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Numerical Simulation and Experimental Analysis of Photonic Band Gap in Hollow-Core Photonic Crystal Fibres
YUAN Jin-Hui, HOU Lan-Tian, ZHOU Gui-Yao, WEI Dong-Bin, CHEN Chao, WANG Qing-Yue, HU Ming-Lie, LIU Bo-Wen
Chin. Phys. Lett. 2008, 25 (5):
1541-1544
.
Based on the full-vector plane-wave method (FVPWM), a hollow-core photonic crystal fibre (HC-PCF) fabricated by using the improved stack-and-draw technique is simulated. Under given propagation constants β, several
effective photonic band gaps with different sizes emerge within the visible wavelength range from 575 to 720nm. The fundamental mode and second-order mode lying in a part of PBGs are investigated. In the transmission spectrum tested, the positions of PBGs are discovered to be shifting to shorter wavelengths. The main reason is the existence of interstitial holes at nodes in the cladding region. In the later experiment, green light is observed propagating in the air-core region, and the result is more consistent with our
theoretical simulation.
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Effects of Fractal Size Distributions on Velocity Distributions and Correlations of a Polydisperse Granular Gas
CHEN Zhi-Yuan, ZHANG Duan-Ming
Chin. Phys. Lett. 2008, 25 (5):
1583-1586
.
By the Monte Carlo method, the effect of dispersion of disc size distribution on the velocity distributions and correlations of a polydisperse granular gas with fractal size distribution is investigated in the same inelasticity. The dispersion can be described by a fractal dimension D, and the smooth hard
discs are engaged in a two-dimensional horizontal rectangular box, colliding inelastically with each other and driven by a homogeneous heat bath. In the steady state, the tails of the velocity distribution functions rise more significantly above a Gaussian as D increases, but the non-Gaussian velocity distribution functions do not demonstrate any apparent universal form for any value of D. The spatial velocity correlations are apparently stronger with the
increase of D. The perpendicular correlations are about half the parallel correlations, and the two correlations are a power-law decay function of dimensionless distance and are of a long range. Moreover, the parallel velocity correlations of postcollisional state at contact are more than twice as large as the precollisional correlations, and both of them show almost linear behaviour of the fractal dimension D.
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High-Pressure and High-Temperature Behaviour of Gallium Oxide
MA Yan-Mei, CHEN Hai-Yong, YANG Kai-Feng, LI Min, CUI Qi-Liang, LIU Jing, ZOU Guang-Tian
Chin. Phys. Lett. 2008, 25 (5):
1603-1605
.
High-temperature and high-pressure behaviours of β-Ga2O3 powder are studied by energy-dispersive x-ray diffraction in a diamond anvil cell (DAC). It is found that the phase transition from the monoclinic β-Ga2O3 to the trigonal α-Ga2O3 occurs at around 19.2GPa under cold compression. By heating the powder to 2000K at 30GPa, we confirm that α-Ga2O3 is the most stable structure at the high pressure. Furthermore, the structural transition from β-Ga2O3 to α-Ga2O3 is irreversible. After laser heating, the recrystallized Ga2O3
has a preferable (012) orientation. This interesting behaviour is also discussed.
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Core Polarization and Tensor Coupling Effects on Magnetic Moments of Hypernuclei
YAO Jiang-Ming, LU Hong-Feng, Hillhouse Greg, MENG Jie, ,
Chin. Phys. Lett. 2008, 25 (5):
1629-1632
.
Effects of core polarization and tensor coupling on the magnetic moments in 13ΛC, 17Λ, and 41ΛCa Λ-hypernuclei are studied by employing the Dirac equation with scalar, vector and tensor potentials. It is found that the effect of core polarization on the magnetic moments is suppressed by Λ tensor coupling. The Λ tensor potential reduces the spin--orbit splitting of pΛ states considerably. However, almost the same magnetic moments are obtained using the hyperon wavefunction obtained via the Dirac equation either with or without the Λ tensor potential in the electromagnetic current vertex. The deviations of magnetic moments for pΛ states from the Schmidt values are found to increase with nuclear mass number.
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Prolate and Oblate Shape Coexistence in 188Pt
LIU Yuan, ZHOU Xiao-Hong, ZHANG Yu-Hu, ZHENG-Yong, LIU Min-Liang, GUO Ying-Xiang, M. Oshima, Y. Toh, M. Koizumi, A. Osa, Y. Hatsukawa, SUN Yang
Chin. Phys. Lett. 2008, 25 (5):
1633-1635
.
A standard in-beam γ-spectroscopy experiment for 188Pt is performed via the
176Yb(18O, 6n) reaction at beam energies of 88 and 95MeV, and the level scheme for 188Pt is established. Prolate and oblate shape coexistence has been demonstrated to occur in 188Pt by applying the projected shell model. The rotation alignment of i13/2 neutrons drives the yrast sequence changing
suddenly from prolate to oblate shape at angular momentum 10h, indicating likely a new type of shape phase transition along the yrast line in 188Pt.
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BEPCII Injector Linac Upgrade and Beam Instabilities
WANG Shu-Hong, PEI Guo-Xi, CHI Yun-Long, CHEN Yan-Wei, CAO Jian-She, KONG Xiang-Cheng, ZHAO Feng-Li, HOU Mi, LIU Wei-Bin, GENG Zhe-Qiao, PEI Shi-Lun, DENG Bing-Lin, CHEN Zhi-Bi
Chin. Phys. Lett. 2008, 25 (5):
1636-1639
.
The upgrade project of the Beijing Electron Positron Collider (BEPCII) and its injector linac is working well. The linac upgrade aims at a higher injection rate of 50mA/min into the storage ring, which requires an injected beam with low
emittance, low energy spread and high beam orbit and energy stabilities. This goal is finally reached recently by upgrading the linac components and by dealing with rich and practical beam physics, which are described in this study.
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Multislit-Based Emittance Measurement of Electron Beam from a Photocathode Radio-Frequency Gun
YAN Li-Xin, DU Ying-Chao, XIANG Dao, LI Ren-Kai, QIAN Hou-Jun, HUANG Wen-Hui, TANG Chuan-Xiang, LIN Yu-Zheng, CHENG Jian-Ping
Chin. Phys. Lett. 2008, 25 (5):
1640-1643
.
Measurement of emittance for a space-charge dominated electron beam from a photocathode rf gun is performed by employing the multislit-based method at Accelerator Laboratory of Tsinghua University. We present the design considerations on the multislit system and the experimental results, with special attention to the study of space charge induced emittance growth. The experimental results are in reasonable agreement with the PARMELA simulations.
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Electronic Curves Crossing in Methyl Iodide by Spin--Orbit Ab Initio Calculation
LI Rui, YAN Bing, ZHAO Shu-Tao, GUO Qing-Qun, LIAN Ke-Yan, TIAN Chuan-Jin, PAN Shou-Fu
Chin. Phys. Lett. 2008, 25 (5):
1644-1645
.
An ab initio investigation of electronic curve crossing in a methyl iodide molecule is carried out using spin--orbit multiconfigurational quasidegenerate perturbation theory. The one-dimensional rigid potential curves and optimized
effective curves of low-lying states, including spin--orbit coupling and relativistic effects, are calculated. The spin--orbit electronic curve crossing between 3Q 0+ and 1Q1, and the shadow minimum in potential energy curve of 3Q0+ at large internuclear distance are found in both sets of the curves according to the present calculations. The crossing position is in the range of
RC-I=0.2370±0.0001nm. Comparisons with other reports are presented.
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L-Shell X-Ray Yields and Production Cross Sections of Zr and Mo Bombarded by Slow Highly Charged Ar16+ Ions
XU Jin-Zhang, DU Juan, CHEN Xi-Meng, SHAO Jian-Xiong, YANG Zhi-Hu, CUI Ying, GAO Zhi-Min, LIU Yu-Wen
Chin. Phys. Lett. 2008, 25 (5):
1649-1652
.
The L-shell x-ray yields of Zr and Mo bombarded by slow Ar16+ ions are measured. The energy of the Ar16+ ions ranges from about 150keV to 350keV. The L-shell x-ray production cross sections of Zr and Mo are extracted from these yields data. The explanation of these experimental results is in the framework of the adiabatic direct-ionization and the binding energy modified BEA approximation. We consider, in the slow asymmetric collisions such as Ar and Mo/Zr, the transient united atoms (UA) are formed during the ion-surface interaction and the direct-ionization is the main mechanism for the inner-shell vacancy production. Generally, the theoretical
results are in good agreement with the experimental data.
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Fluorescence Detection and Buffer Gas Cooling of Trapped Mercury Ions in Paul Trap
SHE Lei, , WANG Wen-Ming, , BAI Lei, , SUN Huan-Yao, , ZHU Xi-Wen, LI Jiao-Mei, GAO Ke-Lin,
Chin. Phys. Lett. 2008, 25 (5):
1653-1656
.
Hg ions are confined in a hyperboloid ion trap. With the rf discharge 202Hg isotope lamp, the fluorescence signal of trapped Hg ions is observed. By means of buffer gas cooling, the ionic temperature is reduced. As a result, the trapping time is increased and the signal-to-noise ratio (SNR) of the fluorescent signal is improved. The temperature of ion cloud is estimated by measuring the space charge shift.
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Bend-Induced Distortion in Large Mode Area Holey Fibre
TAN Xiao-Ling, GENG You-Fu, ZHANG Tie-Li, WANG Wei-Neng, WANG Peng, YAOJian-Quan
Chin. Phys. Lett. 2008, 25 (5):
1661-1663
.
A simplified scheme of bend-induced mode distortion is introduced into bent holey fibres, the distorted mode distribution and mode effective area reduction are investigated using the finite difference method. Numerical results show that the modes of bent holey fibres with small bend radius shift away from the core and are deformed greatly, and the mode areas drop significantly as the bend radius decreases, which severely affects the fibre laser performance. The propagation characteristics of bent holey fibres at
given wavelength are determined by fill factor and normalized bend radius. Finally, the transition normalized bend radius that represents the location of the mode area beginning to fall off is obtained.
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Design of High-Efficiency Diffraction Gratings Based on Rigorous Coupled-Wave Analysis for 800nm Wavelength
KONG Wei-Jin, YUN Mao-Jin, LIU Shi-Jie, JIN Yun-Xia, FAN Zheng-Xiu, SHAO Jian-Da
Chin. Phys. Lett. 2008, 25 (5):
1684-1686
.
We report on the design of a high diffraction efficiency multi-layer dielectric grating with wide incident angle and broad bandwidth for 800nm. The optimized grating can achieve >95% diffraction efficiency in the first order at an incident angle of 5° from Littrow and a wavelength from 770nm to 830nm, with peak diffraction efficiency of >99.5% at 800nm. The electric field distribution of the optimized multi-layer dielectric grating within the gratings ridge is 1.3 times enhancement of the incidence light, which presents
potential high laser resistance ability. Because of its high-efficiency, wide incident, broad bandwidth and potential high resistance ability, the multi-layer dielectric grating should have practical application in Ti:sapphire laser systems.
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Single-SOA-Based Ultrahigh-Speed All-Optical Half Subtracter with PolSK Modulated Signals
LI Pei-Li, HUANG De-Xiu, ZHANG Xin-Liang, WANG Yang
Chin. Phys. Lett. 2008, 25 (5):
1705-1708
.
A novel ultrahigh-speed all-optical half subtracter based on four-wave mixing (FWM) in a single semiconductor optical amplifier (SOA) is proposed. This scheme only requires a single SOA and two input signals without additional light source, so it is quite simple and compact. Due to the polarization-shift-keying (PolSK) modulated signals being used in this scheme, pattern-dependent degradation can be avoided. By numerical simulation, dependence of the critical factors of the logic gate performance, e.g., the output power of logic 1 and extinction ratio (ER), on two input signals power is investigated. In addition, the effect of the gain polarization dependence of SOA is analysed.
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Fabrication of Triplexers Based on Flattop SOI AWG
AN Jun-Ming, WU Yuan-Da, LI Jian, LI Jian-Guang, WANG Hong-Jie, LI Jun-Yi, HU Xiong-Wei
Chin. Phys. Lett. 2008, 25 (5):
1717-1719
.
A triplexer is fabricated based on SOI arrayed waveguide gratings (AWGs). Three wavelengths of the triplexer operate at different diffraction orders of an arrayed waveguide grating. The signals of 1490nm and 1550nm, which are
input from central input waveguide of an AWG, are demultiplexed and the signal of 1310nm, which is input from central output waveguide of an AWG, is uploaded. The tested results show that the downloaded and uploaded signals have flat-top response. The insertion loss is 9dB on chip, the nonadjacent crosstalk is less than -30dB for 1490nm and 1301nm, and is less than -25dB for 1550nm, the 3dB bandwidth equates that of the input light source.
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Sprout Branching of Tumour Capillary Network Growth: Fractal Dimension and Multifractal Structure
KOU Jian-Long, LU Hang-Jun, WU Feng-Min, XU You-Sheng
Chin. Phys. Lett. 2008, 25 (5):
1746-1749
.
A tumour vascular network, characterized as an irregularly stochastic growth, is different from the normal vascular network. We systematically analyse the
dependence of the branching. It is found that anastomosis of tumour on time is according to a number of tumour images, and both the fractal dimensions and multifractal spectra of the tumours are obtained. In the cases studied, the fractal dimensions of the tumour vascular network increase with time and the multifractal spectrum not only rises entirely but also shifts right. In addition, the best drug delivery stage is discussed according to the difference of the singularity exponent δα(δα=αmax}-αmin), which shows some change in the growth process of the tumour vascular network. A common underlying
principle is obtained from our analysis along with previous results.
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Structures and Equation of State of ε-Fe under High Pressure
ZENG Zhao-Yi, LIU Zhong-Li, CHEN Xiang-Rong, CAI Ling-Cang, JINGFu-Qian,
Chin. Phys. Lett. 2008, 25 (5):
1757-1760
.
The equation of state (EOS) and the axial ratio c/a of ε-Fe at high pressures are investigated by using the generalized gradient approximation (GGA) within the plane-wave pseudopotential density functional theory (DFT). The
results show that at the lower pressure, the EOS of ferromagnetic ε-Fe is consistent with the experimental result. While at higher pressure, the EOS of the nonmagnetic ε-Fe is in good agreement with the experimental result. Meanwhile, we find an obvious increase of the axial ratio c/a with pressure, and there is only a small increase with increasing temperature at high pressure.
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Detailed Characteristics of Expansion Velocity of Si from Laser Ablated SiC
CHEN Ming, LIU Xiang-Dong, SUN Yu-Ming, YANG Xin-Mei, ZHAO Ming-Wen, QI Huan-Jun, CHEN Xiu-Fang, XU Xian-Gang
Chin. Phys. Lett. 2008, 25 (5):
1768-1771
.
Optical emission of plasma is used to investigate the characteristics of dynamics distribution in the plume generated by ablation of a SiC sample using Nd:YAG laser. The plume expansion dynamics is characterized by time-of-flight measurement. We find that the profiles of Si (I) (390.55nm) split
into two components and the Si (II) (634.71nm) spectra show two distinct expansion dynamics regions. The time-of-flight measurement of Si(II) (634.71nm) under different laser irradiance conditions, from 0.236GW/cm2 to 1.667GW/cm2, are presented and discussed.
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Synthesis of [100] Wurtzite InN Nanowires and [011] Zinc-Blende InN Nanorods
NIE Chao, ZHANG Rong, XIE Zi-Li, XIU Xiang-Qiang, LIU Bin, FU De-Yi, LIU Qi-Jia, HAN Ping, GU Shu-Lin, SHI Yi, ZHENG You-Dou
Chin. Phys. Lett. 2008, 25 (5):
1780-1783
.
One-dimensional wurtzite InN nanowires and zincblende InN nanorods are prepared by chemical vapour deposition (CVD) method on natural cleavage plane (110) of GaAs. The growth direction of InN nanowires is [100], with wurtzite structure. The stable crystal structure of InN is wurtzite (w-InN), zincblende structure (z-InN) is only reported for 2D InN crystals before.
However, in this work, the zincblende InN nanorods [011] are synthesized and characterized. The SEM and TEM images show that every nanorod shapes a conical tip, which can be explained by the anisotropy of growth process and the theory of Ehrlich--Schwoebel barrier.
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High-Rate Growth and Nitrogen Distribution in Homoepitaxial Chemical Vapour Deposited Single-crystal Diamond
LI Hong-Dong, ZOU Guang-Tian, WANG Qi-Liang, CHENG Shao-Heng, LI Bo, Lü Jian-Nan, Lü Xian-Yi, JIN Zeng-Sun
Chin. Phys. Lett. 2008, 25 (5):
1803-1806
.
High rate (>50μm/h) growth of homoepitaxial single-crystal diamond (SCD) is carried out by microwave plasma chemical vapour deposition (MPCVD) with added nitrogen in the reactant gases of methane and hydrogen, using a
polycrystalline-CVD-diamond-film-made seed holder. Photoluminescence results indicate that the nitrogen concentration is spatially inhomogeneous in a large scale, either on the top surface or in the bulk of those as-grown SCDs. The presence of N-distribution is attributed to the facts: (i) a difference in N-incorporation efficiency and (ii) N-diffusion, resulting from the local growth
temperatures changed during the high-rate deposition process. In addition, the formed nitrogen-vacancy centres play a crucial role in N-diffusion through the growing crystal. Based on the N-distribution observed in the as-grown crystals, we propose a simple method to distinguish natural diamonds and man-made CVD SCDs. Finally, the disappearance of void defect on the top surface of SCDs is discussed to be related to a filling-in mechanism.
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Room-Temperature Ferromagnetism in Semiconducting TiO2-δ Nanoparticles
ZHAO Qian, WU Ping, LI Bao-Ling, LU Zun-Ming, JIANG En-Yong,
Chin. Phys. Lett. 2008, 25 (5):
1811-1814
.
TiO2-δ nanoparticles are synthesized by the sol-gel method and annealed under different reducing atmosphere. The x-ray diffraction patterns show that
anatase is the dominant phase with small amounts of the rutile phase of TiO2-δ for all the samples. Magnetic measurements indicate that the samples annealed in reducing atmosphere exhibit inprecedented room-temperature ferromagnetism, in particular, the saturation magnetization Ms is up to about 8.6×10-3emu/g for the sample annealed in H2/Ar mixture. Analysis of the x-ray photoelectron spectroscopy spectra for the samples processed under
different conditions indicates that the amounts of Ti3+ or Ti2+ cations, namely, the concentration of oxygen vacancies, increase with intensifying reducing atmosphere during processing, which shows that ferromagnetism in this material strongly depends on the concentration of oxygen vacancies. The relationships between the ferromagnetism and the crystal structure as well as the grain size in this material are also discussed.
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Sinusoidal Steady State Analysis on 4H--SiC Buried Channel MOSFETs
ZHANG Tao, LU Hong-Liang, ZHANG Yi-Men, ZHANG Yu-Ming, YE Li-Hui
Chin. Phys. Lett. 2008, 25 (5):
1818-1821
.
With the combined use of the drift-diffusion (DD) model, experimental measured parameters and small-signal sinusoidal steady-state analysis, we extract the Y-parameters for 4H--SiC buried-channel metal oxide semiconductor field effect transistors (BCMOSFETs). Output short-circuit current gain G and Mason's invariant U are calculated for extrapolating unity current gain frequency in the common-source configuration fT and the maximum frequency of oscillation fmax, respectively. Here fT=800MHz and fmax=5GHz are extracted for the 4H--SiC BCMOSFETs, while the field effect mobility reaches its peak value 87cm2/Vs when VGS=4.5V. Simulation results clearly show that the characteristic frequency of 4H--SiC BCMOSFETs and field effect mobility are superior, due to the novel structure, compared with conventional MOSFETs.
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Organic Light Emitting Diodes Using Doped Alq3 as the Hole-transport Layer
LIANG Chun-Jun, WANG Yang, YI Li-Xin
Chin. Phys. Lett. 2008, 25 (5):
1832-1835
.
Effects of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ)
doping on the hole conductivity of Alq3 layer are measured. In the hole-only device of Alq3, the current densities increase in 1--3 orders of magnitude upon doping with F4TCNQ, suggesting that the doping can effectively enhance the hole-injection and hole-transport ability of Alq3. An organic
light-emitting device using an F4TCNQ doped Alq3 layer as the hole-injection and hole-transport layer, and pristine Alq3 as the electron-transport and emitting layer is fabricated and characterized. Bright emission is achieved in the simple OLED with p-doped Alq3 as the hole-transport layer and the intrinsic Alq3 as the electron-transport and emitting layer. The emitting efficiency and brightness of the device are further improved by inserting a thin electron block layer to confine the carrier recombination zone in the middle of the organic layers.
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Effects of Contact Atomic Structure on Electronic Transport in Molecular Junction
XIA Cai-Juan, FANG Chang-Feng, HU Gui-Chao, ZHAO Peng, WANG Yi-Ming, XIE Shi-Jie, LIU De-Sheng,
Chin. Phys. Lett. 2008, 25 (5):
1840-1843
.
Based on nonequilibrium Green's function and first-principles calculations, we investigate the change in molecular conductance caused by different adsorption sites with the presence of additional Au atom around the metal-molecule contact in the system that benzene sandwiched between two Au(111) leads. The motivation is the variable situations that may arise in break junction experiments. Numerical results show that the enhancement of conductance induced by the presence of additional Au is dependent on the adsorption sites of anchoring atom. When molecule is located on top site with the presence of additional Au atoms, it can increase molecular conductance remarkably and present negative differential resistance under applied bias which cannot be found in bridge and hollow sites. Furthermore, the effects of
different distance between additional Au and sulfur atoms in these three adsorption sites are also discussed.
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Switching Characteristics of Phase Change Memory Cell Integrated with Metal-Oxide Semiconductor Field Effect Transistor
XU Cheng, LIU Bo, CHEN Yi-Feng, LIANG Shuang, SONG Zhi-Tang, FENG Song-Lin, WAN Xu-Dong, YANG Zuo-Ya, XIE Joseph, CHEN Bomy
Chin. Phys. Lett. 2008, 25 (5):
1848-1849
.
A Ge2Sb2Te5 based phase change memory device cell integrated with metal-oxide semiconductor field effect transistor (MOSFET) is fabricated using standard 0.18μm complementary metal-oxide semiconductor process
technology. It shows steady switching characteristics in the dc current-voltage measurement. The phase changing phenomenon from crystalline state to amorphous state with a voltage pulse altitude of 2.0V and pulse width of 50ns is also obtained. These results show the feasibility of integrating phase change memory cell with MOSFET.
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Influence of Strain-Reducing Layer on Strain Distribution of Self-Organized InAs/GaAs Quantum Dot and Redshift of Photoluminescence Wavelength
LIU Yu-Min, YU Zhong-Yuan, REN Xiao-Min
Chin. Phys. Lett. 2008, 25 (5):
1850-1853
.
A systematic investigation about the strain distributions around the InAs/GaAs quantum dots using the finite element method is presented. A special attention is paid to influence of an In0.2Ga0.8As strain reducing layer. The numerical results show that the horizontal- and vertical-strain components and the biaxial strain are reinforced in the InAs quantum
dot due to the strain-reducing layer. However, the hydrostatic strain in the quantum dot is reduced. In the framework of eight-band k∙p theory, we study the band edge modifications due to the presence of a strain reducing layer. The results demonstrate that the strain reducing layer yields the decreasing band gap, i.e., the redshift phenomenon is observed in experiments. Our calculated results show that degree of the redshift will increase with the
increasing thickness of the strain-reducing layer. The calculated results can explain the experimental results in the literature, and further confirm that the long wavelength emission used for optical fibre communication is realizable by adjusting the dependent parameters. However, based on the calculated electronic and heavy-hole wave function distributions, we find that the intensity of photoluminescence will exhibits some variations with the
increasing thickness of the strain-reducing layer.
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Solid State Dye Lasers Based on Coumarin 440 and Pyrromethene 567 Codoped Polymethyl Methacrylate
FAN Rong-Wei, LI Xiao-Hui, XIA Yuan-Qin, JIANG Yu-Gang, HE Wei-Ming, CHEN De-Ying
Chin. Phys. Lett. 2008, 25 (5):
1881-1883
.
Laser dye coumarin 440(C440) is codoped with pyrromethene 567 (PM567) into polymethyl methacrylate (PMMA). The effects of C440 concentration on the performance of the solid state dye medium, including spectra property, slope efficiency and photostability, are studied. When C440 is codoped with PM567 at the same concentration 1×10-4mol/L, the highest efficiency and
photostability can be obtained. Compared with the medium based on pure PM567 doped PMMA, about 50% increase in slope efficiency and at least five-fold enhancement in the photostability are observed.
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Eigenmode Splitting in all Hydrogenated Amorphous Silicon Nitride Coupled Microcavity
ZHANG Xian-Gao, CHEN Kun-Ji, QIAN Bo, CHEN San, DING Hong-Lin, LIUKui, WANG Xiang, XU Jun, LI Wei, HUANG Xin-Fan
Chin. Phys. Lett. 2008, 25 (5):
1888-1890
.
Hydrogenated amorphous silicon nitride based coupled optical microcavity is investigated theoretically and experimentally. The theoretical calculation of the transmittance spectra of optical microcavity with one cavity and coupled
microcavity with two-cavity is performed. The optical eigenmode splitting for coupled microcavity is found due to the interaction between the neighbouring localized cavities. Experimentally, the coupled cavity samples are prepared by plasma enhanced chemical vapour deposition and characterized by photoluminescence measurements. It is found that the photoluminescence peak wavelength agrees well with the cavity mode in the calculated transmittance spectra. This eigenmode splitting is analogous to the electron state energy splitting in diatom molecules.
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Broadband Infrared Luminescence from Bismuth-Doped GeS2--Ga2S3 Chalcogenide Glasses
DONG Guo-Ping, XIAO Xiu-Di, REN Jin-Jun, RUAN Jian, LIU Xiao-Feng, QIU Jian-Rong, LIN Chang-Gui, TAO Hai-Zheng, ZHAO Xiu-Jian
Chin. Phys. Lett. 2008, 25 (5):
1891-1894
.
Near-infrared luminescence is observed from bismuth-doped GeS2--Ga2S3 chalcogenide glasses excited by an 808nm laser diode. The emission peak with a maximum at about 1260nm is observed in 80GeS2--20Ga2S3:0.5Bi
glass and it shifts toward the long wavelength with the addition of Bi gradually. The full width of half maximum (FWHM) is about 200nm. The broadband infrared luminescence of Bi-doped GeS2--Ga2S3 chalcogenide glasses may be predominantly originated from the low valence state of Bi, such as Bi+. Raman scattering is also conducted to clarify the structure of glasses. These Bi-doped GeS2--Ga2S3 chalcogenide glasses can be applied potentially in novel broadband optical fibre amplifiers and broadly tunable laser in optical communication system.
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Reactive Mechanical Alloying Synthesis of Nanocrystalline Cubic Zirconium Nitride
QIU Li-Xia, YAO Bin, DING Zhan-Hui, ZHAO Xu-Dong, JI Hong, DU Xiao-Bo, JIA Xiao-Peng, ZHENG Wei-Tao
Chin. Phys. Lett. 2008, 25 (5):
1898-1901
.
Zirconium nitride powders with rock salt structure (γ-ZrNx) are prepared by mechanical milling of a mixture of Zirconium and hexagonal boron nitride
(h-BN) powders. The products are analysed by x-ray diffraction (XRD), canning electron microscopy (SEM), and Raman spectroscopy (RS). The formation mechanism of γ-ZrNx by ball milling technique is investigated in detail. N atoms diffuse from amorphous BN (a-BN) into Zr to form Zr(N) solid solution alloy, then the Zr(N) solid solution alloy decomposes into γ-ZrNx. No
ZrB2 is observed in the as-milled samples or the samples annealed at 1050°C for 2h.
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Mechanism of Enhanced Dielectric Properties of SiC/Ni Nanocomposites
ZHOU Yan, KANG Yu-Qing, FANG Xiao-Yong, YUAN Jie, SHI Xiao-Ling, SONG Wei-Li, CAO Mao-Sheng
Chin. Phys. Lett. 2008, 25 (5):
1902-1904
.
Dielectric properties of SiC/Ni nanocomposites prepared by a simple and facile electroless plating approach at X band are investigated. Compared to the original SiC nanoparticles (SiCP), the real part of the permittivity, ε', and the dielectric loss tangent tan δe of SiC/Ni nanocomposites are clearly enhanced by about 31% and 33%, respectively. The effective equations for complex permittivity of SiC/Ni nanocomposites are proposed. We also calculate ε' and tan δe of SiC/Ni nanocomposites and the calculated results are well consistent with the measured data.
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109 articles
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