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Vol. 53, No. 6 (2004)

2004-03-20
GENERAL
Interactions between two Y-periodic solitons in the(2+1)-dimensional Sawada-Kotera equations
Ruan Hang-Yu
2004, 53 (6): 1617-1622. doi: 10.7498/aps.53.1617
Abstract +
The exact solutions of the (2+1)dimensional Sawada-Kodera(SK) equation are presented by using the bilinear method.The N breather solutions,the solution to describe the interaction between a line solition and a y periodic soliton and the solution to express the interaction between two y periodic soliton are included in the exact solutions.Detailed behaviors of interactions between two y periodic solitons are illustrated both analytically and graphically.For SK equation,the value of interactive constant can only be taken in some range.We can only obtain the repulsive interaction that keeps the shapes of soliton unchanged.
Integrability aspects of solitons’ coupled equation in multi-wavelength system
Li Qi-Liang, Zhu Hai-Dong, Tang Xiang-Hong, Li Cheng-Jia, Wang Xiao-Jun, Lin Li-Bin
2004, 53 (6): 1623-1628. doi: 10.7498/aps.53.1623
Abstract +
We have studied the integralility aspects of solitons' coupled equation in a multi-wavelength system with Lax pair, by using Hirota bilinearization, we obtain one-soliton and two-solitons solutions.
Explicit travelling wave solutions for Zakharov equations
Zhao Chang-Hai, Sheng Zheng-Mao
2004, 53 (6): 1629-1634. doi: 10.7498/aps.53.1629
Abstract +
In this paper, several new traveling wave solutions for Zakharov equations are obtained by using bi function method and Wu elimination method, which include periodic traveling wave solutions and solitary wave solutions. Their physical meaning is also discussed.
A simple method for solving a class of nonlinearly coupled evolution equations in higher dimensional space
Li De-Sheng, Zhang Hong-Qing
2004, 53 (6): 1635-1638. doi: 10.7498/aps.53.1635
Abstract +
In this paper,a class of nonlingearly coupled evolution equations in higher dimensional spaces is reduced to a simple nonlinear evolution equation in lower dimensional spaces by using a simple transformation,and then we can easily obtain the solutions of the original equations by appling existing method to the simple nonlinear evolution equation.
A notes on the variable separation approach
Li De-Sheng, Zhang Hong-Qing
2004, 53 (6): 1639-1642. doi: 10.7498/aps.53.1639
Abstract +
Starting from the B-cklund transformation and using Cole-Hopf transformation,we reduce a class of nonlinear evolution equations in (2+1)-dimensional spaces to a simple nonlinear evolution equation with two arbitrary functions of {x,t} and {y,t}.We can obtain some new exact solutions of the original equations by studying the simple nonlinear evolution equation which includes some solutions obtained by the variable separation approach.
Remarks on “Lewis-Riesenfeld phase” and quantum geometric phase
Li Hua-Zhong
2004, 53 (6): 1643-1646. doi: 10.7498/aps.53.1643
Abstract +
Some misconceptions in an article on the so called “Lewis phase” and quantum geometric phase in Chinese are critically reviewed. We point out the wrong statements given in the paper published in College Physics 21 23,written in Chinese.
The research of properties of the quantum conditional amplitude operator
Zhang De-Xing
2004, 53 (6): 1647-1651. doi: 10.7498/aps.53.1647
Abstract +
This paper analyzes the properties of the quantum conditional amplitude operator.This operator plays a role similar to that of the conditional probability in classical information theory.One argues that the spectrum of the conditional operator that characterizes a quantum bipartite system is invariant under local unitary transformations,and shows its inseparability.It is proven that the conditional amplitude operator of a separable state cannot have an eigenvalue exceeding unity.A related separability condition based on the non-negativity of the von Neumann conditional entropy is obtained.
Bound states of Klein-Gordon equation for ring-shaped non-spherical harmonic oscillator potentials
Lu Fa-Lin, Chen Chang-Yuan
2004, 53 (6): 1652-1656. doi: 10.7498/aps.53.1652
Abstract +
By using the ordinary method of variable separation,the bound states of Klein-Gordon equation of the ring-shaped non-spherical harmonic oscillator with equal scalar and vector potentials are solved. The normalized angular wave function expressed in terms of the universal associatedLegendre polynomial and the normalized radial wave function expressed in terms of the confluent hyper-geometric function are presented. The exact energy spectrum equations are obtained.
A study about the energy-momentum tensor of pure gravitational field part of matter
Lou Tai-Ping
2004, 53 (6): 1657-1661. doi: 10.7498/aps.53.1657
Abstract +
In this paper,the existing forms of matter is supposed to be divided into two parts, one is the pure matter part,and another is the pure gravitational field part.The two parts of existing forms of matter are corresponding to their energy-momentum tensors,respectively.So the total energy-momentum tensor of matter can be expressed as Tμν=T(Ⅰ)μν+T(Ⅱ)μν,where T(Ⅰ)μν and T(Ⅱ)μνare energy-momentum tensors of pure matter part and pure gravitational field part,respectively.By analogy with the electromagnetic theory,a vector is defined as:ωμ≡-c2gμ0/g00,and an antisymmetric tensor is defined as:Dμν=ωμ/xν-ων/xμ,so the energy-momentum tensor of the pure gravitational field part of the matter is supposed to be T(Ⅱ)μν=(DμρDρν-gμνDαβDαβ/4)/4πG.The gravitational field equation which contains pure gravitational field part of matter can be expressed by Rμν-gμνR/2=8πG(T(Ⅰ)μν+T(Ⅱ)μν)/c4.The theory of the gravitational field which contains the energy-momentum tensor of pure gravitational field part of matter can be used in an isolated globular symmetry for pure matter with mass M ,which is time-independent,and the line-element of time-space for the out side of globular symmetry of pure matter can be obtained by ds2=-(1-m/r)-2dr2-r2dθ2-r2sin2θdφ2+(1-m/r)2c2dt2,where m=GM/c2.
Acceleration of a kind of null geodesic
Tian Gui-Hua, Zhao Zheng
2004, 53 (6): 1662-1664. doi: 10.7498/aps.53.1662
Abstract +
When a null geodesic γ0,orthogonal to a space-like two-surface φ,is from φ to q with a point r∈(φ,q)conjugate to φ along γ0(λ),there will be a variation of γ0(λ) which will give time-like curves from φ to q.This is a well-known theory in the famous bood.When the variation vector is not a generalized Jacobi field on the null geodesic γ0,the acceleration of these time-like curves approaches infinity as the time-like curves approach the null geodesic.
Quantum entropy of the non-static black hole in(2+1)dimensions
Sun Ming-Chao
2004, 53 (6): 1665-1668. doi: 10.7498/aps.53.1665
Abstract +
In the tortoise coordinates,the quantum entropy of the non-static black hole in (2+1)dimensions due to scalar fields has been investigated by using the brick-wall model.It is shown that the entropy of scalar fields within the thin region near the horizon has the same structure as that of the black ho1e.In particular,the quantum entropy satisfies the perimeter law of the entropy for the static case.
Quantum thermodynamical properties of the slowly changing nonstationary Kerr-Newman black hole
Wang Gang-Zhu, Wang Ji-Long
2004, 53 (6): 1669-1674. doi: 10.7498/aps.53.1669
Abstract +
Introducing the notion of the local thermal equilibrium,the Hawking effect and the entropy of a nonstationary Kerr-Newman black hole whose metric changes slowly are studied by the method of Damour-Ruffini and the thin film model.First,we obtain the Hawking radiation temperature and the thermal spectrum formula,and show that the Hawking temperature depends on the time and the location on the event horizon,the thermal spectrum is a quasi-black-body's thermal spectrum.Second,we calculate the black hole entropy,which is just the Bekenstein-Hawking entropy with the same geometrical cutoff relationship as in the static and spherical case.The results show that the temperature of the black hole is a local quantity,and the entropy of the nonstationary black hole is also proportional to the horizon area as in the case of stationary black holes.
Effects of pump noise and quantum noise with real and imaginary parts correlated on the dynamic properties of a single-mode laser
Cheng Qing-Hua, Cao Li, Wu Da-Jin, Wang Jun
2004, 53 (6): 1675-1681. doi: 10.7498/aps.53.1675
Abstract +
Adopting the linear approximation method, a loss model for a single-mode laser driven by pump noise and quantum noise whose real and imaginary parts are correlated is studied. We investigated the intensity correlation function, which describes the dynamic property of a laser and varies with time. Moreover, the valid range for the linear approximation method is obtained, and the effects of the intensities of the pump noise and quantum noise on the variance of the laser intensity, and the correlation coefficient between the real and imaginary parts of the quantum noise, are discussed in detail. We find that the valid range is extended in the case of small quantum noise and far form threshold, and it is the largest in the case of small quantum noise, far form threshold and no correlation between the real and imaginary parts of the quantum noise.
Chaotic anti-control of a port control Hamilton system
Tao Jian-Wu, Shi Yao-Wu, Chang Wen-Xiu
2004, 53 (6): 1682-1686. doi: 10.7498/aps.53.1682
Abstract +
Based on the analysis of energy change and dynamical force characteristics for port control Hamiltom (PCH) system, a method of chaotic anti-control is studied via nonlinear output feedback. The proposed method has a clear physical conception and need not estimate the Lyapunov exponent of the chaotic system. This makes the method simpler in practical applications.Numerical studies and computer simulation show the capabilities of this method.
Research on circuitry realization and synchronization of Chen chaotic systems
Li Shi-Hua, Cai Hai-Xing
2004, 53 (6): 1687-1693. doi: 10.7498/aps.53.1687
Abstract +
Based on the work in Int. J. of Bifurcation and Chaos vol.12(2002)1423,we address the circuitry realization problem of Chen chaotic system.We derive available circuit parameters with which we simulate the circuit on the simulation softwareElectronic Workbench.After realizing the Chen system in the circuit,we observe the chaotic figure on the oscillograph.Employing the synchroniation method using single variable coupling feedback,we conduct the synchronization experiments and obtain the parameter range for controlling the synchronization between two Chen's systems.
Secure communication method for fast-varying information signal based on chaotic modulation
Li Jian-Fen, Li Nong, Lin Hui
2004, 53 (6): 1694-1698. doi: 10.7498/aps.53.1694
Abstract +
A new secure communication method based on chaotic modulation is proposed. The parameter of the transmitting system procreated chaotic carrier is modulated by errors from an adaptive controller and information signal. At the same time, the information is directly multiplied by the chaotic carrier in transmission to drive the receiving system. In the receiver, another adaptive controller is used to maintain chaotic synchronization of the transmitting and receiving systems and to recover information signal. Since the synchronization error is independent of information signal,the chaotic modulation for large-amplitude and fast-varying information signals can be achieved. The results of theoretic analysis and numerical simulation show that the proposed method enhances the degree of security of low-dimensional chaotic systems.
The arbitrary order implicit multistep exponential time differencing method and its application for nonlinear systems
Tang Chen, Yan Hai-Qing, Zhang Hao, Liu Ming, Zhang Gui-Min
2004, 53 (6): 1699-1703. doi: 10.7498/aps.53.1699
Abstract +
The arbitrary order implicit exponential time differencing multistep method is proposed for nonlinear systems.We carry out the predictor_corrector method of exponential time differencing.When the method is applied to the nonlinear systems,the effect is admirable.The numerical results show that the accuracy of explicit exponential time differencing multistep method can be enhanced by implicit exponential time differencing multistep method,and the lather is highly accurate and computationally efficient.The exponential time differencing method has been developen and perfected by the present studies.
Synchronization and decoding of chaotic lasers and their optimization
Yan Sen-Lin, Chi Ze-Ying, Chen Wen-Jian, Wang Ze-Nong
2004, 53 (6): 1704-1709. doi: 10.7498/aps.53.1704
Abstract +
In this paper,analog signal with 0.1 to 10 GHz frequencies,digital signal with 0.2 and 0.3 Gbit/s rates and frequency shift keying decoding are studied in chaotic lasers.Influences of the frequency and the amplitude of the encoded signals and rate limit of chaotic shift key of lasers on synchronous error are optimally analyzed.Full_synchronization and pseudo_synchronization are discussed.Optimum of the effects of the parameter mismatch and the feedback coefficient on synchronous error and synchronous time is also discussed.
A self-adaptive bi-particle graph model for scientific collaboration
He Yue, Zhang Pei-Pei, Xu Tian, Jiang Yu-Mei, He Da-Ren
2004, 53 (6): 1710-1715. doi: 10.7498/aps.53.1710
Abstract +
This paper suggests a self-adaptive bi-particle graph model, which describes the collaboration network between the principal investigators and their assistants. The model considers the choices, strategies, competitions, and the induced evolutions of the principal investigators and their assistants as actors as well as the evolution of the whole network. The simulation results of all the different single-particle graphs obtained by different methods of projection show a good agreement with the statistical data of the collaboration between American mathematicians and neuroscientists during 1991 and 1998 That shows a self-adaptive complex network can selforganize to a small world and scale-free structure. This article also discusses the similarities and differences of the simulation results of the different projected single-particle graphs of the bi-particle graph.
Generation of steady and jitter-free ultra-fast electrical pulses with GaAs photoconductive switches
Shi Wei, Ma De-Ming, Zhao Wei
2004, 53 (6): 1716-1720. doi: 10.7498/aps.53.1716
Abstract +
In this paper, experiments of a lateral semi-insulating GaAs photoconductive semiconductor switch triggered by nanosecond, pico-second and femto-second laser pulses were reported. The switches was insulated by solid multi-layer transparent dielectrics. Jitter-free electrical pulse with steady voltage amplitude from the 1mm-gap GaAs switches was observed when biased with a low voltage and triggered by the serial laser pulses. Its change of amplitude was less than 1.2%, the triggered jitter-time was less than 10ps, and pulse width was up to sub-nanosecond. The effect of pulse energy change on the amplitude generated photoconductive semiconductor switch was analyzed. It was indicated that ultra-fast electrical pulse with steady voltage amplitude and pico-second triggered jitter-time can be obtained by controlling switch trigger condition and optimizing the switch design.
Trapping stiffness measurement with brownian motion analysis method at low sampling frequency
Jiang Yu-Qiang, Guo Hong-Lian, Liu Chun-Xiang, Li Zhao-Lin, Cheng Bing-Ying, Zhang Dao-Zhong, Jia Suo-Tang
2004, 53 (6): 1721-1726. doi: 10.7498/aps.53.1721
Abstract +
The Brownian motion analysis is a preferable method to investigate the trapping stiffness of optical tweezers system because of its convenience and simplicity. However, there would be obvious deviation if the detector's response frequency or sampling frequency is low. Such problems are discussed and a solution is brought forward in this article.
Optimum thickness for laser induced thermoelectric voltage effect in high Tc superconductor and CMR thin film
Wang Chong, Zhang Peng-Xiang, Zhang Guo-Yong
2004, 53 (6): 1727-1730. doi: 10.7498/aps.53.1727
Abstract +
Based on the formula of the time dependence of laser-induced voltage in high Tc superconductor(HTSC) and collosal magneto-resistance (CMR) thin films, we have successfully deduced the function of the optimum thickness for producing largest laser-induced thermoelectric voltage. It is indicated that a direct proportional relationship between laser-induced thermoelectric voltage and the reciprocal of thickness does not correctly describe the situation. In fact, an optimum thickness must exist. This function provides the main factor of affecting the design for fast-time-response device. We have discussed the parameter of thin film influencing the optimum thickness, and compared it with experimental result.
A confocal system with two Toraldo pupil filters
Xiao Fan-Rong, Yuan Jing-He, Wang Gui-Ying, Xu Zhi-Zhan
2004, 53 (6): 1731-1734. doi: 10.7498/aps.53.1731
Abstract +
Toraldo pupil filter has been one of the most popular pupil filters. But its use is restricted because of the fabrication. In this article, we propose a confocal system with two Toraldo pupil filters. The function of a multi-zone Toraldo pupil filter, which is difficult to fabricate can be substituted by two relatively simple Toraldo pupil filters.
 A new method for measuring the dynamic behavior of the photorefractive nonlinear parameter
Liu Si-Min, Zhao Hong-E, Guo Ru, Wang Da-Yun, Gao Yuan-Mei, Huang Chun-Fu, Lu Yi
2004, 53 (6): 1735-1741. doi: 10.7498/aps.53.1735
Abstract +
Based on the zscan method, we present a new method, the time-scan method, to measure the dynamic behavior of the photorefractive nonlinear parameter. We prove theoretically and experimentally that the new method is precise and feasible.
ATOMIC AND MOLECULAR PHYSICS
Calculation of wavelengths and oscillator strengths of transition 3d104s—3d94s4p for ions from MoⅩⅣ—RuⅩⅥ
Mu Zhi-Dong, Wei Qi-Ying
2004, 53 (6): 1742-1748. doi: 10.7498/aps.53.1742
Abstract +
In this paper, we calculate the energy levels of configuration 3d-94s4p (J=1/2;3/2,Nth=1—4;1—7) for copper-like sequence ions from GeⅣ—RuⅩⅥ by HXR method. With the important effects, such as correlation effect, quantum electrodynamics (QED) effects and the other effects taken into account, we have made a systemisitic fit calculation for energy levels of ions mentioned above. We predict here the energy levels of configuration 3d-94s4p(J=1/2;3/2,Nth=1—4;1—7) for ions MoⅩⅣ—RuⅩⅥ.The wavelengths, oscillator strengths and probabilities of transition 3d-104s—3d-94s4p(J=1/2; 3/2,Nth=1—4; 1—7) are computed too.
Studies on the potential energy curves of hydride diatomic molecules using energy consistent method
Lu Guang-Hui, Sun Wei-Guo, Feng Hao
2004, 53 (6): 1753-1758. doi: 10.7498/aps.53.1753
Abstract +
By using QCISD/6-311G(d)method, the ground state of SO-2, and its energy, harmonic frequencies, force constants have been calculated. The calculated results are in good agreement with the experimental ones. The analytical potential energy function of SO-2 has been derived based on the many-body expansion theory. The structure and energy of SO-2 can correctly reappear on the potential surface.
Photodissociation study of N2O+(A2Σ+) ions
Xu Hai-Feng, Li Qi-Feng, Zhou Xiao-Guo, Dai Jing-Hua, Liu Shi-Lin, Ma Xing-Xiao
2004, 53 (6): 1759-1765. doi: 10.7498/aps.53.1759
Abstract +
Pure parent ions, N2O+, populated at X2Π(000), were prepared by (3+1) multiphoton ionization of jet cooled N2O molecules at 360.55nm, and then were excited to different vibrational levels of predissociative A2Σ+ state by another laser in the wavelength range of 275—328nm. The total released translational energies 〈ET〉 at different excitation energies were measured with a time of flight (TOF) spectrometer from the TOF broadenings of the NO+ fragment.The 〈ET〉value drops abruptly from ~8000cm-1 to ~1600cm-1 at excitation energy of ~32000cm-1.Further analysis shows that at the excitation energies below 32000cm-1, the dissociation channel is NO+(X1Σ+)+N(4S), and at the energies above 32000cm-1 a new channel, NO+(X1Σ+)+N(2D), is opened and replaces completely the N(4S) channel. The predissociation mechanism of the N2O+(A2Σ+) ions was discussed based on the experimental results.
Geometry and electronic properties of Aun(n =2—9)clusters
Ma Mei-Zhong, Mao Hua-Ping
2004, 53 (6): 1766-1771. doi: 10.7498/aps.53.1766
Abstract +
The possible geometrical and electronic structures of small Aun(n=2—9) clusters are optimized by mean of density functional theory (DFT). The effects of electron correlation is included in these calculations. The ground state equilibrium geometries and the atomization energies of Aun(n=2—9) clusters have been calculated. It is shown that the atomization energy per atom increases with the cluster size.The energy level distribution, the Fermi levels and HOMO-LUMO gaps are investigated. Meanwhile, the electron affinities (EAs) and the ionization potentials (IPs) are calculated. The results are in excellent agreement with those of experiment. The even-odd effects of Fermi energy levels, IPs and EAs with the cluster size are explained.
CLASSICAL AREA OF PHENOMENOLOGY
Time-domain terahertz spectroscopy of (100) MgO and (100) LaAlO3 substrates
Hu Ying, Zhang Cun-Lin, Shen Jing-Ling, X. C. Zhang
2004, 53 (6): 1772-1776. doi: 10.7498/aps.53.1772
Abstract +
THz(teraherz)properties of high-Tc superconductor substrates(100)MgO and (100)LaAlO3 are measured using time-domain spectroscopy at frequency range between 0.2 and 2 THz.The complex refractive index and dielectric function of the MgO substrate is independent of frequencies;those of LaAlO3 increase slightly with increasing frequency.We determine=3.46+i0.001 and=12.27+i0.06 for the MgO substrate and =4.78+i0.02 and =22.5+i0.2 for the LaAlO3 substrate at 1THz.The dielectric loss tanδ of both LaAlO3 and MgO substrate is less than 0.01The tanδ of LaAlO3 in nearly five times larger than MgO,but both of them are less than 0.01.
Theoretical and experimental study of new dark hollow beams
Zhang Lei, Cai Yang-Jian, Lu Xuan-Hui
2004, 53 (6): 1777-1781. doi: 10.7498/aps.53.1777
Abstract +
A new mathematical model named hollow Gaussian beams (HGBs) is introduced to describe the dark hollow beam. The area of the dark region across the HGBs can be easily controlled by properly choosing the beam parameters. An analytical propagation formula for HGBs through paraxial optical system is derived. The evolution properties of the intensity distribution of HGBs in free space propagation are illustrated graphically using the derived propagation formula. By using matrix eigenvalues method, the laser cavity with diffraction optical elements, which can generate the dark hollow beams, was constructed. Dark hollow beams were realized in experiment and its intensity distribution properties in near field and far field were studied. The results derived from the experiment is coincident with those predicted by the theory. The dark hollow beams we have obtained can be used conveniently to analyze atoms manipulation and may provide a new method for atom cooling.
Numerical analysis of the dispersion of subwavelength diffractive microlens
Liu Yu-Ling, Lu Zhen-Wu
2004, 53 (6): 1782-1787. doi: 10.7498/aps.53.1782
Abstract +
Subwavelength diffractive microlenses are analyzed by use of body-of- revolutionary finite-difference time-domain method. The electric field distributions on the focal plane of the element and the distributions from near field to far field are shown. The dispersion property of subwavelength diffractive microlens is investigated. The dispersion curve in the case of incident wavelength different from the design wavelength is shown. Numerical result illustrates the negative dispersion characteristic of the element, and the increase of focal length is faster than the decrease of incident wavelength.
Study of self-erasing of recording process in Zn:Fe:LiNbO3 with the double-carrier four-trap model
Meng Qing-Xin, Gong De-Wei, Zhang Jian-Long, Sun Xiu-Dong
2004, 53 (6): 1788-1792. doi: 10.7498/aps.53.1788
Abstract +
Photorefractive properties of Zn:Fe:LiNbO3 crystals were compared with Fe:LiNbO3 crystals. We described the photoconduction and diffraction efficiency as a function of incident light intensity. The self-erasing of recording process in the Zn:Fe:LiNbO3 crystal is observed. We found that the diffraction efficiency of the crystal increased to a saturation value and then decreased as recording time increases. The phenomena were explained by the double-carrier four-trap model. A suit able exposure schedule is chosen to realize the angle-multiplexed volume holographic storage. We have stored 30 images in the same volume of the crystal.
The frequency modulation effects of the probe field in three level Λ-system
Han Ding-An, Guo Hong, Sun Hui, Bai Yan-Feng
2004, 53 (6): 1793-1798. doi: 10.7498/aps.53.1793
Abstract +
In this paper, the frequency modulation effect of the probe field in a three-level Λ system is discussed. According to the classical equation of motion for the electron, the dielectric susceptibility of the medium is not affected by frequency modulation. Based on the quantum theory and the frequency modulation term expanded in terms of Bessel functions, the effects of the frequency modulation of the probe field on the system are studied, in which, when the modulation frequency of the probe field is large enough, the periodical population evolutions exist in three levels. Meanwhile, the stationary susceptibility of the probe field is given.
Numerical study on the terminating mechanisms of copper vapor laser pulse
Jin Yi, Pan Bai-Liang, Chen Gang, Chen Kun, Yao Zhi-Xin
2004, 53 (6): 1799-1803. doi: 10.7498/aps.53.1799
Abstract +
A self-consistent physical model describing the kinetic process of the longitudinal pulsed discharge-excited copper vapor laser was established, and numerical solutions of the model were obtained. The terminating mechanisms of the copper vapor laser pulse have been further analyzed according to the simulation results. It is shown that the important factors resulting in the termination of laser pulse are the processes of stimulated emission transition, the electron impact excitation of the lower laser level and the depopulation of the upper laser level to the higher excitation levels by electron collisions.
Experimental study on thermal lensing of end-pumped solid-state lasers
Guan Jun, Li Jin-Ping, Cheng Guang-Hua, Chen Guo-Fu, Hou Xun
2004, 53 (6): 1804-1809. doi: 10.7498/aps.53.1804
Abstract +
A laser interferometry method of measuring the thermal lensing of end-pumped solid-state lasers is proposed. This method provides a way easy to be carried out is real-time, having no influence on laser system, with a high spatial resolution for diagnosing thermal lensing. By this method, thermal lensing of end-pumped Nd:YVO4 laser is studied in detail. And this work provide a means for studying the thermal effects of laser medium and designing lasers of this kind.
Passive Q-switched mode locking of double-clading Yb:fiber laser with ion-implanted GaAs
Wang Yong-Gang, Ma Xiao-Yu, Fu Sheng-Gui, Fan Wan-De, Li Qiang, Yuan Shu-Zhong, Dong Xiao-Yi, Song Yan-Rong, Zhang Zhi-Gang
2004, 53 (6): 1810-1814. doi: 10.7498/aps.53.1810
Abstract +
We report the technique of the ion-implanted semi-insulating GaAs wafer used for passive Q-switched mode locking in double-cladding Yb:fiber laser. The wafer was implanted with 400-keV energy, 1016/cm2 dose As+ions, and was annealed at 600℃ for 20 min. At the pump power of 5W, we achieved output power of 200mW. The repetition rate of envelope of Q-switched mode locking is 50-kHz with a FWHM envelope of 4μs. The repetition rate of mode locked pulse train was found to be 15-MHz. This is the first report of such a kind of laser to the best of our knowledge.
Phase transition speed research of metal material at laser irradiation medium strength
Zhang Ke-Yan
2004, 53 (6): 1815-1819. doi: 10.7498/aps.53.1815
Abstract +
Under the condition that there is only solid-liguid transition in a metallic material, we found the laser power density for melting the material. Through analysis of the similarity of some behaviors of solid and ciquid states, we obtain the absorptivity of laser by the metal, and indicate the impossibility to directly calculate the transition rate of the metal. However, we can obtain the transition rate under the irradiation of laser, and find the relationship of the transition rate with the intensity and the frequency of the laser.
Analysis on Z-scan characteristics of cascade structure
Zang Wei-Ping, Tian Jian-Guo, Liu Zhi-Bo, Zhou Wen-Yuan, Mei Can, Song Feng, Zhang Chun-Ping
2004, 53 (6): 1820-1825. doi: 10.7498/aps.53.1820
Abstract +
In this paper, Z-scan characteristics of the cascade structure of nonlinear media are analyzed, analytic and numerical solutions are obtained. Analytic analysis is based on the combination of Gaussian decomposition method (GDM) with the distributed lens method, and numerical calculation is based on the Crank-Nicholson finite difference scheme and fast Hankel transformation. Meanwhile, the conditions and method to apply these two numerical analyses are also given. Comparing analytic solutions with numerical calculation and experimental results, it is shown that they agree very well with each other.
Nonlinear propagation and supercontinuum generation of a femtosecond pulse in photonic crystal fibers
Cheng Chun-Fu, Wang Xiao-Fang, Lu Bo
2004, 53 (6): 1826-1830. doi: 10.7498/aps.53.1826
Abstract +
A theoretical investigation with the method of split-step Fourier is presented on the nonlinear propagation and supercontinuum generation of a femtosecond laser pulse in a photonic crystal fiber. The impact of high-order dispersion and nonlinear effects on spectral shape and band width is simulated and analyzed. It is found that soliton self-frequency shift is generated in a photonic crystal fiber. It is also found that intrapulse stimulated Raman scattering and self-phase modulation result in the fine spectral substructure of the supercontinnum. The band width and smoothing of the supercontinuum are found to be related to the higher-order dispersion and the power of the initial laser pulse.
Influence of Stokes component in reflected light on stimulated Brillouin scattering process
Guo Shao-Feng, Lu Qi-Sheng, Cheng Xiang-Ai, Zhou Ping, Deng Shao-Yong, Yin Yan
2004, 53 (6): 1831-1835. doi: 10.7498/aps.53.1831
Abstract +
A new stimulated Brillouin scattering (SBS) configuration, SSS(Self Stokes Seeding), is presented to describe the influence of Stokes component in a pump light on SBS process. The fast Fourier transform is used to calculate the Stokes energy ratio which denotes the ratio of the energy of Stokes component to that of total pump laser. The coupled SBS equations is solved numerically and the SSS effects is evaluated. The study shows that when the pump laser is reflected normally by the back surface of the flat sample, the Stokes component plays an important role in SBS process, such as decreasing the initiation duration. The larger the Stokes energy ratio is, the shorter the initiation duration is.
Low intensity spatial solitons in centrosymmetric photorefractive materials
Hou Chun-Feng, Meng Qing-Xin, Gong De-Wei, Zhang Jian-Long
2004, 53 (6): 1836-1839. doi: 10.7498/aps.53.1836
Abstract +
The exact bright, dark and grey spatial soliton solutions for the optical wave evolution equation in centrosymmetric photorefractive materials are obtained analytically, and the explicit expressions for the width of these spatial solitons are also presented.
The upconversion luminescence research of Er3+-doped heavy metal oxyfluorosilicate glasses
Xu Shi-Qing, Wang Guo-Nian, Zhang Jun-Jie, Dai Shi-Xun, Hu Li-Li, Jiang Zhong-Hong
2004, 53 (6): 1840-1844. doi: 10.7498/aps.53.1840
Abstract +
The absorption spectrum, upconversion spectra and Raman spectrum of Er3+-doped heavy metal oxyfluorosilicate glasses have been investigated, and luminescence mechanisms of Er3+ in heavy metal oxyfluorosilicate glasses were analyzed. The results showed that blue, green and red emission centered around 411, 525, 543, and 655 nm, corresponding to the 2H9/2→4I15/2,2H11/2→4I15/2,4S3/2→4I15/2, and4F9/2→4I15/2transitions of Er3+ ions, respectively, were simultaneously observed at room temperature under 975 nm diode laser excitation, and the intensity for blue, green and red emissions increases with increasing Er2O3 concentrations. There are two basic upconversion mechanisms: excited state absorption and energy transfer, and a two-photon upconversion process is assigned to the intense green and red emissions, respectively, while a three-photon process is responsible for weak blue upconversion. Raman spectrum indicates that the lead fluoride in the glass network play an important role in upconvesion fluorescence of Er3+.
Guide modes at interface of photonic crystal heterostructures composed of different lattices
Liu Jiang-Tao, Zhou Yun-Song, Wang Fu-He, Gu Ben-Yuan
2004, 53 (6): 1845-1849. doi: 10.7498/aps.53.1845
Abstract +
We have investigated the guide modes in two kinds of two-dimensional photonic crystal heterostructures by using the plane wave expansion method combined with the supercell technique. These heterostructures consist of different air cylinders embedded into host dielectric in different lattices. Namely, One heterostucture is composed of square cylinders in square lattice and hexagon cylinders in triangular lattice (SSTH heterostucture). The other heterostucture is composed of rectangular cylinders in rectangular lattice and circle cylinders in triangular lattice(RRTC heterostucture). We find that the SSTH heterostucture may produce guide modes in absolute photonic band gap (PBG) when introducing relative longitudinal gliding or transverse displacement of the sub-lattices along the interface of the heterostructure. But the RRTC heterostucture can produce guide modes in absolute PBG without any relative longitudinal gliding or transverse displacement. This feature is quite different from other pure dielectric photonic crystals heterostructures.
Electro-optical properties of holographic polymer dispersed liquid crystal devices
Zhang Bin, Liu Yan-Jun, Xu Ke-Shu
2004, 53 (6): 1850-1855. doi: 10.7498/aps.53.1850
Abstract +
Holographic polymer dispersed liquid crystals(HPDLC)are a kind of novel photoelectronic information functional materials. It has the perfect characters including high diffraction efficiency, rapid response and easy manufacture. HPDLC devices are potentially useful for optical communication, panel display, information storage and integrated optics. Based on the study of the diffraction properties optimization of HPDLC,we have established the measurement system for electro-optical properties of the HPDLC device. The influence of different surfactants loading on the anchoring energy of liquid crystal have been explored, which was demonstrated to be a good way to decrease the operating voltage. The experimental results indicated that the index matching plays an important role in improving the contrast ratio of device. The response time was measured and the average response time of 100μs was obtained.
Study on mode degeneracy in photonic crystal fibers
Ren Guo-Bin, Wang Zhi, Lou Shu-Qin, Jian Shui-Sheng
2004, 53 (6): 1856-1861. doi: 10.7498/aps.53.1856
Abstract +
A novel full vector model is applied to analyze the photonic crystal fibers (PCF). From symmetry analysis of modes of a waveguide, we classify the modes of PCF into nondegenerate or degenerate pairs according to the minimum waveguide sectors and its appropriate boundary conditions. We present the modes of PCF that can be labeled by its step index fiber analogs. It is shown that these modes either exhibit the full waveguide symmetry and nondegenerate or occur in degenerate pairs that support this symmetry only in combination. The doublet of the degenerate pairs in which both have the same symmetry as PCF will be split into two nondegenerate modes.
Dispersion properties of high-index-core Bragg fibers
Ren Guo-Bin, Wang Zhi, Lou Shu-Qin, Jian Shui-Sheng
2004, 53 (6): 1862-1867. doi: 10.7498/aps.53.1862
Abstract +
The dispersion properties of high-index core Bragg fibers are investigated by superlattice model. We have analyzed the scaling properties of waveguide dispersion, discussed the dependence of waveguide dispersion on fiber structure parameters: the core radius, radial periodicity and filling ratio of the cladding, and designed an example structure of Bragg fiber for broadband flattened dispersion at 1.55μm.
Study on 1.55μ m AlGaInAs-InP polarization-insensitive semiconductor optical amplifier and its temperature characterizatics
Ma Hong, Chen Si-Hai, Jin Jin-Yan, Yi Xin-Jian, Zhu Guang-Xi
2004, 53 (6): 1868-1872. doi: 10.7498/aps.53.1868
Abstract +
Polarization-insensitive AlGaInAs-InP semiconductor optical amplifier is realized at wavelength of 1.55 μm. The active layer consists of three tensile-strained wells with a strain of 0.35%. The amplifier is fabricated with a ridge waveguide structure. The testing result shows that the amplifiers have an excellent polarization insensitivity (less than 0.5 dB) over the entire range of wavelength (from 1530 to 1580nm). The 1540 nm wavelength optical gain is 20 dB at the bias current of 200 mA. The AlGaInAs-InP optical amplifier shows good temperature characteristics, less than a 3dB reduction in the gain and polarization-insen sitivity when the temperature is raised from 25℃ to 65℃.
Vector analysis of dispersion for the fundamental cladding mode in photonic crystal fibers
Li Shu-Guang, Liu Xiao-Dong, Hou Lan-Tian
2004, 53 (6): 1873-1879. doi: 10.7498/aps.53.1873
Abstract +
The dispersions of the fundamental cladding mode in photonic crystal fibers(PCFs)are computed with a vectorial effective index approach in this paper. By comparing with the results obtained from biorthonormal-basis method or scalar effective method,it is found that the results of this paper are in accordance with that obtained from the biorthonormalbasis method, and that the scalar effective method is a good approximation at a lower air-filling fraction or higher normalized wave-number A/λ. For high accuracy at larger air-filling fraction or lower normalized wave-number A/λ,it is necessary to consider the vectorial method. The relation between effective index of cladding and microstructure of PCFs is discussed. The computation and analysis in this paper can provide a theoretic reference for designing of PCFs.
Numerical study on dispersion compensating property in photonic crystal fibers
Li Shu-Guang, Liu Xiao-Dong, Hou Lan-Tian
2004, 53 (6): 1880-1886. doi: 10.7498/aps.53.1880
Abstract +
The dispersion compensating property in photonic crystal fibers (PCFs) is simulated with a vectorial effective=index approach in this paper. It is found that the dispersion, dispersion slope, and Kappa parameter of PCFs can be designed neatly by changing the air hole size and the pitch in PCFs cladding. We can obtain PCFs with large absolute value of normal dispersion and negative dispersion slope at the wavelength of 1.55μm.Conventional communication nonshifted single-mode fibers (G652) and nonzero-dispersion shifted fibers (NZ-DSF,G655) can be compensated efficiently at wavelengths around 1.55μm low-loss optical communication window. It is demonstrated that there are huge potentials in designing dispersion compensating PCFs.
Numerical analysis of metal melting and evaporating with liquid surface depression
Bo Yong, Wang De-Wu, Ying Chun-Tong
2004, 53 (6): 1887-1894. doi: 10.7498/aps.53.1887
Abstract +
A metal molten-pool is described by the Navier-Stokes and energy equations and the depressed liquid surface is described by the Young-Laplace equations,and the metal evaporation is described by the BGK equation. The velocity and temperature distributions of the pool and the vapor heated by an electron gun are solved by the finite difference method. The numerical results show the evaporation rate of the metal increases with the power of the electron gun, so the vapor density increases and the vapor temperature decreases and the vapor velocity increases. The surface temperature of the pool with the depressed surface is less than the one of the pool with the plane surface, so is the metal evaporation rate. The difference of the evaporation rate between them increases with the power of the electron gun, so the liquid surface depression should be taken into consideration for a high power electron gun.
Modulatory character of microwave reflection behavior in electrorheological fluids
Huang Min, Zhao Xiao-Peng, Wang Bao-Xiang, Yin Jian-Bo, Cao Chang-Nian
2004, 53 (6): 1895-1899. doi: 10.7498/aps.53.1895
Abstract +
The microwave reflection behavior of electrorheological (ER) fluids containing TiO2 coated Kaolinite and Y doped BaTiO3 was investigated in the case that the direction of the TE10 module to the electrical field is vertical. We found that the reflection coefficient of TiO2 coated Kaolinite and Ydoped Ba TiO3 based ER fluids increased with the electrical field. However, the increase of reflection coefficient of Ydoped BaTiO3 based ER fluid was more significant compared with that of TiO2 coated Kaolinite. At the same time, the reflection coefficient of Y doped BaTiO3 ER fluid showed strong dependence on particle volume fraction. There was a critical volume fraction. When the volume fraction was lower than this critical value, the reflection coefficient gradually increased, otherwise the reflection coefficient initially increased and then decreased with electrical field. It was also found that the reflection wave phase of TiO2 coated Kaolinite ER fluid initially increased and reached its maximum value, then declined to a constant. The reflection wave phase of Y doped BaTiO3 ER fluid, however, steadily increased with the electrical field. We considered that the modulatory character of microwave reflection behaviors was attributed to the change in structure, electric properties of ER fluids and dispersed phase under electric field.
Asymptotic estimation for the system of electro-rheological fluids
Ouyang Cheng
2004, 53 (6): 1900-1902. doi: 10.7498/aps.53.1900
Abstract +
By the movement model of ball particles in electrorheological(ER) fluids, the asymptotic behavior of the movement of the particles in ER fluids is considered when the mass of the particles is small. Using the theory of differential inequalities, the expression of asymptotic estimation is given and proved.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
Structure transition and magnetic properties of ((Nd1-xErx)2Co15.5V1.5 compounds
Liu Bao-Yu, Liu Guo-Dong, Wu Guang-Heng, Yang Fu-Ming
2004, 53 (6): 1903-1908. doi: 10.7498/aps.53.1903
Abstract +
Structure and magnetic properties of (Nd1-xErx)2Co15.5V1.5compounds have been investigated by means of x-ray diffraction and magnetic measurements. The results obtained show that the (Nd1-xErx)2Co15.5V1.5 compounds crystallize in the Th2Zn17type structure for lower Er content(x0.5). The two structures coexist in the samples with x=0.4 and 0.5 The lattice constants a and c, and the unit cell volumeV show a decreasing tendency with increasing Er content in both structures. With increasing Er content, at room temperature, the anisotropy of the (Nd1-xErx)2Co15.5V1.5 compounds changes from the easycone type for low Er content(x0.5). The spin reorientation transition is observed for the compounds with x=0.0—0.5, and the spin reorientation temperature Tsr shows a decreasing tendency with increasing Er content. In addition, the Curie temperature TC and saturation magnetization Ms also decrease monotonically with the Er substitution for Nd in (Nd1-xErx)2Co15.5V1.5 compounds.
Liquid phase flow and microstructure formation during rapid solidification
Xu Jin-Feng, Wei Bing-Bo
2004, 53 (6): 1909-1915. doi: 10.7498/aps.53.1909
Abstract +
The characteristics of rapid solidification and microstructure formation of Fe-50wt%Sn hypermonotectic alloy heve been investigated. The rapid solidification microstructure is composed of regular arrays of fiberlike βSn phase, αFe phase distributed in fiber interspacings, and a small amount of metallic compounds. The angle between the fiber array and ribbon surface is within the range of 0—15°. According to the heat transfer equation and NavierStokes equation under melt-spinning condition, the solidification behaviors and microstructure formation processes are analyzed theoretically. It is revealed that the liquid phase flow has a remarkable effect on the phase separation of hypermonotectic alloy. This separation behavior occurs in the bottom of the melt puddle, which is about 200μm from roller surface, where the shapes of separated L2 droplets are deformed by shear stress. The collision/stretch of the separated L2 droplets finally leads to the formation of fiberlike microstructures. Due to the high cooling rate, the peritectic transformation at elevated temperatures is suppressed, thus resulting in the existence of some metastable phase at room temperature.
The rheological behavior of bulk metallic glass Zr41Ti14Cu12.5Ni10Be22.5
Wang Jing-Feng, Liu Lin, Pu Jian, Xiao Jian-Zhong
2004, 53 (6): 1916-1922. doi: 10.7498/aps.53.1916
Abstract +
The temperature dependence of viscosity of the bulk metallic glass Zr41Ti14Cu12.5Ni10Be22.5(Vit1)under constant heating condition was obtained by application of static extension measurement. A few strain rate peaks, which are associated with the glass transition and multistep crystallization, were observed in the temperature-strain rate curve. Above the glass transition temperature, the supercooled liquid of the bulk metallic glass showed the Newtonian rheological characteristic, and its temperature dependences of viscosity in supercooled liquid region can be fitted well with the Vogel-Fulcher-Tammann(VFT) equation. The sample exhibited the fragility parameter D* value of 36, the VFT temperature T0 of 319K and the fragility m value of 30 It was shown that the Vit1 alloy is a strong liquid, similar to sodium silicate liquids. However, the relation between temperature and viscosity deviated from VFT equation below the glass transition temperature.The phenomenon is tentatively interpreted in terms of free-volume model and structure relaxation concept.
Study of indium trihydroxide In (OH)Zr3 for ITO
Zhang Wei-Jia, Wang Tian-Min
2004, 53 (6): 1923-1929. doi: 10.7498/aps.53.1923
Abstract +
The structure of indium trihydroxide In(OH)3 for ITO(Indium Tin Oxide) has been analysed, the Madelung constant and lattice energy of In(OH)3 have been calculated, they are 2.9488 and -509521kJ/mol respectively, and a surface energy approximative expression is given, and then ulteriorly In(OH)3 crystal granule parameters are calculated in preparing nanosized In(OH)3 powder using the method of chemical precipitation,the growth rate 0.012nm/s about is given in this paper.
Pulse laser crystallization of silicon carbon thin films
Yu Wei, He Jie, Sun Yun-Tao, Zhu Hai-Feng, Han Li, Fu Guang-Sheng
2004, 53 (6): 1930-1934. doi: 10.7498/aps.53.1930
Abstract +
The pulsed laser crystallization of amorphous silicon carbon (aSiC) thin films have been implemented by using XeCl excimer laser. The aSiC thin films were prepared on silicon and quartz substrates by pulsed laser deposition. The surface morphology, atomic order and phase of the asdeposited and post annealing films have been analyzed by atomic force microscopy (AFM) and Raman scattering spectroscopy. AFM results show that aSiC films can be nanocrystallized at a proper laser energy. The size of nanocrystals in the post annealing films increases with the laser energy density; the separation into crystalline silicon and carbon after laser annealing is identified through Raman analysis. The mechanism of the pulsed laser crystallization of aSiC films is discussed to account for the post annealing characteristics.
Spectra analysis of Ce:YAlOZr3 single crystals grown by temperature gradient technique
Zeng Xiong-Hui, Zhao Guang-Jun, Xu Jun
2004, 53 (6): 1935-1939. doi: 10.7498/aps.53.1935
Abstract +
YAlO3 single crystal doped with Ce3+ at concentration 1at% was grown by the temperature gradient technique (TGT). The as rown crystal was pink. After H2 annealing or O2 annealing at 1400℃, the crystal turned into colorless. At the same time, the absorption spectra showed obvious changes. A colorcenters model could successfully explain the experimental phenomena. There are selfabsorption and selfexcitation around 330 nm according to the absorption spectrum and luminescence spectra excited by ultraviolet ray. The emission peak of luminescence spectra under ultraviolet ray excitation is around 368 nm and the emission peak of luminescence spectra under x-ray excitation is around 391nm. These results suggest that the self-absorption can be decreased under x-ray excitation. In addition, the emission intensity of the crystals annealed in H2 or air is higher than that of the as-grown crystal sample.
Dynamics of dislocation and global bifurcation for a system
Luo Shi-Yu, Shao Ming-Zhu, Wei Luo-Xia, Liu Zeng-Rong
2004, 53 (6): 1940-1945. doi: 10.7498/aps.53.1940
Abstract +
An external periodic field has been introduced in the Seeger equation; a motion equation of a crystal dislocation has been induced to Duffing function with the hard—spring properties.A global bifurcation of the system and a probable way into the chaos have been discussed by using Melnikov methoud. It shows that the system enters into the critical state , then enters the chaos by the cascading bifurcation, if δ/α is defined and Ω is reduced continuously.
Surface phonons on Ag (110): A study by means of analytic embedded-atom method
Yang Jian-Yu, Deng Hui-Qiu, Hu Wang-Yu
2004, 53 (6): 1946-1951. doi: 10.7498/aps.53.1946
Abstract +
The surface phonons on Ag(110)are studied in the present paper by means of the lattice dynamics and an analytic embeddedatom method(EAM). The phonon frequencies and disperse curves with surface relaxation are in good agreement with the data obtained by the helium atom scattering experiments. The polarization and localization of surface vibration are in accord with the two-dimensional symmetry in the surface. The S2 and S3 surface modes along-direction are predicted, which are in agreement with the helium atom scattering experiments.
The fabrication of high-quality periodic porous alumina templates
Ma Chun-Lan
2004, 53 (6): 1952-1955. doi: 10.7498/aps.53.1952
Abstract +
Porous alumina films can be achieved by anodizing an ultra pure aluminum sheet in proper conditions. Both the distribution and the size of the pores are regular. The depths of the pores are uniquely limited by the anodization time thus very deep pores can be obtained, in the order of mm. Such a porous structure can be employed to serve as the templates for nanosized materials. The Oxalic acid of 0.3mol/L was used in our experiments with the applied DC voltage 40 V. The two-step method was involved to fabricate the templates. The resultant templates exhibit regular porous section. The pore size is ~40—70 nm and the pore-pore spacing is~110 nm. The depth is~0.4 mm. The dependence of the template quality on the solution (oxalic acid) temperature was analyzed and the comparison between the single-step and two-step anodization was made. The results indicate that low solution temperature and two-step method are necessary.
Microstructural features of DC sputtered vanadium oxide thin films
Pan Meng-Xiao, Cao Xing-Zhong, Li Yang-Xian, Wang Bao-Yi, Xue De-Sheng, Ma Chuang-Xin, Zhou Chun-Lan, Wei Long
2004, 53 (6): 1956-1960. doi: 10.7498/aps.53.1956
Abstract +
microstructure, thin films of vanadium oxides, preferred orientation, DC magnetron sputtering
Growth structure and mechanical properties of TiN/SiC nano-multilayers
Lao Ji-Jun, Kong Ming, Zhang Hui-Juan, Li Ge-Yang
2004, 53 (6): 1961-1966. doi: 10.7498/aps.53.1961
Abstract +
The formation of cubic SiC(B1cubic SiC) and its effect on the mechanical properties of TiN/SiC nanomultilayers were studied in this work. The results show that in TiN/SiC mulytilayer, SiC exists as a cubic structure and forms coherent epitaxially grown columnar crystal superlattice with TiN when the thickness of SiC layer is about 06nm. Multilayers show the superhardness effect with the enhancement of hardness and elastic modulus, and the highest hardness excess 60GPa. With the increase of SiC layer thickness, B1SiC transforms into amorphous phase and impedes the coherent epitaxial growth of multilayers. Multilayers present layer structure character composed of TiN nanocrystal and amorphous SiC. Correspondingly, the hardness and elastic modulus of multilayers decrease. The formation of cubic SiC and coherent growth structure of cubic SiC and TiN appear to be likely the origin of the superhardness effect of TiN/SiC nano-multilayers.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Study of CaTiO3 structure under high pressure
Wu Xiang, Qin Shan, Wu Zi-Yu, DongYu-Hui, Liu Jing, Li Xiao-Dong
2004, 53 (6): 1967-1971. doi: 10.7498/aps.53.1967
Abstract +
In situ high-pressure (up to 44-53 GPa) energy dispersive x-ray diffraction experiments have been carried out on CaTiO CaTiO 3, structure, high pressure, equation of state in a diamond anvil cell at room temperature by using synchrotron radiation. Experimental data show that the a and b axes have similar compressibilities with large variation, while the c axis is less compressible with increasing pressure. However, there is no evidence of any structural transformation in this pressure range. The isothermal P-V equation of the state of CaTiO CaTiO 3, structure, high pressure, equation of state is fitted using the Murnaghan equation of state, which yields values of V0=0.2245(6)nm 3 and K 0=222(9) GPa assuming the pressure derivative K′0=4 According to the relation of the pseudo-cubic angle γpc and pressure, the structure of CaTiO CaTiO 3, structure, high pressure, equation of state will reduce its symmetry under hydrostatic pressure.
The study of anti-Stokes photoluminescence properties in the YZr2OZr3:Er3+ nanocrystals
Wang Xin, Shan Gui-Ye, An Li-Min, Chao Ke-Fu, Zeng Qing-Hui, Chen Bao-Jiu, Kong Xiang-Gui
2004, 53 (6): 1972-1976. doi: 10.7498/aps.53.1972
Abstract +
The homogeneous precipitation method was used for preparing nanocrystalline erbium-doped Y2O3 with various molar concentrations. These materials synthesized in the system were characterized with XRD, SEM micrograph and PL spectra. Stokes and antiStokes PL emissions of Y2O3:Er3+ nanocrystals were investigated, whose intensities were varied evidently with a range of dopant erbium ions concentration. When the molarity of dopant erbium ions is close to 2.0%, the relative intensities of anti-Stokes PL spectra are dominant. From the XRD and SEM micrograph, the Y2O3:Er3+ nanocrystal with cubic structure is verified and the distribution of particles size is homogeneous. The experimental results indicate that the anti-Stokes emission results from twophoton absorption process in the Y2O3:Er3+ nanocrystal system.
Spin-orbit and exchange interaction in a HgMnTe magnetic two-dimensional electron gas
Qiu Zhi-Jun, Gui Yong-Sheng, Shu Xiao-Zhou, Dai Ning, Guo Shao-Ling, Chu Jun-Hao
2004, 53 (6): 1977-1980. doi: 10.7498/aps.53.1977
Abstract +
Spin-orbit interaction and spd exchange interaction are investigated by analyzing beating patterns of Shubnikov-de Hass oscillations in a HgMnTe magnetic two-dimensional electron gas (2DEG) at various temperatures.The results show that (1) spin-orbit interaction results in zero-magnetic-field spin splitting in 2DEG; (2) spin-orbit interaction is dominant at low magnetic field, and the total spin-splitting decreases with increasing magnetic field due to the influence of Landau splitting and Zeeman splitting; (3) at a high magnetic field, the spd exchange interaction tends to saturate and the spin splitting corresponds to Zeeman splitting. The experiments demonstrate that the spin splitting deduced from fast Fourier transformation (FFT) of SdH oscillations versus. 1/B is different from zero-magnetic-field spin splitting when Zeeman spin splitting is comparable to zero-magnetic-field spin splitting.
Microscopic origins of the spin-Hamiltonian parameters for 3d2 state ions in a crystal
Yang Zi-Yuan
2004, 53 (6): 1981-1988. doi: 10.7498/aps.53.1981
Abstract +
By adopting the intermediate-field scheme, the microscopic origins of the spin-Hamiltanian (SH) parameters for 3d2ion at trigonal (C3v, D3, D3d) symmetry, taking into account the spinspin(SS) and spin-other-orbit(SOO) coupling interactions omitted in previous publications, have been investigated on the basis of complete diagonalization method(CDM). We find that the SH parameters arise from four microscopic mechanisms, i.e. (1) Spin-orbit(SO) coupling mechanism; (2) SS coupling mechanism; (3) SOO coupling mechanism; (4) SO-SS-SOO combined coupling mechanism. The SO coupling mechanism in the four coupling mechanisms is the most important one, but the contributions to zero-field splitting parameter D from other three coupling mechanisms cannot be omitted.
Spin polarization study on one-dimensional ferromagnetic metal/conjugated polymers
Fu Ji-Yong, Ren Jun-Feng, Liu De-Sheng, Xie Shi-Jie
2004, 53 (6): 1989-1993. doi: 10.7498/aps.53.1989
Abstract +
We investigated theoretically the properties of spin polarization in organic polymer contacting magnetic atoms. Dependence of the spin polarization on the strength of the electron-phonon coupling in a polymer and the spin-dependent effect of the interface coupling were discussed. By modulating the strength of spin splitting, we found that the spin polarization within an organic chain is weaker than that within a metal chain, but stronger than that within a semiconductor.
Investigation of the model of the discharge properties of the unbalanced magnetron sputtering system
Mu Zong-Xin, Li Guo-Qing, Che De-Liang, Huang Kai-Yu, Liu Cui
2004, 53 (6): 1994-1999. doi: 10.7498/aps.53.1994
Abstract +
The voltage current property of the unbalanced magnetron sputtering (UMS) system has significant influence on the sputtering process and films deposition process. Based on the analysis of the relationship between unbalanced magnetic field and properties of the unbalanced magnetron sputtering system, according to Child law the model of the V-I property of the UMS system is set up. Comparisons between the model calculation results and the experimental data indicate that the model correctly expresses the relation between the unbalanced magnetic field and the discharge properties of the UMS system.
 Left-right coupling of circularly polarized light propagating inside biaxially gyrotropic left-handed media
Shen Jian-Qi, Zhuang Fei
2004, 53 (6): 2000-2004. doi: 10.7498/aps.53.2000
Abstract +
The left-right coupling of circularly polarized light in biaxially gyrotropic left-handed media is considered in the present paper. It is shown that this left-right coupling gives rise to the frequency shifts of both left and right handed polarized light propagating inside the biaxially gyrotropic left-handed media. In addition, we discuss the physical origin of left-right couplings of polarized light (i.e.,the nonlocal polarization effect), and its potential applications (e.g., controllable position-dependent frequency shifts) in information science.
Study on optical properties of diamond films by means of infrared spectroscopic ellipsometry
Shen Hu-Jiang, Wang Lin-Jun, Fang Zhi-Jun, Zhang Ming-Long, Yang Ying, Wang Lin, Xia Yi-Ben
2004, 53 (6): 2009-2013. doi: 10.7498/aps.53.2009
Abstract +
We have made spectroscopic ellipsometric measurement to characterize the structure of diamond films in infrared region (2.5—12.5μm). These films are grown respectively by microwave plasma chemical vapor deposition (MPCVD) and hot filament chemical vapor deposition (HFCVD). It is found that the establishment of appropriate models has the strongest influence on the fit of ellipsometric spectra. The best fit is achieved for MPCVD film with a 77.5nm middle layer of SiO2, and for HFCVD film with a 879nm rough surface layer included by Bruggeman effective medium approximation. Finally, the refractive index (n) and the extinctive coefficient (k) are calculated for both films, which show that the film grown by MPCVD is optically better than by HFCVD apparently.
Investigation of defect properties in doped diamond films
Hu Xiao-Jun, Li Rong-Bin, Shen He-Sheng, He Xian-Chang, Deng Wen, Luo Li-Xiong
2004, 53 (6): 2014-2018. doi: 10.7498/aps.53.2014
Abstract +
The defect properties in chemical vapor deposition diamond films doped by sulfur and boron were investigated by the Doppler broadening measurements and electron paramagnetic resonance (EPR). The results show that the defects annihilating the positrons is almost the same in various doped films, and the interactions between the dopants and the positrons are not distinct. In addition, a small amount of boron atoms can improve the quality of diamond films. The EPR signals of the diamond films arise from carbon dangling bonds.
The electron trap effect of the sulfur + gold sensitization center on the photoelectron behaviors
Li Xiao-Wei, Li Xin-Zheng, Jiang Xiao-Li, Yu Wei, Tian Xiao-Dong, Yang Shao-Peng, Fu Guang-Sheng
2004, 53 (6): 2019-2023. doi: 10.7498/aps.53.2019
Abstract +
The temporal behavior of free photoelectrons and shallow-trapped electrons in the T grains AgBrI emulsion was detected with the microwave absorption and dielectric spectrum detection technique. The results indicate that the effect of sensitization center on the photoelectron decay differs in different time ranges of the first-order decay curves, and that the electron trap effects of sulfur+gold sensitization center change from shallow trap to deep trap with increasing sensitization density. The optimal sensitization density of sulfur+gold was obtained on the basis of the relationship between the sensitization density and the decay time.
Effect of magnetostatic field on the microstructure of magnesium alloy
Bao Wei-Ping, Xu Guang-Ming, Ban Chun-Yan, Cui Jian-Zhong
2004, 53 (6): 2024-2028. doi: 10.7498/aps.53.2024
Abstract +
Magnesium alloy is a light alloy material with potential applications,but many problems need to be studied for it.In the experiment the process of solidification and the microstructure of magnesium alloy under the effect of magnetostatic field was studied.Some phenomena were found that the microstructures of magliesium alloy were changed obviously:the thickness of grain boundary was reduced,the content of solute in the grain was increased apparently and reduced slightly in the grain boundary.The analysis showed that urlder the effect of magnetostatic field the microstructure of magnesium alloy was improved,and this has great significance to improve the propenies of magnesium alloy.