bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of spatio-temporal chaos in coupled map lattices by state feedback
Authors: Jiang Pin-Qun  , Wang Bing-Hong  , Xia Qing-Hua  , Bu Shou-Liang  ,   中国科学技术大学近代物理系，合肥 230026
Published: December 2020

In this paper, the stable control of spatiotemporal chaos in coupled map lattices is realized by state feedback method. The feedback mode can be either delayed or without delay. The control mode can be either continuous or pulsate. The numerical simulation results demonstrate that this method is an effective one.
Wear resistance of Ti-implanted H13 steel using covering implantation technology
Authors: Yang Jian-Hua  , Zhang Tong-He  ,   (1)北京师范大学射线束和材料工程教育部重点实验室,北京　100875; (2)南通工学院物理部,南通　226007；北京师范大学射线束和材料工程教育部重点实验室,北京　100875
Published: December 2020

Ti and C ions extracted from a metal vapor vacuum arc ion source were implanted into H13 steel, with an implantation dose of 3×1017cm-2,an extractio n acceleration 48kV,and an average ion beam flux between 20 and 47μAcm-2. Rutherf ord backscattering (RBS) spectrum was used to measure the Ti concentration depth profile in H13 steel after Ti ion implantation. The surface microstructure observation was carried out using glancing xray diffraction analysis(GXRD). Wear test
results showed that the wear rate of the implanted layer dropped by about 40% for Ti ，C dual implantation. In addition, the Ti implantation was found to significant ly reduce the friction coefficient of steel H13. The wear mechanisms of the impl anted layer were discussed by results of RBS and GXRD.
Judd-Ofelt parameters determined experimentally for nanoparticles Gd2O3:Eu3+
Authors: Liu Chun-Xu  , Zhang Jia-Hua  , Lü Shao-Zhe  , Liu Jun-Ye  ,   中国科学院长春光学精密机械与物理研究所，激发态物理国家重点实验室，长春　130033
Published: December 2020

The spectral properties of nanoparticles Gd2O3:Eu3+ have been investigated by using Judd Ofelt theory at 77K. Intensity parameters Ωλ(λ＝2，4) were calculated using the experimental data of 5D0→7F2 and 5D0→7F4 transitions by taking the magnetic dipole transition 5D0→7F1 as reference. The intensity of the transition is almost completely unaffected by the local environment. It is indicated that intensity parameter Ωλ changes with the variation of diameter of nanoparticles Gd2O3:Eu3+,dramatically different from that of the bulk material.With decreasing diameter of the nanoparticles Gd2O3:Eu3+ from 135 to 15nm,the quantum efficiency of the emitting level 5D0 reduces from 23.6% to 4.6%. The smaller the diameter of nanoparticles Gd2O3:Eu3+, the bigger the ratio of surface to volume and the more the surface defect.It is the enhancing of the non radiation channels that results in the decrease of the quantum efficiency. The other two non radiation channels, charge (Eu3+-O2-) transfer state and multiphonon nonradiative re excitaton, were also studied.
Simulation of pulse shortening phenomena in high power microwave tube using PIC method
Authors: Gong Yu-Bin  , Zhang Zhang  , Wei Yan-Yu  , Meng Fan-Bao  , Fan Zhi-Kai  , Wang Wen-Xiang  ,   (1)电子科技大学大功率微波电真空器件技术国防科技重点实验室，成都 610054; (2)中国工程物理研究院应用电子学研究所，绵阳　621900
Published: December 2020

Pulse shortening is an universal phenomenon in highpower microwave tubes, which hinders the improvement of microwave output energy. So far, it is also an unres olved problem in the field of high-power microwave devices. In this paper, the relativistic backward wave tube (RBWO) is treated as an example to study the pul se shortening phenomena. The influences of explosive emission in the inner surface of RBWO and fluctuation of the relativistic electron beam on the pulse width and output power are investigated by means of the particle in cell(PIC) method .Through the simulation results, some useful conclusions have been drawn. The explosive emission in the surface of the slow wave structure due to intense elec tric field is one of the most important factors causing pulse shortening in high-power microwave tube. The fluctuation of the electron beam can also lead to pulse shortening. Some methods to overcome pulse shortening are given in this paper.
A new ADI-FDTD analysis in electromagnetic scattering
Authors: Yan Yu-Bo  , Li Qing-Liang  , Wu  Zhen-Sen
Published: December 2020

This paper proposes a new set of alternative direction implicit finite_di fference time_domain (ADI_FDTD) equations. In conventional ADI_FDTD, the update equation is related to several field components in cells nearby, which will lead to some difficulties in two regions:1) around the boundary region between the p erfectly ma tched layer (PML) and the scattering field; 2) around the adjacent bounda ry. Especially, in the region around the adjacent boundary, owing to the inciden t wave, we shou ld make a judgment about the situation of every component and modify the update equation. It is potential to make a solution to one_dimensional or two_dimension al problem. However, in three_dimensional (3D) analysis, one equation concerns w ith el even components and there exist several tens of cases to be modified. This makes the scheme very tedious and impossible to realize. This paper adopts the spli t field difference formation in the whole computation regime to analyse the sca ttering problem. Because the equations in the scattering field region have the same expr essi ons as those in PML absorber except for some coefficients, the boundary in the r egion mentioned above can be ignored. Due to simplicity of the split field equation, the new ADI_FDTD formula in 3D problem has only five compon ents to be cons idered and four modifications at the adjacent boundary to be made. Finally, we utilize this new method to compute some electromagnetic scattering numerical examples, and the results are in excellent agreement with those ob tained w ith other algorithm and the measured data. Moreover, the new method have 6-7 tim es higher efficiency in terms of the CPU time.
Influence of spatial localization on the threshold of quasi-state cavities in random lasers
Authors: Liu Jin-Song  , Wang Hong  ,   华中科技大学激光技术国家重点实验室,武汉　430074
Published: December 2020

Laser phenomena in random media have been studied bas ed on the localized theory for optical waves in finite random media. The relatio n ship between spatial localization and amplification for quasi_state modes ha s been investigated by use of the finite difference time domain method. T he spatial profile and the spectra characteristics of quasi_state modes are dete r mined by analyzing the localized processes of optical light beams in random medi a without gain. The amplification and threshold of quasi_state modes are analyze d in random media with gain. Results show that the quasi_state mode with a stron ger spatial localization has lower threshold and can be amplified preferentially .
Digital optical operation in multilateral systemby bacteriorhodopsin film
Authors: Gu Li－Qun  , Chen Gui－Ying  , Guo Zong－Xia  , Zhang Chun－Ping  , Tian Jian－Guo  , Zhang Guang－Yin  , Q. W. Song  ,   (1)Department of Electrical Engineering and Computer Science,Syracuse University,Syracuse，NY 13244，USA; (2)南开大学物理学院，天津　300071
Published: December 2020

Bacteriorhodopsin film has a special property of complementary suppression modulated transmission of yellow and blue beams. Resolving the transmission rate equ ations of the yellow and blue beams, the analytical formulae are obtained and gr aphic results are shown. We put forward a multilateralsystem computational mod el of digital optical matrix addition and subtraction operations without carry a nd abdication respectively. The novel model and frame of basic optical computati on are constructed, and the optimized project of digital optical matrix addition and subtraction operations are designed.
Birefringence phenomena in a random distributed　microstructure fiber
Authors: Hu Ming－Lie  , Wang Qing－Yue  , Li Yan－Feng  , Ni XiaoChang  , Zhang Zhi－Gang  , Wang Zhuan  , Chai Lu  , Hou Lan－Tian  , Li Shu－Guang  , Zhou Gui－Yao  ,   (1)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; (2)燕山大学红外光纤与传感研究所，秦皇岛　066004
Published: December 2020

A random distributed microstructure fiber in which strong asymmetry was introduced around a puresilica core was reported. Femtosecond laser pulses with duration of 35?fs from a Ti:sapphire laser oscillator were coupled into this fiber, and then periodic color rings were observed from the side of the fiber when the supercontinuum light propagated along the fiber. We attributed this phenomenon to
the polarization beating of the supercontinuum light in this highly birefringent microstructure fiber. Measurement showed that the fiber had a beat length of approximately 1?mm at a central wavelength of 600?nm, which is in good agreement with the result of calculation. A new method is proposed to measure the beat length directly in a highly birefringent microstructure fiber.
Determination of upconversion state lifetime and upconversion mechanisms of Er3+ in tellurite glasses
Authors: Wen Lei  , Yang Jian-Hu  , Hu Li-Li  ,   中国科学院上海光学精密机械研究所,上海　201800
Published: December 2020

We compared the lifetime values of the upconversion state for Er3+doped tellurite glass with and without halide ions as determined by direct excitation mechanism, with the results measured by upconversion excitation method. The results indicate that upconversion excitation lengthens the lifetime value largely compared with the direct excitation. The intensity of the upconversion fluorescen ce of the two kinds of glasses was discussed, which showed that it becomes stron ger with the addition of the halide ions than that without the halide ions. The upconversion mechanisms and power-dependent intensities were also determined and explained.
A study on luminescence dynamics of solid-state cathodoluminescence of MEH-PPV
Authors: Qu Chong  , Xu Zheng  , Teng Feng  , Qian Lei  , Yu Wen－Ge  , Quan Shan-Yu  , Xu Xu-Rong  ,   (1)北京交通大学光电子技术研究所,北京　100044; (2)北京交通大学光电子技术研究所,北京　100044　临沂师范学院物理系,临沂　276005　; (3)北京交通大学光电子技术研究所,北京　100044　天津经济技术开发区博士后工作站天津中环三津有限公司分站,天津　300457
Published: December 2020

Based on the layer-optimized method, the devices of sandwiched structure are pr oduced by compounding MEH-PPV and SiO2 In three different voltage regions of alternating current, the devices luminesce differently. When the voltage is low, red emission is obtained; and if the voltage is high, blue emission is acquired. The superposition of the above two emissions is obtained when the voltage is moderate. The red or blue emission belongs to the solidstate cathodoluminesc ence, it originates from the accelerated electrons in SiO2, which bombard the organic layers. By the study on the optic characteristics of the devices, the sc opes and regulations of spectra shift are analyzed.
Boron-doped silicon nanowires grown by plasmaenhanced chemical vapor deposition
Authors: Zeng Xiang－Bo  , Liao Xian－Bo  , Wang Bo  , Diao Hong－Wei  , Dai Song－Tao  , Xiang Xian－Bi  , Chang Xiu－Lan  , Xu Yan－Yue  , Hu Zhi－Hua  , Hao Hui－Ying  , Kong Guang－Lin  ,   (1)清华大学物理系，原子分子纳米科学教育部重点实验室,北京　100084; (2)中国科学院半导体研究所表面物理国家重点实验室,北京　100083
Published: December 2020

Boron-doped (B-doped) silicon nanowires have been successfully synthesi zed by plasma-enhanced chemical vapor deposition (PECVD) at 440℃ using silane as the Si source, diborane(（B2H6）) as the dopant gas and Au as the catalyst. It is desirable to extend this technique to the growth of silicon nanowire pn jun ctions because PECVD enables immense chemical reactivity.
Cardy-Verlinde formula and thermodynamics of the two parameter five-dimensional rotating black hole*
Authors: Zhang Li-Chun  , Zhao Ren  ,   雁北师范学院物理系,大同　037000
Published: December 2020

In this paper, in the two-parameter five-dimensional(5D) rotating black hole, we discuss the thermodynamic parameters corresponding to the black hole's horizon and the thermodynamic parameters corresponding to the cosmological horizon. It is obtained that the entropy of cosmological horizon can be written in the form of Cardy-Verlinde formula. However, if we want to write the entropy of the bla ck hole's horizon in the form of Cardy-Verlinde formula, we have to use the met hods offered by Abbott and Deser to calculate the mass of the 5D black hole with double- spinning parameter. Through the research, we can give the relation among the thermodynamic parameters of the 5D black hole, that is, the differential ex pression of the first law of thermodynamics.
On the prediction of chaotic time series using a new generalized radial basis function neural networks
Authors: Li Jun  , Liu Jun-Hua  ,   西安交通大学电气工程学院,西安  710049
Published: December 2020

Radial basis function (RBF) networks have been widely used for function approximation and pattern classification as an alternative to conventional feedforward neural networks. A novel generalized RBF neural network model is presented. The form of RBF is determined by a generator function, and then an easily implementable gradient decent learning algorithm for training the new generalized RBF networks is given. Simultaneously, a fast dynamic learning algorithm based on Kalman filter is also proposed to improve the performance and accelerate the convergence speed of the new generalized RBF networks. The generalized RBF neural networks based on Kalman filtering dynamic learning algorithm is then applied to the chaotic time series prediction on the Mackey-Glass equation and the Henon map to test the validity of this proposed model. Simulation results show that the new generalized RBF networks can accurately predict chaotic time series. It provides an attractive approach to study the properties of complex nonlinear system model and chaotic time series.
Optical feedback characteristics of two orthogonally polarized light beams in a HeNe laser during cavity tuning
Authors: Liu Gang  , Zhang Shu-Lian  , Xu Ting  , Zhu Jun  , Li Yan  ,   清华大学精密仪器测试技术与仪器国家重点实验室，北京  100084
Published: December 2020

We can get optical feedback signals of the two orthogonally polarized light beams in a HeNe laser during the cavity tuning process when the period of the driving signal of the feedback mirror is set much shorter than that of the cavity mirror. The experiments are done under three different optical feedback conditions: only perpendicular light is fed back, only parallel light is fed back and both lights are fed back. When both lights are fed back, there is a phase delay less then 180 degrees between the two lights' intensity curves. When only one polarized light is fed back into the laser cavity, the two lights' intensity curves are inverted with respect to each other. We can subtract one light's intensity curve from the other one to improve the sensitivity of the optical feedback system. Especially when only perpendicular light is fed back, both lights' modulation amplitudes are large in a wide range of gain curve with the DC component stable. This property can be used to reduce the miscount of the system.
Laser-induced thermal analysis for mask layer of transmitted-aperture type super-RENS in optical storage
Authors: Shen Quan-Hong  , Xu Duan-Yi  , Qi Guo-Sheng  , Hu Heng  , Liu Rong  ,   清华大学精密仪器与机械学系，光盘国家工程研究中心，北京  100084
Published: December 2020

The forming of transmitted-aperture in Sb layer of Super-RENS was studied based on laser-induced thermal model with Gauss assumption. The optical transmit model was created with optical admittance characteristic matrix. A numerical simulation was carried out by FEMLAB to understand the forming process of the aperture. The simulation results showed that transmitted aperture would not be formed until the exposure power exceeded a threshold within a certain pulse time, further more, the aperture size would be increased if the power was raised. The static writing experiment for transmitted-aperture type Super-RENS was carried out. The experiment results well agree with the simulation. It is concluded that a laser-induced thermal model could well describe the forming of aperture in Sb layer of transmitted-aperture type Super-RENS in optical data storage.
Suppression of pulse impairments due to cross-phase modulation by frequency domain phase conjugation
Authors: Bu Yang  , Wang Xiang-Zhao  ,   中国科学院上海光学精密机械研究所信息光学实验室，上海  201800
Published: December 2020

The use of optical frequency domain phase conjugation (FDPC) to suppress pulse impairments due to cross-phase modulation (XPM) in optical fiber systems is proposed. Evolution of Gaussian pulses in the system using midway FDPC is analyzed theoretically and simulated numerically. It is found that pulse waveform impairments induced by XPM can be suppressed effectively by FDPC. The impairments due to group-velocity dispersion and self-phase modulation can be suppressed simultaneously. Suitable initial time delay and pulse chirp of pulses can improve the suppression and compensation for the distortion.frequency domain phase conjugation, cross-phase modulation, group-velocity dispersion, self-phase modulation can be suppressed simultaneously. Suitable initial time delay and pulse chirp of pulses can improve the suppression and compensation for the distortion.
Dopant effects on martensitic transition and magnetic properties of Ni51.5Mn25Ga23.5 materials
Authors: Zhu Zhi-Yong  , Wang Wen-Quan  , Miao Yuan-Hua  , Wang Yan-Song  , Chen Li-Jie  , Dai Xue-Fang  , Liu Guo-Dong  , Chen Jing-Lan  , Wu Guang-Heng  ,   (1)吉林大学物理学院，长春  130023; (2)中国科学院物理研究所  北京凝聚态物理国家实验室，北京  100080
Published: December 2020

Ni51.5Mn23M2Ga23.5 materials are to reveal the dopant effect on the martensitic transition and the magnetic propert ies. We found that the dopants Ti, Zr, Hf, V, Nb, and Ta lower the martensitic transition temperature of the sample, but W increases it. The martensitic trans ition temperature is very sensitive to the atomic size when the valence electron ic concentration keeps constant for the doping elements. The dopants Ti, Zr, Hf or V decrease the magnetic moment of Mn atom in the martensite at low temperatur e, while Nb, Ta or W enhance it. A corresponding variation of TC of t he materials is not observed, which indicates that the influence of the lattice change of martensitic transition on the magnetic properties should also be ta lken into account.
Blue shift of Raman peaks of coated BaTiO3 nanoparticles
Authors: Xu Cun-Ying  , Zhang Peng-Xiang  , Yan Lei  ,   昆明理工大学材料与冶金工程学院，昆明  650093
Published: December 2020

Nanosized BaTiO3 coated with dodecybensulphonic acid (DBS) and stearic acid (St) was prepared using the hydrothermal procedure. The average size of DBS/BaTiO3 and St/BaTiO3 is about 60nm, much smaller than the that of 100nm of the uncoated particles prepared under similar conditions. Raman spectra from the coated particles were measured, and scattering signals from both BaTiO3 and the coatings were observed. It was found that the Raman peaks of BaTiO3 shift toward higher frequency(blue shift), instead of the red shift generally observed when the particle size is reduced, and the linewidth increases when the grain is coated. Meanwhile, we found that different coating show different amount of Raman shifts. We discussed the possible origin of the blue shift.
Effect of external magnetic field on the coherence properties of degenerated two-level atomic system
Authors: Zhao Jian-Ming  , Wang Li-Rong  , Zhao Yan-Ting  , Ma Jie  , Xiao Lian-Tuan  , Jia Suo-Tang  ,   量子光学和光量子器件国家重点实验室，山西大学物理电子工程学院，太原  030006
Published: December 2020

The electromagnatically induced absorption (EIA) is obtained in degenerated cycled cesium atomic two-level transition of 6S1/2F=4—6P3/2F'=5. The effect of the magnetic field on coherence of the atom is also investigated experimentally. When external magnetic field is applied, the mixed structure of electromagnetically induced absorption and transparency is obtained in the transition of 6S1/2F=4—6P3/2F'=5. The experimental results are in agreement with theoretical analysis of C.Y. Ye et al. (2002).
Fine tracking in space laser communication
Authors: Liu Xi-Min  , Liu Li-Ren  , Sun Jian-Feng  , Lang Hai-Tao  , Pan Wei-Qing  , Zhao Dong  ,   中国科学院上海光学精密机械研究所信息光学实验室，上海  201800
Published: December 2020

Fine tracking plays an important role in space laser communication, and the Fine Pointing Mirror(FSM) is a key component in fine tracking system. Based on the optical vector reflection law, the accurate optical characteristics of FSM is deduced, which serves as the theoretical basis for fine tracking study. A fine tracking control system based on the FSM accurate optical characteristic is introduced. For system regulation, two important improvements to the simplex method are obtained. Then a digital simulation of the fine tracking is given. So an accurate control of the FSM is accomplished and the accuracy of the fine tracking system is improved. The diffractive superresolution theory is introduced into the space laser communication. By using 3-zone phase pupil filter, the point spread function (PSF) of the optical system is modified, and the optical energy distribution at the focal plane is modified accordingly. Then the diffraction spot size is decreased, and the optical resolution is increased, so the accucy of the fine tracking system is improved.
Application of phase features in recognizing 3-D objects
Authors: Shen Jin-Yuan  , Li Xian-Guo  , Chang Sheng-Jiang  , Zhang Yan-Xin  ,   (1)南开大学现代光学研究所,光电信息技术科学教育部重点实验室,天津  300071; (2)郑州大学信息工程学院，郑州  450052
Published: December 2020

A new approach based on phase features combined with neural network model is proposed for recognizing 3-D objects. The phase features of an object were extracted by wavelength-scanning digital holography and numerical reconstruction technique. A BP neural network with one hidden-layer trained by reconstructed images of three pyramids was used to recognize other pyramids with some variance, and the correct recognition rate of these pyramids is up to 100%. The simulation results demonstrate that the method is effective.
Three-photon-absorption induced fluorescence and optical limiting properties of a new organic compound
Authors: Liu Jun-Hui  , Mao Yan-Li  , Ma Wen-Bo  , Wu Yi-Qun  , Han Jun-He  , Zhai Feng-Xiao  ,   (1)河南大学物理与信息光电子学院，开封  475001; (2)中国科学院上海光学精密机械研究所，上海  201800
Published: December 2020

Three-photon-absorption-induced frequency up-conversion fluorescence emission has been observed in a solution of 4-2-(7-(4-amido styrene)-9,9-di(2-ethyl hexyl)-9H-fluorene-2-) ethylene) aniline (BASF) in N,N-dimethylformamide(DMF), pumped with 38ps Q-switched 1064nm laser pulses. The spectral peak of the observed fluorescence emission is located in the 456—775nm range, and the intensity dependence of the visible emission on the IR excitation obeys the cubic law. At higher solute concentration and moderate IR excitation intensity levels, obvious optical limitation behavior has been observed due to three-photon-absorption. The measured nonlinear absorption coefficient and the molecular three-photon-absorption cross section are 4.34×10-20cm3/Ｗ2 and 2.4×10-39cm6/Ｗ2, respectively.
Self-starting mode-locked femtosecond Ti:sapphire laser using saturable Bragg reflector(SBR)
Authors: Wang Yi-Shan  , Liu Hong-Jun  , Cheng Zhao  , Zhao Wei  , Wang Yong-Gang  , Ma Xiao-Yu  , Zhang Zhi-Gang  ,   (1)天津大学精密仪器与光电子工程学院超快激光实验室,天津  300072; (2)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;天津大学精密仪器与光电子工程学院超快激光实验室,天津  300072; (4)中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室，西安  710068
Published: December 2020

Stable self-starting mode-locking states in a compact Ti: sapphire laser incorporating a home-made SBR with low loss double quantum-well and low temperature and surface state hybrid absorber are investigated experimentally. The three mode-locking states, i.e. the passive mode-locking with a saturable absorber, the solition mode-locking and the Kerr-lens mode-locking have been successfully demonstrated. In this laser, chirped mirrors are used for dispersion compensation, and the 18 fs pulses are produced from the Kerr-lens mode-locking at 4.5W pump power, and output power is 150mW.
Application of dispersion compensator based on chirped fiber gratings in ultra long-hual DWDM system
Authors: Tan Zhong-Wei  , Zheng Kai  , Liu Yan  , Fu Yong-Jun  , Chen Yong  , Cao Ji-Hong  , Ning Ti-Gang  , Dong Xiao-Wei  , Ma Li-Na  , Jian Shui-Sheng  ,   北京交通大学光波技术研究所，北京  100044
Published: December 2020

An application of chirped fiber grating in an ultra long-hual DWDM system is presented in the paper. The interaction between the chirped fiber gratings at different wavelengths are analyzed for the first time. A method of prolonging the distance between gratings to surpass the coherent length of the light source is proposed to suppress the interaction between the gratings. By using chirped fiber gratings, we realized a transmission system of 8×10Gbit/s signal on G.652 fiber over 1500km.
Wavelet-transform in terahertz time-domain spectroscopy
Authors: Deng Yu-Qiang  , Xing Qi-Rong  , Lang Li-Ying  , Chai Lu  , Wang Qing-Yue  , Zhang Zhi-Gang  ,   (1)天津大学精密仪器与光电子工程学院超快激光研究室，光电信息技术科学教育部重点实验室，天津  300072; (2)天津大学精密仪器与光电子工程学院超快激光研究室，光电信息技术科学教育部重点实验室，天津  300072;北京大学信息科学与技术学院量子电子学研究所，北京  100871
Published: December 2020

The application of the wavelet-transform to terahertz time-domain spectroscopy (THz-TDS) is described. Using wavelet-transform to analyze the time-domain signals passing through water vapor measured by time-domain spectroscopy, we got the absorption spectra of water vapor in the frequency range from 0.5 to 2.5THz, which agree well with the results reported in the literature. Moreover, wavelet-transform in THz-TDS opens up a new way for the analysis of the time-domain properties of absorption spectra of water vapor.
Gain characteristics of high-concentration Er3+/Yb3+-codoped phosphate fiber amplifier
Authors: Song Feng  , Su Rui-Yuan  , Fu Qiang  , Qin Bin  , Tian Jian-Guo  , Zhang Guang-Yin  ,   南开大学光子学中心，天津  300071
Published: December 2020

The gain characteristics of Er3+/Yb3+-codoped phosphate fiber amplifier pumped with light of 980nm wavelength are theoretically studied in this paper. With the help of rate equations and the propagation equation of Er3+/Yb3+-codoped phosphate fiber, we analyzed the effects of concentration of erbium and ytterbium ions, pump power, signal power and fiber length on the gain characteristics of the co-doped fiber amplifier. Comparison with singly erbium-doped fiber amplifier was also made. It is shown that the sensitization of Yb3+ decreases the clustering effect of erbium ions in the fiber and the gain and pump efficiency of Er3+/Yb3+ co-doped fiber are apparently higher than that of singly erbium-doped fiber. Numerical results also demonstrate that considerable signal gain of 10dB can be achieved in a 3.2cm-long fiber amplifier with 20dBm(100mW) pumping power at 980 nm.
High-frequency properties of the disk-loaded waveguide filled with plasma
Authors: Zhang Yong  , Mo Yuan-Long  , Xu Rui-Min  , Yan Bo  , Xie Xiao-Qiang  ,   (1)电子科技大学电子工程学院微波工程系,成都  610054; (2)电子科技大学物理电子学院,成都  610054
Published: December 2020

Based on the Maxwell equations, the general equation of the slow-wave structure filled with plasma in the finite magnetic field is derived. The dispersion equation and interaction impedance expression of the disk-loaded waveguide filled with plasma in the strong longitudinal magnetic field are studied. The result shows that the frequency of the TM01 mode upshifts and interaction impedance increases as the density of the plasma increases. When a periodic structure is loaded with plasma, the spectrum consists of abundant TG modes (Trivelpiece-Gould modes). As the plasma density increases to a certain degree, the TM01 mode of the disk-loaded waveguide overlaps the TG mode and these two modes will couple with each other and form the new hybrid modes G1, G2. If the relativistic Traveling-Wave Tube (TWT) works on the hybrid mode, there will be new working mechanism.
Calculation of conductance of quantum point contact in STM
Authors: Li Qian-Guang  , Xu Hai-Xia  , Li Yi  , Li Zhi-Yang  ,   华中师范大学物理科学与技术学院,武汉  430079
Published: December 2020

The conductance of quantum point contact in scanning tunneling microscope is calculated by modal matching and scattering matrix method. The results show that the conductance of the nano-structure formed during quantum point contact in STM is quantized, which becomes more obvious as the radius and cone angle of the nano-structure decreases. The quantitative behavior could be observed more easily with semiconductors than with metals.
Electronic energy loss of the latent track in heavy ion-irradiated polyimide
Authors: Sun You-Mei  , Liu Jie  , Zhang Chong-Hong  , Wang Zhi-Guang  , Jin Yun-Fan  , Duan Jing-Lai  , Song Yin  ,   中国科学院近代物理研究所,兰州  730000
Published: December 2020

In the interaction process of a swift heavy ion (SHI) and polymer, a latent track with radius of several nanometers appears near the ion trajectory due to the dense ionization and excitation. To describe the role of electronic energy loss (dE/dX)e, multi-layer stacks (with different dE/dX) of polyimide (PI) films were irradiated by different SHIs (1.158GeV Fe56 and 1.755GeV Xe136) under vacuum at room temperature. Chemical changes of modified PI films were studied by Fourier Transform Infrared (FTIR) spectroscopy. The main feature of SHI irradiation is the degradation of the functional group and creation of alkyne. The chain disruption rate of PI was investigated in the fluence range from 1×1011 to 6×1012 ions/cm2 and a wider energy stopping power range (2.2 to 5.2 keV/nm for Fe56 ions and 8.6 to 11.3 keV/nm for Xe136 ions). Alkyne formation was observed over the electronic energy loss range of interest. Assuming the saturated track model (the damage process only occur in a cylinder of area σ), the mean degradation and alkyne formation radii in tracks were deduced for Fe and Xe ion irradiation, respectively. The results were validated by the thermal spike model and the threshold electronic energy loss of track formation Set in PI was deduced. The analysis of the irradiated PI films shows that the predictions of the thermal spike model are in qualitative agreement with the curve shape of experimental results.
Magnon lifetime of two-dimensional insulating ferromagnet at low temperature
Authors: Cheng Tai-Min  , Xianyu Ze  , Du An  ,   东北大学理学院物理系，沈阳  110006
Published: December 2020

A magnon-phonon interaction model is built in two-dimensional insulating ferromagnet. By using Matsubara Green function theory, we have studied the magnon damping -ImΣ*(1)(k), and calculated the magnon damping -ImΣ*(1)(k) curve on the main symmetric point and line in the Brillouin zone for different parameters of the system. It is concluded that at the boundary of Brillouin zone there is a strong magnon damping. But the magnon damping is very small on zones of small wave vectors, and magnon damping has maximal value at very low temperature. The influences of longitudinal phonon and transverse phonon on the magnon damping are compared, and the influences of the parameters are also illustrated. According to expression -ImΣ*(1)(k)=/(2τ), the magnon lifetime is discussed.
Energy spectrum analysis of donor-center quantum dots
Authors: Gu Juan  , Liang Jiu-Qing  ,   山西大学理论物理研究所，太原  030006
Published: December 2020

Within the effective mass approximation, the energy spectra of the donor- center quantum dot system in Gaussian confining potential are calculated by using the method of numerical matrix diagonalization. The results show that the property of the ground and low-lying states of the quantum dot is rather sensitive to the size and the strength of confinement potential.
Study of temperature dependent electroluminescence of InGaN/GaN multiple quantum wells using low temperature scanning near-field optical microscopy
Authors: Xu Geng-Zhao  , Liang Hu  , Bai Yong-Qiang  , Lau Kei-May  , Zhu Xing  ,   (1)北京大学物理学院人工微结构与介观物理国家重点实验室，北京  100871; (2)香港科技大学电子工程系光子学技术中心，香港
Published: December 2020

Though GaN based semiconductor materials and devices have achieved giant commerc ial success, there were few reports on their electroluminescent near-field optic al studies at low temperature. In this paper we present our results of the elect roluminescent near-field images and spectra at both room temperature and liquid nitrogen temperature by using a lab-made low temperature scanning near-field opt ical microscope. We found that with the decreasing of sample temperature, the fl uctuation of electroluminescent intensity in the near-field images is reduced gr eatly and the peak photon energy of the spectra emitted from the quantum wells e xhibits a blue-shift at first and then a red-shift. A new spectral peak emerges at higher photon energy at liquid nitrogen temperature. According to our analysi s, this higher photon energy peak is attributed to the transition from the botto m of conduction band to the acceptor energy states in the p-GaN cap layer.
Density functional theory study on the atomic structure and electronic states of Cu(100) (2×22)R45°-O surface
Authors: Cai Jian-Qiu  , Tao Xiang-Ming  , Chen Wen-Bin  , Zhao Xin-Xin  , Tan Ming-Qiu  ,   浙江大学物理系，杭州  310027
Published: December 2020

The surface structure, relaxation, and oxygen adsorbed (2×22)R45° Cu(100) surf ace are studied by ab initio total energy calculation. The calculated atomic str ucture for the Cu(100) (2×22)R45°-O surface is quite close to the experiments except the positions of surface layer Cu atoms. The adsorbed O atoms is lying ap proximately 0.02 nm above the outermost Cu layer and produces a hybridized band and yields some localized surface states around 6.4 eV below EF. The calculated work function for studied oxygen adsorbed surface phase is 4.58 eV, w hich is close to that of clear Cu(100) surface (～4.53 eV). It is concluded that the bonding between adsorbate and substrate copper atoms is approximately limit ed to the first surface layer.
Influence of O adsorbed on different surfaces of NixCu1－x on the segregation of Cu
Authors: Zhang Hui  , Zhang Guo-Ying  , Wang Rui-Dan  , Zhou Yong-Jun  , Li Xing  ,   沈阳师范大学物理科学与技术学院，沈阳  110034
Published: December 2020

The atomic structural models of the(100) and (110) surface of the Nix Cu1-x disordered binary alloy were set up when surface segregation is considered or not by computer programming.Then the models of the chemisorption of O on both surfaces were set up with the coverage θ=0.5. The electronic struc ture of O chemisorbed on the (100) and (110) surfaces of the NixCu1-x disordered binary alloy was calculated (considering and not consider ing the segregation).The calculated results show that (1) the chemisorption lowe rs the surface density of states of the disordered binary alloy,the energy band is widened, and the covalent bonds between the d electron of Ni and the s and p electron of O are stronger than that of Cu, (2) the O adsorbed on the (110) surf ace is more stable than on the (100) surface, and (3) the chemisorption of O on the surface restricts the surface segregation of Cu and this kind of influence i s obvious at the first layer.
Phase structures and local electron structures of Gd-doped YBa2Cu3O7－δ systems
Authors: Chen Zhen-Ping  , Xue Yun-Cai  , Su Yu-Ling  , Gong Shi-Cheng  , Zhang Jin-Cang  ,   (1)上海大学物理系，上海  200463; (2)郑州轻工业学院技术物理系，郑州  450002
Published: December 2020

The Gd substituted Y1-xGdxBa2Cu3O7-δ systems are studied systematically by positron annihilation and x-r ay diffraction. The x-ray results show that the crystal parameters and crystal v olume of the systems increase with the increase of Gd content. However, all the substituted samples maintain the single orthorhombic phase as YBa2Cu3O7-δ (YBCO) sample does. The positron annihilation result s show that positron lifetimes depend on the Gd content strongly. According to t he positron annihilation result, the local electronic density on Cu-O chain is c alculated. The result shows the local electronic density decreases with the incr ease of the Gd content, while the Tc increases with the decrease of t he local electronic density. The relationship between the local electronic densi ty and superconductivity is different from the substitution on Cu site, which ma y be one of the reasons why the mixed rare earth cuprate superconductor has a hi gher critical electric current density than the YBCO. These experimental results give the corresponding positron experiment data for the application of cuprate superconductors and study of the mechanism.
Influence of NiFeNb seed layer on hysteresis loops of permalloy films
Authors: Zhang Cui-Ling  , Zheng Rui-Lun  , Teng Jiao  ,   (1)北京科技大学材料科学与工程学院，北京  100083; (2)西南师范大学物理学院，重庆  400715; (3)重庆工商大学理学院，重庆  400067
Published: December 2020

The(Ni79Fe21)1-xNbx(5nm)/(Ni79Fe21) (20nm)/Ta(3nm) films are prepared with the (Ni79Fe21)1-xNbx seed layers. The grain size, hyste resis loops and surface roughness of samples are measured and the variations of hysteresis loops with the Nb atomic concentration in the seed layers are analyze d. The results show the microstructure of the permalloy films grown on the seed layers is improved. The coercivity and the (B·H)m in the hysteresis loop is minimal at x=23%.　The influence of seed layers on the hysteresis loops is partly duc to the different excitation energy of different seed layers, which result in different roughness of the surface of the seed layers film, hence the different microstructure of the permalloy films.
Effect of Dy-doping on the properties of Sr2Bi4Ti5O18 ferroelectric ceramics
Authors: Qiang Feng  , Zhu Jun  , Mao Xiang-Yu  , Chen Xiao-Bing  ,   扬州大学物理科学与技术学院,扬州  225002
Published: December 2020

Ferroelectric Sr2Bi4-xDyxTi5O18 (SBDT-x, x= 0—0.20) ceramic samples were prepared using the conventional solid-state reaction method. x-ray diffraction patterns (XRD) of SBDT-x ceramics show that doping with a small amount of Dy does not change the crystal structur e of Sr2Bi4Ti5O18 (SBTi). Their Curi e temperature (Tc) and dielectric loss (tanδ) decrease with Dy dopin g amount. The remnant polarization (2Pr) of SBDT-x increases at first , then decreases with increasing of Dy content. When Dy content is 0.01, the 2Pr reaches a maximum value of 20.1 μC·cm-2. The variation of 2Pr for SBDT-x relates to space charge density, internal strain an d structure distortion. (Bi2O2)2+ layer acting as an insulating layer and space charge storage plays an important role in their ferroelectric properties in BLSFs. The incorporation of doping ions into (Bi2O2)2+ layer may destroy its original function and deteriorate the ferroelectric property.
Photorefractive gain property and optimization of dynamic holographic gratings in arbitrarily cut sillenite crystal
Authors: Hu Yi  ,   北京交通大学物理系，北京  100044
Published: December 2020

We study the influence of vectorial wave coupling on the wave eigenmodes in an arbitrarily-cut photorefractive and optically active piezo-electric sillenite cry stal, and solve the vectorial equations for weak two-wave coupling. We deal exac tly with the vectorial wave coupling in an optically inactive piezo-electric cry stal by solving the scalar equations. By doing so we calculate the signal gains in the optically active and the optically inactive crystals and discuss the cont ributions of the isotropic and the anisotropic coupling to the gain, respectivel y. We optimize the signal gain of the optically active crystal and apply the re sults to a BSO and BTO crystal. We also investigate the influence of the piezo-e lectric and elasto-optic effect on the optimum gain for (110),(111),(112) and th eir equivalent cuts.
Hyperchaos synchronization and control using intermittent feedback
Authors: Ma Jun  , Liao Gao-Hua  , Mo Xiao-Hua  , Li Wei-Xue  , Zhang Ping-Wei  ,   (1)广西民族学院电子与通信工程学院，南宁  530006; (2)广西师范大学物理与信息工程学院，桂林  541004; (3)湖南理工学院物理与电子信息系，岳阳  414006; (4)兰州理工大学物理系，兰州  730050
Published: December 2020

Based on the stability theory,intermittent feedback scheme is proposed to synchronize and control the four-dimensional continuous hyperchaotic Rssler and LC systems. The systems are directed to reach arbitrary desired target within about 8 to 35 time units and realize complete synchronization within about 15 to 50 time units under this scheme by selecting right autonomous period Ta, controlling period Ts and gain coefficient k.The advantage of this scheme is that the controller is designed analytically in detail,not only relying on the common numerical simulation.The controller works only on certain period and the system develops freely in other periods. The numerical simulation results confirmed its effectiveness and gave evidence that shorter transient period before reaching desired target requires bigger feedback coefficient k,and it is consistent with the theoretical analysis.
Cellular automaton model of traffic flow based on safety driving
Authors: Mou Yong-Biao  , Zhong Cheng-Wen  ,   西北工业大学翼型、叶栅空气动力学国家重点实验室，西安  710072
Published: December 2020

Considering the condition of having a stationary vehicle ahead, a new one-dimensional cellular automaton model emphasizing high safety is proposed to reduce the probability of rear-end collision in the Nagel-Schreckenberg model. The simulation results reveal the presence of metastable state, nonequilibrium phase transition and hysteresis effects, which have been observed in real traffic. Due to the introduction of the safety probability, traffic flow near the critical density will turn to a synchronized flow at low speed, rather than the jam state. So the probability of rear-end collision will be reduced and the traffic capacity may be increased at high traffic density.
Spectrum analysis on dissipative motion in finite systems
Authors: Yuan Chang-Qing  , Zhao Tong-Jun  , Wang Yong-Hong  , Zhan Yong  ,   河北工业大学理学院，天津  300130
Published: December 2020

Dynamical problems about energy dissipation in a finite multi-degree of freedom Hamiltonian system are studied. The energy dissipation in the relevant system is realized by numerical simulation. By employing power spectrum analysis on q(t) or p(t) of the motion in the relevant system, it is found that during the dissipative process, distribution of the power spectral density about the motion extends to both lower and higher frequencies. The more irrelevant degrees of freedom are, the broader the distribution extends. Higher frequencies decrease as time evolves but there are no remarkable changes for lower frequency components.
Y-splitting of dark stripe in photoisomerization polymers
Authors: Li Yang-Gang  , Wang Xiao-Sheng  , She Wei-Long  , Jiang De-Sheng  ,   中山大学光电材料与技术国家重点实验室，广州  510275
Published: December 2020

In photoisomerization polymer，the evolvement and some related properties of the dark stripe，in which the light field has a phase jump on both sides of the summetrical axis，are simulated by numerical method.The numerical results show that if the phase jump differs from π，the incident dark stripe will split into two grey stripes called Y-splitting, and the larger the phase jump (from 0 to π)，the smaller the Y-splitting.The numerical results also show that the angle between the phase-lead-branch and the direction of incidence is almost a constant for different phase jumps，while that of the phase-lag-branch varies with the phase jump.The angle between the two branches is unchanged under the condition of the same phase jump and different incident intensity.Besides，the numerical results also show that the refractive index change induced by Y-splitting in the material can act as a wave-guide，which leads an incident Gauss beam to form a Y-splitting.
Unilateral coupling synchronization of spatiotemporal chaos in the Bragg acousto-optic bistable system
Authors: Yue Li-Juan  , Shen Ke  ,   (1)长春理工大学物理系，长春  130022; (2)长春理工大学物理系，长春  130022;东北师范大学物理系，长春  130024
Published: December 2020

The one- and two-dimensional coupled map lattices in nonlinear dynamic system are used as the system model. We report a method with which the spatiotemporal chaos can be synchronized using unilateral coupling in two Bragg acousto-optic bistable spatial extended systems. The synchronization can be realized by appropriately selecting the coupling strength and the equilibrium coefficient. By calculating the largest conditional Lyapunov exponent, we obtain the minimum coupling strength for achieving the synchronization and the functional relationship between the minimum coupling strength and the system parameters. Our simulation shows that the synchronization can also be realized under the influence of small random noise, so this method is robust.
Reflection and negative refraction of left-handed metamaterials at microwave frequencies
Authors: Zheng Qing  , Zhao Xiao-Peng  , Fu Quan-Hong  , Zhao Qian  , Kang Lei  , Li Ming-Ming  ,   西北工业大学电流变技术研究所，西安  710072
Published: December 2020

We experimentally investigated the microwave reflection of the negative permeability material composed of periodical arrays of the copper split-ring resonators (SRRs).The negative dielectric materials are composed of periodical arrays of copper wires and left-handed materials(LHMs) in a planar slab waveguide, and the microwave is incident to the surface in different directions.We also investigated the negative refraction through a prism fabricated from the LHMs.The experimental results show that for the negative permeability materials,there is a reflection peak at the resonance frequencies of the SRRs, and the reflectivity of the negative dielectric material is closed to 0dB.A single smaller reflection peak occurs in the reflected curve of the LHMs,the reflectivity of which increases with the incident direction,that is,the reflection increases.The reflection peak has a shift with respect to the transmission peak. It is demonstrated that negative refractive index of -0.796 occurs in the LHMs at the frequency o 800MHz.
Structural, transport and magnetic properties of KxCoO2·yH2O(x<0.2, y≤0.8)
Authors: Fu Guang-Cai  , Li Ming-Xing  , Dong Cheng  , Guo Juan  , Yang Li-Hong  ,   (1)上海大学化学系,上海  200436; (2)上海大学化学系,上海  200436;中国科学院物理研究所超导国家重点实验室，北京  100080; (3)中国科学院物理研究所超导国家重点实验室，北京  100080
Published: December 2020

Layered potassium cobaltate K0.36CoO2 has been successfully synthesized from KOH fluxes at 480℃. The K0.36CoO2 sample can be oxidized and intercalated with water by treatment in KMnO4 and K2S2O8 solutions. K0.12CoO2·0.8H2O and K0.16CoO·0.6H2O have been obtained after the KMnO4 and K2S2O8 treatment, respectively. The diffraction peaks of K0.12CoO2·0.8H2O and K0.16CoO2·0.6H2O can be well indexed by a hexagonal cell similar to the monolayer hydrate NaxCoO2·yH2O. After dehydration, the major phases have an orthorhombic structure similar to Na0.5CoO2 and show semiconductor behavior. Both K0.12CoO2·0.8H2O and K0.16CoO2·0.6H2O are primari paramagnetic and show metallic behavior. K0.16CoO2·0.6H2O has a spin-glass-like transition or other magnetic fluctuations around 56K. The spin-glass-like transition or the regions of magnetic phase separation are reduced in K0.12CoO2·0.8H2O due to the increasing of the intercalated water. We also discussed similarities and differences between the structural and physical properties of KxCoO2 and NaxCoO2.
Effect of current density on physical and chemical properties of microarc oxidation coatings of aluminium alloy
Authors: Wu Han-Hua  , Wang Jian-Bo  , Long Bei-Yu  , Lü Xian-Yi  , Long Bei-Hong  , Jin Zeng-Sun  , Bai Yi-Zhen  , Bi Dong-Mei  ,   (1)大连理工大学物理系，三束材料改性国家重点实验室，大连  116024; (2)吉林大学超硬材料国家重点实验室，长春  130012; (3)吉林大学物理学院，长春  130023; (4)吉林大学物理学院，长春  130023;吉林大学超硬材料国家重点实验室，长春  130012
Published: December 2020

Ultra-hard ceramic coatings with microhardness of 42.14GPa have been synthesized on the Al alloy substrate by microarc oxidation (MAO) technique. The effects of anodic current density ja and the ratio of cathodic to anodic current density jc/ja on the mechanical property and phase composition of MAO coatings have been studied by microhardness test and x-ray diffraction, respectively. In addition, the microstructure and corrosion resistance of the coatings were analyzed by scanning electron microscopy and pitting corrosion test, respectively. The results show that the samples prepared at high anodic current density consist mainly of α-Al2O3, while the samples fabricated at low anodic current density are composed almost entirely of γ-Al2O3. Microhardness test shows that these kinds of samples have high hardness, and the microhardness of the coating prepared at ja=15A/dm2 and jc/ja=0.7 is t highest of all coatings prepared. Pitting corrosion test shows that the structure of coatings is strongly influenced by the variation in jc/ja.