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Collective Transverse Flow in Intermediate Energy Heavy-Ion Collisions
ZHANG Fang, ZUO Wei, , HU Bi-Tao, YONG Gao-Chan, ZHOU Zhen-Xiao
Chin. Phys. Lett. 2009, 26 (12):
122101
.
DOI: 10.1088/0256-307X/26/12/122101
Within the hadronic transport model IBUU04, we study the density-dependent symmetry energy by using the neutron-proton differential flow from the 132Sn+124Sn reactions at beam energies of 200, 400, 600 and 800MeV per nucleon. The strong effect of the symmetry energy is shown at the incident beam energy of 400MeV/A. The small medium-effect of the neutron-proton differential flow is also found. We also study the neutron-proton differential flows with impact parameters of 3, 5, 7fm. It is found that in semi-central collisions the sensitivity of the neutron-proton differential flow to the symmetry energy is larger.
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Polarization Gradient Cooling by Zeeman-Effect-Assisted Saturated Absorption
HAN Shun-Li, CHENG Bing, ZHANG Jing-Fang, XU Yun-Fei, WANG Zhao-Ying, LIN Qiang
Chin. Phys. Lett. 2009, 26 (12):
123702
.
DOI: 10.1088/0256-307X/26/12/123702
A novel and simple method to realize polarization gradient cooling (PGC) is reported. The stabilizing, shifting and rapid tuning of the frequency of the external cavity diode laser is realized by using the Zeeman-effect-assisted Doppler-free saturated absorption technique. Based on this convenient technique, 87Rb cold atoms are captured from room-temperature background vapor in the magneto-optical trap (MOT). Meanwhile, the steady-state number, the density and the lifetime of atoms in the MOT are measured. Subsequently, a frequency-fast-varying circuit is designed to realize PGC, which is demonstrated effectively and reliably in experiments. The temperature of the cold atom cloud is measured by two different methods, which coincide with each other.
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An Efficient Photon Conversion Efficiency Ammonia Terahertz Cavity Laser
QI Chun-Chao, ZUO Du-Luo, LU Yan-Zhao, TANG Jian, YANG Chen-Guang, KE Lin-Da, CHENG Zu-Hai,
Chin. Phys. Lett. 2009, 26 (12):
124201
.
DOI: 10.1088/0256-307X/26/12/124201
An efficient ammonia terahertz (THz) cavity laser is reported experimentally. Unlike the past design schemes such as hole couplers and freestanding mesh couplers, in our systems the input and output couplers are fabricated by depositing nickel capacitive metallic meshes on ZnSe and high-resistivity silicon substrates. Thus the couplers not only can be constructed as an F-P oscillator but also can be used as sealed windows that are easier to perform the adjustment of alignment with. To enhanceTHz laser output energy and photon conversion efficiency, the dominant factors such as pump intensity and gas pressure are investigated experimentally. Finally, a 1.35mJ terahertz radiation of ammonia laser with 90μm wavelength (3.33THz) operating at 1.09kPa pumped by a 402mJ TEA CO2 laser with 9R (16) line is generated, and photon conversion efficiencies of 6.5% are achieved.
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Numerical Investigation and Optimization of SBS-Based Slow-Light Using Filtered Incoherent Pump
ZHENG Di, PAN Wei, YAN Lian-Shan, LUO Bin, ZOU Xi-Hua, WEN Kun-Hua, JIANG Ning
Chin. Phys. Lett. 2009, 26 (12):
124202
.
DOI: 10.1088/0256-307X/26/12/124202
The performance of stimulated Brillouin scattering (SBS)-based slow light using a novel spectrally-sliced broadband incoherent pump source is numerically studied. The profile of the pump-power spectrum is determined by the transmission spectra of the optical filter followed by the polarized broadband incoherent pump source. We also investigate the performance of Gaussian-type and super-Gaussian-type filtering under different spectrally-sliced
bandwidths and pump power levels for 2.5Gbit/s return-to-zero pulse (50% duty-cycle). The pulse broadening is characterized by the full width of half maximum (FWHM) and the rms pulse width, respectively. However,the results obtained by the two kinds of measurement methods deviate from each other with increasing pump power. Compared with the regular Gaussian-type filtering, the pulse broadening can be significantly reduced using super-Gaussian-type filtering at the cost of a small reduction in delay time. Furthermore, the maximum improvement in pulse broadening of ∆ BFWHM =28.4% and ∆ B RMS =10.4% is achieved by using a five-order super-Gaussian-type filter and a pump power of 500mW.
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Analysis of Optical Readout Sensitivity for Uncooled Infrared Detector
CHENG Teng, ZHANG Qing-Chuan, JIAO Bin-Bin, CHEN Da-Peng, WU Xiao-Ping
Chin. Phys. Lett. 2009, 26 (12):
124206
.
DOI: 10.1088/0256-307X/26/12/124206
An optical readout uncooled infrared detector, employing a substrate-free focal plane array with pitch size 60μm, is established. The reflector deformation induced by the stress mismatching of the bi-layer structure is discussed and, in turn, a universal solution to determine both the optical readout sensitivity and the optimal filter position is found. By applying this solution, the optical readout sensitivity for the ideal plane reflector could theoretically increase by 80% as compared with the conventional operation, and the sensitivity loss caused by the reflector deformation can also be reduced to a reasonable level.
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Measurement of the Carrier Recovery Time in Semiconductor Optical Amplifier Based on Dual-Pump Four-Wave Mixing Technology
CHENG Cheng, ZHANG Xin-Liang, ZHANG Yu, ZHOU En-Bo, LIU Lei, ZHANGYin, HUANG De-Xiu
Chin. Phys. Lett. 2009, 26 (12):
124208
.
DOI: 10.1088/0256-307X/26/12/124208
A scheme of measuring the carrier recovery time in semiconductor optical amplifiers (SOAs) based on dual pump Four-wave mixing technology is presented. The carrier recovery times under 120mA, 180mA 240mA and 300mA injected currents are measured to be 111ps, 81ps, 71ps and 53ps, respectively. The carrier recovery time of the spacing between the two umps is also investigated. The experimental results show that the conversion efficiency keeps constant when the spacing of the two pumps varies within a small range.
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Q-Switched Tm:YAG Laser Intracavity-Pumped by a 1064nm Laser
MA Qing-Lei, ZONG Nan, XIE Shi-Yong, YANG Feng, GUO Ya-Ding, XU Jia-Lin, BO Yong, PENG Qin-Jun, CUI Da-Fu, XU Zu-Yan
Chin. Phys. Lett. 2009, 26 (12):
124211
.
DOI: 10.1088/0256-307X/26/12/124211
We report a Q-switched 2-μm Tm:YAG laser based on intracavity-pumped by a 1064-nm Nd:YAG laser operating at room temperature for the first time. An average output power of 5.1W is obtained with the repetition rate of 30kHz and a pulse width of 300ns. In addition, we demonstrate a 12.5-W continuous-wave 2-μm Tm:YAG laser, which is, to our best knowledge, the highest power for intracavity-pumping configuration.
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Low Threshold and High Conversion Efficiency Nanosecond Mid-Infrared KTA OPO
ZHONG Kai, LI Jian-Song, CUI Hai-Xia, XU Deng-Gang, WANG Yu-Ye, ZHOU Rui, WANG Jing-Li, WANG Peng, YAO Jian-Quan,
Chin. Phys. Lett. 2009, 26 (12):
124213
.
DOI: 10.1088/0256-307X/26/12/124213
Based on a Type II non-critically phase-matched KTA crystal, a low-threshold and high conversion efficiency mid-infrared optical parametric oscillator (OPO) pumped by a diode-end-pumped Nd:YVO4 laser is demonstrated. The OPO threshold is only 0.825W. The maximum output power of 435mW at 3.47μm is achieved with the repetition rate of 30kHz, corresponding to an optical-to-optical conversion efficiency of 4.4%. The photon conversion efficiency is as high as about 64%. The pulse width is 3.5ns with a peak power of 4kW for the maximum output power.
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Coulomb Explosion and Energy Loss of Energetic C20 Clusters in Dense Plasmas
WANG Gui-Qiu, LI Wen-Kun, WANG You-Nian
Chin. Phys. Lett. 2009, 26 (12):
125203
.
DOI: 10.1088/0256-307X/26/12/125203
The molecular dynamics (MD) method is used to simulate the interactions of energetic C20 clusters with the dense plasma targets within the framework of the linear Vlasov-Poisson theory. The influences of various clusters (H2, N2, C20 and C60 respectively) on stopping power are discussed. The simulation results show that the vicinage effects in the Coulomb explosion dynamics and the stopping power are strongly affected by the variations in the cluster speed and the plasma parameters. Coulomb explosions are found to proceed faster for higher speeds, lower plasma densities and higher electron temperatures. In addition, the cluster stopping power is strongly enhanced in the early stages of Coulomb explosions due to the vicinage effect, but this enhancement eventually diminishes, after the cluster constituent ions are sufficiently separated. For the large and heavy clusters, the stopping power ratio reaches much higher values in the early stage of Coulomb explosion owing to the constructive interferences in the vicinage effect.
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Transition Metal Silicide Nanowires Growth and Electrical Characterization
PENG Zu-Lin, LIANG S., DENG Luo-Gen
Chin. Phys. Lett. 2009, 26 (12):
127301
.
DOI: 10.1088/0256-307X/26/12/127301
We report the characterization of self-assembled epitaxially grown transition metal, Fe, Co, Ni, silicide nanowires (TM-NW) growth and electrical transport properties. NWs grown by reactive deposition epitaxy on various silicon surfaces show a dimension of 10nm by 5nm, and several micrometers in length. NW orientations strongly depend on substrate crystal orientation, and follow the substrate symmetry. By using conductive-AFM (c-AFM), the electron transport properties of one single NW were measured, the resistivity of crystalline nickel silicide NW was estimated to be 2×10-2Ω・cm.
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Ultrafast Photophysics of Star-Like Molecules with Benzene and Triazine Core
FENG Wen-Ke, KONG Sheng, XIAO Li-Xin, MENG Kang, WANG Shu-Feng, GONG Qi-Huang
Chin. Phys. Lett. 2009, 26 (12):
127801
.
DOI: 10.1088/0256-307X/26/12/127801
Static and transient spectroscopic characters of newly synthesized start-like molecules, 1,3,5-tri(10-butyl-3-propenyl-10H-phenothiazine)-benzene (TP3B) and 2,4,6-tri(10-butyl-3-propenyl -10H-phenothiazine)-[1,3,5]triazine (TP3T), are studied using static, picosecond fluorescence and femtosecond transient absorption spectroscopy. The results show that when the benzene group is in the center, a large conjugation system is formed, while a fast electron-transfer process happens when the center group is triazine.
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An SPICE Model for PCM Based on Arrhenius Equation
LI Xi, SONG Zhi-Tang, CAI Dao-Lin, CHEN Xiao-Gang, JIA Xiao-Ling
Chin. Phys. Lett. 2009, 26 (12):
128501
.
DOI: 10.1088/0256-307X/26/12/128501
Based on the temperature dependence of the Arrhenius law, an HSPICE compact module using Verilog-A language for phase change memory (PCM) is presented. In the model of this HSPICE compact module, the basic theory that the resistance of the amorphous semiconductor has relations with the activation energy and temperature is used, and an assumption that this theory can be expanded to describe the crystalline semiconductor is employed. Moreover, since an objective reality that the resistance of the semiconductor determines the temperature and the temperature affects the resistance inversely is inevitable, coupling with such positive feedback, this model can reproduce the real-time characteristics of the memory cell accurately. The simulation results show that this model can reproduce the features of the PCM cell well. It can be used in the PCM circuit design and further analysis.
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Further Discussion on Polaron Existence in Dry DNA
LI Xiao-Hong, ZHANG Yu-Yu, LIU Tao, WANG Ke-Lin,
Chin. Phys. Lett. 2009, 26 (12):
128701
.
DOI: 10.1088/0256-307X/26/12/128701
We study the interaction between holes and molecular vibrations on dry DNA by using the extended Firsov's model. The ground state energy, calculated by using two Hilbert spaces, Fock state space and coherent state space, is confirmed. The polaron binding energy, defined with the ground state energy, is 0.014eV, much less than the thermal energy 0.026eV at room temperature 300K, which means that polarons are difficult to form self-trapping at room temperature and Anderson localization will prevent a metallic state on dry DNA. The results are consistent with the available experiments.
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76 articles
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