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Wildly Tunable, High-Efficiency MgO:PPLN Mid-IR Optical Parametric Oscillator Pumped by a Yb-Fiber Laser
LIU Shan-De, WANG Zhao-Wei, ZHANG Bai-Tao, HE Jing-Liang, HOU Jia, YANG Ke-Jian, WANG Rui-Hua, LIU Xun-Min
Chin. Phys. Lett. 2014, 31 (2):
024204
.
DOI: 10.1088/0256-307X/31/2/024204
We demonstrate a wildly tunable, high-efficiency mid-infrared (mid-IR) output-coupled single resonant optical parametric oscillator (OC-SRO) pumped by a Yb-fiber laser. The compact mid-infrared source employs a 50-mm-long, multi-grating MgO-doped periodically poled lithium niobate (MgO-PPLN) crystal, providing as much as 1.73 W idler power at 3.012 μm, and 1.27 W signal power at 1645 nm, corresponding to an overall conversion efficiency of 41.7% and a slope efficiency of 77.9%. In particular, the mid-infrared output power of 1.03 W and 0.67 W are obtained at 3.7 μm and 3.9 μm, respectively, with an optical-to-optical conversion efficiency of 14.3% and 9.3%. Furthermore, the idler light is tunable from 3 μm to 3.9 μm by changing the periods from 31 to 28.5 μm, with the output power >1 W over 78% of the tuning range. Our experimental results are pump power limited and further mid-IR power and conversion efficiency could be obtained with a suitable high-power pump source. The total OC-SRO output power rms at 2.6 W is about 0.6% during 2 h measurement.
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A 5.9-mJ 500-Hz Electro-Optic Q-Switched 1053 nm Nd:LiLuF4 Laser
YANG Qi, ZHU Xiao-Lei, LU Ting-Ting, MA Jian, HANG Yin, CHEN Wei-Biao
Chin. Phys. Lett. 2014, 31 (2):
024205
.
DOI: 10.1088/0256-307X/31/2/024205
An efficient and high power 1053 nm electro-optic Q-switched Nd:LiLuF4 laser, end-pumped by two fiber coupled laser diodes at wavelength 806 nm, is reported for the first time. With an incident pump power of 24.4 W, the maximum laser output power of 7.3 W is achieved in free-running mode, and the optical conversion efficiency is 29.8%. For the Q-switched operation, the shortest pulse width of 17 ns is obtained at the pulse repetition rate of 500 Hz, corresponding to the pulse energy of 5.9 mJ with the peak power of 0.35 MW.
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A Hertz-Linewidth Ultrastable Diode Laser System for Clock Transition Detection of Strontium Atoms
LI Ye, LIN Yi-Ge, WANG Qiang, WANG Shao-Kai, ZHAO Yang, MENG Fei, LIN Bai-Ke, CAO Jian-Ping, LI Tian-Chu, FANG Zhan-Jun, ZANG Er-Jun
Chin. Phys. Lett. 2014, 31 (2):
024207
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DOI: 10.1088/0256-307X/31/2/024207
The frequencies of two 698 nm external cavity diode lasers (ECDLs) are locked separately to two independently located ultrahigh finesse optical resonant cavities with the Pound–Drever–Hall technique. The linewidth of each ECDL is measured to be ~4.6 Hz by their beating and the fractional frequency stability below 5×10?15 between 1 s to 10 s averaging time. Another 698 nm laser diode is injection locked to one of the cavity-stabilized ECDLs with a fixed frequency offset for power amplification while maintaining its linewidth and frequency characteristics. The frequency drift is ~1 Hz/s measured by a femtosecond optical frequency comb based on erbium fiber. The output of the injection slave laser is delivered to the magneto-optical trap of a Sr optical clock through a 10-m-long single mode polarization maintaining fiber with an active fiber noise cancelation technique to detect the clock transition of Sr atoms.
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In Vivo Magnetic Particle Targeting by Local Gradient Field of Interstitial Seeds Magnetized in an Ex Vivo Uniform Field
LI Xiao-Qiang, ZHENG Lu, WANG Xu-Fei
Chin. Phys. Lett. 2014, 31 (2):
024701
.
DOI: 10.1088/0256-307X/31/2/024701
The possibility of in vivo magnetic particle targeting by the locally induced gradient field of interstitial ferromagnetic implants, magnetized in an ex vivo uniform field, is evaluated by a modelling analysis. A simplified 3D model analogous to a torso size, with a continuous laminar flow through the volume with the typical velocity and viscosity values of in vivo blood flow and a ferromagnetic seed inserted in the volume center vertical to the flow, is used to evaluate the magnetic particle capturing efficiency by the seed, which is magnetized in a uniform field. The initial modelling results indicate that for 1–10 μm iron oxide particles transporting with a blood flow of 0.5–5 mm/s, the seeds of tungsten steel, magnet steel and cast cobalt all present an effective particle capturing efficiency, which shows a fast initial increase and a slow saturation with the increasing magnetic field, a quasilinear increase with the increasing particle size, and a nonlinear decrease with the increasing blood velocity.
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Ultrathin Carbon Nanotubes for Efficient Energy Storage: a First-Principles Study
WANG Xue-Qing, WANG Yu-Sheng, WANG Yu-Cang, WANG Fei, SUN Qiang, JIA Yu
Chin. Phys. Lett. 2014, 31 (2):
026801
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DOI: 10.1088/0256-307X/31/2/026801
On the basis of first-principles density functional calculations, the present study sheds theoretical insight on ultrathin carbon nanotube (UCNT) and hydrogenated ultrathin carbon nanotube (HUCNT) for use as potential materials not only for Li-ion battery anode but also for high-capacity hydrogen storage. The highest Li storage capacities in UCNT and HUCNT can be of LiC4 and LiC4H2, respectively, which are higher than that in graphite and LiC6. Binding between Li (Ca) atoms and these materials are found to be enhanced considerably. Each Li (Ca) atom may bind multi-hydrogen molecules, and the adsorption energies are ideally suited for storing hydrogen under ambient conditions, and the predicted weight percentage of molecular hydrogen are in the range of 6.4–12 wt% exceeding the target set by the United States Department of Energy.
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Enhanced Output Power of Near-Ultraviolet Light-Emitting Diodes by p-GaN Micro-Rods
WANG Dong-Sheng, ZHANG Ke-Xiong, LIANG Hong-Wei, SONG Shi-Wei, YANG De-Chao, SHEN Ren-Sheng, LIU Yang, XIA Xiao-Chuan, LUO Ying-Min, DU Guo-Tong
Chin. Phys. Lett. 2014, 31 (2):
027101
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DOI: 10.1088/0256-307X/31/2/027101
Near-ultraviolet (UV) InGaN/AlGaN light-emitting diodes (LEDs) are grown by low-pressure metal-organic chemical vapor deposition. The scanning electronic microscope image shows that the p-GaN micro-rods are formed above the interface of p-AlGaN/p-GaN due to the rapid growth rate of p-GaN in the vertical direction. The p-GaN micro-rods greatly increase the escape probability of photons inside the LED structure. Electroluminescence intensities of the 372 nm UV LED lamps with p-GaN micro rods are 88% higher than those of the flat surface LED samples.
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Magnetic Properties of Co-Doped TiO2 Films Grown on TiN Buffered Silicon Substrates
XIA Yu-Qian, SUN Lei, XU Hao, HAN Jing-Wen, ZHANG Yi-Bo, WANG Yi, ZHANG Sheng-Dong
Chin. Phys. Lett. 2014, 31 (2):
027501
.
DOI: 10.1088/0256-307X/31/2/027501
Co-doped TiO2 thin films are grown on TiN buffered silicon substrates by the pulsed laser deposition method and then hydrogenated. Transmission electron microscopy and high-angle annular dark-field scanning transmission electron microscopy measurements have shown that the TiN buffer layer can suffer a 400°C deposition temperature and prevent the growth of silicon dioxide on silicon. After that, the room temperature ferromagnetism behaviors are observed in the hydrogenated samples, which are measured by the alternating gradient magnetometer. X-ray photoelectron spectroscopy and x-ray absorption fine structure measurements have revealed the existence of cobalt clusters. According to the material analysis, the magnetic behavior after hydrogenation is suggested to be induced by the enhancement of cobalt clusters.
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Band Alignment and Band Gap Characterization of La2O3 Films on Si Substrates Grown by Radio Frequency Magnetron Sputtering
LIU Qi-Ya, FANG Ze-Bo, JI Ting, LIU Shi-Yan, TAN Yong-Sheng, CHEN Jia-Jun, ZHU Yan-Yan
Chin. Phys. Lett. 2014, 31 (2):
027702
.
DOI: 10.1088/0256-307X/31/2/027702
La2O3 films are grown on Si (100) substrates by the radio-frequency magnetron sputtering technique. The band alignment of the La2O3/Si heterojunction is analyzed by the x-ray photoelectron spectroscopy. The valence-band and the conduction-band offsets of La2O3 films to Si substrates are found to be 2.40±0.1 and 1.66±0.3 eV, respectively. Based on O 1s energy loss spectrum analysis, it can be noted that the energy gap of La2O3 films is 5.18±0.2 eV, which is confirmed by the ultra-violet visible spectrum. According to the suitable band offset and large band gap, it can be concluded that La2O3 could be a promising candidate to act as high-k gate dielectrics.
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Analysis of Intrinsic Degradation Mechanism in Organic Light-Emitting Diodes by Impedance Spectroscopy
ZHENG Rui, HUANG Wen-Bo, XU Wei, CAO Yong
Chin. Phys. Lett. 2014, 31 (2):
027703
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DOI: 10.1088/0256-307X/31/2/027703
The organic light-emitting diodes (OLEDs) in the sandwiched structures ITO/poly[3,4-ethylenedioxythiopene] (PEDOT)/poly[9,9-dioctylfluorene-co-4,7-di-2-thienyl-2,1,3-benzothiadiazole] (PFO-DBT15)/Ba/Al are fabricated. We use impedance measurements to investigate the degradation of aged OLEDs. A detailed analysis of the impedance spectra as functions of frequency and dc bias yields information about the injection of the interfacial electrode and the transport properties of emissive layer changes. Morphology differences between degraded and undegraded devices can also be observed by a scanning electron microscope. We perform comparative studies of the impedance spectroscopy (IS) of undegraded and degraded devices by both experiment and simulation approaches to explain the degradation mechanism for OLEDs. The IS of the undegraded device can be well understood by simply adopting the conventional RC equivalent circuits. For the degraded device, however, the successful model of the impedance spectroscopy results needs to take into account the more complicated situations, and we adopt a constant phase element to meet the experimental and simulated data and discuss the reasons caused by the problem.
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Influence of ITO, Graphene Thickness and Electrodes Buried Depth on LED Thermal-Electrical Characteristics Using Numerical Simulation
XUE Sheng-Jie, FANG Liang, LONG Xing-Ming, LU Yi, WU Fang, LI Wan-Jun, ZUO Jia-Qi, ZHANG Shu-Fang
Chin. Phys. Lett. 2014, 31 (2):
028501
.
DOI: 10.1088/0256-307X/31/2/028501
Finite elements methods are used to investigate the thermal?electrical characteristics of gallium?nitride (GaN) light-emitting diodes (LEDs) with different transparent conductive layers (TCLs) and buried depths of electrodes, where the transparent conductive layers include indium tin oxide (ITO), graphene (Gr) and the combination of them (ITO/Gr). The optimal material parameters and the precision and accuracy of the simulation model are validated. Moreover, the parameters' sensitivity analysis is carried out as well. The results indicate that the LED with the TCL of a 100-nm ITO or 4-layer Gr has a good thermal-electrical performance from the viewpoint of the maximum temperature and the current density deviation of multiple quantum well (MQW), where the maximum temperature occurs at the n-Pad rather than p-Pad. The compound TCL with a 20-nm ITO and 3-layer Gr reaches a thermal-electrical performance better than that of a 100-nm ITO or 4-layer Gr. Moreover, their maximum temperatures decrease about -0.43% and 1.21%, and the current density uniformities increase up to -6.09% and 17.41%, respectively. Furthermore, when the electrode buried depth is 0.51 μm, the thermal-electrical performance of the GaN LEDs can be further improved.
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Sensing Characteristics of Shear-Mode AlN Solidly Mounted Resonators with a Silicone Microfluidic System in Viscous Media
XIONG Juan, GUO Peng, SUN Xi-Liang, WANG Sheng-Fu, HU Ming-Zhe, GU Hao-Shuang
Chin. Phys. Lett. 2014, 31 (2):
028502
.
DOI: 10.1088/0256-307X/31/2/028502
AlN solidly mounted resonators with silicone microfluidic systems vibrating in shear mode are fabricated and characterized. The fabrication process is compatible with integrated circuits and the c-axis tilted AlN films are deposited, which allow in-liquid operation through excitation of the shear mode. The silicone microfluidic system is mounted on top of the sensor chip to transport the analyses and confine the flow to the active area. The properties of sensor operation in air, deionized water, ethanol, isopropanol, 80% glycol aqueous solution, glycol, and olive oil are characterized. The effects of different viscosities on the resonance frequency shift and Q-factor of the sensor have been discussed. The sensitivity and Q value in glycol of the sensor are 1.52 MHz cm2/μg and around 60, respectively. The results indicate the potential of a highly sensitive microfluidic sensor system for the applications in viscous media.
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The Distinguished Charge-Trapping Capability of the Memory Device with Al2O3-Cu2O Composite as the Charge Storage Layer
LU Jian-Xin, OU Xin, LAN Xue-Xin, CAO Zheng-Yi, LIU Xiao-Jie, LU Wei, GONG Chang-Jie, XU Bo, LI Ai-Dong, XIA Yi-Dong, YIN Jiang, LIU Zhi-Guo
Chin. Phys. Lett. 2014, 31 (2):
028503
.
DOI: 10.1088/0256-307X/31/2/028503
A memory device Si/Al2O3/Al2O3-Cu2O/Al2O3/Pt is fabricated by using atomic layer deposition and rf-magnetron sputtering techniques. The memory device including the composite of Al2O3 and Cu2O as the charge storage layer shows a distinguished charge trapping capability. At a working voltage of ±11 V a memory window of 9.22 V is obtained. The x-ray photoelectron spectroscopic study shows a shoulder from Cu2+ ions around the peak of Cu1+ ions. It is suggested that the charge-trapping mechanism should be attributed to the defect states formed by the inter-diffusion at the interface of two oxides.
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Effects of pH on Oxaliplatin-Induced Condensation of Single DNA Molecules
ZHANG Hong-Yan, JI Chao, LIU Yu-Ru, LI Wei, LI Hui, DOU Shuo-Xing, WANG Wei-Chi, ZHANG Ling-Yun, XIE Ping, WANG Peng-Ye
Chin. Phys. Lett. 2014, 31 (2):
028701
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DOI: 10.1088/0256-307X/31/2/028701
By using magnetic tweezers, atomic force microscope and mass spectrometry, we study the effects of pH on oxaliplatin-induced DNA condensation, the DNA persistence length, the amounts of micro-loops and of oxaliplatin bound to DNA. It is found that the DNA condensation degree, the amounts of micro-loops and of oxaliplatin bound to DNA increase with the decrease in the pH value while the DNA persistence length has an opposite behavior. The observed effects may be related to the drug resistance of cancer cells.
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Reconstruction of New Holographic Chaplygin Gas Model with Viscosity
WU Ya-Bo, TONG Hai-Dan, YANG Hao, LU Jian-Bo, ZHAO Yue-Yue, LU Jun-Wang, ZHANG Xue
Chin. Phys. Lett. 2014, 31 (2):
029801
.
DOI: 10.1088/0256-307X/31/2/029801
We investigate the interacting new holographic dark energy (HDE) with viscosity. Specifically, we not only study the dynamical evolutions of the new HDE with viscosity and the influences of viscosity as well as the coupling constant on the equation of state for the new HDE, but also establish the correspondence between the new HDE with viscosity and variable generalized Chaplygin gas (VGCG) models in the flat Friedmann–Robertson–Walker universe. Furthermore, we also reconstruct the potential and the dynamics of VGCG as the scalar field. By analysis we show that for the new holographic Chaplygin gas model, if the related parameters to the potential satisfy some constraints, the accelerated expansion can be achieved. These research results can reduce to the ones without viscosity.
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40 articles
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