflection spectra of deep trench structures by means of effective medium approximation (EMA) and rigorous coupled-wave analysis (RCWA) reveals that the RCWA based method is accurate but time consuming while the EMA based calculation is much faster but less accurate. The proposed CEMA method is based on EMA but a dispersion corrected factor is added to calculate the refractive index of each effective medium. The dispersion corrected factor is found to be in inverse proportion to the square of the wavelength, and relates to the period, material and void fraction of trench structures. Simulations carried out on a lot of complex multi-layered trench structures, such as the bottle trench structure, demonstrate that the CEMA method is not only fast in calculation but also accurate enough in comparison with the RCWA based method. It is expected that the proposed CEMA method can be applied to deep trench measurement by model-based infrared spectroscopy (MBIR), thus has further potential applications such as real time etching process monitoring of micro/nano scale high-aspect-ratio deep trench structures in manufacturing microelectronics and microelectromechanical system (MEMS) devices.
The Cartesian momentum and the kinetic operators on curved surfaces
Authors: Liu Quan-Hui  ,   湖南大学理论物理研究所，长沙  410082
Published: December 2020

For describing particles moving on the two dimensional curved surfaces, we can use either the intrinsic local coordinates or the Cartesian coordinates. The representation of the momentum operators differs from each other in these two kinds of coordinates, the former ones depend on the intrinsic geometrical quantities, but the latter case depend on a geometrical invariant, namely the mean curvature. Taking the operator-ordering problem into consideration, the kinetic operator for the former case can be expressed in a possibly unique way, while that for latter case can be expressed in two different ways.
Microscopic optical potentials in 6Li scattering by nuclei
Authors: Ma Yin-Qun  , Ma Zhong-Yu  ,   (1)中国原子能科学研究院，北京  102431; (2)中国原子能科学研究院，北京  102431；太原师范学院物理系，太原  030001
Published: December 2020

A parameter-independent microscopic optical potential of nucleus-nucleus interaction is presented by a folding model with the isospin dependent complex nucleon-nuclear potential, which is calculated in the framework of the Dirac-Bruecker-Hartree-Fock approach. Investigations on 6Li scattering by 12C, 28Si, 40Ca, 58Ni, 90Zr, and 208Pb over a wide range of incident energy and scattering angle with the microscopic nucleus-nucleus optical potential is presented. To take account of the breakup effect of 6Li and the high order dynamic effect in the reaction a modification factor NR in the real part and an enhancing factor NI in the imaginary part of the microscopic optical potential are introduced. We take the imaginary part enhancing factor NI=3.0, which has been obtained in the previous study on 6He scattering by 12C. The modification factor NR is found to be almost constant with respect to the incident energy and target mass number. The calculations with NR≈0.5—0.6 and NI=3.0 well reproduce the experimental elastic scattering data for all targets and incident energies investigated. Our parameter-independent model should be of value in the description of the nucleus-nucleus scattering of many-body systems, especially unstable nucleus-nucleus systems.
A new way of uniform splitting of the optical power by directional coupling between the photonic crystal waveguides
Authors: Zhu Gui-Xin  , Yu Tian-Bao  , Chen Shu-Wen  , Shi Zhe  , Hu Shu-Juan  , Lai Zhen-Quan  , Liao Qing-Hua  , Huang Yong-Zhen  ,   (1)南昌大学物理系，南昌  330031; (2)中国科学院半导体研究所，北京  100083
Published: December 2020

Directional coupler can be constructed by putting multiple photonic crystal waveguides together. The propagation of the optical field entering this system symmetrically was analysed numerically according to self-imaging principle. On the basis of this structure, ultracompact multiway beam splitter was designed and the ones with three and four output channels were discussed in details as examples. By simply tuning the effective refractive index of two dielectric rods in the coupler symmetrically to induce the redistribution of the power of the optical field, uniform or free splitting can be achieved. Compared with the reported results, this way is simpler, more feasible and more efficient and has extensive practical value in future photonic integrated circuits.
Multi-scale simulation of the deformation in nano-indentation under different crystal orientations
Authors: Wang Hua-Tao  , Qin Zhao-Dong  , Ni Yu-Shan  , Zhang Wen  ,   复旦大学力学与工程科学系，上海  200433
Published: December 2020

The nano-indentation process of an fcc Al film under three different crystal orientations (x［1 1 1］,y［1 1 0］,z［1 1 2］; x［1 1 2］,y［1 1 1］,z［1 1 0］ and x［1 1 0］,y［0 0 1］,z［1 1 0］) are studied using the quasi-continuum method. The load-displacement responses of the film under different crystal orientations are presented respectively. The local atomics in the regions where sharp deformation occurred are plotted to analyse their mechanisms on atomic scale. The results show that the micro-mechanisms of the deformation in the film are different for different crystal orientations. Under the orientation of x［1 1 1］, y［1 1 0］, z［1 1 2］, in which the indentation direction is parallel to the close-arranged plane, the deformation in the film is mainly dominated by the dislocation nucleation caused by the slip of the plane, and the hardness and the out-of-plane displacement of the crystal are large. Under the x［1 1 2］,y［1 1 1］,z［1 1 0］ orientation, in which the indentation direction is perpendicular to the close-arranged plane, the deformation in the film is mainly dominated by the deformation twinning, and both the hardness and the out-of-plane displacement of the crystal are the largest. Under the x［1 1 0］, y［0 0 1］, z［1 1 0］ orientation, in which the indentation direction is at some degrees inclined to the close-arranged plane, the deformation in the film starts from a small dislocation line nucleating on a slip plane at the beginning of the loading and then deformation twinning is formed with the increasing loading, and the hardness and the out-of-plane displacement of the crystal are the smallest.