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Volume 23 Issue 1
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Original Articles
Miura Transformation for the TD Hierarchy
ZHU Jun-Yi, GENG Xian-Guo
Chin. Phys. Lett. 2006, 23 (1): 1-3 .  
Abstract   PDF(pc) (176KB) ( 907 )
Based on the spectral problem associated with the TD hierarchy, a recursion relation for the adjoined spectral problem is obtained, by which the TD hierarchy is transformed into the modified one. As a special example, the first nontrivial member in the modified hierarchy is reduced to an integrable Heisenberg spin equation.
Rational Solutions in a Coupled Burgers System
Chin. Phys. Lett. 2006, 23 (1): 4-6 .  
Abstract   PDF(pc) (287KB) ( 536 )
Three types of the rational solutions for a new coupled Burgers system are studied in detail in terms of the reduction and decoupled procedures. The first two types of rational solutions are singular and valid for one type of model parameter c>0, and another type of rational solutions is nonsingular at any type and valid for another type of model parameter c<0.
Scalar Field Model of Dark Energy In the Double Complex Symmetric Gravitational Theory
SHAO Ying, GUI Yuan-Xing, WANG Wei
Chin. Phys. Lett. 2006, 23 (1): 7-9 .  
Abstract   PDF(pc) (192KB) ( 546 )
The scalar field model of dark energy is established in the double complex symmetric gravitational theory. The universe we live in is taken as the real part of double complex space MC4(J). The two cases of scalar field (ordinary and phantom scalar field) are discussed in a unified way. Not only can the double Friedmann equations be obtained, but also the equation of state for dark energy, potential V(Ф) and scalar field Ф can be expressed. Hence, a new method is proposed to study dark energy and the evolution of the universe.
The Singular Kane Oscillator
Babayev A. M., Cakmaktepe S.
Chin. Phys. Lett. 2006, 23 (1): 10-12 .  
Abstract   PDF(pc) (212KB) ( 479 )
The energy spectrum of carriers in narrow band gap semiconductor nanocrystals are studied theoretically taking into account the nonparabolicity of charge carriers dispersion laws. The confinement potential of nanocrystals is approximated to be λr21r-2, and the dispersion laws are considered within the framework of the three-band Kane model.
Resonance-Radiation Force Exerted by a Circularly Polarized Light on an Atomic Wave Packet
YE Yong-Hua, ZENG Gao-Jian, LI Jin-Hui
Chin. Phys. Lett. 2006, 23 (1): 13-16 .  
Abstract   PDF(pc) (228KB) ( 409 )
We study the behaviour of an atomic wave packet in a circularly polarized light, and especially give the calculation of the radiative force exerted by the circularly polarized light on the atomic wave packet under the resonance condition. A general method of the calculation is presented and the result is interesting. For example, under the condition that the wave packet is very narrow or/and the interaction is very strong, no matter whether the atom is initially in its ground state or excited state, as time approaches to infinity, the resonance-radiation force exerted by the light on the atom approaches to zero. If the atom is initially in its ground state and excited state with the probability 1/2 respectively, and if the momentum density is a even function, then the resonance-radiation force exerted by the light on the atom is equal to zero.

Probabilistic Teleportation of an Unknown Two-Particle State with a Four-Particle Pure Entangled State and Positive Operator Valued Measure
YAN Feng-Li, DING He-Wei
Chin. Phys. Lett. 2006, 23 (1): 17-20 .  
Abstract   PDF(pc) (196KB) ( 949 )
We propose a scheme for probabilistic teleportation of an unknown two-particle state with a four-particle pure entangled state and positive operator valued measure (POVM). In this scheme the teleportation of an unknown two-particle state can be realized with certain probability by performing two Bell state measurements, a proper POVM and a unitary transformation.
Quasinormal Modes of a Coupled Scalar Field in the Acoustic Black Hole Spacetime
CHEN Song-Bai, JING Ji-Liang
Chin. Phys. Lett. 2006, 23 (1): 21-24 .  
Abstract   PDF(pc) (216KB) ( 592 )
By using the third-order Wentzel--Kramers--Brillouin approximation and the monodromy methods, the quasinormal modes of a coupled scalar field in the canonical non-rotating acoustic black hole spacetime are investigated. It is shown that the coupling between the scalar field and background metric affects the quasinormal frequencies. At low overtones, both the real part and the magnitude of imaginary part increase with the couple factor ξ. For the larger ξ, both of them are almost linearly related to the couple factor. At high overtones, it is found that the frequency formula of the quasinormal modes is 2πω/k=ln[1+2cos(√9-24ξ/5)π]-i(2n+1)π, which means that when ξ is larger, the real part is the linear function of ξ1/2.
Lower Bounds on Negative Energy Densities for the Scalar Field in Flat Spacetime
SHU Wei-Xing, YU Hong-Wei, REN Zhong-Zhou, WU Pu-Xun, LI Fei
Chin. Phys. Lett. 2006, 23 (1): 25-28 .  
Abstract   PDF(pc) (222KB) ( 438 )
We obtain a lower bound on the spacetime-weighted average of the energy density for the scalar field in four-dimensional flat spacetime. The bound takes the form of a quantum inequality. The inequality does not rely on the quantum state and its form is only related to the weights, namely the spacetime sampling functions which are assumed to be smooth, positive and compactly supported. It is found that the inequality is just equal to the temporal quantum energy inequality. When the characteristic length of the temporal sampling function tends to zero, the lower bound becomes divergent. This is consistent with the fact that the spatial restriction on negative energy density does not exist in four-dimensional spacetime.
Intensity Correlation Function and Associated Relaxation Time of a Saturation Laser Model with Correlated Noises
ZHU Ping, CHEN Shi-Bo, MEI Dong-Cheng
Chin. Phys. Lett. 2006, 23 (1): 29-31 .  
Abstract   PDF(pc) (200KB) ( 455 )
We investigate the intensity correlation function C(s) and its associated relaxation time Tc for a saturation model of single-mode laser with correlated noises. The expressions of C(s) and Tc are derived by means of the projection operator method, and effects of correlations between an additive noise and a multiplicative noise are discussed by numerical calculation. Based on the calculated results, it is found that the correlation strength λ between the additive noise and the multiplicative noise can enhance the fluctuation decay of the laser intensity.

Global Chaos Synchronization between Two New Different Chaotic Systems via Active Control
SUN Feng-Yun
Chin. Phys. Lett. 2006, 23 (1): 32-34 .  
Abstract   PDF(pc) (189KB) ( 1109 )
We present chaos synchronization between two new different chaotic systems by using active control. The proposed controller ensures that the states of the controlled chaotic response system asymptotically synchronizes the states of the drive system. Numerical simulations are shown to verify the result.
Transitions to Long-Resident States in Coupled Chaotic Oscillators
AO Bin, ZHENG Zhi-Gang
Chin. Phys. Lett. 2006, 23 (1): 35-38 .  
Abstract   PDF(pc) (282KB) ( 515 )
The behaviour of coupled chaotic oscillators before complete synchronization is investigated. Long-time residence of trajectories appears besides one of the saddle foci. The tendency that orbits of the two oscillators get closer becomes faster with the increasing coupling strength. The diffusion of phase difference between the two oscillators is first enhanced and then suppressed. There are exact correspondences among these phenomena. The mechanism of these correspondences is explored. These phenomena uncover the route to synchronization of coupled chaotic oscillators.
Numerical Determination of the Critical Value for the (1+1)-Dimensional Sine-Gordon Model
YUAN Qing-Xin, DING Guo-Hui
Chin. Phys. Lett. 2006, 23 (1): 39-41 .  
Abstract   PDF(pc) (221KB) ( 577 )
A new procedure of potential importance sampling method is applied to investigate the phase transition of the (1+1)-dimensional sine-Gordon model. With this method, we obtain the Kosterlitz--Thouless-type phase transition critical value of β2cong 8π with a relative error as small as 0.4%.
Self-Assembly of Micro-Parts onto Si Substrates at Liquid--Liquid Interface
LIU Mei, ZHANG Jian-Gang, LV Yao, XIA Shan-Hong
Chin. Phys. Lett. 2006, 23 (1): 42-44 .  
Abstract   PDF(pc) (216KB) ( 842 )
We report a new approach for the self-assembly of cuboid micro-parts onto Si substrates to construct three-dimensional microstructures. To perform assembly, the Si substrates are prepared with a deep cavity array as binding sites. An aggregate composed of hundreds of uniformly aligned micro-parts is formed at the C10F18--H2O interface. The micro-parts are arranged by passing the substrate through the aggregate of micro-parts, thus the micro-parts are left on the substrate, and then the substrate is vibrated ultrasonically in the solution, making it possible for the micro-parts to fall into the cavities on the substrate. Finally the substrate is pulled out of the solution after assembly. This technique could give a high yield of up to 70%, providing a new method for micro-assembly.
Is Kano--Nucleon Interaction Consistent with Pentaquark
DENG Cheng-Rong, PING Jia-Lun,
Chin. Phys. Lett. 2006, 23 (1): 45-47 .  
Abstract   PDF(pc) (225KB) ( 443 )
The quark-delocalization colour-screening model is employed to calculate the effective potential between nucleon and kaon. The results show that the potentials are attractive in the I=0 channel and repulsive in the I=1 channel. The interactions are very weak between K+n or K0p due to the cancellation between I=0 and I=1. It is possible to have a high s-wave resonance (1615MeV), but the width may be too wide to be observed in the experiments.
Investigation of Dilaton--Gluon Coupling Potential in Charmonium Family
PING Rong-Gang, CHEN Hong, PING Rong-Xiang
Chin. Phys. Lett. 2006, 23 (1): 48-51 .  
Abstract   PDF(pc) (233KB) ( 838 )
The behaviour of dilaton--gluon coupling (DGC) potential is investigated by studying charmonium spectra, annihilation rates and E1 transition rates systematically. We find that in the non-relativistic quantum chromodynamics approximation, the charmonium properties can be described by the DGC potential.
Asymptotic Normalization Coefficient of 27P → 26Si + p and Radius of 27P Halo
GUO Bing, LI Zhi-Hong, LIU Wei-Ping, BAI Xi-Xiang
Chin. Phys. Lett. 2006, 23 (1): 52-54 .  
Abstract   PDF(pc) (233KB) ( 470 )
The asymptotic normalization coefficient of the virtual decay 27P → 26Si + p is extracted to be 1840±240fm-1 from the peripheral 26Mg(d,p)27Mg reaction using charge symmetry of mirror pair, for the first time. It is then used to derive the rms radius of the valence proton in the ground state of 27P. We obtain the rms radius 2>1/2 = 4.57 ± 0.36fm, significantly larger than the matter radius of 27P. The probability of the valence proton outside the matter radius of 27P is found to be 73%. The present work supports the conclusion that the 27P ground state has a proton halo structure.
Astrophysical Reaction Rates of the 8Li(p,\pmb \gamma)9Beg.s. Direct Capture Reaction
SU Jun, LI Zhi-Hong, GUO Bing, LIU Wei-Ping, BAI Xi-Xiang, ZENG Sheng, LIAN Gang, YAN Sheng-Quan, WANG Bao-Xiang, WANG You-Bao
Chin. Phys. Lett. 2006, 23 (1): 55-57 .  
Abstract   PDF(pc) (247KB) ( 982 )
Based on the angular distribution of the 8Li(d,n)9Beg.s. reaction at Ec.m.=8.0MeV and distorted wave Born approximation analysis, the single particle spectroscopic factor S1,3/2 for the ground state of 9Be = 8Li otimes p is derived to be 0.64 ± 0.21. In addition, we deduce the astrophysical S-factors and rates of the 8Li(p,γ)9Beg.s. direct capture reaction at energies of astrophysical interests.
Deformations and B(E2) Values of Ne and Mg Nuclei around
ZHI Qi-Jun, REN Zhong-Zhou,
Chin. Phys. Lett. 2006, 23 (1): 58-60 .  
Abstract   PDF(pc) (194KB) ( 458 )
The ground-state deformations and B(E2) values of Ne and Mg nuclei around N=20 are studied within the framework of the macroscopic--microscopic (MM) model with isospin-dependent Nilsson potential. The calculated results are compared with those obtained from standard Nilsson parameters and with experimental ones. It is found that the calculations with new Nilsson parameters well reproduce the experimental large deformations and B(E2) values for Ne and Mg nuclei around N=20. The N=20 shell closure of Ne and Mg isotopes disappears in the MM model and this agrees with experimental data.
First Principles Study on NaxLi1-xFePO4 As Cathode Material for Rechargeable Lithium Batteries
OUYANG Chu-Ying, WANG De-Yu, SHI Si-Qi, WANG Zhao-Xiang, LI Hong, HUANG Xue-Jie, CHEN Li-Quan
Chin. Phys. Lett. 2006, 23 (1): 61-64 .  
Abstract   PDF(pc) (209KB) ( 615 )
The electronic structure and ionic dynamic properties of pure and Na doped (Li site) LiFePO4 have been investigated by first-principles calculations. The band gap of the Na doped material is much narrow than that of the undoped one, indicating of better electronic conductive properties. First-principles based molecular dynamic simulations have been performed to examine the migration energy barriers for the Li ion diffusion. The results shown that the energy barriers for Li diffusion decreased a little along the one-dimensional diffusion pathway, indicating that the ionic conductive property is also improved, as compared with the high valance doping (such as Cr) cases.
Influence of Morse Potential on DNA Dynamics
Chin. Phys. Lett. 2006, 23 (1): 65-68 .  
Abstract   PDF(pc) (226KB) ( 396 )
Based on the Peyrard--Bishop--Dauxois (i.e. the extended Peyrard--Bishop) model of DNA dynamics, the transversal hydrogen interaction is modelled by Morse potential and the impact of the Morse parameters on the DNA dynamics is investigated. In particular, we show how modulation of the signal, moving through the DNA chain, depends on those parameters. It is also shown that the DNA dynamics represents the interplay between dispersion and nonlinearity. Finally, we discuss the values of coupling constants k and K.
Ground-State Ionization Potentials for Lithium through Neon Isoelectronic Sequences with Z = 37--82
Chin. Phys. Lett. 2006, 23 (1): 69-72 .  
Abstract   PDF(pc) (211KB) ( 1166 )
The ground-state ionization potentials of different isoelectronic sequences are calculated systemically with the multi-configuration Dirac--Fock method. The relativistic corrections, Breit and QED effects are included in the calculation. These results are compared with the scanty existing theoretical and experimental data in the literature, Analytical expressions are obtained for expressing our theoretical data along the different sequences.
Observation of Atomic Emission Enhancement by fs-ns Dual-Pulse Laser-Induced Breakdown Spectroscopy
YAN Li-Xin, ZHANG Yong-Sheng, ZHANG Li-Rong, LIU Jing-Ru, CHENG Jian-Ping, Lü Min
Chin. Phys. Lett. 2006, 23 (1): 73-74 .  
Abstract   PDF(pc) (187KB) ( 687 )
An experiment of a 500-fs KrF laser pulse incident upon a high density supersonic O2 gas jet synchronously with an ns frequency-doubled Nd:YAG laser pulse is performed in orthogonal configuration. Significant atomic emission enhancement of over forty-fold is observed with an optical multi-channel analyser. The enhancement effect is probably attributed to the different ionization mechanisms between fs and ns laser pulses.
Photoionization of Ge13 in the Inner-Shell 2p Excitation Energy Region
LIANG Gui-Yun, ZHAO Gang
Chin. Phys. Lett. 2006, 23 (1): 75-78 .  
Abstract   PDF(pc) (235KB) ( 438 )
The photoionization cross sections of the levels belonging to the ground configuration [Ne]3s23p63d of Ge13 are investigated using the fully relativistic R-matrix method in the 2p-3d excitation region. The photoionization cross section is dominated by 2p-3d resonances. The detailed resonance structures are described and analysed with the resonance positions, widths and oscillator strengths to be determined. Good agreement is obtained between the length and velocity forms of the resonance oscillator strengths. The relative difference is less than 8%.
A Method for Determining the Phase Transition Point of the Bose--Einstein Condensation by Judging the Fitting Errors
MA Xiu-Quan, CHEN Shuai, YANG Fan, XIA Lin, ZHOU Xiao-Ji, WANG Yi-Qiu, CHEN Xu-Zong,
Chin. Phys. Lett. 2006, 23 (1): 79-82 .  
Abstract   PDF(pc) (300KB) ( 505 )
In this paper, We demonstrate an approach to determine the phase transition point and critical temperature of Bose-Einstein condensation. During the fitting sequence of time-of-flight images, for just one picture we take four kinds of different calculations instead of only one. By calculating the quantitative least-square errors, which have always been neglected before, we find out that this value can act as a criterion to judge the status of atom clouds. Using this criterion, we can not only discriminate the status around the phase transition point, but can also find the critical point precisely. Also with this method, we can achieve the totally automatical running of calculating programs without human's judgments.

Effect of Laser Cooling on Frequency Standard of Single Ca+ Ion Trapped in a Radio-Frequency Paul Trap
WU Li-Jin, SHI Ting-Yun, GAO Ke-Lin
Chin. Phys. Lett. 2006, 23 (1): 83-86 .  
Abstract   PDF(pc) (234KB) ( 875 )
The source of systematic frequency shift of single-ion optical frequency standard of 40Ca+ ion trapped in endcap trap and laser-cooled to a few of mK is analysed and calculated. Second-order Doppler shift, Stark shift due to micromotion and thermal motion, blackbody Stark shift and ac Stark shift are calculated for the ground state and excited 3d 2D5/2 state. The Hertz-level measurement of the optical clock frequency in a single 40Ca+ ion can be performed.
Laser-Induced Continuum Structure of NO Molecules in Two-Colour Femtosecond Pulsed Laser Fields
WANG Sen-Ming, YUAN Kai-Jun, CONG Shu-Lin
Chin. Phys. Lett. 2006, 23 (1): 87-90 .  
Abstract   PDF(pc) (263KB) ( 755 )
The method of quantum wave packet dynamics is used to study the multiphoton ionization of NO molecules via a two-photon Raman coupling and a laser-induced continuum structure (LICS) state in two-colour strong femtosecond pulsed laser fields. Time-and energy-resolved photoelectron energy spectra are calculated for describing three photoionization channels. The population transfers through the LICS and the Raman coupling passages are discussed.
Semiclassical Approach to Non-Sequential Double Ionization of Diatomic Molecules in Strong Laser Field
LIU Jie, CHEN Jing,
Chin. Phys. Lett. 2006, 23 (1): 91-94 .  
Abstract   PDF(pc) (230KB) ( 803 )
We develop a semiclassical model to describe the non-sequential double ionization of diatomic molecules in an intense linearly polarized field, achieving insight into the two-electron correlation effect in the ionization dynamics. Compared to the experimental data of nitrogen molecules, our model shows a good agreement in the tunnelling regime and a qualitative agreement in the over-barrier regime. We find that the classical collisional trajectories are the main source of the double ionization in the tunnelling regime. As a prediction of our theory, we also calculate the double ionization ratios of H222+H22+ for hydrogen molecules and predict a ratio less than that of nitrogen molecules.
Multi-Electron Processes in 13C6+ Ions with Neon Collisions in Energy Region 4.15--11.08keV/u
RUAN Fang-Fang, CAI Xiao-Hong, YU De-Yang, LU Rong-Chun, SHAO Cao-Jie, LU Jun, CUI Ying, SHAO Jian-Xiong, XU Xu, ZHANG Hong-Qiang, DING Bao-Wei, YANG Zhi-Hu, CHEN Xi-Meng
Chin. Phys. Lett. 2006, 23 (1): 95-98 .  
Abstract   PDF(pc) (242KB) ( 570 )
The cross-section ratios of double-, triple-, quadruple-, and the total multi-electron processes to the single electron capture process (σDESC, σTESC, σQESC and σMESC as well as the relative ratios among reaction channels in double-electron active, triple-electron active and quadruple-electron active are measured in 13C6+--Ne collision in the energy region of 4.15--11.08keV/u by employing position-sensitive and time-of-flight coincident techniques. It is determined that the cross-section ratios σDESC, σTESC, σQESC and σMESC are approximately the constants of 0.20±0.03, 0.16±0.04, 0.06±0.02 and 0.42±0.05. These values are obviously smaller than the predictions of the molecular Coulomb over-the-barrier model (MCBM) [J. Phys. B 23 (1990) 4293], the extended classical over-the-barrier model (ECBM) [J. Phys. B 19 (1986) 2925] and the semiempirical scaling laws (SL) [Phys. Rev. A 54 (1996) 4127]. However, the relative ratios among partial processes of DE, TE and QE are found to depend on collision energy, which suggests that the collision dynamics depends on the collision velocity. The limitation of velocity-independent character of ECBM, MCBM and SL is undoubtedly shown.
Stopband Phenomena in the Passband of Left-Handed Metamaterials
ZHAO Xiao-Peng, ZHAO Qian, ZHANG Fu-Li, ZHAO Wei, LIU Ya-Hong
Chin. Phys. Lett. 2006, 23 (1): 99-102 .  
Abstract   PDF(pc) (234KB) ( 622 )
Stopband phenomena are reported in the passband of left-handed metamaterials. The samples with linear defect are designed by removing one layer of split ring resonators (SRRs). It is shown that the left-handed transmission peaks have a distinct transform with the relative deviation of the SRRs centre from the wire centre δ, from a single left-handed peak, double left-handed peaks with different magnitude to no transmission peak, i.e. left-handed properties of metamaterials disappear. Numerical simulation shows that the change of δ makes the effective permeability shift at a frequency range, where stopband occurs. It is thought that the stopband in left-handed passband is due to the symmetry breaking between SRRs and wires in the metamaterials.
Total Field and Scattered Field Technique for Fourth-Order Symplectic Finite Difference Time Domain Method
SHA Wei, HUANG Zhi-Xiang, WU Xian-Liang, CHEN Ming-Sheng
Chin. Phys. Lett. 2006, 23 (1): 103-105 .  
Abstract   PDF(pc) (246KB) ( 589 )
Using symplectic integrator propagator, a three-dimensional fourth-order symplectic finite difference time domain (SFDTD) method is studied, which is of the fourth order in both the time and space domains. The method is nondissipative and can save more memory compared with the traditional FDTD method. The total field and scattered field (TF-SF) technique is derived for the SFDTD method to provide the incident wave source conditions. The bistatic radar cross section (RCS) of a dielectric sphere is computed by using the SFDTD method for the first time. Numerical results suggest that the SFDTD algorithm acquires better stability and accuracy compared with the traditional FDTD method.
Nonparaxial Dark-Hollow Gaussian Beams
GAO Zeng-Hui, LÜ, Bai-Da
Chin. Phys. Lett. 2006, 23 (1): 106-109 .  
Abstract   PDF(pc) (230KB) ( 479 )
The concept of nonparaxial dark-hollow Gaussian beams (DHGBs) is introduced. By using the Rayleigh--Sommerfeld diffraction integral, the analytical propagation equation of DHGBs in free space is derived. The on-axis intensity, far-field equation and, in particular, paraxial expressions are given and treated as special cases of our result. It is shown that the parameter f =1/kw0 with k being the wave number and w0 being the waist width determines the nonparaxiality of DHGBs. However, the parameter range, within which the paraxial approach is valid, depends on the propagation distance. The beam order affects the beam profile and position of maximum on-axis intensity.
The Carrier--Envelope Phase of Focused Few-Cycle Laser Pulses
ZHOU Yong-Heng, JIANG Hong-Bing, GONG Qi-Huang
Chin. Phys. Lett. 2006, 23 (1): 110-112 .  
Abstract   PDF(pc) (197KB) ( 516 )
The Gouy phase shift modulates the carrier-envelope phase of a focused few-cycle laser pulse. We investigate the variations of the carrier--envelope (CE) phase of a pulsed Gaussian beam on and off the axis by the first-order approximation and numerical calculation. The CE phase undergoes a π shift from minus infinity to infinity, and it changes fastest with distance at the focus. The variation of CE phase on propagation distance is nearly independent of pulse duration Δt when Δt is greater than 10fs and the first order approximation fits this result very well. The maximum difference of CE phase between a pulse with duration of one cycle and the result of first-order approximation is 0.09.
Beam Displacement in a Layered Configuration due to Formation of Standing Waves
WANG Li-Gang
Chin. Phys. Lett. 2006, 23 (1): 113-115 .  
Abstract   PDF(pc) (201KB) ( 554 )
We obtain a large positive lateral shift of a light beam reflected from a layered configuration due to the formation of the unusual standing wave, which acts like the forward surface wave. An explicitly analytic condition to obtain the large lateral shift is presented. Finally we present a numerical simulation for the lateral displacement of a Gaussian beam.
Optical Security System Based on the Biometrics Using Holographic Storage Technique with a Simple Data Format
Jun Won AN
Chin. Phys. Lett. 2006, 23 (1): 116-119 .  
Abstract   PDF(pc) (282KB) ( 1005 )
We implement a first practical holographic security system using electrical biometrics that combines optical encryption and digital holographic memory technologies. Optical information for identification includes a picture of face, a name, and a fingerprint, which has been spatially multiplexed by random phase mask used for a decryption key. For decryption in our biometric security system, a bit-error-detection method that compares the digital bit of live fingerprint with of fingerprint information extracted from hologram is used.
Cluster States from Quantum Logic Gates with Trapped Ions in Thermal Motion
YANG Wen-Xing, ZHAN Zhi-Ming, LI Jia-Hua
Chin. Phys. Lett. 2006, 23 (1): 120-123 .  
Abstract   PDF(pc) (217KB) ( 471 )
Following the recent proposal by Briegel et al. [Phys. Rev. Lett. 86 (2001) 910], a procedure is proposed for one-step realizing quantum control phase gates with two trapped ions in thermal motion. It is shown
that the scheme can also be used to create a new special type of entangled states, i.e., cluster states of many trapped ions. In the scheme the two-trapped ions are simultaneously excited by a single laser beam and the frequency of the laser beam is slightly off resonance with the first lower vibration sideband of the trapped ions. The distinct advantage of the scheme is that it does not use the vibrational mode as the data bus. Furthermore, our scheme is insensitive to both the initial motional state and heating (or decay) as long as the system remains in the Lamb--Dicke regime.
Ion Cleaning of Facets for Improving the Reliability of High Power 980nm Semiconductor Lasers
SHU Xiong-Wen, XU Chen, TIAN Zeng-Xia, SHEN Guang-Di
Chin. Phys. Lett. 2006, 23 (1): 124-125 .  
Abstract   PDF(pc) (166KB) ( 763 )
We report a simple and available way of improving the reliability of high power InGaAs 980nm lasers by cleaning the facets using Ar ion before the protecting films have been coated. The Ar cleaning can remove the impurity and the oxide on the air-cleaved facets of laser diodes. It is proven that the way has marked effect on reducing the gradual degradation rate of laser diodes and improving the catastrophic--optical--damage threshold.
Dual-Wavelength Distributed Feedback Laser for CWDM Based on Non-Identical Quantum Well
XIE Hong-Yun, PAN Jiao-Qing, ZHAO Ling-Juan, ZHU Hong-Liang, WANG Lu-Feng, WANG Wei
Chin. Phys. Lett. 2006, 23 (1): 126-128 .  
Abstract   PDF(pc) (203KB) ( 751 )
Using non-identical quantum wells as the active material, a new distributed-feedback laser is fabricated with period varied Bragg grating. The full width at half maximum of 115nm is observed in the amplified spontaneous emission spectrum of this material, which is flatter and wider than that of the identical quantum wells. Two wavelengths of 1.51μm and 1.53μm are realized under different work conditions. The side-mode suppression ratios of both wavelengths reach 40dB. This device can be used as the light source of coarse wavelength division multiplexer communication systems.
A Q-Swicthed All-Solid-State Single-Longitudinal-Mode Laser with Adjustable Pulse-Width and High Repetition Rate
ZHOU Jun, XU Shi-Zhong, HOU Xia, WEI Hui, CHEN Wei-Biao
Chin. Phys. Lett. 2006, 23 (1): 129-131 .  
Abstract   PDF(pc) (215KB) ( 762 )
A single-longitudinal-mode (SLM) laser-diode pumped Nd: YAG laser with adjustable pulse width is developed by using the techniques of pre-lasing and changing polarization of birefingent crystal. The Q-switching voltage is triggered by the peak of the pre-lasing pulse to achieve the higher stability of output pulse energy. The output energy of more than 1mJ is obtained with output energy stability of 3% (rms) at 100Hz. The pulse-width can be adjusted from 30ns to 300ns by changing the Q-switching voltage. The probability of putting out single-longitudinal-mode pulses is almost 100%. The laser can be run over four hours continually without mode hopping.
Transverse Mode Formation in Longitudinally Pumped Miniature Slab Lasers
XU Jian-Qiu, YE Xin, FANG Tao
Chin. Phys. Lett. 2006, 23 (1): 132-134 .  
Abstract   PDF(pc) (202KB) ( 421 )
The formation of transverse modes in longitudinally pumped miniature slab lasers is investigated theoretically and experimentally. The longitudinally non-uniform gain-guiding is studied by expanding the electric field into the Hermite--Gaussian functions that satisfy boundary conditions of the resonator. Non-Gaussian transversal beam profiles in the near field are found and the beam diameter is reduced when the pump spot becomes smaller. The experimental observation agrees with the theoretical calculation.
High Efficiency Pulse Acetone Liquid Raman Laser Using DCM Fluorescent Dye as the Enhancement Medium
CHENG Andrew Yuk-Sun, YANG Jing-Guo, CHAN Mau-Hing
Chin. Phys. Lett. 2006, 23 (1): 135-138 .  
Abstract   PDF(pc) (211KB) ( 631 )
Pumped by a frequency-doubled Nd:YAG laser, 10-Hz repetition rate, 320-mJ pump energy, and 5.1-ns pulse width, a liquid Raman laser using acetone as the Raman shifting medium has been established. The residual pump laser pulse and the generated Stokes pulse are directed to a DCM dye cell for energy enhancement of the Stokes pulse. The Raman laser system is capable to produce a laser pulse at wavelength 630nm, with single pulse energy of 120mJ, peak power of 70MW and an average power of 1200mW. The energy conversion efficiency is 37.5%, or equivalently a quantum efficiency of 44.5%.
Second Harmonic Generation of Femtosecond Laser at One Micron in a Partially Deuterated KDP
ZHENG Wan-Guo, QIAN Lie-Jia, YUAN Peng, LUO Hang, ZHU He-Yuan
Chin. Phys. Lett. 2006, 23 (1): 139-142 .  
Abstract   PDF(pc) (209KB) ( 998 )
Partially deuterated KDP is an ideal nonlinear crystal for second-harmonic generation (SHG) of femtosecond lasers at 1μm, which features with vanished group-velocity mismatch at its retracing point of phase-matching. We numerically investigate the characteristics of SHG with femtosecond lasers in a partially deuterated KDP, which shows that group-velocity dispersion plays an important role. This spectrally non-critical phase-matching configuration can support both high efficiency and large acceptance bandwidth.
Laser Phase Determination and Transfer Function to Directly Measure the Temporal Structure of a Narrow Bandwidth Attosecond EUV Pulse
GE Yu-Cheng
Chin. Phys. Lett. 2006, 23 (1): 143-146 .  
Abstract   PDF(pc) (258KB) ( 540 )
A laser phase determination method and a transfer function that includes a proportional term of a measured photoelectron energy spectrum are presented to directly measure the detailed temporal structure of a narrow bandwidth attosecond extreme-ultraviolet (EUV) pulse. The method is based on the spectrum measurement of an electron generated by EUV photo-ionization interacting with a femtosecond laser field. The results of the study suggest that measurements should be taken at 0° or 180° with respect to the linear laser polarization. The method has a temporal measurement range of about half a laser oscillation period. The temporal resolution also depends on the jitter and control precision of the laser and EUV pulses.
Soliton and Periodic Travelling Wave Solutions for Quadratic Nonlinear Media
LIN Ji, CHENG Xue-Ping, YE Li-Jun
Chin. Phys. Lett. 2006, 23 (1): 147-150 .  
Abstract   PDF(pc) (285KB) ( 515 )
Many sets of the soliton and periodic travelling wave solutions for the quadratic X(2) nonlinear system are obtained by the Backlund transformation and the trial method. The property of the propagation for some travelling waves is investigated.

Optical Recording Properties of Metal-Azo Dye as Recording Medium with Super-Resolution Near-Field Structure
CHEN Wen-Zhong, WU Yi-Qun, WANG Yang, GAN Fu-Xi
Chin. Phys. Lett. 2006, 23 (1): 151-153 .  
Abstract   PDF(pc) (219KB) ( 441 )
A novel metallized azo dye has been synthesized. The absorption spectra of the thin film and thermal characteristic are measured. Static optical recording properties with and without the Bi mask layer super-resolution near-field structure (Super-RENS) of the metal-azo dye are investigated. The results show that the metal-azo dye film has a broad absorbance band in the region of 450--650nm and the maximum absorbance wavelength is located at 603nm. It is also found that the new metallized azo dye occupies excellent thermal stability, initiatory decomposition temperature is at 270°C and the mass loss is about 48% in a narrow temperature region (15°C). The complex refractive index N (N=n+ik) is measured. High refractive index (n=2.45) and low extinction coefficient (k=0.2) at the recording wavelength 650nm are attained. Static optical recording tests with and without Super-RENS are carried out using a 650nm semiconductor diode laser with recording power of 7mW and laser pulse duration of 200ns. The AFM images show that the diameter of recording mark on the dye film with the Bi mask layer is reduced about 42%, compared to that of recorded mark on the dye film without Super-RENS. It is indicated that Bi can well performed as a mask layer of the dye recording layer and the metallized azo dye can be a promising candidate for recording media with the super-resolution near-field structure.
Electro-Magnetic Control of Vortex Shedding Behind a Circular Cylinder
CHEN Zhi-Hua, FAN Bao-Chun, Nadine AUBRY, ZHOU Ben-Mou
Chin. Phys. Lett. 2006, 23 (1): 154-157 .  
Abstract   PDF(pc) (295KB) ( 596 )
Both open- and closed-loop control algorithms have been developed for suppressing of vortex shedding behind a circular cylinder in an electrically low-conducting fluid. For the open-loop control, the localized Lorentz forces are generated parallel to the cylinder surface, which have the accelerated effect to the fluid. Furthermore, two closed-loop control methods have been derived from the equations of motion capable of determining at all times the intensity of the Lorentz force to control the vortex shedding of a cylinder.
Fishbone Instability Excited by Barely Trapped Electrons
WANG Zhong-Tian, LONG Yong-Xing, DONG Jia-Qi, WANG Long, Fulvio Zonca
Chin. Phys. Lett. 2006, 23 (1): 158-160 .  
Abstract   PDF(pc) (215KB) ( 358 )
Fishbone instability excited by barely trapped suprathermal electrons (BTSEs) in tokamaks is investigated theoretically. The frequency of the mode is found to close to procession frequency of BTSEs. The growth rate of the mode is much smaller than that of the ideal magnetohytrodynamic (MHD) internal kink mode that is in contrast to the case of trapped ion driven fishbone instability. The analyses also show that spatial density gradient reversal is necessary for the instability. The correlation of the results with experiments is discussed.
Effects of Beam Energy Spread on the Weibel Instability in Fast Ignitor Scenarios
CAI Hong-Bo, ZHU Shao-Ping, ZHENG Chun-Yang, HE Xian-Tu, LI Ji-Wei
Chin. Phys. Lett. 2006, 23 (1): 161-164 .  
Abstract   PDF(pc) (266KB) ( 615 )
The effects of transverse temperature distribution on the Weibel instability in a laser produced plasma are studied analytically by using a three dimensional waterbag model. It is found that the purely transverse Weibel instability can be stabilized for the case in which the electron beam has a more symmetric transverse temperature distribution. This analytical expectation is supported by our two dimensional particle-in-cell simulations.

Jump Conditions of a Shock with Current in Cylindrical Non-Neutral Plasma
HE Yong, HU Xi-Wei, HU Ye-Min
Chin. Phys. Lett. 2006, 23 (1): 165-168 .  
Abstract   PDF(pc) (238KB) ( 399 )
Jump conditions of the parameters (mass flow, momentum flow and energy flow) of a shock with current (thereby, electric and magnetic field) in cylindrical non-neutral plasma are presented and derived from Maxwell’s equations and two fluid equations for electron and ion fluid. The critical Mach number for the shock existence is calculated, which depends on the shock carried current, the ion charge, and the composition of the magnetic and thermal pressure. The numerical results show that both the strength and profiles of the downstream shock parameters will be affected obviously by the shock carried current, electric and magnetic field in the two-dimensional shock.
Effects of Flow Rate Variation on SiCln (n<3) Densities in SiCl4 Plasmas
WANG Zhao-Kui, LIN Kui-Xun, LIN Xuan-Ying, LOU Yan-Hui, ZHU Zu-Song
Chin. Phys. Lett. 2006, 23 (1): 169-171 .  
Abstract   PDF(pc) (198KB) ( 808 )
Radicals produced by the plasma enhanced chemistry vapour deposition technique in SiCl4 plasma are identified by mass spectrometry using our newly proposed straight-line fit method. Since flow rate is one of the most important parameters in depositing thin films, we present the effects of SiCl4 flow rate variation on SiCln (n<3) densities. The experimental results demonstrate that Si and SiCln (n=1,2) densities decrease with increasing SiCl4 flow rate. After reaching the minimum values at a flow rate of 17 and 13sccm, respectively, Si and SiCln (n=1,2) densities slightly increase with further increase of flow rate to 20.5sccm. These results could be interpreted to which the depletion fraction of SiCl4 decreases and the residence time of SiCl4 molecule becomes shorter, with the increasing SiCl4 flow rate. In order to obtain high-quality poly-Si films with high growth rate, it is better to use smaller flow rate of SiCl4 source gas for depositing films.

Improvement of Electrical Properties of the Ge2Sb2Te5 Film by Doping Si for Phase-Change Random Access Memory
QIAO Bao-Wei, FENG Jie, LAI Yun-Feng, LING Yun, LIN Yin-Yin, TANG Ting-Ao, CAI Bing-Chu, CHEN Bomy
Chin. Phys. Lett. 2006, 23 (1): 172-174 .  
Abstract   PDF(pc) (232KB) ( 1044 )
Si-doped Ge2Sb2Te5 films have been prepared by dc magnetron co-sputtering with Ge2Sb2Te5 and Si targets. The addition of Si in the Ge2Sb2Te5 film results in the increase of both crystallization temperature and phase-transition temperature from face-centred-cubic (fcc) phase to hexagonal (hex) phase. The resistivity of the Ge2Sb2Te5 film shows a significant increase with the Si doping. When doping 11.8 at.% of Si in the film, the resistivity after 460°C annealing increases from 1 to 11mΩ .cm and dynamic resistance increase from 64 to 99Ω compared to the undoped Ge2Sb2Te5 film. This is very helpful to writing current reduction of phase-change random access memory.
Possible Mechanism of Plasticity Influenced by Magnetic Field
LIU Zhao-Long, FAN Tian-You, HU Hai-Yun
Chin. Phys. Lett. 2006, 23 (1): 175-177 .  
Abstract   PDF(pc) (188KB) ( 717 )
The strain energy of an edge dislocation in an external static magnetic field is determined by the theory of elasticity and electrodynamics according to the Volterra dislocation model for continuous media. The results show that the strain energy of the edge dislocation in paramagnetic states is increased due to static magnetic field and the increase in the energy of the dislocation is capable of influencing the dislocation depinning which leads to the change of plasticity. This gives an explanation on plasticity induced by magnetic field.
Optimization of Energy Scope for Titanium Nitride Films Grown by Ion Beam-Assisted Deposition
LI Wei, MA Zhong-Quan, WANG Ye, WANG De-Ming
Chin. Phys. Lett. 2006, 23 (1): 178-181 .  
Abstract   PDF(pc) (220KB) ( 572 )
The deposited energy during film growth with ion bombardment, correlated to the atomic displacement on the surface monolayer and the underlying bulk, has been calculated by a simplified ion-solid interaction model under binary collision approximation. The separated damage energies caused by Ar ion, different for the surface and the bulk, have been determined under the standard collision cross section and a well-defined surface and bulk atom displacement threshold energy of titanium nitride (TiN). The optimum energy scope shows that the incident energy of Ar+ around 110eV for TiN (111) and 80eV for TiN (200) effectively enhances the mobility of adatom on surface but excludes the damage in underlying bulk. The theoretical prediction and the experimental result are in good agreement in low energy ion beam-assisted deposition.
TiNi Monatomic Chains Stabilized by Alloying: a First-Principles Study
LI Ai-Yu, WANG Xiao-Chun, WEN Yu-Hua, ZHU Zi-Zhong
Chin. Phys. Lett. 2006, 23 (1): 182-185 .  
Abstract   PDF(pc) (240KB) ( 885 )
Total energies and electronic structures calculations are performed for the monatomic TiNi alloy chains with the linear and zigzag structures. The pure Ti and pure Ni atomic chains have also been computed on equal footing, serving as reference systems. The results shows that the stability of one-dimensional chains can be enhanced by alloying, i.e. the cohesive energies of TiNi alloy chains are larger than the corresponding pure Ti and Ni ones, in both the linear and zigzag structures. The stability effect by alloying is associated with changes of the electronic properties, such as the lowering of the density of states at the Fermi level and more covalently bonding between the Ti and Ni sites. Compared to the zigzag TiNi chain, the stability of linear TiNi chains has been more increased.
Electronic Structures of the Filled Tetrahedral Semiconductor Li3AlN2
MA Chun-Lan, PAN Tao
Chin. Phys. Lett. 2006, 23 (1): 186-188 .  
Abstract   PDF(pc) (265KB) ( 859 )
The first-principles total energy calculations with the local density approximation (LDA) and the plane wave pseudopotential method are employed to investigate the structural properties and electronic structures of Li3AlN2. The calculated lattice constants and internal coordination of atoms agree well with the experimental results. Detailed studies of the electronic structure and the charge-density redistribution reveal the features of the strong ionicity bonding of Al-N and Al-Li, and strong hybridizations between Li and N in Li3AlN2. Our band structure calculation verifies Li3AlN2 is a direct gap semiconductor with the LDA gap value of about 2.97eV and transition at G.
Relaxation of Dense Electron Plasma Induced by Femtosecond Laser in Dielectric Materials
SUN Quan, JIANG Hong-Bing, LIU Yi, ZHOU Yong-Heng, YANG Hong, GONG Qi-Huang
Chin. Phys. Lett. 2006, 23 (1): 192-192 .  
Abstract   PDF(pc) (218KB) ( 802 )
Electron plasma induced by a focused femtosecond pulse (130fs, 800nm) in dielectric materials (Soda Lime glass, K9 glass, and SiO2 crystal) is investigated by pump-probe shadow imaging technology. The relaxation of the electron plasma in the conduction band is discussed. In SiO2 crystals, a fast self-trapping process with a trapping time of 150fs is observed, which is similar to that in fused silica. However, in Soda Lime glass and K9 glass, no self-trapping occurs, and two decay processes are found: one is the energy relaxation process of conduction electrons within several picoseconds, another is an electron-hole recombination process with a timescale of 100ps. The electron collision time τ in the conduction band is also measured to be in the order of 1fs in all of these materials.
Ground State of a Two-Electron Quantum Dot with a Gaussian Confining Potential
XIE Wen-Fang
Chin. Phys. Lett. 2006, 23 (1): 193-195 .  
Abstract   PDF(pc) (204KB) ( 988 )
We investigate the ground-state properties of a two-dimensional two-electron quantum dot with a Gaussian confining potential under the influence of perpendicular homogeneous magnetic field. Calculations are carried out by using the method of numerical diagonalization of Hamiltonian matrix within the effective-mass approximation. A ground-state behaviour (singlet→triplet state transitions) as a function of the strength of a magnetic field has been found. It is found that the dot radius R of the Gaussian potential is important for the ground-state transition and the feature of ground-state for the Gaussian potential quantum dot (QD), and the parabolic potential QDs are similar when R is larger. The larger the quantum dot radius, the smaller the magnetic field for the singlet-triplet transition of the ground-state of two interacting electrons in the Gaussian quantum dot.
Structural Peculiarities and Magnetic Properties of Nanoscale Terbium in Tb/Ti and Tb/Si Multilayers
A. V. Svalov, V. O. Vas’kovskiy, G. V. Kurlyandskaya, J. M. Barandiaran, I. Orue, N. N. Schegoleva, A. N. Sorokin
Chin. Phys. Lett. 2006, 23 (1): 196-199 .  
Abstract   PDF(pc) (241KB) ( 868 )
The structure and the magnetic properties of rf-sputtered nanoscale Tb in [Tb/Ti]n and [Tb/Si]n multilayers have been studied experimentally. It is found that the structure of Tb layers changes, transforming from a fine-crystalline state of Tb into an amorphous state as the magnetic layer thickness decreases. The observed displacement of a magnetic ordering temperature to the lower temperature range and the shift of magnetic hysteresis obtained in the ZFC-FC terms may be caused by the size effect and the amorphization. Both the first and the second suppress the exchange interaction and decrease the crystalline magnetic anisotropy. The type of material of nonmagnetic spacers between the Tb layers plays a certain role in these changes.
Monte Carlo Simulation of Magnetization Behaviour of Co Nanowires
ZHONG Ke-Hua, HUANG Zhi-Gao, FENG Qian, JIANG Li-Qin, YANG Yan-Min, CHEN Zhi-Gao
Chin. Phys. Lett. 2006, 23 (1): 200-203 .  
Abstract   PDF(pc) (235KB) ( 544 )
Based on the Monte Carlo method, we simulate the magnetization curves with various magnetic field orientations for various single Co nanowires at room temperature. The simulated switching field as a function of angle θ between the field and the wire axis is consistent well with the experimental data. Correspondingly, the coercivity as a function of angle θ is presented, which together with the switching field plays an important role on explaining the magnetic reversal mechanism. It is found that the angular dependence of coercivity depends on the diameter of nanowires, and the coercivity and switching field versus θ deviate markedly from the prediction from the classical uniform rotation mode in the chain-of-sphere model. Furthermore, the magnetic reversal configurations display that magnetization reversal in the wires with small diameters is a nucleation-propagation process, and it is similar to the curling spread process in the larger wires.
Trapping Effects in CdSiO3:In3+ Long Afterglow Phosphor
KUANG Jin-Yong, LIU Ying-Liang
Chin. Phys. Lett. 2006, 23 (1): 204-206 .  
Abstract   PDF(pc) (216KB) ( 798 )
Trapping effects in CdSiO3:In3+ long afterglow phosphor based on photoluminescence (PL) and thermoluminescence (TL) curves are studied. The results of TL show that two intrinsic defects associated with peaks at 346 and 418K appear in the undoped CdSiO3 phosphor; whereas only one strong cadmium vacancy VCd'' defect associated with peak at 348K appears in the Cd1-xInxSiO3 phosphor due to the chemical nonequivalent substitutions of Cd2+ ions by In3+ ions. This chemical nonequivalent substitution of In3+ ions into the CdSiO3 host produced the highly dense cadmium vacancy VCd'' trap level at 348K, which resulted in the origin of the long afterglow phenomenon. The findings has enlarged the family of non-rare-earth doped long afterglow phosphors available, and offers a promising approach for searching long afterglow phosphor.
Studies of Spectroscopic Ellipsometry in Cd1-xMnxTe/CdTe Superlattices
CHEN Chen-Jia, WANG Xue-Zhong, Vittorio BELLANI, Angiolino STELLA
Chin. Phys. Lett. 2006, 23 (1): 207-210 .  
Abstract   PDF(pc) (232KB) ( 482 )
Cd1-xMnxTe/CdTe superlattices and thin films were grown by molecular beam epitaxy on GaAs (001) substrates. Spectroscopic ellipsometry measurements were performed on Cd1-xMnxTe/CdTe superlattices with compositions x=0.4, 0.8, and Cd1-xMnx thin films with x=0.2, 0.4, 0.6 at room temperature in the photon energy range 1.4--5eV. In superlattices the pseudodielectric functions measured by ellipsometry show specific features related to the exciton transition between quantized interbands. The exciton transitions related to the heavy holes of 11H, 22H, and 33H are observed and identified. In thin films spectroscopic ellipsometry allows the clear identification of the energy gap E0. Additionally, critical point transitions are observable in both the spectra of the superlattices and films. Photoreflectance spectra were also performed at room temperature in order to compare with our ellipsometry results. After taking into account the strain-induced and quantum confinement effects, the theoretical calculations are in good agreement with our experimental spectra. Ellipsometry appears to be a suited technique to monitor the MBE growth, ultimately also in situ, of diluted magnetic low-dimensional systems.
Nanoscale Lasers Based on Carbon Peapods
HE Shao-Long, SHEN Jian-Qi
Chin. Phys. Lett. 2006, 23 (1): 211-213 .  
Abstract   PDF(pc) (238KB) ( 484 )
A scheme of nanoscale lasers based on the so-called carbon peapods is examined in detail. Since there is considerable cylindrical empty space in the middle of a single-wall carbon nanotube (SWCNT), it can serve as a laser resonant cavity that consists of two highly reflecting alignment ``mirrors'' separated by a distance. These mirrors refer to the ordered arrays of C60 inside SWCNTs, which have photonic bandgap structures. Meanwhile, ideally single-mode lasers are supposed to be produced in the nanoscale resonant cavity.
Grow Large High-Quality Diamonds with Different Seed Surfaces
ZANG Chuan-Yi, JIA Xiao-Peng, MA Hong-An, LI Shang-Sheng, TIAN Yu, XIAO Hong-Yu
Chin. Phys. Lett. 2006, 23 (1): 214-216 .  
Abstract   PDF(pc) (237KB) ( 671 )
Large high-quality type Ib diamond crystals have been grown with different seed surfaces by temperature gradient method at 5.5GPa, 1500--1600K, with NiMnCo alloy as the metal solvent. Compared with {100} as the growth surface, the growth region of large high-quality diamond crystals with {111} as the growth surface at a higher growth rate shifts markedly from lower temperatures (suitable for {100}-facet growth) to higher temperatures (suitable for {111}-facet growth). However, regardless of different growth surfaces, {100} or {111}, the grown crystals of sheet-shaped shape are most difficult for metal inclusions to be trapped into, and whether or not matched growth between the seed surfaces and the growth temperatures determines the crystal shapes. In view of the growth rates, large high-quality diamond crystals of sheet-shaped shapes can be grown at a growth rate of above 2.5mg/h, while the growth rate of large high-quality diamond c
Agglomeration Evolution of Nano-Particles Aluminium in Normal Incident
YAN Zheng-Xin, WU Jing-He, HU Dong, YANG Xiang-Dong
Chin. Phys. Lett. 2006, 23 (1): 217-219 .  
Abstract   PDF(pc) (246KB) ( 515 )
Agglomeration behaviour of nano-particle aluminium (nano-Al) in normal incident shock waves is investigated by our devised shock tube technology. The morphology, particle size, agglomeration process of nano-Al studied in normal incident shock waves are comprehensible evaluated by x-ray diffraction, transmission electron microscopy and scanning electron microscopy. The above-mentioned techniques show that the high strength and temperature of incident shock wave give a chance for activity of nano-Al in the reactions and decrease the agglomeration, and the morphology of agglomeration is affected by the temperature of nano-Al reaction region. The dynamic temperature of reaction region determined by the intensity ratio of two AlO bands is 2602K, which is closer to nano-Al actual reacted temperature than the determined temperature of ordinary methods (i.e. six channel instantaneous optical pyrometer; plank black body radiation law, etc.)
MBE Growth of Highly Relaxed Si0.45 Ge0.55 Films with Very Low Misfit Dislocation Density on Si (001) Substrates
LU Xiang-Dang, ZHANG Xiang-Jiu, YANG Hong-Bin, FAN Yong-Liang, HUANG Wei-Ning, SUN Yan-Qing
Chin. Phys. Lett. 2006, 23 (1): 220-222 .  
Abstract   PDF(pc) (231KB) ( 788 )
We investigate the molecular-beam-epitaxy growth of highly relaxed Si0.45Ge0.55 films with very low dislocation densities. By using the Si3N4 film as the mask material, the Si0.45Ge0.55 film can be grown on a compositionally stepwise graded SiGe buffer layer in 3μm×3μm windows on a Si (001) substrate. Raman scattering spectroscopy measurement shows that more than 90% strain of the Si0.45Ge0.55 film is relaxed, and almost neither misfit dislocation lines nor etch pits of thread dislocations could be observed when the sample is etched by the modified Schimmel etchant. We suggest that the results can be explained by influence of the edge-induced strain relaxation of the epitaxial film and the edge-induced stress of the mask material.
Self-Assembled TiO2/PSS Multilayer Films Studied by Slow Positron Spectroscopy
HAO Wei-Chang, PAN Feng, WANG Tian-Min, ZHOU Chun-Lan, WEI Long
Chin. Phys. Lett. 2006, 23 (1): 223-226 .  
Abstract   PDF(pc) (230KB) ( 507 )
TiO2/PSS nano-structured multilayer films are fabricated by a layer-by-layer self-assembly method, and the deposition process and interface structure of films are studied in detail by slow positron spectroscopy. The results indicate that injection energy of positron at the interface between the substrate and the film shows a linear dependence on the number of bilayer, which suggests that the repeatability of the depositing process is good, and the thickness of films shows a linear increase with the number of bilayers adding. The calculated result of the film thickness shows that there is an overlay between the adjacent TiO2 nanoparticle layers.
Magnetic-Field-Induced Strains of Bonded Ni--Mn--Ga Melt-Spun Ribbons
GUO Shi-Hai, ZHANG Yang-Huan, LI Jian-Liang, QI Yan, QUAN Bai-Yun, WANG Xin-Lin
Chin. Phys. Lett. 2006, 23 (1): 227-230 .  
Abstract   PDF(pc) (207KB) ( 534 )
Non-stoichiometric Ni50Mn27Ga23 polycrystalline ribbons are prepared by melt-spinning technique. The magnetic-field-induced strain (MFIS) of Ni--Mn--Ga bulk alloy prepared by bonding the melt-spun ribbons is obtained. The experimental results show that Ni50Mn27Ga23 bonded ribbons exhibit a typical thermal-elastic shape memory effect in the thickness direction. The martensitic transformation strain of bonded ribbons is an expansive strain of about 0.3\% without the magnetic field and a contractive strain of about -0.46% at the magnetic field of 1T. The field can not only enhance the value of the martensitic transformation strain of the bonded ribbons, but can also change the direction of the strain. The bonded ribbons alloy presents negative MFIS and obtains a larger value of the strain though influenced by the adhesive between the ribbons. Therefore, the preparation technique of the Ni--Mn--Ga bulk alloy by bonding melt-spun ribbons is helpful to get rid of the size restriction of the ribbon and to broaden the applications of the ribbons.
Photoinduced Transformation between Charge Carrier and Spin Carrier in Polymers
MEI Yuan, ZHAO Chang, SUN Xin,
Chin. Phys. Lett. 2006, 23 (1): 231-234 .  
Abstract   PDF(pc) (215KB) ( 359 )
By dynamical simulations, we show a transforming process between neutral soliton (spin carrier) and charged soliton (charge carrier) in polymers via photo-excitation, taking a polaron as the transitional bridge. It is photoinduced transformation between spin carrier and charge carrier. In this way, we demonstrate an access for polymers to be applied to spintronics.
A New Type of Terahertz Waveguides
LOU Shu-Qin, GUO Tie-Ying, FANG Hong, LI Hong-Lei, JIAN Shui-Sheng
Chin. Phys. Lett. 2006, 23 (1): 235-238 .  
Abstract   PDF(pc) (232KB) ( 627 )
A new type of THz waveguides, which employs a solid polyethylene rod as the core and polyethylene tubes in a periodic array of square lattice as the cladding, is proposed. Optical properties of this new THz waveguide, especially in dispersion, confinement loss and single mode property, are investigated in detail with the plane wave expansion method and the beam propagation method. Numerical results demonstrate that the new THz waveguide can reach not only low dispersion but also low confinement loss at single mode propagation. Therefore, the square lattice structure is a better candidate as THz waveguides than the triangular ones.
A Transient-State Simulation of Ionization Effects in a Microwave Tube
GONG Hua-Rong, GONG Yu-Bin, WEI Yan-Yu, LU Zhi-Gang, FAN Mei, WANG Wen-Xiang
Chin. Phys. Lett. 2006, 23 (1): 239-242 .  
Abstract   PDF(pc) (257KB) ( 521 )
A model for studying the ionization effects in a microwave tube has been developed. This model is simulated by a two-dimensional particle-in-cell code with the Mont Carlo collision model for the electron-neutral ionization process. The transient-state process of ion noise and ion focusing effects are observed. A simple theory about ion motion is given for interpreting the phenomenon of the ion moving to the wall of the tube when the beam is not neutralized. The computed result agrees with the experiment and simulation result.
Slow-Wave Characteristics of Elliptical Corrugated Waveguides with a Concentric Circular Hole
XU Jin, WANG Wen-Xiang, YUE Ling-Na, WEI Yan-Yu, GONG Yu-Bin
Chin. Phys. Lett. 2006, 23 (1): 243-246 .  
Abstract   PDF(pc) (243KB) ( 347 )
We present the formulation of elliptical corrugated waveguides with a concentric circular hole using the field-matching method and the addition theorem for Mathieu functions. The dispersion equation and the mean interaction impedance of this structure are derived separately. The numerical results, which are generally based on the current approach, agree well with the results obtained by the commercial software package CST. As a slow-wave structure, this structure has potential applications in high power microwave amplifiers and possibly filtering structures.
Current-Enhanced Quantum Well Solar Cells
LOU Chao-Gang, SUN Qiang, XU Jun, ZHANG Xiao-Bing, LEI Wei, WANG Bao-Ping, CHEN Wen-Jun, QIAO Zai-Xiang
Chin. Phys. Lett. 2006, 23 (1): 247-248 .  
Abstract   PDF(pc) (186KB) ( 453 )
We present the experimental results that demonstrate the enhancement of the short-circuit current of quantum well solar cells. The spectral response shows that the introduction of quantum wells extends the absorption spectrum of solar cells. The current densities under different truncated spectrums significantly increase, showing that quantum well solar cells are suitable to be the middle cells of GaInP/GaAs/Ge triple-junction solar cells to increase their overall conversion efficiency.
Fast Theoretical Simulation for Design of Helical Flux Compression Generators
YANG Xian-Jun, DONG Zhi-Wei
Chin. Phys. Lett. 2006, 23 (1): 249-251 .  
Abstract   PDF(pc) (227KB) ( 907 )
A theoretical scheme is derived to achieve the numerical simulation of helical flux compression generator (HFCG) design, by which not only any physical approximation is not made, but also numerical simulation can be fast obtained. In particular, an analytic formula to calculate the inductance is deduced, which is extremely close to the experimental results. The physical process of relevant interesting physical quantity, such as inductance, enlarging current, and magnetic flux density, can be calculated to compare with the experimentally quantitative results.
Single Photon Detector at Telecom Wavelengths for Quantum Key Distribution
LIU Yun, WU Qing-Lin, HAN Zheng-Fu, DAI Yi-Min, GUO Guang-Can
Chin. Phys. Lett. 2006, 23 (1): 252-255 .  
Abstract   PDF(pc) (212KB) ( 688 )
Using InGaAs/InP avalanche photodiodes as sensors and coaxial cables as reflection lines to reject spike signals, we have firstly employed the ``timing filtering'' gates to pick out avalanche signals and have realized the single photon detection at 1550nm in the temperature range of thermoelectric cooling. A ratio of the dark count rate to the detection efficiency was obtained to be 9×10-5 at 223K. When the detector is applied to a practical quantum key distribution system, the transmission distance can reach 89.5km and the repetition rate can reach 0.33MHz.
Effect of Al Doping in the InGaN/GaN Multiple Quantum Well Light Emitting Diodes Grown by Metalorganic Chemical Vapour Deposition
LU Yu, YANG Zhi-Jian, PAN Yao-Bo, XU Ke, HU Xiao-Dong, ZHANG Bei, ZHANG Guo-Yi
Chin. Phys. Lett. 2006, 23 (1): 256-258 .  
Abstract   PDF(pc) (207KB) ( 695 )
The effect of Al doping in the GaN layer of InGaN/GaN multiple quantum-well light emitting diodes (LEDs) grown by metalorganic chemical vapour deposition is investigated by using photoluminescence (PL) and high-resolution x-ray diffraction. The full width at half maximum of PL of Al doped LEDs is measured to be about 12nm. The band edge photoluminescence emission intensity is enhanced significantly. In addition, the in-plane compressive strain in the Al-doped LEDs is improved significantly and measured by reciprocal space map. The output power of Al-doped LEDs is 130mW in the case of the induced current of 200mA.
Evolving Networks with Nonlinear Assignment of Weight
Chin. Phys. Lett. 2006, 23 (1): 259-262 .  
Abstract   PDF(pc) (198KB) ( 798 )
We propose a weighted evolving network model in which the underlying topological structure is still driven by the degree according to the preferential attachment rule while the weight assigned to the newly established edges is dependent on the degree in a nonlinear form. By varying the parameter α that controls the function determining the assignment of weight, a wide variety of power-law behaviours of the total weight distributions as well as the diversity of the weight distributions of edges are displayed. Variation of correlation and heterogeneity in the network is illustrated as well.
Stability of Random Networks under Evolution of Attack and Repair
CHI Li-Ping, YANG Chun-Bin, CAI Xu
Chin. Phys. Lett. 2006, 23 (1): 263-266 .  
Abstract   PDF(pc) (205KB) ( 694 )
With a simple model, we study the stability of random networks under the evolution of attack and repair. We introduce a new quantity, i.e. invulnerability I(s), to describe the stability of the system. It is found that the network can evolve to a stationary state. The stationary value Ic has a power-law dependence on the initial average degree , with the slope about -1.5. In the stationary state, the degree distribution is a normal distribution, rather than a typical Poisson distribution for general random graphs. The clustering coefficient in the stationary state is much larger than that in the initial state. The stability of the network depends only on the initial average degree , which increases rapidly with the decrease of .
Energetic Electron Pitch Angle Diffusion due to Whistler Wave during Terrestrial Storms
XIAO Fu-Liang, HE Hui-Yong
Chin. Phys. Lett. 2006, 23 (1): 267-270 .  
Abstract   PDF(pc) (255KB) ( 526 )
A concise and elegant expression of cyclotron harmonic resonant quasi-pure pitch-angle diffusion is constructed for the parallel whistler mode waves, and the quasi-linear diffusion coefficient is prescribed in terms of the whistler mode wave spectral intensity. Numerical computations are performed for the specific case of energetic electrons interacting with a band of frequency of whistler mode turbulence at L approx 3. It is found that the quasi-pure pitch-angle diffusion driven by the whistler mode scatters energetic electrons from the larger pitch-angles into the loss cone, and causes pitch-angle distribution to evolve from the pancake-shaped before the terrestrial storms to the flat-top during the main phase. This probably accounts for the quasi-isotropic pitch-angle distribution observed by the combined release and radiation effects satellite spacecraft at L approx 3.
Influence of Hyperon on 1S0 Superfluidity of Nucleons in Neutron Star Matter
CHEN Wei, LAM Yu-Yiu, WEN De-Hua, LIU Liang-Gang
Chin. Phys. Lett. 2006, 23 (1): 271-274 .  
Abstract   PDF(pc) (244KB) ( 639 )
We investigate the property of 1S0 superfluidity of neutrons and protons in the neutron star matter. On the basis of the result, we study the effects of hyperons on the 1S0 pairing gaps of the two species of the particles. The parameter sets we use are for the Hartree approximation of the relativistic σ-ω model and the mean field approximation of the Walecka model, respectively. The predicted domain of superfluidity is very close to other works, whereas differences appear in the predicted value of the maximum gap. It is found that Σ-, Λ and Ξ- have some influences, the scales of which depend on hyperon-meson coupling constants we use besides other factors, on the 10 superfluidity of protons in some density range, and do not have influence on superfluidity of neutrons. Other hyperons have no influence on the 1S0 superfluidity of neutron and proton due to these hyperons appearing after 1S0 neutron and proton pairs disappear.
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