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Measurement of Berry Phase Associated with Higher Dimensional Orbital Angular Momentum of Light by Interference Method
XU Yuan, HUANG Yuan-Yuan, HU Ling, ZHANG Pei, WEI Dong, LI Hong-Rong, GAO Hong, LI Fu-Li
Chin. Phys. Lett. 2013, 30 (10):
100304
.
DOI: 10.1088/0256-307X/30/10/100304
Berry phase of higher-dimensional orbital angular momentum of light is studied. When an Nth order orbital state, described by a vector in (N+1)-dimensional space, evolves through a closed path in space of orbital states, there will exist a higher order orbital Berry phase. We calculate this phase by using the matrix transformation theory. A direct measurement of the higher-order orbital Berry phase is also carried out by the interference method. The experimental results are in good agreement with the theoretical description, which shows that the Berry phase is proportional to the orbital angular momentum of light.
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A Photoacoustic Imaging System with Optimized Real-Time Parallel Reconstruction
FENG Ting, YUAN Jie, YU Yao, ZHOU Yu, XU Guan
Chin. Phys. Lett. 2013, 30 (10):
100702
.
DOI: 10.1088/0256-307X/30/10/100702
Biomedical photoacoustic tomography (PAT) provides anatomical, functional, metabolic, molecular, and genetic contrasts of vasculature, hemodynamics, oxygen metabolism, biomarkers, and gene expression. These attributes bring PAT to a wide variety of applications in clinical medicine and preclinical research. We report the development of a real-time PAT imaging system, which integrates signal scanning, image reconstruction and displaying photoacoustic images in real time. An optimized back projection algorithm for PAT imaging is proposed and tested on a latest graphics process unit based card. The whole system is built and tested in an experiment for monitoring moving blood events to validate the real-time performance of this system to image moving events.
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Semileptonic Production of Scalar and Tensor p-Wave Charmed Mesons
JIANG Yue, WANG Guo-Li, WANG Tian-Hong, JU Wan-Li
Chin. Phys. Lett. 2013, 30 (10):
101101
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DOI: 10.1088/0256-307X/30/10/101101
With the same constituents of quark and antiquark, the p-wave state has a higher mass than the corresponding s-wave state, but the relativistic corrections are much larger in the processes of which p-wave mesons are involved. Considering this, the relativistic Bethe–Salpeter method is applied to estimate the branching fractions of semileptonic decays B(s)→D*(sJ)lν (J=0,2). Our predictions are Br[B0s→D*+s0(2317)l?ν]=0.50%, Br[B0s→D*+s2(2573)l?ν]=0.40%, Br[B?→D*00(2400)l?ν]=0.79%, Br[B?→D*02(2460)l?ν]=0.28%, Br[B0→D*+0(2400)l?ν]=0.58% and Br[B0→D*+2(2460)l?ν]=0.27%.
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Experimental Measurement of the Absolute Frequencies and Hyperfine Coupling Constants of 133Cs Using a Femtosecond Optical Frequency Comb
JIN Li, ZHANG Yi-Chi, XIANG Shao-Shan, WANG Li-Rong, MA Jie, ZHAO Yan-Ting, XIAO Lian-Tuan, JIA Suo-Tang
Chin. Phys. Lett. 2013, 30 (10):
103201
.
DOI: 10.1088/0256-307X/30/10/103201
High resolution two-photon spectrum of the transitions 6S1/2→6P3/2→8S1/2, 9S1/2 and 6S1/2→6P1/2→7D3/2 in neutral 133Cs are presented in a room-temperature vapor cell using a femtosecond optical frequency comb. Spectra are obtained by scanning the repetition frequency of the femtosecond optical frequency comb over the two-photon hyperfine structure. The centroid frequency of the 6S1/2→8S1/2, 9S1/2, 7D3/2 transitions are 729009798.80(17) MHz, 806761363.96(11) MHz, and 780894762.595(23) MHz, respectively. The hyperfine coupling constants of the corresponding states are also obtained. The results are consistent with the previous measurements.
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Reduction of the Differential Light Shift by the Spatial Periodicity in an Optical Lattice
YUE Xu-Guang, XU Xia, CHEN Xu-Zong, ZHOU Xiao-Ji
Chin. Phys. Lett. 2013, 30 (10):
103701
.
DOI: 10.1088/0256-307X/30/10/103701
We study the spatial periodicity effects on the differential light shift of noninteracting atoms in an optical lattice. Through the Rabi-spectrum approach, when the wavelength of the optical lattice is not magic, a reduction to the differential light shift is expected. The reduction results from the Bloch bands induced by the quantized motion in the periodic potential. Taking the microwave transition of rubidium atoms as an example, this reduction at some wavelengths can reach one order of magnitude, compared to the data without considering the spatial profile of the optical lattice. When the atomic temperature is considered, the differential light shift increases or decreases with temperature, depending on the wavelength of the lattice. Our results should be beneficial for microwave optical lattice clock and precision measurements.
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A High Power InGaN-Based Blue-Violet Laser Diode Array with a Broad-Area Stripe
CHEN Ping, ZHAO De-Gang, FENG Mei-Xin, JIANG De-Sheng, LIU Zong-Shun, ZHANG Li-Qun, LI De-Yao, LIU Jian-Ping, WANG Hui, ZHU Jian-Jun, ZHANG Shu-Ming, ZHANG Bao-Shun, YANG Hui
Chin. Phys. Lett. 2013, 30 (10):
104205
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DOI: 10.1088/0256-307X/30/10/104205
An array of high power InGaN/GaN multi-quantum-well laser diodes with a broad waveguide is fabricated. The laser diode structure is grown on a GaN substrate by metal-organic chemical vapor deposition. The laser diode array consists of five emitter stripes which share common electrodes on one laser chip. The electrical and optical characteristics of the laser diode array are investigated under the pulse current injection with 10 kHz frequency and 100 ns pulse width. The laser diode array emits at the wavelength of 409 nm, which is located in the blue-violet region, and the threshold current is 2.9 A. The maximum output light peak power is measured to be 7.5 W at the wavelength of 411.8 nm under the current of 25 A.
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Photodarkening-Induced Absorption and Fluorescence Changes in Yb Fibers
CHEN Gui, XIE Lu, WANG Yi-Bo, ZHAO Nan, LI Hai-Qing, JIANG Zuo-Wen, PENG Jing-Gang, YANG Lü-Yun, DAI Neng-Li, LI Jin-Yan
Chin. Phys. Lett. 2013, 30 (10):
104208
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DOI: 10.1088/0256-307X/30/10/104208
We study the photodarkening effect in a double clad ytterbium-doped silica fiber fabricated by modified chemical vapor deposition and solution doping. A common measurement technology for photodarkening is used to study the photodarkening-induced absorption spectra. We present a fast and simple method to observe the PD effect by measurement of the fluorescence spectra. The method proposed here can be used to observe the influence for a short time, and thus reduces the requirements of system stability and heat management. It is obtained that under the condition of 45.5% Yb ion inversion level, photodarkening-induced excessive loss at an equilibrium state is above 4.5 dB/m and florescence intensity degradation is above 10% after 500 min pumping at 1041 nm for the home-made normal Yb/Al co-doped silica fiber.
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Surface Oxidation Properties in a Topological Insulator Bi2Te3 Film
GUO Jian-Hua, QIU Feng, ZHANG Yun, DENG Hui-Yong, HU Gu-Jin, LI Xiao-Nan, YU Guo-Lin, DAI Ning
Chin. Phys. Lett. 2013, 30 (10):
106801
.
DOI: 10.1088/0256-307X/30/10/106801
Bi2Te3 films are grown on (111)-oriented GaAs substrates by using the hot wall epitaxy method and the surface oxidation properties in the films are investigated by x-ray photoelectron spectroscopy, Raman spectroscopy, and x-ray diffraction. The results show that the films are c-axis oriented. Two pairs of new peaks in the XPS spectra involved with the binding energies from Bi 4f and Te 3d electrons correspond to Bi–O–Te bonds. Besides the A1g1, Eg2 andA1g2 vibration modes from Bi2Te3 films, two new peaks at 93.5 cm?1 and 123 cm?1 are observed in Raman spectra, which are assigned to α-Bi2O3 and TeO2, respectively. Our results are helpful for analyzing the degradation mechanism of topological surface states in Bi2Te3.
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Hydrogen Storage Capacity Study of a Li+Graphene Composite System with Different Charge States
SUI Peng-Fei, ZHAO Yin-Chang, DAI Zhen-Hong, WANG Wei-Tian
Chin. Phys. Lett. 2013, 30 (10):
107306
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DOI: 10.1088/0256-307X/30/10/107306
Based on first-principles plane-wave calculations, we firstly reconfirm that the Li+graphene complex can be taken as a hydrogen storage medium with capacity of 12.8wt%. Then metal adsorption properties of this Li+graphene system with different charge states are investigated. Finally, the hydrogen storage ability of the charging system is calculated. Our calculations show that adding positive charge on a Li+graphene composite results in a conspicuous reduction of Li 2s and Li 2p orbital occupation with respect to the C 2p state. As a result, a stronger bonding between Li and graphene is formed, and a special double-layer hydrogen adsorption structure has been found. Compared to the neutral system, utilizing the positive charged Li+graphene to store hydrogen molecules can solve the issue of clustering of metal atoms after releasing hydrogen, and can improve hydrogen storage capacity up to a gravimetric density of 20.4wt%, correspondingly one adsorbed Li atom can effectively absorb up to seven H2 molecules.
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Structure and Absorbability of a Nanometer Nonmetallic Polymer Thin Film Coating on Quartz Used in Piezoelectric Sensors
GU Yu, LI Qiang, TIAN Fang-Fang, XU Bao-Jun
Chin. Phys. Lett. 2013, 30 (10):
108101
.
DOI: 10.1088/0256-307X/30/10/108101
We present a new type of gas piezoelectric sensor taking quartz piezoelectric crystal as the basal material and nanometer nonmetallic polymer thin film coating as the surface. The coating, plated by vacuum electron beam dispersion (EBD) coating technology, is carried out by employing a nanometer nonmetallic polymer thin film that has properties of selecting and identifying characteristic materials. An experimental survey shows that EBD coating technology can produce a uniform thickness of the thin film coating, and the physical and chemical analyses show that the coating has a high performance of absorption using the method of infrared spectroscopy. Meanwhile, the absorption and sensitivity performance of the thin film coating will change if other organic materials are added to the coated thin film. Through the measurement of the thin film coating, the feature of sensitivity to the change of humidity is acquired. Based on the above description, a new type of gas piezoelectric sensor is designed and manufactured reasonably, which provides a valid method to rapidly monitor and distinguish complex gases.
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Fabrication and Characterization of Single-Crystalline AgSbTe Nanowire Arrays
YANG You-Wen, LI Tian-Ying, ZHU Wen-Bin, MA Dong-Ming, CHEN Dong
Chin. Phys. Lett. 2013, 30 (10):
108102
.
DOI: 10.1088/0256-307X/30/10/108102
Ternary semiconducting AgSbTe2 nanowire arrays were synthesized for the first time by using the direct-current electrodeposition technique. X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and transmission electron microscopy analyses indicate that the nanowire arrays are high filling, ordered, single crystalline and the nanowires have a highly preferential orientation grown along the [100] direction. Annealing studies show that compared with other temperatures, annealing at 100°C can significantly increase the crystallinity of AgSbTe2 nanowires. The optical absorbance spectra of the AgSbTe2 nanowire arrays show that the optical band gap has a strong blue shift with decreasing the diameter of the nanowire.
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Effect of Hydrogen and Nitrogen Carrier Gas Ratio on the Structural and Optical Properties of AlInGaN Alloy
FENG Xiang-Xu, LIU Nai-Xin, ZHANG Lian, ZHANG Ning, ZENG Jian-Ping, WEI Xue-Cheng, LIU Zhe, WEI Tong-Bo, WANG Jun-Xi, LI Jin-Min
Chin. Phys. Lett. 2013, 30 (10):
108103
.
DOI: 10.1088/0256-307X/30/10/108103
Undoped AlInGaN epilayers on GaN templates with different hydrogen (H2) and nitrogen (N2) carrier gas ratios (1:8, 2:8, and 3:8 as samples 1, 2 and 3, respectively) were grown. When the flow ratio of H2 and N2 rises from 1:8 to 3:8, an indium composition decrease from 3% to 1.2% is observed while the aluminum content stays constant at any flow ratio. Due to the quantum-dot-like effect, photoluminescence intensity is enhanced in the sample with the low carrier gas flow ratio of H2/N2. However, the potential well caused by indium uneven distribution is nonuniform, which is more severe in the sample with carrier gas flow ratio 1:8. The process of carrier transfer from shallow to deep potential wells would be more difficult to accomplish, resulting in the reduction of the photoluminescence intensity. This is found to be consistent with the carriers' lifetime with the help of time-resolved photoluminescence.
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The Effect of Using 1-Dodecanethiol as a Processing Additive on the Performances of Polymer Solar Cells
YANG Shao-Peng, WANG Tie-Ning, SHI Jiang-Bo, ZHANG Ye, LI Xiao-Wei, FU Guang-Sheng
Chin. Phys. Lett. 2013, 30 (10):
108401
.
DOI: 10.1088/0256-307X/30/10/108401
We introduce 1-Dodecanethiol (DT) to poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester based polymer solar cells as a processing additive. When the amount of DT is 1vol%, the device performance is best. A final power conversion efficiency of 3.1% is achieved, which is an improvement of more than 40% compared to the reference solar cell without DT. To investigate the causes of improvement of the PCE, UV-vis spectroscopy, external quantum efficiency (EQE) is measured and an AFM is used. The enhanced photovoltaic performances are discussed in terms of optical properties and the film morphology.
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Osmolyte Effects on the Unfolding Pathway of β-Lactoglobulin
MENG Wei, PAN Hai, QIN Meng, CAO Yi, WANG Wei
Chin. Phys. Lett. 2013, 30 (10):
108701
.
DOI: 10.1088/0256-307X/30/10/108701
There are large amounts of osmolytes inside cells, which impact many physiological processes by complicated mechanisms. The osmolyte effects on the stability and folding of proteins have been studied in detail using simple two-state folding proteins. However, many important functional proteins fold in complex pathways involving various intermediates. Little is known about the osmolyte effects on the folding and unfolding of these proteins. It is noted that β-lactoglobulin (BLG) is an example of such proteins, whose unfolding involves an obvious intermediate state. Using equilibrium chemical denaturation and stopped-flow kinetics, we investigate the unfolding of BLG in the presence of different osmolytes, e.g., glycerol, ethylene glycol (EG) and poly(ethylene glycol)400 (PEG400). It is found that all these osmolytes can stabilize the unfolding intermediate by modulating the relative unfolding kinetics of the native and the intermediate states. The stabilization effects are similar for EG and PEG400 but distinct for glycerol. Since the unfolding intermediates of many proteins are directly related to protein misfolding diseases, evaluation of the osmolyte effects for the unfolding of these proteins in vitro should be beneficial for the understanding of the occurrence of the related diseases in vivo.
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60 articles
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