bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of chaos control based on adaptive pulse perturbation
Authors: Gong Li-Hua  ,   达县师范高等专科学校物理系，达州  635000
Published: December 2020

The method of chaotic control system based on adaptive pulse perturbation is pro posed this paper. Combining the method of parameter pulse perturbation with the adaptive control policy, the adaptive controller that can produce appropriate pu lse strength to realize chaos control is designed. The system can be stabilized to the different periodic orbits or fixed points by using the method to simulate the chaotic Rssler continuous system and Hnon discrete map. Furthermore, the simulation results showes that this control method has strong robustness.
Contributions of the surface resistance of high-temperature superconducting films to the insertion loss of the microwave filters
Authors: Li Hong-Cheng  , Wang Rui-Lan  , Wei Bin  , Zheng Dong-Ning  ,   (1)清华大学物理系，北京  100084; (2)中国科学院物理研究所超导国家实验室,北京  100080; (3)中国科学院物理研究所超导国家实验室,北京  100080;清华大学物理系，北京  100084
Published: December 2020

In this paper it is shown that the influence of the surface resistance of the high_temperature superconductors (HTS) on the insertion losses of the microwave filters with various poles and central frequencies was analyzed using simulat ion software for the electrical circuits. It is shown that HTS thick films or HT S thin films with relatively high surface resistance can be used to construct lo w insertion loss microwave filter with a few poles or with low central frequency . But high_quality epitaxial thin films must be used to construct low loss microwave filter with many poles (more than 8-poles) or with high central frequency (higher than 6GHz).
Split Monte Carlo for impulse responses on the infrared indoor channels on the basis of Phong’s model
Authors: Zhang Hai-Tao  , Cui Rui-Zhen  , Wang Dong-Sheng  , Yan Ping  , Chen Gang  , Liu Qiang  ,   清华大学精密仪器与机械学系光子与电子研究中心，摩擦学国家重点实验室，北京  1000 84
Published: December 2020

A split Monte Carlo (SMC) algorithm, based on the Phong's model, for the estimation of the impulse response on the infrared indoor channels is presented. It can be applied to the indoor channel including various reflection patterns, includi ng diffuse, mirror and other non_Lambert reflections.The simulation of the indoo r optical channel by SMC method based on the Phong's model can benefit significa ntly the design of high performance infrared systems. The calculation is much fa ster than the classical deterministic method, and the speed advantage is more ob vious at a large number of reflections.
Self-compression of high-intensity femtosecond laser pulses in air
Authors: Chen Xiao-Wei  , Liu Jun  , Zhu Yi  , Leng Yu-Xin  , Ge Xiao-Chun  , Li Ru-Xin  , Xu Zhi-Zhan  ,   中国科学院上海光学精密机械研究所强场激光物理国家重点实验室，上海  201800
Published: December 2020

Pulse self-compression in air is experimentally demonstrated by use of 1kHz femtosecond laser pulses with input power on the order of GW. Under the conditions of different initial chirps, the temporal and spectral characteristics of the output pulse after being focused in air are studied in detail as a function of i nput pulse energy. The experimental results show that, the temporal duration of high-intensity femtosecond laser pulses could be shortened solely through nonlinear propagation in air, without any additional dispersion compensation. Moreover, with the input pulse negatively chirped, we observed that the spectrum and pulse duration could be compressed simultaneously, and near sech2 trans form-limited output pulses shorter than original laser pulse source were obtained.
High-order quasi-phase matching harmonic generation in two-dimensional nonlinear photonic crystal
Authors: Ma Bo-Qin  , Wang Ting  , Sheng Yan  , Ni Pei-Gen  , Cheng Bing-Ying  , Zhang Dao-Zhong  ,   中国科学院物理研究所，北京  100080
Published: December 2020

The high-order collinear and non-collinear quasi-phase matching harmonic generations were realized in a two-dimensional periodically poled LiNbO3 wit h square lattice by tuning the input wavelength. The output spots lay at different symme tric positions with respect to the input beam of picosecond pulse, and the relat ive intensities of spots at certain wavelengths were measured. The high-order no nlinear harmonic processes were also realized by tuning the input angle. The exp erimental and theoretical results are in good agreement with each other. Our stu dies might be beneficial to the development of optics integration and compact de vices.
Controlling the bistability and self-pulsation characteristics of two-segment bistable laser diode based on delayed optoelectronic feedback
Authors: Jia Xin-Hong  , Wu Zheng-Mao  , Lin Xiao-Dong  , Bai Xi  , Xia  Guang-Qiong  ,   (1)西南师范大学物理学院,重庆  400715; (2)西南师范大学物理学院,重庆  400715;重庆大学光电技术与系统教育部重点实验室，重庆  400044
Published: December 2020

In this paper, the delayed optoelectronic feedback is introduced to the absorption region in order to control the bistability and self-pulsation characteristics of the two-segment bistable laser diode (TBLD). The rate equations have been used to model numerically the effects of feedback gain and delay time. The result s show that the stable region of TBLD varies periodically with the delayed time; the bistable region shrinks with increasing delay time; the stability can beenhanced at certain values of delayed time, and the instability can be reached more easily for negative optoelectronic delayed feedback.
Properties of spatial optical solitons to different degrees of nonlocality
Authors: Cao Jue-Neng  , Guo Qi  ,   华南师范大学信息光电子科技学院，广州  510631
Published: December 2020

The propagation of optical beams in nonlocal nonlinear media is modeled by the nonlocal nonlinear Schrdinger equation.In this paper,discussed is the propagation properties of the optical spatial solitons in the media to different degrees of the nonlocality.An iteration algorithm based on the split_step Fourier method is presented to obtain the solutions of the solitons. The profiles of the solitons to different degrees of the nonlocality are numerically obtained in the assu mption that nonlinear response of the media is Gaussian. The stability of the so lutions is also demonstrated numerically,which shows that the stable solitons ca n survive to different degrees of nonlocality. The amplitude profiles of the sol iton transit gradually and continuously from a Gaussian function in the strongly nonlocal case into a hyperbolic secant function in the local case. The critical power for the solitons decreases as the nonlocality decreases. The weaker the n onlocality,the slower the soliton phase that has a linear relation with the prop agation distance increases.
Fabrication of carbon nanotube rings
Authors: Zhang Ping  , Li Ping-Jian  , Hou Shi-Min  , Zhang Qi-Feng  , Wu Jin-Lei  ,   北京大学电子学系，北京  100871
Published: December 2020

Nanotube rings were fabricated with a high yield by heating the lightly etched c arbon nanotubes under ambient conditions that were produced by chemical vapor deposition method. These rings, typically 300nm in diameter, were characterized using atomic force microscopy, transmission electron microscopy and scanning ele ctron microscopy. The structure and yield of nanotube rings depended strongly o n the heating temperature and time. Our researches suggest that the optimal heat ing temperature ranges from 510 ℃ to 530 ℃, and that the heating time up to 1 20 min is favorable for the increase of the yield. At high temperatures, the est erification of carboxyl functional groups attached at the nanotube ends resulted in the bending of straight nanotubes into closed rings.
Ultrashort laser pulse up-conversion amplification based on modulation instability
Authors: Wu Kun  , Wu Jian  , Xu Han  , Zeng He-Ping  ,   华东师范大学物理系，光谱学与波谱学教育部重点实验室，上海  200062
Published: December 2020

Colored conical emission via spatiotemporal modulational instability was observe d in second harmonic generation of untrashort laser pulses. By injecting accurat ely synchronized white_light super_continuum seed pulses, frequencies with maxim al gain corresponding to the seed angle were amplified. The amplified pulse exhi bited 150 μJ pulse energy and 60 nm spectral width (full width at half maximum) centered around 500 nm. Wide tunable range of the output wavelength up to 290 n m was realized by adjusting the input angle of the seed pulses.
Synchrotron radiation study on Au/GaN(0001) interface with low coverage
Authors: Zou Chong-Wen  , Sun Bai  , Wang Guo-Dong  , Zhang Wen-Hua  , Xu  Peng-Shou  , Pan Hai-Bin  , Xu Fa-Qiang  , Yin Zhi-Jun  , Qiu Kai  ,   (1)中国科学技术大学国家同步辐射实验室,合肥  230029; (2)中国科学院固体物理研究所,合肥  230031
Published: December 2020

Synchrotron radiation photoemission spectroscopy (SRPES) is used to study the in itial growth mode of the gold deposition on the surface of GaN, the Schottky bar rier height (SBH) and the electronic structure at the interface of the Au/GaN(00 01) system. The results show that at the initial stage chemical reaction exists between the Au and GaN substrate. Over the reaction layer, the growth mode of Au deposition is 3D island mode. The SBH is examined by the SRPES and the result i s 14eV, which is consistent with other experiment reports. Analyzing the ene rgy shift of valence band and the Au core level, the interface chemical reaction is confirmed. The theoretical calculation by linear augmented plane wave method gives the density of states. According to the calculation results, the principl e of the interface reaction is discussed.
The charge storage and its stability in corona charged polypropylene non-woven fabrics used as air filters
Authors: Ji Zhong-Bao  , Xia Zhong-Fu  , Shen Li-Li  , An Zhen-Lian  ,   同济大学波耳固体物理研究所，上海  200092
Published: December 2020

The charge storage ability and its stability in polypropylene(PP) non_woven fabric electret used as an air filter material was discussed. The influence of tempe rature and environmental humidity on the charge stability was investigated. The role of material structure in the influence of humidity on charge stability was analyzed. It was found that the charge stability can be improved obviously by th ermal treatment, including aging after charging at room temperature and charging at elevated temperatures. Experimental results demonstrate that PP non_woven fa bric electret shows very good charge storage lifetime in ambient atmosphere. The transport of detrapped charge is controlled by the slow retrapping effect.
Structure and magnetic properties of FePt/Ag nano-granular films with perpendicular magnetic anisotropy
Authors: Li Bao-He  , Hwang Pol  , Yang Tao  , Feng Chun  , Zhai Zhong-Hai  , Zhu Feng-Wu  ,   (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;北京工商大学数理部，北京  100037; (3)北京科技大学材料物理与化学系，北京  100083;金日成综合大学物理系，朝鲜平壤
Published: December 2020

［FePt 2 nm/Ag d nm］10 (d=0—11) multilayers were prepared on single crystal MgO(100) substrates kept at room temperature and 250 ℃ by means of magnetosputtering. L10-FePt/Ag granular films with perpendicular magn etic anis otropy and high coercivity have been obtained after vacuum annealing the multila yers deposited on substrates kept at 250 ℃ for 15 min. X-ray diffraction result s indicate that FePt particles have a strong ［001］ orientation. The size of Fe Pt particles decreases with the increase of the thickness of Ag layer. After vac uum annealing the ［FePt 2 nm/Ag 9 nm］10 films at 600 ℃ for 15 min, FePt /Ag granular films are obtained with only 8 nm of particle size and 692 kA/m of coercivity. Isothermal magnetization remanence and dc-demagnetization remanence measurements show that no magnetic exchange coupling between magnetic particles can be observed. Such a kind of films is suitable for future ultra-density perp endicular magnetic recording medium.
Optical properties of Bi3.25La0.75Ti3O12 and Bi3.25Nd0.75Ti3O12 thin films prepared by a chemical solution method
Authors: Ma Jian-Hua  , Meng Xiang-Jian  , Sun Jing-Lan  , Hu Zhi-Gao  , Chu Jun-Hao  ,   (1)中国科学院上海技术物理研究所红外物理国家重点实验室，上海  200083; (2)中国科学院上海技术物理研究所红外物理国家重点实验室，上海  200083;山东大学晶体材料国家重点实验室，济南  250100
Published: December 2020

The optical properties of Bi3.25La0.75Ti3O 12 (BLT) and Bi 3.25Nd0.75Ti3O12 (BNT) thin films de posited on (111)Pt/Ti/ SiO2/Si substrates by a chemical solution method were investigated. B oth BLT a nd BNT thin films showed single phase of bismuth-layered structure. The BNT fil m composed of the homogeneous and large rod-like grains, while the grains in BLT film were small. The optical constants (refractive index and extinction coeffic ient) in the wavelength range of 200—1700nm and the thickness of the films we re obtained by spectroscopic ellipsometry measurements. The optical band gaps o f BLT and BNT were estimated to be 430 and 361eV, respectively. The disper sion of the refractive index in the interband transition region was analyzed by using the single electronic oscillator model.
Electrostatic pinning effects on localized vibrational modes around a bipolaron in polythiophene
Authors: Xie Zun  , An Zhong  , Li You-Cheng  , Liu Ying  ,   (1)河北师范大学物理学院，石家庄  050016; (2)河北师范大学物理学院，石家庄  050016;河北工业大学材料学院，天津  300130
Published: December 2020

Based on the extended two-dimensional Su_Schrieffer_Heeger model of polythiophene, we have studied numerically the pinning effects of the Coulumb interaction o n the localized vibrational modes around a bipolaron in polythionphene. Some new localized vibrational modes are found. The numerical results are almost in good agreement with the results of optical absorption experiments.
Formation of L10-FePt nanoparticles with the precursor of [(Fe/Pt/Fe)/Ag]n multilayer at lowered annealing temperature
Authors: Zhu Yun  , Cai Jian-Wang  ,   中国科学院物理研究所磁学国家重点实验室，北京  100080
Published: December 2020

Microstructure and magnetic properties of [(Fe/Pt/Fe)/Ag]n multilayer films after ex situ annealing at various temperatures have been investigated. The results indicate that, the multilayer starts to transform to isolated L10-FePt nanoparticles embedded in Ag matrix after annealing at temperatures above 400℃ . The formation of the face_center tetragondal (fct) phase at relatively low tem peratures seems to relate with the rapid diffusion at the interface of "Fe/Pt/Fe " and the defects caused by Ag, and the high migration speed as well as the much smaller surface free energy of Ag leads to the separation of FePt nanoparticles , which is evidenced by the result of ΔM measurements.
A theoretical scheme for multi-user quantum authentication and key distribution in a network
Authors: Yang Yu-Guang  , Wen Qiao-Yan  , Zhu Fu-Chen  ,   (1)北京邮电大学理学院，北京  100876; (2)现代通信国家重点实验室，成都  610041
Published: December 2020

A theoretical scheme for multi-user quantum authentication and key distribution in a network is proposed. Similar to the authentication architecture of the netw ork in classical cryptography, a distributed client/server architecture with the shared Einstein-Podolsky-Rosen(EPR) entangled pairs between each user and his t rusted server used for the authentication and key distribution is proposed. Base d on this architecture, any-to-any multi-user quantum authentication and key dis tribution is realized. The trusted server only provides the authentication betwe en users and swaps the entanglement between the particles so as to entangle the particles of the two users who want to communicate secretly. The key generation is performed by the requesting user. Each user in a network only shares Einstein -Podolsky-Rosen entangled pairs with the trusted server and communicates with th e trusted server through the classical channel and quantum channel. Users need n ot share EPR entangled pairs with each other so that the number of EPR pairs in the network is reduced from O(n2) to O(n).
Pseudo-random number generator based on TD-ERCS chaos and its statistic characteristics analysis
Authors: Sheng Li-Yuan  , Cao Li-Ling  , Sun Ke-Hui  , Wen Jiang  ,   中南大学物理科学与技术学院，长沙  410083
Published: December 2020

To analyze the security of tangent-delay ellipse reflecting cavity-map system (TD-ERCS) from the point view of cryptography, a simple pseudo-random number generator (PRNG) is proposed with parallel TD-ERCS in this paper. Users' keys are n o longer fixed, and can be chosen in the interval [264, 26 72] arbitr arily in the PRNG. By testing the basic statistic characteristics such as equili brium, runs and correlation of the binary pseudo-random sequences (viz. TD-ERCS sequences) being generated from the PRNG, and comparing with m-sequences, the lo gistic sequences, Chebyshev sequences and SCQC sequences, the experimental resul ts show that TD-ERCS sequences have better statistic characteristics.
Suppression of chaotic motion in a class of piecewise-smooth systems by using sine periodic force
Authors: Wang Lin-Ze  , Zhao Wen-Li  ,   杭州电子科技大学计算机学院，杭州  310018
Published: December 2020

This paper studies how to suppress the abnormal vibration in a dynamic system wi th clearance. The abnormal vibration contains the bifurcations or chaotic motio n due to the change of some parameters of the nonlinear system. This paper prop oses a method to suppress chaotic motion by applying an external periodical for ce to the system. The periodical force is adjusted according to some real-time a lgorism related to an error between real-time states and the states when the sy stem is stable. This method has been applied to a two-degree-freedom impact vibration system. With numerical simulation, the effectiveness of the method is demonstrated.
Investigation on electro-strain effect in Rh-doped BaTiO3 single crystals
Authors: Zhou Dan  , Lin Di  , He Tian-Hou  , Feng Zu-Yong  , Xu Hai-Qing  , Luo Hao-Su  ,   (1)中国科学院上海硅酸盐研究所高性能陶瓷和超微结构国家重点实验室，上海  2018 00; (2)中国科学院上海硅酸盐研究所高性能陶瓷和超微结构国家重点实验室，上海  2018 00;中国科学院研究生院，北京  100039
Published: December 2020

The electric-field-induced strain in Rh-doped BaTiO3 single crystals increases with increasing ageing time at 80℃. After 27 days' ageing, the strain can reach 1.11% under bipolar field cycling conditions. However, the strain under mo nopolar field cycles is strongly dependent on the drive frequency and reaches as high as 0.95% at frequency of 0.01Hz. The hysteresis loop (P-E curve) of the aged sample is similar to a wasp-waisted hysteresis loop. Ageing can significant ly improve the electro-strain effect in the Rh-doped BaTiO3 crystal a nd make t he BaTiO3 crystal a promising and lead-free material for novel applic ations in ultra-large strain and nonlinear actuators.
A method for analyzing the coupling of 3-D tapered rib waveguides with Fibers
Authors: Liu Jing-Wei  , Chen Shao-Wu  , Yu Jin-Zhong  ,   中国科学院半导体研究所光电研究发展中心,北京  100083
Published: December 2020

The fields in 3-dimensional tapered waveguides are unstable compared with the fields in the straight waveguides. In the case of waveguide-to-fiber coupling and fiber-to-waveguide coupling, a sequence of short straight waveguides has been modeled to approximate the 3-dimensional tapered waveguide; and the unstable incident and reflected fields, as well as their derivatives, were determined by the beam propagation method(BPM). Then free space radiation mode(FSRM) was employed to calculate the reflected and transmitted powers. Analysis results of the coupling of fiber with silicon-on-insulator(SOI) tapered rib waveguides showed the feasibility of the method.
A model of the absorption of electromagnetic waves by weakly ionized plasma and the numerical calculation
Authors: Song Fa-Lun  , Cao Jin-Xiang  , Wang Ge  ,   中国科学技术大学近代物理系, 合肥  230027
Published: December 2020

It is shown in three different ways that the wave equation varying with time and the Helmholtz equation are equally effective for analysing the transmission of electromagnetic waves from the weakly ionized plasma in the plane geometry. Eve n when the scale length of plasma approaches the waves length, the electromagnet ic waves are still simple harmonic waves. The properties of transmission of elec tromagnetic waves from the weakly ionized and highly collisional plasma are stud ied numerically. The results show that the highly collisional plasma is a good m icrowave absorber.
First-principles study on tetragonal BaTiO3 ferroelectric
Authors: Xue Wei-Dong  , Chen Zhao-Yong  , Yang Chun  , Li Yan-Rong  ,   (1)电子科技大学微电子与固体电子学院，成都  610054; (2)电子科技大学微电子与固体电子学院，成都  610054;四川师范大学化学系，成都  610066
Published: December 2020

Based on the generalized gradient approximation (GGA), the totalenergy, overlap populations and valence charges in the case of Ti atoms moving along c axi s in cubic and tetragonal phases were calculated by using ultrasoft pseudopotent ials (USP) plane wave method. It was demonstrated that the energy of tetragonal BaTiO3 was the lowest when Ti atoms move along the c axis by up to 0012n m, and the spontaneous polarization was 0261C/m2 , which was consistent with experimental results. Moreover, it was also confirmed that the ferroelectric st ability of BaTiO3 could be attributed to the orbital hybridization of 2p orbit of oxygen atom and 3d orbit of Ti atom.
Higher-order nonlinear responses in weakly nonlinear composite materials within the effective medium approximation
Authors: Gu Li-Ping  , Gao Lei  ,   (1)常熟理工学院物理系，常熟  215006; (2)苏州大学物理系，苏州  215006;常熟理工学院物理系，常熟  215006
Published: December 2020

Based on the spectral representation theory and the perturbative expansion metho d, the general expressions for effective nonlinear responses (χe a nd ηe) are derived for any complicated micro structures. The higher_orde r nonlinear response of two_component composite is studied by using the effectiv e medium approximation. The effective dielectric constant of the composite is gi ven by ε～e=εe+χe|E0|2+ηe|E0|4. The effe ctive cubic order nonlinear response χe and the higher_order response ηe for the whole volume fraction p of the nonlinear component ar e investigated and the general expressions of χeand ηeare g iven in this paper. We also perform numerical simulations for χe and ηe in the case of complex dielectric constant of the nonlinear co mponent. The effect of the higher order nonlinear responses on the effective di electric constant of the composite is theoretically studied.
A numerical method for two-phase flow in micro channels and its application to droplet control by electrowetting on dielectric
Authors: Wang Fei  , He Feng  ,   清华大学工程力学系，北京  100084
Published: December 2020

With the development of micro chemical and medical analysis in MEMS, micro-fluid-control chip becomes more and more popular. Based on discrete droplet control system, chemical and medical analysis is applied in the micro chip lab. The change of voltage between the dielectric layer of the electrode controls the wettability of a droplet on a dielectric solid surface and then makes it possible to create,transport,merge and cut the micro droplets. This paper presents a numerical method to simulate the droplet motion by electrowetting on dielectric (EWOD). The second-order projection method is carried out to solve N-S equations and level set function. The interface is captured as zero level set. Dynamic contact angle for fluid contacting a solid surface by the electric potential is used to evaluate the wettability of fluid by EWOD. The numerical scheme is based on staggered MAC grid. Numerical simulations are used to capture the interface between two kinds of fluids in micro channels, the shapes of micro droplets resting on the horizontal solid surface under different electric potential and the transportation of a micro droplet in a parallel-plate channel when electrodes are activated.
A highly efficient beam propagation method for modeling step-index waveguides with tilt interface
Authors: Yu He-Jun  , Xia Jin-Song  , Yu Jin-Zhong  ,   中国科学院半导体研究所集成光电子学国家重点联合实验室，北京  100083
Published: December 2020

Based on a new finite-difference scheme and Runge-Kutta method together with transparent boundary conditions(TBCs), a novel beam propagation method to model step-index waveguides with tilt interfaces is presented. The modified scheme provides an precies description of the tilt interface of the nonrectangular waveguide structure, showing a much better efficiency and accuracy comparing with the previously presented formulas.
Determination of anisotropic liquid crystal layer parameters by spectroscopic ellipsometer
Authors: Mu Quan-Quan  , Liu Yong-Jun  , Hu Li-Fa  , Li Da-Yu  , Cao Zhao-Liang  , Xuan Li  ,   (1)中国科学院长春光学精密机械与物理研究所应用光学国家重点实验室，长春  130033; (2)中国科学院长春光学精密机械与物理研究所应用光学国家重点实验室，长春  130033;中国科学院研究生院,北京  100049
Published: December 2020

Spectroscopic ellipsometry is widely used in measuring the refractive index and thickness of optical isotropic thin layers. A simple method using spectroscopic ellipsometry to measure uniaxial liquid crystal layer is introduced. A UVISEL spectroscopic phase modulated ellipsometer is used to measure the ordinary refractive index, extraordinary refractive index and thickness of the liquid crystal layer in a parallel-aligned liquid crystal cell. The phase retardation Δnd is measured in transmission mode. The results show that the spectroscopic ellipsometry can be used to measure the anisotropic multilayer liquid crystal cell with high precision.
Study on the structure and stability of the AlxOy(x=1—2,y=1—3) molecules by deusity function theory
Authors: Shen Xiao-Hong  , Gao Tao  , Luo Shun-Zhong  , Ma Mei-Zhong  , Xie An-Dong  , Zhu Zheng-He  ,   (1)四川大学原子分子物理研究所，成都  610065; (2)四川大学原子分子物理研究所，成都  610065;西华大学物理实验中心，成都  610039; (3)中国工程物理研究院, 绵阳  621900
Published: December 2020

The geometric configuration, electronic structures and vibrational frequency of the AlxOy(x=1—2,y=1—3) molecules were calculated with B3LYP method at 6-311++g** level. The calculations show that the ground states of AlxOy molecules can be rapidly obtained by adding one or two O atoms to the different positions of Oy clusters with the aid of the software Gaussview 3.7, and taking into account of possible symmetries. Analysis of the geometrical parameters of ground state structure reveals that the atoms have chained or planar structure only. Analysis of the energy of ground state structure shows that Al atoms tend to bind with three other atoms. With one Al atom in the molecule the ground state structures multiplicity is two, with two Al atoms in the molecule, the ground state structures multiplicity is one except for Al2O3, of which the ground state structures multiplicity is three.
Spatially angular multiplexing in ultra-short pulsed digital holography
Authors: Wang Xiao-Lei  , Zhai Hong-Chen  , Wang Yi  , Mu Guo-Guang  ,   南开大学现代光学研究所,天津  300071;教育部光电信息技术科学重点实验室，天津  300071
Published: December 2020

Ultra-fast dynamic process can be recorded by ultra-short pulsed digital holography with angular multiplexing technique, in which the angle between reference beam and object beam has to be restricted to within a few degrees due to the restricted pixel size of CCD in the recording. In this report, spatially angular multiplexing technique is introduced, and the its applicability has been proved through a simulation experiment of digital holography with CW laser. Besides, optical set-up based on this technique is designed. Computation result shows that a series of dynamic multi-images in nanosecond time scale of ultra-fast process can be automatically recorded on a piece of digital hologram.
Modeling RAL experiment to test our simulation
Authors: Qiao Xiu-Mei  , Zhang Guo-Ping  , Zhang Tan-Xin  ,   (1)北京应用物理与计算数学研究所,北京  100088; (2)中国工程物理研究院北京研究生部，北京  100088
Published: December 2020

A code series for transient collisional excitation (TCE ) was newly developed based on the previous code series for QSS scheme, the TCE Ne-like Ge 19.6nm X-ray laser experiment done by RAL in 2000 was modeled to test our code series, a relatively good fit is obtained which provides convenience for our study of TCE scheme.
Strongly nonlocal elliptical spatial optical soliton
Authors: Qin Xiao-Juan  , Guo Qi  , Hu Wei  , Lan Sheng  ,   (1)华南师范大学光子信息技术广东省高校重点实验室,广州  510631; (2)华南师范大学光子信息技术广东省高校重点实验室,广州  510631;华南师范大学信息光电子科技学院传输光学实验室,广州  510631
Published: December 2020

We investigate the propagation of the elliptical Gussian beam in strongly nonlocal nonlinear media with an elliptically symmetric response.We derive analytical formulas for the evolution of the beam parameters and conditions for the formation of nonlocal elliptical spatial optical soliton.
Analysis of band gap in honeycomb photonic crystal heterostructure
Authors: Guan Chun-Ying  , Yuan Li-Bo  ,   哈尔滨工程大学理学院,哈尔滨  150001
Published: December 2020

In the present paper, a new kind of honeycomb photonic crystal heterostructure(PCH) is proposed. The band gap structure of this photonic crystal heterostructure is investigated with supercell technique based on the plane-wave expansion method. The configuration of heterostructure and the corresponding band structures are obtained and the guide modes are analyzed. Furthermore, the influences of longitudinal sideslipping and transverse displacement of lattices on the band gap structures are discussed. It may provide a new configuration to generate guide modes. The achieved results show that the guide modes can exist in this heterostructure without any shift of lattices, and guide modes are highly sensitive to transverse shift, while sideslipping affects guide modes only slightly.
Information preservation method for micro-scale flow with temperature variation
Authors: Xue Xiao-Bo  , Yao Zhao-Hui  , He Feng  ,   清华大学航天航空学院,北京  100084
Published: December 2020

Based on the information preservation(IP) method, a simple effective temperature model is presented. The IP method with new temperature model can simulate the flow which has temperature variation. Moreover, studies show that when the local density gradient of the simulated flow is large, it will cause numerical divergence if the second order central difference scheme of the mass conservation equation is used to update the information density. So the first order upwind scheme is recommended to update the information density for the flow with large density gradient.
Electron cyclotron current drive under different operational regimes in tokamak plasma
Authors: Gong Xue-Yu  , Peng Xiao-Wei  , Xie An-Ping  , Liu Wen-Yan  ,   南华大学核科学技术学院，衡阳  421001
Published: December 2020

With a given density profile of plasma,the temperature profiles of the plasma operating in the negative central magnetic shear mode,the H-mode and L-mode of conventional magnetic shear,are calculated respectively by applying the energy equation of electrons and ions,according to the thermal conductivity in different operational regimes.And then the electron cyclotron current drive and wave power deposition in the above modes are investigated with the relativistic Fokker-Planck equation incorporated into a ray tracing code.The result shows that in the mode of negative central magnetic shear,the current drive efficiency is the highest,meanwhile the zones of power deposition and current profile are wide.In the H-mode of conventional magnetic shear,the current drive efficiency is low,and the zones of power deposition and current profile are narrow.In the L-mode of conventional magnetic shear,the current drive efficiency is the lowest,the zones of power deposition and current profile are very narrow.
Noise as a representation for reliability of light emitting diode
Authors: Hu Jin  , Du Lei  , Zhuang Yi-Qi  , Bao Jun-Lin  , Zhou Jiang  ,   (1)西安电子科技大学技术物理学院，西安  710071; (2)西安电子科技大学微电子学院，西安  710071
Published: December 2020

Through the research of the internal structure of Light Emitting Diode (LED), we discovered that the interface trap density and diffusion current ratio are key factors determining the performance of LED, and they are also closely related to the reliability of LED. Among the many kinds of internal noises in LED, low-fre quency 1/f noise describes the interfoce trap density and diffuse current ratio effectively. Based on the mechanism of carrier number fluctuation and carrier mo bility fluctuation of 1/f noise, we put forward the electrical model and 1/f noi se model of LED. We also measured the electrical noise of the device over a wide range of current. Experimental results agree well with the proposed model. Usin g the experimental data, the relationship between noise and the performance and reliability of LED is established. It is proved that the larger the noise magnit ude, the nearer the current exponent is to 2, leading to the degradation of devi ce reliability and significant rise in device invalidation rate.
Deep level transient spectroscopy studies of Er and Pr implanted GaN films
Authors: Song Shu-Fang  , Chen Wei-De  , Xu Zhen-Jia  , Xu Xu-Rong  ,   (1)北京交通大学光电子研究所，北京  100044; (2)北京交通大学光电子研究所，北京  100044;中国科学院半导体研究所，北京  100083; (3)中国科学院半导体研究所，北京  100083
Published: December 2020

Deep level transient spectroscopy measurements were used to characterize the ele ctrical properties of metal organic chemical vapor deposition grown undoped, Er- implanted and Pr-implanted GaN films. Only one deep level located at 0.270 eV be low the conduction band was found in the as-grown GaN films. But four defect le vels located at 0.300 eV, 0.188 eV, 0.600 eV and 0.410 eV below the conduction b and were found in the Er-implanted GaN films after annealing at 900 ℃ for 30 mi n, and four defect levels located at 0.280 eV, 0.190 eV, 0.610 eV and 0.390 eV b elow the conduction band were found in the Pr-implanted GaN films after annealin g at 1050 ℃ for 30min. The origins of the deep defect levels are discussed. Aft er annealing at 900℃ for 30min in a nitrogen flow, Er-related 1538nm luminescen ce peaks could be observed for the Er-implanted GaN sample. The energy-transfer and luminescence mechanism of the Er-implanted GaN film are described.
Preparation and growth of SrBi4Ti4O15 ferroelectric thin film by sol-gel method
Authors: Huang Ping  , Xu Ting-Xian  , Cui Cai-E  ,   (1)太原理工大学理学院，太原  030024; (2)太原理工大学理学院，太原  030024;天津大学材料学院，先进陶瓷与加工技术教育部重点实验室，天津  300072; (3)天津大学材料学院，先进陶瓷与加工技术教育部重点实验室，天津  300072
Published: December 2020

The stable strontium bismuth titanate (SBTi) precursor solution were prepared us ing strontium chloride, bismuth nitrate, tetrabulyl titranate as raw materials, with citric acid as complex agent, ethylene glycol as cross linker, and ethanol absolute, water, hydrochloric acid as solvents of tetrabulyl titranate, strontiu m chloride, bismuth nitrate, respectively. SBTi thin films with enhanced a-axis orientation were prepared on Pt/Ti/Si02/Si substrates by the Sol-Gel method. Wit h the aid of ESEM and XRD, the effects of annealing time and the number of coati ngs on microstructure crystallization and growth behavior of SBTi thin films wer e investigated. The results indicate that the pyrochlore phase was restrained su ccessfully by layer-by-layer rapid thermal annealing method. The crystallization of the film was enhanced with the increase of coating number. Because of the an isotropic growth of SBTi crystals and the suppressed growth in (119) direction b y the thickness of single-annealed layer, the intensity of (200) and (119) peaks increase with the increase of layers, and the former increase more quickly.Howe ver, the intensity of (00l) peak decreased with the increase of layers, so the r elative intensity of (200) ［I(200)/I(119)，I(200)/I(0010)］ and (119) ［I(119)/ I(0010)］ increases with the increase of layers.
Effect of excitation frequency on microcrystalline silicon materials prepared by VHF-PECVD
Authors: Gao Yan-Tao  , Zhang Xiao-Dan  , Zhao Ying  , Sun Jian  , Zhu Feng  , Wei Chang-Chun  ,   南开大学光电子薄膜器件与技术研究所，天津  300071
Published: December 2020

Hydrogenated microcrystalline silicon (μc-Si:H) materials was prepared by plasm a enhanced chemical vapor deposition (PECVD) at silane concentration 6% and 7% w ith changing excitation frequency (40—70MHz). Relationship between excitation f requency and electrical, structural characteristics and deposition rate of the m aterials was studied. The results indicate that the crystalline volume fraction (Xc) decrease firstly and then increase with the increase of excitati on frequency. But the photosensitivity and the deposition rate be have adversely with the change of excitation frequency. The reason of change of structure and deposition rate of thin films with excitation frequency was studied by optical e mission spectroscopy.
A covariant gravitational field equation including the contribution of gravitational field
Authors: Lou Tai-Ping  ,   东北大学材料与冶金学院，沈阳  110004
Published: December 2020

Using the four-leg metric tensor λ(α)μ, a gravitational field 4-vector potential for index μ is defined as ω(α)μ≡-cλ(α)μ, and a covariant gravitational field equation that includes the gravitational field contribution is proposed as Rμν-gμνR/2+Λgμν=8πG(T(Ⅰ)μν+T(Ⅱ)μν)/c4, where Λ is Einstein's cosmic constant， T(Ⅰ)μν and T(Ⅱ)μν are energy-momentum tensor of pure matter part and pure gravitational field part, respectively. The covariant energy-momentum tensor of gravitational field that belongs to the part of the gravitational source can be constructed as T(Ⅱ)μν=c2(D(α)μρDρν(α)-gμνD(α)τγDτγ(α)/4)/4πG, where D(α)μν≡ω(α)μ;ν-ω(α)ν;μ. The static spherically symmetric gravitational field, the missing mass and the gravitational field quantization are discussed.
Photonic switching and logic gating with strongly nonlocal spatial optical solitons
Authors: Guo Qi  , Zhang Xia-Ping  , Hu Wei  , Shou Qian  ,   华南师范大学光子信息技术广东省高校重点实验室，广州  510631
Published: December 2020

Based on the (1+1)-dimensional Snyder-Mitchell model,discussed is the interactions of a pair of optical beams and the three optical beams with some frequencies and polarizations co-propagating in (1+1)-dimensional strong nonlocal nonlinear media.The exact analytical solutions of the interactions are obtained for the arbitrarily oblique incident beams.The interactions of strongly nonlocal spatial optical solitons are the specific cases of such interactions.Through the collisional behavior of the solitons,the photonic switching/logic are presented.The optimal designs of these photonic devices are discussed.
Experimental investigation of phase detection and compensation in coherent combining of fiber laser array
Authors: Xiao Rui  , Hou Jing  , Jiang Zong-Fu  ,   国防科技大学光电科学与工程学院，长沙  410073
Published: December 2020

Recently, the coherent combining of high power fiber laser array has become a hotspot of research internationally, and the phase control electronics contributed greatly to the success of the coherent combining. A high-speed wavefront sensor is introduced to sample the wavefront and actively control the phase state of each individual optical fiber in a high average power fiber laser array,and accordingly the phase-locked output of the whole system is achieved.A single signal lightwave is taken as example in the paper,the research results are presented.We conclude from the research results that when closing the phase control feedback loop the phasefront can be locked to the quiescent state of phase.
A novel fiber strain sensor based on laser’s transient regime
Authors: Luo Shao-Jun  , Guo Wen-Gang  , Yang Xiu-Feng  , Lü Fu-Yun  , Lü Chao  ,   (1)Lightwave Department,Institute for Infocomm Research,Singapore  637723; (2)Lightwave Department,Institute for Infocomm Research,Singapore  637723;南开大学物理科学学院，天津  300071;南开大学光电信息技术科学教育部重点实验室，天津  300071; (3)南开大学物理科学学院，天津  300071;南开大学光电信息技术科学教育部重点实验室，天津  300071
Published: December 2020

A novel fiber strain sensor based on the fiber laser's transient regime is reported. A Sagnac fiber loop and a fiber Bragg grating(FBG) that also acts as the sensing element form the linear Fabry-Perot cavity, in which a long-period grating(LPG) is inserted. The original peak wavelength of the FBG, whose bandwidth is 0.23nm, is 1557.98nm and located on the left side of the LPG dip (1557.4nm). The light reflected from the Sagnac loop and the FBG is transmitted through the LPG twice in each round trip, and the transmission loss increases with the strain-induced wavelength shift of the FBG, which in turn modifies the laser build-up time. The strain value can be obtained by measuring the build-up time of the laser. In the present experiment, the sensor's sensitivity and resolution can be adjusted by simply controlling the pumping level. When the pump pulse's high level and low level are 32 and 6mW, respectively, a sensitivity of 7×10-6ε/μs and resolution of 7×10-7ε are achieved.
Nonclassical feature of the field in the two-atom Tavis-Cummings model with atomic motion
Authors: Wang Zhong-Chun  ,   盐城师范学院物理系,盐城  224002
Published: December 2020

We study the nonclassical feature of the field in the two-atom Tavis-Cummings model with atomic motion using the quantum theory. The influence of atomic motion, the field mode structure and the field initial states on the properties of the light squeezing and the photon antibunching are discussed.
Influence of the discharge tube aperture on the deexcitation of lower level in UV Cu+ laser
Authors: Chen Gang  , Pan Bai-Liang  , Mao Bang-Ning  , Xia Ting-Ting  , Yao Zhi-Xin  ,   浙江大学物理系，杭州  310027
Published: December 2020

Based on the kinetic process of UV Cu+ laser in longitudinal nanosecond-pulsed discharge, the necessary condition for the population inversion between the upper and lower laser levels has been obtained. The experimental phenomenon that the laser power increases rapidly with the decrease of the discharge tube aperture has been analyzed theoretically. It is pointed out that the radiation trapping of lower laser level could be restrained effectively by reducing the tube radius, resulting in the increase of depopulation rate of lower laser level and the laser power.
Monte Carlo simulation of the effect of impact ionization in thin-film electroluminescent devices
Authors: He Qing-Fang  , Xu Zheng  , Liu De-Ang  , 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

By fitting the empirical pseudopotential band structure data using piecewise pol ynomials, an analytical band model of ZnS is presented for thin-film electrolumi nescent devices. The density of states and scattering rates are calculated using the above model. As compared with the results from the full band model, we have shown that our model, which takes less time, has the same precision as that obt ained from the full band model. Using Monte Carlo method, we simulated the field -dependent electron occupation functions of 1st and 2nd bands, electron energy d istribution functions under four-electron fields and the dependence of electron energy on time with or without impact ionization. This shows that the inter-vall ey scattering, inter-band scattering and impact ionization are important for tra nsporting electrons among valleys. Another important result is that the effect o f impact ionization on current multiplication and electron energy distribution i s also discussed.
Fabrication of nanoimprint mold by multilayer film deposition technique
Authors: Zhang Yong-Jun  , Li Wei  , Meng Xiang-Dong  , Yang Jing-Hai  , Hua Zhong  , Xu Jun  , Huang Xin-Fan  , Chen Kun-Ji  ,   (1)吉林师范大学物理学院，四平  136000; (2)吉林师范大学物理学院，四平  136000;南京大学物理系,固体微结构物理国家重点实验室，南京  210093; (3)南京大学物理系,固体微结构物理国家重点实验室，南京  210093
Published: December 2020

To overcome the difficulties in the fabrication of the nanoimprint mold with lin ewidth smaller than 50nm, we deposited a-Si/SiNx multilayer films in plasma enhanced chemical vapor deposition system and then prepared the relieo-n anomold on the cleaved section of the multilayer films by selectively etching or reactive ion etching process. Due to the slow deposition rate, the thickness of the sublayer, and therefore the size of the strips and grooves can be controlle d on the nanometer scale by altering deposition time. The smallest width we get by now is the 20nm strips and 20nm pitches，which is better than that fabricated by electron beam lithography.
Photosensitive breaking of fluorescent labeled microtubules and its mechanism
Authors: Xu Chun-Hua  , Liu Chun-Xiang  , Guo Hong-Lian  , Li Zhao-Lin  , Jiang Yu-Qiang  , Zhang Dao-Zhong  , Yuan Ming  ,   (1)中国科学院物理研究所,凝聚态物理中心光物理实验室,北京  100080; (2)中国农业大学生物学院植物生理学与生物化学国家重点实验室,北京  100094
Published: December 2020

It is reported that fluorescent microtubules may break under irradiation. However, the process and mechanism are not well understood. In this paper, we study the process of light-induced microtubule breaking by optical tweezers and find the breakup of protofilaments in microtubule is not simultaneous but proceeds step-by-step. After a series of biological experiments, we confirm that free radicals are the main reason for the photosensitive breaking of microtubule. According to the results of optical tweezers experiments, the mechanism of free radicals acting on microtubule is infered.
Research on EUV spectra of highly ionized titanium
Authors: Yang Zhi-Hu  , Du Shu-Bin  , Zeng Xian-Tang  , Ren Shou-Tian  , Song Zhang-Yong  , Su Hong  , Wang You-De  ,   (1)中国科学院近代物理研究所,兰州  730000; (2)中国原子能研究院,北京  102413
Published: December 2020

The spectrum of highly ionized titanium was studied by means of the beam-foil technique.Titanium ions were provided by the HI-13 tandem accelerator at China Institute of Atomic Energy.The experimental results are compared with those of laser-produced plasmas. Numerous lines attributed to Ti ⅩⅥ to ⅩⅧ ransitions have been identified,and three of them were newly measured, which were attributed to 2s2p2 4P3/2—2p3 2D3/2, 2s2p2 1S0—2sp3 1P1 and 4p 1P0—5d 1P1　transitions.
On line measurement of maximal torsional strength of micro level structure
Authors: Ruan Yong  , Huan Yong  , Zhang Da-Cheng  , Zhang Tai-Hua  , Wang Yang-Yuan  ,   (1)北京大学微电子学研究院，北京  100871; (2)中国科学院力学研究所非线性力学国家重点实验室，北京  100080
Published: December 2020

In the design and fabrication of microelectronic system(MEMS)devices, the process based on silicon is a main technolog which draws great attention of researchers. Bonding technology including silicon to glass and silicon to silicon is fundamental for bulk silicon MEMS devices.For MEMS devices, the bonding area is from the micrometer to millimeter scale, thus traditional methods to test bonding strength are no longer feasible. Measuring the strength at that scale has become the bottle-neck for MEMS development. We first define a new way, with which a series of single crystal cantilever beam was taken to test the maxal shear stress of bonding strength in the micro area.The experiment gives curves of torsional strength versus the bonding area and torsional strength versus the probe movement distance, the designer can use them to determine the bonding area according to the required torque for their MEMS devices.
Microwave transmission properties of tunable one-dimensional metamaterials
Authors: Wang Su-Ling  , Zhang Ye-Wen  , He Li  , Li Hong-Qiang  , Chen Hong  ,   同济大学波耳固体物理研究所, 上海  200092
Published: December 2020

A new design of metamaterials of one dimensional periodic structure is presented in this paper and the transmission parameters are measured. The experiment results indicate that when the bias voltage rises the left-hand passband will move toward higher frequencies. Based on transmission line theory, the dispersive equation of the tunable metamaterials is given. The results of the theory agree very well with those of the experiments.
Theoretical analysis of optimum parameters for complete forbidden bands of three-dimensional photonic crystals with typical lattice structures
Authors: Liu Huan  , Yao Jian-Quan  , Li En-Bang  , Wen Wu-Qi  , Zhang Qiang  , Wang Peng  ,   天津大学精仪学院激光与光电子研究所,天津  300072;教育部光电信息技术科学重点实验室,天津  300072;南开大学、天津大学联合研究院,天津  300072
Published: December 2020

Based on plane wave expansion method, the influence of factors such as lattice structure, dielectric constant ratio and filling ratio on three-dimensional photonic crystals with fcc, diamond and woodpile structures is studied. Of these structures, the fcc structure, owing to its high symmetry, is only fit for close-packed lattice prepared by inverted-opal method. The diamond structure easily generates good complete band gaps with high band gap ratio, and also the complete forbidden band that is needed can be obtained by adjusting some parameters in the experiment. The woodpile structure can produce big band gaps in a wider parameter range than the other two structures, which offers convenience for preparing three-dimensional photonic crystals in the laboratory. For all three kinds of three-dimensional photonic crystal structures, their band gap width and band gap ratio can be improved with the increase of dielectric constant ratio. In this paper, some interesting phenomena not noticed in the former papers are also presented.