Current Issue

Volume 27 Issue 5
Online Date:
Previous Issue    Next Issue
GENERAL
The Multi-Function Jaulent-Miodek Equation Hierarchy with Self-Consistent Sources
YU Fa-Jun
Chin. Phys. Lett. 2010, 27 (5): 050201 .   DOI: 10.1088/0256-307X/27/5/050201
Abstract   PDF(pc) (283KB) ( 428 )
The multi-functions of soliton equation hierarchy with self-consistent sources is constructed. Then, the Jaulent-Miodek (JM) equation hierarchy with self-consistent sources is derived. Furthermore, the multi-function JM equation hierarchy with self-consistent sources is presented by using the higher-dimensional Lax pairs.
A New Kind of Integration Transformation in Phase Space Related to Two Mutually Conjugate Entangled-State Representations and Its Uses in Weyl Ordering of Operators
LV Cui-Hong, FAN Hong-Yi,
Chin. Phys. Lett. 2010, 27 (5): 050301 .   DOI: 10.1088/0256-307X/27/5/050301
Abstract   PDF(pc) (316KB) ( 370 )
Based on the two mutually conjugate entangled state representations |ξ> and |η>, we propose an integration transformation in ξ-η phase space , and its inverse transformation, which possesses some well-behaved transformation properties, such as being invertible and the Parseval theorem. This integral transformation is a convolution, where one of the factors is fixed as a special normalized exponential function. We generalize this transformation to a quantum mechanical case and apply it to studying the Weyl ordering of bipartite operators, regarding to (Q1-Q2)↔(P1-P2) ordered and simultaneously (P1+P2)↔(Q1+Q2) ordered operators.
Evolution of Number State to Density Operator of Binomial Distribution in the Amplitude Dissipative Channel
FAN Hong-Yi, REN Gang
Chin. Phys. Lett. 2010, 27 (5): 050302 .   DOI: 10.1088/0256-307X/27/5/050302
Abstract   PDF(pc) (291KB) ( 412 )
We show that passing through the amplitude dissipative channel the initial pure number state density operator is evolved into the density operator of binomial distribution (a mixed state), and the binomial distribution parameter is just equal to e-2kt,where κ is the dissipative parameter of the channel. We solve the corresponding master equation to obtain the operator-sum representation of the density operator by virtue of the entangled state representation, which seems to be a convenient approach.
Evolutionarily Stable Strategies in Quantum Hawk-Dove Game
Ahmad Nawaz, A. H. Toor
Chin. Phys. Lett. 2010, 27 (5): 050303 .   DOI: 10.1088/0256-307X/27/5/050303
Abstract   PDF(pc) (256KB) ( 705 )
We quantize the Hawk-Dove game by using the most general form of a pure initial state to investigate the existence of pure and mixed evolutionarily stable strategies (ESS). An example is considered to draw a comparison between the classical and quantum version of the game. Our choice of the most general initial quantum state enables us to make the game symmetric or asymmetric. We show that for a particular set of game parameters where there exists only mixed ESS in the classical version of the game, quantization allows even a pure strategy to be an ESS for the symmetric game in addition to mixed ESS. On the other hand only pure strategy ESS can exist for the asymmetric quantum version of the Hawk-Dove game.
Fidelity Susceptibility in the SU(2) and SU(1,1) Algebraic Structure Models
ZHANG Hong-Biao, TIAN Li-Jun,
Chin. Phys. Lett. 2010, 27 (5): 050304 .   DOI: 10.1088/0256-307X/27/5/050304
Abstract   PDF(pc) (620KB) ( 409 )
We mainly explore the fidelity susceptibility based on the Lie algebraic method. On physical grounds, the exact expressions of fidelity susceptibilities can be respectively obtained in SU(2) and SU(1,1) algebraic structure models, which are applied to one-body system and many-body systems, such as the single spin model, the single-mode squeeze harmonic oscillator model and the BCS model. In terms of the double-time Green-function method, our general conclusions are illustrated with two models which exhibit the fidelity susceptibilities at the finite temperature and Τ=0.
Squeezing-Displacement Dynamics for One-Dimensional Potential Well with Two Mobile Walls where Wavefunctions Vanish
FAN Hong-Yi, CHEN Jun-Hua, WANG Tong-Tong
Chin. Phys. Lett. 2010, 27 (5): 050305 .   DOI: 10.1088/0256-307X/27/5/050305
Abstract   PDF(pc) (277KB) ( 365 )
We show that the dynamics for a particle confined in a one-dimensional potential well with two mobile boundaries where wavefunctions vanish can be converted to the case as if the boundary was time-independent at the expense of an appropriate time-dependent Hamiltonian. The squeezing-displacement operator can be derived, and the corresponding Hamiltonian is determined by the situation of mobile boundaries.
A New Quantum Secure Direct Communication Scheme with Authentication
LIU Dan, PEI Chang-Xing, QUAN Dong-Xiao, ZHAO Nan
Chin. Phys. Lett. 2010, 27 (5): 050306 .   DOI: 10.1088/0256-307X/27/5/050306
Abstract   PDF(pc) (278KB) ( 868 )
A new quantum secure direct communication (QSDC) scheme with authentication is proposed based on polarized photons and EPR pairs. EPR pairs are used to transmit information, while polarized photons are used to detect Eve and their encoding bases are used to transmit authentication information. Alice and Bob have their own identity number which is shared by legal users only. The identity number is encoded on the bases of polarized photons and distilled if there is no Eve. Compared with other QSDC schemes with authentication, this new scheme is considerably easier and less expensive to implement in a practical setting.
Mechanical and Thermal Properties of the AH of FRW Universe
WEI Yi-Huan
Chin. Phys. Lett. 2010, 27 (5): 050401 .   DOI: 10.1088/0256-307X/27/5/050401
Abstract   PDF(pc) (282KB) ( 386 )
We calculate the work made out by the apparent horizon (AH) of the Friedmann-Robertson-Walker (FRW) universe and the heat flux through the AH from the first law of thermodynamics. We discuss the mechanical properties of the AH and analyze the universe model for which the mechanical properties can change. Finally, the thermal properties of the AH of FRW universe are discussed.
Chaotic Dynamics of a Josephson Junction with Nonlinear Damping
LI Fei, PAN Chang-Ning, ZHANG Dong-Xia, TANG Li-Qiang
Chin. Phys. Lett. 2010, 27 (5): 050501 .   DOI: 10.1088/0256-307X/27/5/050501
Abstract   PDF(pc) (523KB) ( 544 )
We study the chaotic dynamics of a Josephson junction with nonlinear damping. It is found that with the increasing dc bias the system undergoes a process from a biperiodical state to a chaotic one via a period-doubling route. Interestingly, when the value of the dc bias increases further, the number of the chaotic attractors also increases accordingly. These chaotic attractors appear one after another in different intervals and regions with time. Through a feedback controlling strategy the chaos can be effectively suppressed. We also find that the current between the two separated superconductors of the junction can increase or decrease monotonously with time in some parameter spaces.
Adaptive Function Projective Synchronization of Discrete Chaotic Systems with Unknown Parameters
WU Zhao-Yan, FU Xin-Chu
Chin. Phys. Lett. 2010, 27 (5): 050502 .   DOI: 10.1088/0256-307X/27/5/050502
Abstract   PDF(pc) (312KB) ( 592 )
Adaptive function projective synchronization of discrete-time chaotic systems with unknown parameters is considered. Based on the contraction mapping theorem, proper controllers and estimators are designed. Illustrative examples are provided to show the effectiveness of this method.
Cluster Consensus of Nonlinearly Coupled Multi-Agent Systems in Directed Graphs
LU Xiao-Qing, Francis Austin, CHEN Shi-Hua
Chin. Phys. Lett. 2010, 27 (5): 050503 .   DOI: 10.1088/0256-307X/27/5/050503
Abstract   PDF(pc) (384KB) ( 662 )
We investigate the cluster consensus problem in directed networks of nonlinearly coupled multi-agent systems by using pinning control. Depending on the community structure generated by the group partition of the underlying digraph, various clusters can be made coherently independent by applying feedback injections to a fraction of the agents. Sufficient conditions for cluster consensus are obtained using algebraic graph theory and matrix theory and some simulations results are included to illustrate the method.
Determination of Mean Thickness of an Oxide Layer on a Silicon Sphere by Spectroscopic Ellipsometry
ZHANG Ji-Tao, LI Yan, LUO Zhi-Yong, WU Xue-Jian
Chin. Phys. Lett. 2010, 27 (5): 050601 .   DOI: 10.1088/0256-307X/27/5/050601
Abstract   PDF(pc) (485KB) ( 459 )
One of the biggest obstacles to reduce the uncertainty of the Avogadro constant NA is such that there will be an oxide layers on the surface of a silicon sphere. The thickness of this layer is measured by a modified spectroscopic ellipsometer, which can eliminate the influence of the curved surface, and the results are calibrated by x-ray reflectivity. Fifty positions distributed nearly uniformly on the surface of the silicon sphere are measured twice. The results show that the mean thickness of the overall oxide layer is 3.75 nm with the standard uncertainty of 0.21 nm, which means that the relative uncertainty component of NA owing to this layer can be reduced to 1.2× 10-8.
Preparation and Humidity Sensing Properties of KCl/MCM-41 Composite
LIU Li, KOU Li-Ying, ZHONG Zhi-Cheng, WANG Lian-Yuan, LIU Li-Fang, LI Wei
Chin. Phys. Lett. 2010, 27 (5): 050701 .   DOI: 10.1088/0256-307X/27/5/050701
Abstract   PDF(pc) (561KB) ( 489 )
KCl/mobil composition of matter-41 (MCM-41) composite has been synthesized via a heat-treating process and characterized by x-ray diffraction, high resolution transmission electron microscopy, and nitrogen adsorption/desorption isotherms. In contrast with pure MCM-41, KCl/MCM-41 composite exhibits improved humidity sensing properties within the relative humidity range of 11-95%. The impedance of KCl/MCM-41 composite changes by about four orders of magnitude over the whole humidity range with the response time and the recovery times are about 30 s and 35 s, respectively. Small humidity hysteresis and good stability are also observed based on our product. These results make our product a good candidate in fabricating humidity sensors with high performances and low synthetic complexity.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Prospects on Determining Electric Dipole Moments of Σand Ξ Hyperons at BESIII
ZHANG Feng, GAO Yuan-Ning, HUO Lei
Chin. Phys. Lett. 2010, 27 (5): 051101 .   DOI: 10.1088/0256-307X/27/5/051101
Abstract   PDF(pc) (350KB) ( 364 )
The electric dipole moment ofΣ(or Ξ) hyperon, dΣ(or dΞ), can be detected by analyzing the angular distribution in the decay process of J/φ→. The dependence of dΣ(or dΞ) on the free parameters describing the angular distribution is studied in detail with a Monte Carlo simulation based on 109 J/ψ events expected in one year data taking at BESIⅢ. The result shows that an expected upper limit with 10-16~10-18 e cm on dΣ (or dΞ) can be achieved depending on the true values of free parameters.
Bs Semileptonic Decays to Ds and Ds* in Bethe--Salpeter Method
ZHANG Jin-Mei, WANG Guo-Li
Chin. Phys. Lett. 2010, 27 (5): 051301 .   DOI: 10.1088/0256-307X/27/5/051301
Abstract   PDF(pc) (376KB) ( 379 )
Using the relativistic Bethe-Salpeter method, the electron energy spectrum and the semileptonic decay widths of are calculated. We obtain a large branching fraction =, which can be easily detected in future experiments.
NUCLEAR PHYSICS
Neutron Spectroscopic Factors of 7Li and Astrophysical 6Li(n,γ)7Li Reaction Rates
SU Jun, LI Zhi-Hong, GUO Bing, BAI Xi-Xiang, LI Zhi-Chang, LIU Jian-Cheng, WANG You-Bao, LIAN Gang, ZENG Sheng, WANG Bao-Xiang, YAN Sheng-Quan, LI Yun-Ju, LI Er-Tao, FAN Qi-Wen, LIU Wei-Ping
Chin. Phys. Lett. 2010, 27 (5): 052101 .   DOI: 10.1088/0256-307X/27/5/052101
Abstract   PDF(pc) (630KB) ( 527 )
Angular distributions of the 7Li(6Li,6Li)7Li elastic scattering and the 7Li(6Li,7Lig.s.)6Li,7Li(6Li,7Li0.48)6Li transfer reactions at Ec.m.=23.7 MeV are measured with the Q3D magnetic spectrograph. The optical potential of 6Li+7Li is obtained by fitting the elastic scattering differential cross sections. Based on the distorted wave Born approximation (DWBA) analysis, spectroscopic factors of 7Li=6 are determined to be 0.73±0.05 and 0.90±0.09 for the ground and first exited states in 7Li, respectively. Using the spectroscopic factors, the cross sections of the direct neutron capture reactions and the astrophysical reaction rates are derived.
Emission of Neutral Pions with High Transverse Momenta in A-A and p-p Collisions at Energies Available at the BNL Relativistic Heavy Ion Collider
FAN San-Hong, MENG Cai-Rong, LIU Fu-Hu
Chin. Phys. Lett. 2010, 27 (5): 052501 .   DOI: 10.1088/0256-307X/27/5/052501
Abstract   PDF(pc) (385KB) ( 373 )
Invariant neutral pion (π0) yields in Au-Au and Cu-Cu collisions and invariant π0cross sections in p-p collisions are studied in the framework of a two-cylinder model. The considered distributions of neutral pions at the maximum energy of the relativistic heavy ion collider (RHIC) have a tail part in the region of high transverse momentum. A two-component distribution based upon the two-cylinder model is used to describe the experimental data of the PHENIX collaboration.
Influence of the Nucleon Hard Partons Distribution on J/Ψ Suppression in a GMC Framework
WANG Hong-Min, HOU Zhao-Yu, SUN Xian-Jing
Chin. Phys. Lett. 2010, 27 (5): 052502 .   DOI: 10.1088/0256-307X/27/5/052502
Abstract   PDF(pc) (443KB) ( 394 )
In a Glauber Monte Carlo framework, taking into account the transverse spatial distribution of hard partons in the nucleon, we analyze the nuclear modification factor Rd Au for J/φ in d+Au collisions with EPS09 shadowing parametrization. After the influence of nucleon hard partons distribution is considered, a clearly upward correction is revealed for the dependence of Rd Au on Ncoll in peripheral d+Au collisions, however, an unconspicuous correction is shown for the results versus pT. The theoretical results are in good agreement with the experimental data from PHENIX.
Rapidity Losses in Heavy-Ion Collisions from AGS to RHIC Energies
ZHOU Feng-Chu, YIN Zhong-Bao, ZHOU Dai-Cui
Chin. Phys. Lett. 2010, 27 (5): 052503 .   DOI: 10.1088/0256-307X/27/5/052503
Abstract   PDF(pc) (370KB) ( 507 )
We study the rapidity losses in central heavy-ion collisions from AGS to RHIC energies with the mean rapidity determined from the projectile net-baryon distribution after collisions. The projectile net-baryon distribution in the full rapidity range is obtained by phenomenologically removing the target contribution at the forward rapidity region from the experimental net-baryon measurements and taking into account the projectile contribution in the backward rapidity region. Based on the full projectile net-baryon distributions, calculations show that the rapidity loss stops increasing from the SPS top energy to RHIC energies, indicating that baryon transport does not depend strongly on energy at high energies.
Gallium Nitride Room Temperature α Particle Detectors
LU Min, ZHANG Guo-Guang, FU Kai, YU Guo-Hao
Chin. Phys. Lett. 2010, 27 (5): 052901 .   DOI: 10.1088/0256-307X/27/5/052901
Abstract   PDF(pc) (380KB) ( 704 )
Gallium Nitride (GaN) room temperature α particle detectors are fabricated and characterized, whose device structure is Schottky diode. The current-voltage (I-V) measurements reveal that the reverse breakdown voltage of the detectors is more than 200 V owing to the consummate fabrication processes, and that the Schottky barrier and ideal factor of the detectors are 0.64 eV and 1.02, respectively, calculated from the thermionic transmission model. 241Am α particles pulse height spectra from the GaN detectors biased at -8 V is obviously one Gauss peak located at channel 44 with the full width at half maximum (FWHM) of 15.87 in channel. One of the main reasons for the relatively wider FWHM is that the air between the detectors and isotope could widen the spectrum.
Optimization of Experimental Discharge Parameters to Increase the Arc Efficiency of the Bucket Ion Source
YU Li-Ming, LEI Guang-Jiu, CAO Jian-Yong, ZHONG Guang-Wu, JIANG Shao-Feng, ZOU Gui-Qing, JIANG Tao, LU Da-Lun, ZHANG Xian-Ming, LIU He
Chin. Phys. Lett. 2010, 27 (5): 052902 .   DOI: 10.1088/0256-307X/27/5/052902
Abstract   PDF(pc) (629KB) ( 773 )
Arc efficiency is a critical criterion for assessing the performance of the ion source. High arc efficiency is necessary for a high power ion source, because it can decrease the load of the arc power supply. Thus the relationship between the discharge parameters (gas pressure, arc voltage, filament current, bias resistance connecting between the anode and plasma grid) and the arc efficiency is investigated in experiment especially. It is found that with increasing pressure, the arc efficiency increases fast if the pressure is below 0.4 Pa, but when it is above 0.4 Pa, the arc efficiency remains unchanged or increases slowly. If we increase the arc voltage or filament current, the arc efficiency decreases. The bias resistance also influences the arc efficiency, at the same pressure the arc efficiency increases with resistance.
Varying Track Etch Rates along the Fission Fragments' Trajectories in CR-39 Detectors
N. Ali, E. U. Khan, A. Waheed, S. Karim, F. Khan, A. Majeed
Chin. Phys. Lett. 2010, 27 (5): 052903 .   DOI: 10.1088/0256-307X/27/5/052903
Abstract   PDF(pc) (384KB) ( 664 )
We determine the behavior of track etch rate VT along the tracks in CR-39 detectors exposed to fission fragments from 252Cf source. CR-39 detectors are etched at 70°C in different concentrations of Na2CO3-mixed 6M NaOH solutions for different etching time intervals of 5-10 min starting from 15 min up to 210 min. Two values of track etch rate are determined along the fission fragment trajectories. The variation in VT is correlated with the energy loss rate of the fission fragment in the detector material.
ATOMIC AND MOLECULAR PHYSICS
Chip-Based Square Wave Dynamic Micro Atom Trap
DAN Lin, , YAN Hui, , WANG Jin, ZHAN Ming-Sheng,
Chin. Phys. Lett. 2010, 27 (5): 053201 .   DOI: 10.1088/0256-307X/27/5/053201
Abstract   PDF(pc) (698KB) ( 442 )
We propose a scheme for a chip-based dynamic micro atom trap where the trap potentials are created by square wave radiation and an inhomogeneous static magnetic field. The parameters of this kind of trap array can be modulated dynamically. Both one-dimensional (1-D) and two-dimensional (2-D) trap array potentials for 6Li atoms are discussed. The 1-D trap is combined by a square wave radiation (6 kHz) and a gradient magnetic field (300 G/cm), the array constant of 1-D trap is 0.85 μm. Since the trap array does not require any laser field, it can be easily integrated on a chip and it is useful in applications of scalable quantum information processing.
A Novel Observation of "a Sharp Absorption Line" Using Much More Broad Laser Lights: Quantum Interference in the Autoionization Spectra of Sc
ZHONG Zhi-Ping, GAO Xiang, ZHANG Xiao-Le, LI Jia-Ming,
Chin. Phys. Lett. 2010, 27 (5): 053202 .   DOI: 10.1088/0256-307X/27/5/053202
Abstract   PDF(pc) (589KB) ( 379 )
The most accurate measurements in physical sciences will be precision spectroscopic experiments which are based on the usage of most narrow lines in cooperation with interference phenomena. We present a novel experimental observation of ``a sharp absorption resonance line'' with much more broad laser lights. The mechanism of such a novel phenomenon will be elucidated and its implications will be discussed.
Collision of Low Energy Proton with Ethylene
WANG Zhi-Ping, WANG Jing, ZHANG Feng-Shou,
Chin. Phys. Lett. 2010, 27 (5): 053401 .   DOI: 10.1088/0256-307X/27/5/053401
Abstract   PDF(pc) (413KB) ( 376 )
In the framework of the time-dependent local density approximation, applied to valence electrons, coupled non-adiabatically to molecular dynamics of ions, we investigate the microscopic mechanism of collisions between low energetic protons and ethylene. Not only the amount of energy lost by the projectile, but also the electronic and vibronic excitations of the target are identified. We find that the energy loss of the proton and excitation dynamics of the target depends sensitively on the impact energy.
Ionization Detection of Ultracold Ground State Cesium Molecules
JI Zhong-Hua, WU Ji-Zhou, MA Jie, FENG Zhi-Gang, ZHANG Lin-Jie, ZHAO Yan-Ting, WANG Li-Rong, XIAO Lian-Tuan, JIA Suo-Tang
Chin. Phys. Lett. 2010, 27 (5): 053701 .   DOI: 10.1088/0256-307X/27/5/053701
Abstract   PDF(pc) (387KB) ( 405 )
Photoassociation of ultracold atoms is an important method for producing stable ultracold molecules with extensive applications. Ion spectroscopy technique, which has higher sensitivity compared with trap loss spectroscopy and fragment spectroscopy, plays an important pole in the research of photoassociation spectroscopy. Based on ion spectroscopy technique, a complete experimental system is employed to produce and detect the ultracold ground state molecules, including the equipment of photoionization and time-of-fight mass spectroscopy. Ultracold ground state cesium molecules are demonstrated by the ionization detection technique. The number of the ground-state molecules produced in our MOT is measured. In addition, the relationship of the time interval of the cesium atom ion and the cesium molecular ion to the metal grid voltage is studied for the optimization of the experimental parameters.
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)
Rayleigh Scattering for An Electromagnetic Anisotropic Medium Sphere
LI Ying-Le, WANG Ming-Jun, DONG Qun-Feng, TANG Gao-Feng
Chin. Phys. Lett. 2010, 27 (5): 054101 .   DOI: 10.1088/0256-307X/27/5/054101
Abstract   PDF(pc) (492KB) ( 378 )
Based on the scales theory of electromagnetic waves, the analytical expression of electrical fields inside an anisotropic medium sphere is studied. Differential scattering cross section and radar cross section (RCS) for an anisotropic spherical target are presented. The correctness of the obtained results is tested. The simulation results show that the scattering of an anisotropic sphere has the property of a dipole radiation under the condition of Rayleigh scattering. The larger the dielectric constant is, the stronger the dipole scattering is. Anisotropy in magnetism only has an effect on differential RCS. These results provide a theoretical base for the identification of anisotropic targets.
Characteristics and New Measurement Method of NCSFs of Individual Color Mechanisms of Human Vision
GE Jing-Jing, WANG Zhao-Qi, WANG Yan, ZHAO Kan-Xing
Chin. Phys. Lett. 2010, 27 (5): 054201 .   DOI: 10.1088/0256-307X/27/5/054201
Abstract   PDF(pc) (602KB) ( 402 )
We propose a new method for determining neural
contrast sensitivity functions (NCSFs) of isolated color mechanisms based
on the measurements of wave-front aberrations and isoluminant color
contrast sensitivity functions (CSFs). Compared with the traditional
method, this technique avoids the coherent noise and speckle noise, which
are brought by the interference of laser beams, and has great
flexibility for the measurements of NCSF of different color mechanisms.
Our experiments indicate that the mean NCSF and CSF of the red mechanism
are higher than those of the green mechanism, respectively, while those of
the blue mechanism are the lowest. However the relative heights of the
peak of NCSF and CSF between red and green mechanisms vary in subjects.
There are some individuals whose peak values of NCSF and/or CSF of green
mechanism are higher than that of the red mechanism. The NCSFs and CSFs of
isolated color mechanisms all exhibit the similar characteristics and
variation tendency. With the statistical average, the NCSFs of the red,
green and blue mechanisms are higher than the corresponding CSFs in the
whole spatial frequency. Compared with the corresponding CSFs curves, the
peaks of the NCSFs of isolated color mechanisms shift toward higher
spatial frequencies, especially for that of blue mechanism which has a
largest shift of 3.9 c/deg.
A Phase-Controlled Optical Parametric Amplifier Pumped by Two Phase-Distorted Laser Beams
REN Hong-Yan, QIAN Lie-Jia, YUAN Peng, ZHU He-Yuan, FAN Dian-Yuan
Chin. Phys. Lett. 2010, 27 (5): 054202 .   DOI: 10.1088/0256-307X/27/5/054202
Abstract   PDF(pc) (473KB) ( 499 )
We theoretically study the phase characteristic of optical parametric amplification (OPA) or chirped pulse OPA (OPCPA) pumped by two phase-distorted laser beams. In the two-beam-pumped optical parametric amplification (TBOPA), due to spatial walk-off, both of the pump phase distortions will be partly transferred to signal in a single crystal so as to degrade the signal beam-quality, which will be more serious in high-energy OPCPA. An OPA configuration with a walkoff-compensated crystal pair is demonstrated for reducing the signal phase distortion experienced in the first stage and ensuring the signal phase independent of two pump phase distortions through the second crystal, hence maintaining the signal beam-quality. Such a TBOPA is similar to the conventional quantum laser amplifier by means of eliminating its sensitivity to the phase and number of the pump beams.
Broadband Convergence of 40GHz-ROF and 10-Gb/s WDM-PON Systems in the Duplex Access Network
ZHANG Li-Jia, XIN Xiang-Jun, LIU Bo, ZHANG Qi, WANG Yong-Jun, YU Chong-Xiu
Chin. Phys. Lett. 2010, 27 (5): 054203 .   DOI: 10.1088/0256-307X/27/5/054203
Abstract   PDF(pc) (380KB) ( 541 )
A broadly converged 40G-ROF and 10-Gb/s WDM-PON multi-service access system is proposed and experimentally demonstrated. This scheme consists of an integrated system of 40G-ROF and 10-Gb/s WDM-PON simultaneously transmitting independent 2.5-Gb/s wireless and 10-Gb/s wire signal. At the base station, it employs a remodulation scheme, which is achieved by remodulating the upstream OOK signal on the DPSK downstream signal, to reduce the cost of the base station. The transmission experiment is carried out over a 25-km-long single mode fiber (SMF-28). The results show that the sensitivities of downstream PON and ROF signal are −14.5 dBm and −21.5 dBm, respectively, and the sensitivity of upstream signal is−25.3 dBm.
Fabrication and Characterization of High Power InGaN Blue-Violet Lasers with an Array Structure
JI Lian, ZHANG Shu-Ming, JIANG De-Sheng, LIU Zong-Shun, ZHANG Li-Qun, ZHU Jian-Jun, ZHAO De-Gang, DUAN Li-Hong, YANG Hui,
Chin. Phys. Lett. 2010, 27 (5): 054204 .   DOI: 10.1088/0256-307X/27/5/054204
Abstract   PDF(pc) (534KB) ( 634 )
InGaN/GaN multi-quantum-well-structure
laser diodes with an array structure are successfully fabricated on
sapphire substrates. The laser diode consists of four emitter stripes
which share common electrodes on one laser chip. An 800-μm-long cavity
is formed by cleaving the substrate along the orientation using laser scriber. The threshold current and voltage of the
laser array diode are 2A and 10.5V, respectively. A light output peak
power of 12W under pulsed current injection at room temperature is
achieved. We simulate the electric properties of GaN based laser diode in
a co-planar structure and the results show that minimizing the difference
of distances between the different ridges and the n-electrode and
increasing the electrical conductivity of the n-type GaN are two effective
ways to improve the uniformity of carrier distribution in emitter stripes.
Two pairs of emitters on a chip are arranged to be located near the two
n-electrode pads on the left and right sides, and the four stripe emitters
can laser together. The laser diode shows two sharp peaks of light output
at 408 and 409nm above the threshold current. The full widths at half
maximum for the parallel and perpendicular far field patterns are
8° and 32°, respectively.
A Hybrid Method of Solving the Electromagnetic Inverse Scattering Problem in Lossy Medium
YANG Xi, ZHANG Yu, GOU Ming-Jiang, SHI Qing-Fan, SUN Gang
Chin. Phys. Lett. 2010, 27 (5): 054205 .   DOI: 10.1088/0256-307X/27/5/054205
Abstract   PDF(pc) (581KB) ( 402 )
A hybrid method of solving the electromagnetic inverse scattering problem in a lossy medium is proposed. The gradient search method is first used to determine the spatial distribution of the target, then the Monte Carlo method is selected to calculate the conductivity and permittivity of the scatterer. The results of numerical experiments verify that the hybrid method of combining the two ways is high-precision, efficient, and suited to global optimization.
Wavelength Modulation Absorption Spectroscopy Using a Frequency-Quadruped Current-Modulated System
SHAO Jie, SUN Hui-Juan, WANG Hui, ZHOU Wei-Dong, WU Gen-Zhu,
Chin. Phys. Lett. 2010, 27 (5): 054206 .   DOI: 10.1088/0256-307X/27/5/054206
Abstract   PDF(pc) (546KB) ( 475 )
A wavelength modulation absorption spectrometry (WMAS) with a frequency-quadruped system is demonstrated. The frequency-quadruped system consists of a two-frequency doubled external enhancement cavity with KNO3 and BBO crystals, and a current-modulated 906-nm single mode external cavity diode laser (ECDL), which generates the tunable wavelength modulated radiation at 226.7 nm used to detect the NO absorption line that belongs to the combined Q22(10.5) and QR12(10.5) lines of γ(0,0) band within the A2Σ+ -X2Π electronic transition system. The 1st, 2 nd and 3rd harmonic spectra are accomplished to show that it is possible to detect samples using the frequency quadruped system combined with the WMAS technique that can find practical applicability in the future.
Intensity Spatial Profile Analysis of a Gaussian Laser Beam at Its Waist Using an Optical Fiber System
ZHANG Liangmin
Chin. Phys. Lett. 2010, 27 (5): 054207 .   DOI: 10.1088/0256-307X/27/5/054207
Abstract   PDF(pc) (302KB) ( 1268 )
In many applications, it is important to know the waist of a laser beam. However, it is impossible to measure it directly because the intensity is high at the waist. We have used an optical fiber-scan system to characterize the Gaussian intensity profile of a focused femtosecond laser beam. The measurement system employs a single-mode optical fiber that is fixed on a motorized three-dimensional translation stage to collect the laser energy and the other end is connected to an optical power meter to measure the intensity profile. Using the measure data and geometry formulas, one can calculate the beam waist and far-field divergence angle of a laser beam. The measured beam waist size is essentially consistent with the result of theoretical fit.
Silicon-Based Asymmetric Add-Drop Microring Resonators with Ultra-Large Through-Port Extinctions
XIAO Xi, LI Yun-Tao, YU Yu-De, YU Jin-Zhong
Chin. Phys. Lett. 2010, 27 (5): 054208 .   DOI: 10.1088/0256-307X/27/5/054208
Abstract   PDF(pc) (1478KB) ( 437 )
We theoretically simulate and experimentally demonstrate ultra-large through-port extinctions in silicon-based asymmetrically-coupled add-drop microring resonators (MRs). Through-port responses in an add-drop MR are analyzed by simulations and large extinctions are found when the MR is near-critically coupled. Accurate fabrication techniques are applied in producing a series of 20 μm-radii add-drop microrings with drop-side gap-widths in slight differences. A through-port extinction of about 42.7 dB is measured in an MR with through- and drop-side gap-width to be respectively 280 nm and 295 nm. The large extinction suggests about a 20.5 dB improvement from the symmetrical add-drop MR of the same size and the through-side gap-width. The experimental results are finally compared with the post-fabrication simulations, which show a gap-width tolerance of >30 nm for the through-port extinction enhancement.
Measurement of Ultrashort Laser Pulse Width in a Wide Spectrum Range Using Dimethyl Sulfoxide by Optical Kerr Effect Technique
KONG De-Gui, CHANG Qing, YE Hong-An, GAO Ya-Chen, ZHANG Li-Xin, WANG Yu-Xiao, ZHANG Xue-Ru, YANG Kun, SONG Ying-Lin,
Chin. Phys. Lett. 2010, 27 (5): 054209 .   DOI: 10.1088/0256-307X/27/5/054209
Abstract   PDF(pc) (484KB) ( 576 )
We illustrate that applying the optical Kerr effect technique to dimethyl sulfoxide (DMSO) can determine the width of laser pulses in a wide spectrum range that is transparent. Different from many other simple molecular liquids, such CS2, and toluene, DMSO responds to both 130 fs 800 nm laser pulses and 248 fs 400 nm laser pulses with electronic motions only. Therefore, the observed signal as a function of time reflects the temporal distribution of the intensity. We verify our illustration by both the autocorrelation technique and spectra analysis.
Synthesis of Fiber Bragg Gratings with Right-Angled Triangular Spectrum
LI Li-Sha, FENG Xuan-Qi
Chin. Phys. Lett. 2010, 27 (5): 054210 .   DOI: 10.1088/0256-307X/27/5/054210
Abstract   PDF(pc) (332KB) ( 519 )
The spectrum shape of conventional fiber Bragg gratings is near-rectangular. By means of a discrete layer peeling method we numerically study fiber Bragg gratings with right-angled triangular spectrum. Fiber Bragg grating structures with single- and multi-channel right-angled triangular spectra are synthesized. These kinds of devices provide potential applications in wavelength interrogation in optical sensor systems.
Generation of Sub-2 Cycle Optical Pulses with a Differentially Pumped Hollow Fiber
ZHANG Wei, TENG Hao, YUN Chen-Xia, ZHONG Xin, HOU Xun, WEI Zhi-Yi
Chin. Phys. Lett. 2010, 27 (5): 054211 .   DOI: 10.1088/0256-307X/27/5/054211
Abstract   PDF(pc) (462KB) ( 533 )
We report the generation of optical pulses with an energy of 0.55 mJ and duration of 1.6-cycle (4.4 fs) at repetition rate of 1 kHz using a differentially pumped hollow fiber and chirped mirrors. Compared to the statically gas-filled scheme, the differentially pumping hollow fiber is demonstrated to support more energy output with higher transmission efficiency, and to increase the spectral broadening due to a reduction of ionization defocusing in plasma at the fiber entrance. The differentially pumping technique is proved to be an effective way to obtain optical pulses with mono-cycle and higher energy.
Residual Doppler Effect on Electromagnetically Induced Transparency in a Zeeman Sublevel System
HU Zhen-Yan, LI Lu-Ming, CHEN Pei-Rong, SUN Xin
Chin. Phys. Lett. 2010, 27 (5): 054212 .   DOI: 10.1088/0256-307X/27/5/054212
Abstract   PDF(pc) (414KB) ( 712 )
We investigate the residual Doppler effect on the linewidth of electromagnetically induced transparency (EIT) in a Zeeman sublevel system where a careful experimental design ensures the smallest measurement error. The overall measurement error of the EIT linewidth is estimated to be less than 5%. We present the linear dependence of EIT resonance broadening at small angular deviation in detail. The theoretical analysis exploits the dependence of this feature and shows the qualitative agreement between numerical results and experimental results.
Suppercontinuum Generation in InP Nano Inner Cladding Fibers
DUAN Yu-Wen, ZHANG Ru, WANG Jin, CHEN Xi, ZHONG Kun
Chin. Phys. Lett. 2010, 27 (5): 054213 .   DOI: 10.1088/0256-307X/27/5/054213
Abstract   PDF(pc) (388KB) ( 389 )
The InP nano inner cladding fiber is fabricated by the method of modified chemical vapor deposition. The thickness of the InP nano thin film is about 16 nm. A 20 dB supercontinuum over 100 nm in the telecommunication band is generated by infecting 1550 nm, 120 fs, 50 MHz repetition rate optical pulse into this kind of fiber. Moreover, the results indicate that the width of the supercontinuum spectra can be influenced by the fiber length and pump power. The longer fiber at higher pump power can produce broader supercontinuum spectrum.
A Combined Reconstruction Algorithm for Limited-View Multi-Element Photoacoustic Imaging
YANG Di-Wu, XING Da, ZHAO Xue-Hui, PAN Chang-Ning, FANG Jian-Shu
Chin. Phys. Lett. 2010, 27 (5): 054301 .   DOI: 10.1088/0256-307X/27/5/054301
Abstract   PDF(pc) (506KB) ( 522 )
We present a photoacoustic imaging system with a linear transducer array scanning in limited-view fields and develop a combined reconstruction algorithm, which is a combination of the limited-field filtered back projection (LFBP) algorithm and the simultaneous iterative reconstruction technique (SIRT) algorithm, to reconstruct the optical absorption distribution. In this algorithm, the LFBP algorithm is exploited to reconstruct the original photoacoustic image, and then the SIRT algorithm is used to improve the quality of the final reconstructed photoacoustic image. Numerical simulations with calculated incomplete data validate the reliability of this algorithm and the reconstructed experimental results further demonstrate that the combined reconstruction algorithm effectively reduces the artifacts and blurs and yields better quality of reconstruction image than that with the LFBP algorithm.
Capillary Rise in a Single Tortuous Capillary
CAI Jian-Chao, YU Bo-Ming, MEI Mao-Fei, LUO Liang
Chin. Phys. Lett. 2010, 27 (5): 054701 .   DOI: 10.1088/0256-307X/27/5/054701
Abstract   PDF(pc) (571KB) ( 1169 )
The impact of convolutedness of capillary on the capillary rise of wetting liquid in a single tortuous capillary is studied. By introducing tortuosity and fractal dimension for a tortuous capillary, analytical expression for time evolution of the height/weight of capillary rise is obtained. It is found that the accumulated weight of liquid imbibed into a single tortuous capillary is independent of the shape of a capillary in the early rising stage.
Intermittency and Thermalization in Turbulence
ZHU Jian-Zhou, Mark Taylor
Chin. Phys. Lett. 2010, 27 (5): 054702 .   DOI: 10.1088/0256-307X/27/5/054702
Abstract   PDF(pc) (576KB) ( 373 )
A dissipation rate, which grows faster than any power of the wave number in Fourier space, may be scaled to lead a hydrodynamic system to actually or potentially converge to its Galerkin truncation. Actual convergence here means the asymptotic truncation at a finite wavenumber kG above which modes have no dynamics; and, we define potential convergence for the truncation at kG which, however, grows without bound. Both types of convergence can be obtained with the dissipation rate μ[cosh (κ/κ_c)-1]that behaves as k2 (newtonian) and exp{κ/κ_c}for small and large κ/κ_c respectively. Competing physics of cascade, thermalization and dissipation are discussed for numerical Navier-Stokes turbulence, emphasizing the intermittency growth issue.
Generation Mechanism of Liquid Column during the Burst of a Rising Bubble near a Free Surface
WANG Han, ZHANG Zhen-Yu, YANG Yong-Ming, ZHANG Hui-Sheng
Chin. Phys. Lett. 2010, 27 (5): 054703 .   DOI: 10.1088/0256-307X/27/5/054703
Abstract   PDF(pc) (404KB) ( 457 )
In the frame of inviscid and incompressible flow and by neglecting surface tension effects, the dynamical mechanism of the generation and the development of the liquid column during the burst of a rising bubble near a free surface is studied theoretically and numerically by the volume-of-fluid method.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
Electron Emission Suppression from Cathode Surfaces of a Rod-Pinch Diode
GAO Yi, YIN Jia-Hui, SUN Jian-Feng, ZHANG Zhong, ZHANG Peng-Fei, SU Zhao-Feng
Chin. Phys. Lett. 2010, 27 (5): 055201 .   DOI: 10.1088/0256-307X/27/5/055201
Abstract   PDF(pc) (746KB) ( 459 )
The theory and method of suppressing electron emission from cathode surfaces is introduced, including increasing the emission threshold, reducing the surface electric field and shielding the emitted electrons. The stainless steel-graphite and Teflon-graphite composite cathodes are designed to test the above methods for a rod-pinch diode. The experiments are performed on the inductive voltage adder, and the results indicate that the Teflon-graphite composite cathode is effective in suppressing electron emission from the specified cathode surface, while the stainless steel-graphite composite cathode fails. The reasons are analyzed theoretically.
First Charge Exchange Recombination Spectroscopy Diagnostic in HL-2A Tokamak
HAN Xiao-Yu, DUAN Xu-Ru, YANG Li-Mei, YU De-Liang, ZHONG Wu-Lv, FU Bing-Zhong, LIU Yong, LIU Yi, YAN Long-Wen, YANG Qing-Wei
Chin. Phys. Lett. 2010, 27 (5): 055202 .   DOI: 10.1088/0256-307X/27/5/055202
Abstract   PDF(pc) (372KB) ( 550 )
Spatially resolved measurements of ion temperature are crucial for understanding plasma dynamics. A charge exchange recombination spectroscopy diagnostic system based on a heating neutral beam is installed on the HL-2A tokamak. An optical collection system is designed in accordance with the actual geometry of HL-2A and the CVI 529.2 nm (n= 8→ 7) charge-exchange recombination line. Preliminary measurements show that the CX signals have enough signal-to-noise ratio (SNR). The ion temperature and its profiles are obtained through this system for the first time.
Characteristics of a Novel Water Plasma Torch
NI Guo-Hua, MENG Yue-Dong, CHENG Cheng, LAN Yan
Chin. Phys. Lett. 2010, 27 (5): 055203 .   DOI: 10.1088/0256-307X/27/5/055203
Abstract   PDF(pc) (591KB) ( 3289 )
Relying on heat generated by plasma arc heating liquid water into steam as a swirl gas, a water plasma torch has the distinctive steam generation structure, which has various applications such as in the treatment of organic waste and hydrogen production for fuel cells in future vehicles. The operational features of the water plasma torch and water phase change process in the discharge chamber are investigated based on the temporal evolution of the voltage and current. The optical emission spectrum measurement shows that the water molecule in the plasma is decomposed into H, OH and O radicals. As the electrodes do not require water-cooling, the thermal efficiency of the torch is very high, which is confirmed by analytical calculation and experimental measurement.
Propagation Characteristics of Whistler-Mode Chorus during Geomagnetic Activities
ZHOU Qing-Hua, HE Yi-Hua, HE Zhao-Guo, YANG Chang
Chin. Phys. Lett. 2010, 27 (5): 055204 .   DOI: 10.1088/0256-307X/27/5/055204
Abstract   PDF(pc) (534KB) ( 436 )
A recently introduced ray-tracing method is adopted to study the propagation characteristics of whistler-mode chorus during different geomagnetic activities by using a global core plasma density model. Numerical calculations show that chorus waves tend to settle on a preferable magnetic shell L in the vicinity of the plasmapause. During high geomagnetic activity, the plasmapause position moves inward close to the Earth and chorus trajectories move inward together with plasmapause. The trajectory move closer to the plasmapause asθ increases. Chorus wave with lower frequencies will reflect multiple times while chorus wave with higher frequencies reflect once at the plasmapause before settling on the vicinity of the plasmapause. The current results present a first detailed study on the propagation characteristics of chorus during geomagnetic activities, and may account for the observation that chorus tends to be present in the vicinity of the plasmapause.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES
Quantitative Characterization of Partial Dislocations in Nanocrystalline Metals
NI Hai-Tao, ZHANG Xi-Yan, ZHU Yu-Tao
Chin. Phys. Lett. 2010, 27 (5): 056101 .   DOI: 10.1088/0256-307X/27/5/056101
Abstract   PDF(pc) (332KB) ( 563 )
Partial dislocations in nanocrystalline metals are introduced and a modified dislocation density formula for partial dislocations is established by x-ray line profile analysis theories. Effects of factors on the determination of partial dislocation density are discussed. From the correlation between the partial and perfect dislocations, partial dislocation density is simply quantitative characterized by drawing on the evaluation methodology of perfect dislocations. Dislocation densities of nanocrystalline nickel calculated from two different equations are compared additionally.
Frequency Response of the Sample Vibration Mode in Scanning Probe Acoustic Microscope
ZHAO Ya-Jun, CHENG Qian, QIAN Meng-Lu
Chin. Phys. Lett. 2010, 27 (5): 056201 .   DOI: 10.1088/0256-307X/27/5/056201
Abstract   PDF(pc) (1028KB) ( 498 )
Based on the interaction mechanism between tip and sample in the contact mode of a scanning probe acoustic microscope (SPAM), an active mass of the sample is introduced in the mass-spring model. The tip motion and frequency response of the sample vibration mode in the SPAM are calculated by the Lagrange equation with dissipation function. For the silicon tip and glass assemblage in the SPAM the frequency response is simulated and it is in agreement with the experimental result. The living myoblast cells on the glass slide are imaged at resonance frequencies of the SPAM system, which are 20 kHz, 30 kHz and 120 kHz. It is shown that good contrast of SPAM images could be obtained when the system is operated at the resonance frequencies of the system in high and low-frequency regions.
Temperature-Dependent Raman Spectrum of Hexagonal YMnO3 Films Synthesized by Chemical Solution Method
LIU Yue-Feng, WANG Bei, ZHENG Hai-Wu, LIU Xiang-Yang, GU Yu-Zong, ZHANG Wei-Feng
Chin. Phys. Lett. 2010, 27 (5): 056801 .   DOI: 10.1088/0256-307X/27/5/056801
Abstract   PDF(pc) (428KB) ( 905 )
We study the temperature-dependent Raman spectrum of hexagonal YMnO3 films prepared by a chemical solution method. There are seven Raman peaks (3A1+E1+4E2) of the film identified at room temperature. From the results of temperature dependence of the Raman spectrum, it is deduced that the YMnO3 film has a magnetic phase transition temperature of about 123 K. The temperature variation phonon mode at 685 cm-1 shows an anomalous frequency variation near 123 K, suggesting either a more complex mechanism of spin-phonon coupling or strong mixing of phonon modes. The reason for the higher antiferromagnetic Néel temperature TN of the film than that of the bulk counterpart is also discussed.
The Influence of Au-Doping on Morphology and Visible-Light Reflectivity of TiN Thin Films Deposited by Direct-Current Reactive Magnetron Sputtering
NA Yuan-Yuan, WANG Cong, LIU Yu
Chin. Phys. Lett. 2010, 27 (5): 056802 .   DOI: 10.1088/0256-307X/27/5/056802
Abstract   PDF(pc) (1052KB) ( 482 )
Ti, TiN and Au-TiN (Au content: from 0.5% to 7.7%) thin films were deposited on stainless steel substrates by dc reactive magnetron sputtering with a metal Ti target. The crystal structure, surface morphology and visible-light reflectivity of the films for different film compositions are studied in detail. Distinctly different surface morphologies appear for the Ti, TiN and Au-TiN thin films. It can be observed that the surface morphology of the TiN film is affected by the Au-doping, when the Au content increases from 0% to 7.7%, surface roughness enlarges from 62.4 to 82.8 nm. Moreover, visible-light reflectivity varies significantly with increasing Au contents in the TiN films. However, the reflectivity of the TiN thin film at 550-800 nm is higher than that of the Au-TiN thin film. The present work illustrates the dependence of metal elements on the surface morphology and on the reflectivity of Au-TiN thin films. It is speculated that the addition of Au can suppress the formation and growth of TiN grains so that it changes the surface morphology and the Au-TiN thin film has potential applications in spectral selective coating.
Research of Equilibrium Composition Map in Conic Quantum Dots
ZHAO Wei, YU Zhong-Yuan, LIU Yu-Min, FENG Hao, XU Zi-Huan
Chin. Phys. Lett. 2010, 27 (5): 056803 .   DOI: 10.1088/0256-307X/27/5/056803
Abstract   PDF(pc) (384KB) ( 346 )
We present equilibrium composition maps in InGaAs/GaAs conic strained quantum dots, using the finite element method and quadratic programming optimization method. The axis-symmetric model is adopted. We compare the steep islands with the shallow islands and determine the influence of entropic energy. The difference of equilibrium composition maps between the single dot and the quantum dot stacks is also discussed.
Large-Area Self-Assembly of Rubrene on Au(111) Surface
LIU Xiao-Qing, KONG Hui-Hui, CHEN Xiu, DU Xin-Li, CHEN Feng, LIU Nian-Hua, WANG Li,
Chin. Phys. Lett. 2010, 27 (5): 056804 .   DOI: 10.1088/0256-307X/27/5/056804
Abstract   PDF(pc) (2142KB) ( 424 )
Large-area self-assembly of rubrene has been fabricated on Au(111) surface and studied by scanning tunnelling microscopy. The rubrene monolayer on Au(111) surface is characterized by well-ordered row-like structures similar to the a-b plane of rubrene single crystal. However, the directions of the neighboured molecular rows are opposite to each other. In a two-layer film of rubrene on Au(111) surface, the arrangements of the top molecular rows are determined by the underneath rows, suggesting an orthorhombic crystal structure with a=1.26 nm, b=4.36 nm, c=0.17 nm for multilayer of rubrene on Au(111).
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Quantum Mechanical Study on Tunnelling and Ballistic Transport of Nanometer Si MOSFETs
DENG Hui-Xiong, JIANG Xiang-Wei, TANG Li-Ming
Chin. Phys. Lett. 2010, 27 (5): 057101 .   DOI: 10.1088/0256-307X/27/5/057101
Abstract   PDF(pc) (524KB) ( 415 )
Using self-consistent calculations of million-atom Schrödinger-Poisson equations, we investigate the I-V characteristics of tunnelling and ballistic transport of nanometer metal oxide semiconductor field effect transistors (MOSFET) based on a full 3-D quantum mechanical simulation under nonequilibtium condition. Atomistic empirical pseudopotentials are used to describe the device Hamiltonian and the underlying bulk band structure. We find that the ballistic transport dominates the I-V characteristics, whereas the effects of tunnelling cannot be neglected with the maximal value up to 0.8 mA/μm when the channel length of MOSFET scales down to 25 nm. The effects of tunnelling transport lower the threshold voltage Vt. The ballistic current based on fully 3-D quantum mechanical simulation is relatively large and has small on-off ratio compared with results derived from the calculation methods of Luo et al.
Spectral Response and Photoelectrochemical Properties of Cd1-xZnxSe Films
N. J. Suthan Kissinger, G. Gnana Kumar, K. Perumal, J. Suthagar
Chin. Phys. Lett. 2010, 27 (5): 057102 .   DOI: 10.1088/0256-307X/27/5/057102
Abstract   PDF(pc) (396KB) ( 411 )

Cd1-xZnxSe films with different zinc contents are deposited by an electron beam evaporation technique onto glass substrates for applications in solid-state photovoltaic devices. The structural, optical and photoelectrochemical (PEC) properties of Cd1-xZnxSe films are studied. The host material Cd1-xZnxSe is prepared by the physical vapor deposition method of electron beam evaporation technique (PVD: EBE) under a pressure of 1× 10-5 mbar. The x-ray diffractogram indicates that these alloy films are polycrystalline in nature, hexagonal structure with strong preferential orientation of the crystallites along (002) direction. The optical properties shows that the band gap Eg varies from 2.08 to 2.84 eV as zinc content varies from 0.2 to 0.8. A PEC cell of the configuration n-Cd1-xZnxSe/Na2S-S-NaOH is fabricated and the dynamic current-voltage characteristics in the dark atmosphere have been examined at room temperature. It has been found that both Voc and Isc decrease with the photoelectrode composition x. Efficiency η and fill factor (FF) also show similar variations. The material properties would be altered and excellently controlled by controlling the system composition x.

Mechanism of Visible Photoactivity of F-Doped TiO2
GUO Mei-Li, ZHANG Xiao-Dong, LIANG Chun-Tian, JIA Guo-Zhi
Chin. Phys. Lett. 2010, 27 (5): 057103 .   DOI: 10.1088/0256-307X/27/5/057103
Abstract   PDF(pc) (529KB) ( 859 )
We calculate the electronic structure and optical properties of F-doped anatase TiO2. The results indicate that the band gap of F-doped TiO2 increases slightly compared with the pure TiO2. However, it is interesting that the visible absorption of F-doped TiO2 located between 600 and 700 nm is observed, and it enhances gradually with the increasing F concentration. Furthermore, according to the results of densities of states and imaginary part of dielectric functionε2(ω), we propose that the transition between Ti 3d and Ti 3d states may be responsible for the visible absorption, but not the band gap narrowing.
Variation of Optical Quenching of Photoconductivity with Resistivity in Unintentional Doped GaN
HOU Qi-Feng, WANG Xiao-Liang, XIAO Hong-Ling, WANG Cui-Mei, YANG Cui-Bai, LI Jin-Min
Chin. Phys. Lett. 2010, 27 (5): 057104 .   DOI: 10.1088/0256-307X/27/5/057104
Abstract   PDF(pc) (448KB) ( 420 )
The optical quenching of photoconductivity under dual illumination in GaN samples with different resistivity is investigated to reveal the variation of deep levels. The samples are grown by metal organic chemical vapour deposition without intentional doping. Quenching bands centered at 1.35 eV, 1.55 eV, 1.98 eV, and 2.60 eV are observed. It is found that the 1.98 eV quenching band is dominated in all the samples and the 2.60 eV band is observed only in the high-resistivity samples. The possible defect levels responsible for the quenching bands and the origin of different quenching behaviour at 2.60 eV are discussed. It is suggested that the defect level responsible for quenching at 2.60 eV plays an important role for the enhancement of resistivity.
Thermoelectric Performances of Free-Standing Polythiophene and Poly(3-Methylthiophene) Nanofilms
LU Bao-Yang, LIU Cong-Cong, LU Shan, XU Jing-Kun, JIANG Feng-Xing, LI Yu-Zhen, ZHANG Zhuo
Chin. Phys. Lett. 2010, 27 (5): 057201 .   DOI: 10.1088/0256-307X/27/5/057201
Abstract   PDF(pc) (718KB) ( 910 )

Thermoelectric performances of free-standing polythiophene (PT) and poly(3-methylthiophene) (PMeT) nanofilms with high tensile strength electrosynthesized from boron trifluoride diethyl etherate (BFEE) are systematically investigated. They display decent electric conductivity (47 and 73 S·cm-1), high Seebeck coefficient (130 and 76 μV·K-1) and low thermal conductivity (0.17 and 0.15 W·m-1·K-1) at room temperature. Their figure of merit can reach 3.0×10-2 at 250 K, higher than that of many other conducting polymers. The decrease of charge carrier concentration resulting from volatile and water-sensitive dopants from BFEE leads to the decrease of electrical conductivity but a substantial increase of the Seebeck coefficient, making their figure-of-merit values maintained at more than 10-2 even after prolonged storage (two months). Moreover, free-standing PT and PMeT exhibit much better thermoelectric performances than those in pressed pellets due to the good arrangement of the polymer chains and preferably oriented structure in films. It therefore provides a way to improve the thermoelectric performances of conducting polymers by controlling regularity of the extended conjugated chain structure and/or the chain packing to achieve high charge mobility.

Spin Current Through Triple Quantum Dot in the Presence of Rashba Spin-Orbit Interaction
LI Jin-Liang, LI Yu-Xian
Chin. Phys. Lett. 2010, 27 (5): 057202 .   DOI: 10.1088/0256-307X/27/5/057202
Abstract   PDF(pc) (383KB) ( 423 )
A spin device with three normal metal leads via triple quantum dot in the presence of Rashba spin-orbit interaction is proposed, which is free from magnetic field or magnetic material. Using nonequilibrium Green's function technique, we investigate the spin current through the three-quantum-dot device. It is found that the spin current can be affected by the strength of the Rashba spin-orbit interaction, Coulomb interaction, the energy of the quantum dot and the bias voltage of the lead. The periodic oscillation of spin current can be controlled by tuning the Rashba spin-orbit interaction.
The Anomalous Effect of Interface Traps on Generation Current in Lightly Doped Drain nMOSFET's
MA Xiao-Hua, GAO Hai-Xia, CAO Yan-Rong, CHEN Hai-Feng, HAO Yue
Chin. Phys. Lett. 2010, 27 (5): 057301 .   DOI: 10.1088/0256-307X/27/5/057301
Abstract   PDF(pc) (456KB) ( 384 )
The anomalous phenomenon of generation current IGD in the lightly doped drain (LDD) nMOSFET measured under the drain bias VD-step mode is reported. We propose an assumption of activated (A) and frozen (F) traps for the VD-step mode: The A traps contributes to IGD while the F process can make them lose the roles as generation centers. The A and F regions can form the F-A region. The comparison of the F and A regions decides the role of the F-A region. The experiments confirm the assumption.
Shape-Controlled Synthesis and Related Growth Mechanism of Pb(OH)2 Nanorods by Solution-Phase Reaction
CHENG Jin, , ZOU Xiao-Ping, SONG Wei-Li, CAO Mao-Sheng, SU Yi, YANG Gang-Qiang, , Lü Xue-Ming, ZHANG Fu-Xue,
Chin. Phys. Lett. 2010, 27 (5): 057302 .   DOI: 10.1088/0256-307X/27/5/057302
Abstract   PDF(pc) (957KB) ( 999 )

We present a simple method to synthesize Pb(OH)2 nanorods by solution-phase reaction. Rod-like lead hydroxide precipitates are obtained by mixing lead nitrate with a concentration of about 0.01 M and potassium hydroxide with concentration of about 0.03 M in an aqueous solution. Sodium chloride as an additive is premixed with the lead nitrate aqueous solution. The presence of chloride ions in the precursor solution results in the rod-like morphology of lead hydroxide precipitates. The growth mechanism of the lead hydroxide nanorods is discussed.

Infrared Absorption Spectra of Undoped and Doped Few-Layer Graphenes
XU Yue-Hua, JIA Yong-Lei, ZHOU Jian, DONG Jin-Ming
Chin. Phys. Lett. 2010, 27 (5): 057303 .   DOI: 10.1088/0256-307X/27/5/057303
Abstract   PDF(pc) (438KB) ( 533 )
The infrared absorption spectra of undoped few-layer graphenes with the layer number of N= 1-6, the hole- and electron-doped few-layer graphenes with the layer number of N= 1-4 have been studied based upon the tight-binding model. It is found that in contrast with the featureless optical spectrum of the undoped monolayer graphene, the undoped AB-stacking bi-, tri-, tetra- and more-layer graphene exhibit characteristic jumps in their infrared absorption (IR) spectra, which are caused by coupling between different layers. It is also found that the clear peaks exist in the IR spectra of the hole or electron-doped bi-, tri- and tetra-layer graphenes, which are induced by the strong IR transitions between their parallel valence or conduction bands. Based upon their different IR spectra, a powerful experimental tool has been proposed to identify accurately the layer number and doping type for the few-layer graphenes.
Observation of Coulomb Oscillations with Single Dot Characteristics in Heavy Doped Ultra Thin SOI Nanowires
FANG Zhong-Hui, ZHANG Xian-Gao, CHEN Kun-Ji, QIAN Xin-Ye, XU Jun, HUANG Xin-Fan, HE Fei
Chin. Phys. Lett. 2010, 27 (5): 057304 .   DOI: 10.1088/0256-307X/27/5/057304
Abstract   PDF(pc) (471KB) ( 375 )
Nanowire devices with back gate are fabricated in a heavy doped ultra thin SOI layer by electron beam lithography. Regular and periodic Coulomb oscillations with single dot behavior are observed in an appropriate back gate voltage range. The oscillation period can be determined by the back gate capacitance. The role of the back gate can control the electrical characteristics from the multi-dot junction regimes to the single dot junction regimes. These Coulomb oscillations due to single-electron tunneling are not smeared out by thermal vibration energy when the temperature is less than 40 K.
Blue Luminescent Properties of Silicon Nanowires Grown by a Solid-Liquid-Solid Method
PENG Ying-Cai, FAN Zhi-Dong, BAI Zhen-Hua, ZHAO Xin-Wei, LOU Jian-Zhong, CHENG Xu
Chin. Phys. Lett. 2010, 27 (5): 057305 .   DOI: 10.1088/0256-307X/27/5/057305
Abstract   PDF(pc) (496KB) ( 524 )
Silicon nanowires (SiNWs) were grown directly from n-(111) single-crystal silicon (c-Si) substrate based on a solid-liquid-solid mechanism, and Au film was used as a metallic catalyst. The room temperature photoluminescence properties of SiNWs were observed by an Xe lamp with an exciting wavelength of 350 nm. The results show that the SiNWs exhibit a strongly blue luminescent band in the wavelength range 400-480 nm at an emission peak position of 420 nm. The luminescent mechanism of SiNWs indicates that the blue luminescence is attributed to the oxygen-related defects, which are in SiOx amorphous oxide shells around the crystalline core of SiNWs.
White Emitting ZnS Nanocrystals: Synthesis and Spectrum Characterization
HUANG Qing-Song, DONG Dong-Qing, XU Jian-Ping, ZHANG Xiao-Song, ZHANG Hong-Min, LI Lan
Chin. Phys. Lett. 2010, 27 (5): 057306 .   DOI: 10.1088/0256-307X/27/5/057306
Abstract   PDF(pc) (744KB) ( 444 )
Spherical organic-bonded ZnS nanocrystals with 4.0± 0.2 nm in diameter are synthesized by a liquid-solid-solution method. The photoluminescence spectrum of sample ([S2-]/[Zn2+] =1.0) shows a strong white emission with a peak at 490 nm and ~ 170 nm full widths at half maximum. By Gauss fitting, the white emission is attributed to the overlap of a blue emission and a green-yellow emission, originating from electronic transitions from internal S2- vacancies level to valence band and to the internal Zn2+ vacancy level, respectively. After sealingZnS nanocrystals onto InGaN chips, the device shows CIE coordinates of (0.29,0.30), which indicates their potential applications for white light emitting diodes.
Microwave Magnetic Properties and Natural Resonance of ε-Co Nanoparticles
YANG Yong, XU Cai-Ling, QIAO Liang, Li Xing-Hua, LI Fa-Shen
Chin. Phys. Lett. 2010, 27 (5): 057501 .   DOI: 10.1088/0256-307X/27/5/057501
Abstract   PDF(pc) (508KB) ( 685 )
Owing to the novel crystal structure, ε-Co nanoparticles with an average diameter of 12 nm are synthesized and the microwave magnetic properties of the epoxy resin composite with 50 vol% εCo particles are measured in the frequency range 0.1-7 GHz. The experimental resonance frequency (4.7 GHz) matches well with the values obtained by the theoretical calculation with the Kittel equation and fitting the experimental permeability dispersion curve via the Landau-Lifshitz equation. Hence the resonance peak is attributed to natural resonance mode. This work is believed to be beneficial for further understanding microwave applications of the novel ε-Co nanoparticles.
Effective Anisotropy in Magnetically Nd2Fe14B/α-Fe Nanocomposite
GUO Jia-Jun, CHEN Lei, ZHAO Xu, FAN Su-Li, CHEN Wei
Chin. Phys. Lett. 2010, 27 (5): 057502 .   DOI: 10.1088/0256-307X/27/5/057502
Abstract   PDF(pc) (451KB) ( 403 )
Considering different contact situations of grains, we investigate the effects of exchange-coupling interaction on effective anisotropies of magnetically soft α-Fe grains, hard Nd2Fe14B grains and Nd2Fe14B/α-Fe nanocomposite. An expression of effective anisotropy suitable for different degrees of exchange-coupling between grains is presented. The calculation results show that the exchange-coupling interaction increases the average anisotropy of soft grains and decreases that of hard grains. The effective anisotropy of Nd2Fe14B/α-Fe nanocomposite decreases smoothly with decreasing grain size when the grain size is larger than 20 nm while it decreases dramatically with further decrease of the grain size. In order to maintain high coercivity in Nd2Fe14B/α-Fe nanocomposite, the grain size should not be less than 20nm.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Improvement of AlN Film Quality by Controlling the Coalescence of Nucleation Islands in Plasma-Assisted Molecular Beam Epitaxy
ZHANG Chen, HAO Zhi-Biao, REN Fan, HU Jian-Nan, LUO Yi
Chin. Phys. Lett. 2010, 27 (5): 058101 .   DOI: 10.1088/0256-307X/27/5/058101
Abstract   PDF(pc) (530KB) ( 486 )
The influence of nucleation coalescence on the crystalline quality of AlN films grown on sapphire by plasma-assisted molecular beam epitaxy is investigated. The coalescence speed is controlled by the V/Ⅲ ratio chosen for the growth after nucleation. A slightly Al-rich condition, corresponding to slow coalescence, can significantly reduce the density of edge threading dislocation (TD), which is found to be dominant in AlN epilayers. The cross-sectional TEM image of the AlN epilayer grown under this condition clearly reveals an automatically formed boundary where an abrupt decrease of edge TD density occurs.
Preparation of Functional Gradient Material n-PbTe with Continuous Carrier Concentration
ZHU Pin-Wen, HONG You-Liang, WANG Xin, CHEN Li-Xue, IMAI Yoshio
Chin. Phys. Lett. 2010, 27 (5): 058102 .   DOI: 10.1088/0256-307X/27/5/058102
Abstract   PDF(pc) (439KB) ( 929 )
Functional gradient materials (FGMs) in thermoelectric materials can raise the maximal power output of the thermoelectric generator (TEG). We report an FGM of n-PbTe with continuous carrier concentration successfully prepared by a unidirectional solidification method. The continuous carrier concentration for n-PbTe was optimized by different dopants of PbI2, Al and Zr and solidifying temperature. The effective maximum outputting power for continuous FGM PbTe is about 30% larger than that for jointed FGM PbTe.
Deposition Behavior and Mechanism of Ni Nanoparticles on Surface of SiC Particles in Solution Systems
XU Hui, KANG Yu-Qing, ZHANG Lu, JIN Hai-Bo, WEN Bo, WEN Bao-Li, YUAN Jie, CAO Mao-Sheng
Chin. Phys. Lett. 2010, 27 (5): 058103 .   DOI: 10.1088/0256-307X/27/5/058103
Abstract   PDF(pc) (753KB) ( 435 )
Ni-deposited SiC particles are prepared successfully by a facile chemical reaction approach. The structure and morphology analyses demonstrate the Ni nanoparticles have been deposited on the surface of SiC particles. The deposition behavior of Ni on the surface of SiC particles is investigated. Pd-Sn catalytic nuclei formed in the pretreatment process promote the redox reaction and lead to the reduction of Ni2+ to metal nickel. Moreover, the kinetic mechanism of the reaction process of Ni2+ and has also been discussed in detail. Kinetic models have been established.
A Single Photon Counting Detector Based on One-Dimensional Vernier Anode
YANG Hao, ZHAO Bao-Sheng, SHENG Li-Zhi, LI Mei, YAN Qiu-Rong, LIU Yong-An
Chin. Phys. Lett. 2010, 27 (5): 058501 .   DOI: 10.1088/0256-307X/27/5/058501
Abstract   PDF(pc) (564KB) ( 428 )
The mathematical expression on decoding the one-dimensional (1D) Vernier anode is deduced theoretically, and the corresponding 1D-Vernier anode collector is developed. A photon counting imaging and detection system is constructed based on a 1D-Vernier anode detector and electronic readout subsystem. With wavelengths of 253.7 nm from the mercury lamp as the ultraviolet emission source, the spatial resolution of the prototype is proved to be better than 100 μm along the x-direction in experiment.
Extrinsic Base Surface Passivation in High Speed “Type-II'” GaAsSb/InP DHBTs Using an InGaAsP Ledge Structure
LIU Hong-Gang, JIN Zhi, SU Yong-Bo, WANG Xian-Tai, CHANG Hu-Dong, ZHOU Lei, LIU Xin-Yu, WU De-Xin
Chin. Phys. Lett. 2010, 27 (5): 058502 .   DOI: 10.1088/0256-307X/27/5/058502
Abstract   PDF(pc) (577KB) ( 515 )
Type-Ⅱ GaAsSb/InP DHBTs with selectively-etched InGaAsP ledge structures are fabricated and characterized for the first time. The novel InGaAsP/GaAsSb/InP DHBTs with a 20 nm lattice-matched GaAsSb base and a 75 nm InP collector have a dc current gain improvement by a factor of 2 and a cutoff frequency ƒT of 190 GHz. The InGaAsP ledge design provides a simple but effective approach to suppress the extrinsic base surface recombination and enable GaAsSb/InP DHBTs to further increase the operating frequencies and integration levels for millimeter wave applications.
Detecting Overlapping Communities Based on Community Cores in Complex Networks
SHANG Ming-Sheng, CHEN Duan-Bing, ZHOU Tao,
Chin. Phys. Lett. 2010, 27 (5): 058901 .   DOI: 10.1088/0256-307X/27/5/058901
Abstract   PDF(pc) (346KB) ( 1028 )
The identification of communities is significant for the understanding of network structures and functions. Since some nodes naturally belong to several communities, the study of overlapping community structures has attracted increasing attention recently, and many algorithms have been designed to detect overlapping communities. We propose a new algorithm. The main idea is first to find the core of a community by detecting maximal cliques and then merging some tight community cores to form the community. Experimental results on two real networks demonstrate that the present algorithm is more accurate for detecting overlapping community structures, compared with some well-known results and methods.
Increase of Traffic Flux in Two-Route Systems by Disobeying the Provided Information
SUN Xiao-Yan, JIANG Rui, WANG Bing-Hong,
Chin. Phys. Lett. 2010, 27 (5): 058902 .   DOI: 10.1088/0256-307X/27/5/058902
Abstract   PDF(pc) (558KB) ( 384 )
We propose a modified two-route traffic model by considering some dynamic vehicles disobeying the provided information for three feedback strategies: travel time information feedback (TTF), mean velocity information feedback (MVF) and congestion coefficient information feedback (CCF). The previous two-route traffic model shows that the flux of the system decreases as the ratio of dynamic vehicle increases for TTF and MVF. However, simulation results show that the flux of the system remains almost unchanged for TTF, MVF and CCF in our modified model. Our studies may be helpful for managing the real traffic system.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
Prediction and Elimination of Multiples Based on Energy Flux Conservation Theorem and Prediction Operator Equation
He Li, LIU Hong, DING Ren-Wei, LI Bo
Chin. Phys. Lett. 2010, 27 (5): 059101 .   DOI: 10.1088/0256-307X/27/5/059101
Abstract   PDF(pc) (433KB) ( 484 )
The received wave field including primaries and all of the multiples can be associated with the reflection coefficients which are only primaries by a prediction operator and two equations: the energy flux conservation equation and the prediction operator equation that is developed from the Levinson recursion and can be easily solved by Li group method under a two-dimensional condition. Given reflection coefficients, the prediction operator can be obtained by solving the prediction operator equation. By the energy flux conservation equation, the reciprocal of the prediction operator times the conjugate of it, the wave field can be predicted, in which both of the surface multiples and the internal multiples are involved. On the other hand, if the wave field is given, based on the energy flux conservation equation solved by the 2D spectral factorization, a fully automated data-driven algorithm is developed to remove the surface multiples as well as the internal multiples.
76 articles