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Influences of Modulated Noise on Normalized Intensity Fluctuation in a Single-Mode Laser
WANG Jun, CAO Li, , WU Da-Jin,
Chin. Phys. Lett. 2004, 21 (2):
246-249
.
The influences of the two forms of modulated noises, i.e., the bias signal-modulated noise and the direct signal-modulated noise, on the normalized intensity fluctuation (NIF) are investigated, and the results of the two forms of modulation are compared detailedly. We find that a minimum for the case of the bias signal modulation appears in the curve of the dependence of the NIF upon the quantum and pump noise intensities when the correlation coefficient between the quantum noise and the pump noise is negative. However, the NIF for the case of the direct signal modulation is independent of the correlation coefficient between the two noises. Moreover, at the same parameter region, the NIF for the bias signal modulation is only one-eighth as much as that for the direct signal modulation.
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Phase Synchronization as a Mechanism of Controlling Spatiotemporal Chaos via External Periodic Signal
SANG Hai-Bo, , HE Kai-Fen,
Chin. Phys. Lett. 2004, 21 (2):
254-257
.
We find that phase synchronization (PS) is a mechanism in which the spatiotemporal chaos (STC) can be suppressed to a spatially regular (SR) state by applying an external periodic signal in a one-dimensional driven drift-wave system. In the driving wave coordinate, the nonlinear system can be transformed to a set of coupled oscillators moving in a periodic potential. In this multi-dimensional system, the internal modes are slaved one by one through PS by the control signal. Two types of responses of the internal modes to the external periodic signal are observed. For some modes, the stabilization is through frequency-locking; while for the other modes, a special kind of PS without frequency-locking, namely multi-looping PS, is developed.
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Spectra of Highly Ionized Sulfur below 200Å
YANG Zhi-Hu, WANG You-De, MA Xin-Wen, LIU Hui-Ping, SU Hong, ZHANG Yan-Ping, XIAO Guo-Qing
Chin. Phys. Lett. 2004, 21 (2):
287-290
.
Spectra of carbon-, boron-, beryllium-, lithium-, helium-, and hydrogen-like sulfur ions were obtained and studied for the wavelengths below 200Å and the energy of 80 MeV by using beam-foil method. Thirty-five lines have been identified, in which fifteen lines are newly accurately measured. The spectra were analysed based on the theoretical results and other experimental data.
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Optical Transition Probability of Sm3+ Ions in a Polymer Optical Fiber
ZHENG Zhi-Qiang, LIANG Hao, MING Hai, ZHANG Qi-Jin, HAN Xin-Hai, WANG Guan-Zhong, XIE Jian-Ping
Chin. Phys. Lett. 2004, 21 (2):
291-294
.
We investigate optical absorption and emission spectra of Sm3+ ions in Sm(DBM)3Phen-doped polymethyl methacrylate (PMMA). Based on the Judd-Ofelt theory, the optical intensity parameters are calculated to be Ω2 = 13.76 x 10-20cm2, Ω4 = 3.41 x 10-20cm2, Ω6 = 4.01 x 10-20cm23 Phen-doped polymethyl methacrylate. The optical intensity parameters have been used to calculate the total radiative transition rate (676.57 s-1) and radiative lifetime (147 μs) of the 4G5/2 exciting state. The stimulated emission cross-sections σij and the fluorescence branch ratios for the 4G5/2 → 6FJ' and 4G5/2 → 6FJ' transitions are also evaluated. The analysis reveals that Sm(DBM)3Phen-doped PMMA is promising for applications in rare-earth-doped polymer devices.
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Wide-Band Polarisation-Insensitive High-Output-Power Semiconductor Optical Amplifier Based on Thin Tensile-Strained Bulk InGaAs
WANG Shu-Rong, LIU Zhi-Hong, WANG Wei, ZHU Hong-Liang, ZHANG Rui-Ying, ZHOU Fan, WANG Lu-Feng, DING Ying
Chin. Phys. Lett. 2004, 21 (2):
310-312
.
A polarization-insensitive semiconductor optical amplifier (SOA) with a very thin active tensile-strained InGaAs bulk has been fabricated. The polarization sensitivity of the amplifier gain is less than 1 dB over both the entire range of driving current and the 3 dB optical bandwidth of more than 80 nm. For optical signals of 1550 nm wavelength, the SOA exhibits a high saturation output power +7.6 dBm together with a low noise figure of 7.5 dB, fibre-to-fibre gain of 11.5 dB, and low polarization sensitivity of 0.5 dB. Additionally, at the gain peak 1520 nm, the fibre-to-fibre gain is measured to be 14.1 dB.
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Diode-Pumped Self Q-Switched and Mode-Locking Nd3+, Cr4+:YAG Laser
LI Chun-Yong, LI Ping-Xue, LI De-Hua, FENG Bao-Hua, FU Pan-Ming, ZHANG Zhi-Guo, ZHANG Shi-Wen
Chin. Phys. Lett. 2004, 21 (2):
313-315
.
Using Nd3+, Cr4+:YAG as a laser crystal and saturable absorber simultaneously, we obtain a self-Q-switched and mode-locking laser at 1.06 μm with straight cavity structure. Self mode-locking phenomenon was observed at an intracavity intensity of only about 2000 W/cm1. More than 90% modulation depth is achieved at an intracavity intensity of less than 3.0 x 104 W/cm2 for the first time. The Q-switched pulse width and repetition rate are found to be connected with the cavity length and the output power.
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Compact First-Order Polarization Mode Dispersion Compensator Based on Birefringent Crystals
YANG Chang-Xi, LI Shi-Guang, MIAO Hou-Xun, TIAN Yu, ZHANG En-Yao, JIN Guo-Fan
Chin. Phys. Lett. 2004, 21 (2):
326-328
.
We report a new first-order polarization-mode-dispersion (PMD) compensator based on birefringent crystals and magneto-optic polarization controllers. The compensator shows the response time of 150μs, insertion loss smaller than 3 dB, and maximum differential group delay of 44.6 ps. Compared to the first-order PMD compensators reported so far, our PMD compensator exhibits fast response time, low insertion loss, compact size, broad bandwidth, and immunity to environmental vibrations.
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Effects of Ag Doping on Magnetoresistance of La0.833K0.167MnO3 Polycrystalline Perovskite Manganites
WU Jian, ZHANG Shi-Yuan
Chin. Phys. Lett. 2004, 21 (2):
382-385
.
The microstructure, magnetic and transport properties of the heterogeneous system with a nominal composition (1/m)Ag2O-La0.833K0.167MnO3 (1/m is molar ratio with m = 32, 16, 8, 4, and 2) have been studied. The x-ray diffraction patterns show that all the samples are the two-phase composite and consist of a magnetic La0.833K0.167MnO3 (LKMO) perovskite phase and a nonmagnetic metal Ag phase. The room-temperature magnetoresistance (MR) effect is enhanced significantly due to the addition of Ag. For the m = 4 sample, we obtain the MR values up to 32% under a lower field of 0.5 T and 67% under a higher field of 5.5 T at the temperature of 300 K, which are much larger than the corresponding MR values (10% and 35%) of the LKMO sample without Ag. In the low temperature range from 4.2 K to 250 K, the MR values of the Ag-added samples however decrease with the increasing Ag content in the samples. The effect is discussed qualitatively by using the relative contribution from the intrinsic MR effect and the extrinsic MR effect including the spin-polarized-tunneling and spin-dependent scattering effects in different temperature regions.
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Synthesis and Magnetic Properties of the Intercalation Compound FePS3(CoCp2)0.40
LIN Jun, DAI Yao-Dong, HE Yun, HUANG Hong-Bo, XIAO Fan, XIA Yuan-Fu
Chin. Phys. Lett. 2004, 21 (2):
386-388
.
Intercalation compound FePS3(CoCp2)0.40 (CoCp2 = cobaltocene) was synthesized, and the crystal structure and magnetic properties were studied by x-ray diffraction, magnetic susceptibility measurement, and Mössbauer spectroscopy. The crystal structure was indexed to monoclinic unit cell with a = 5.996Å, b = 10.106Å c = 12.511Å, β = 105.916°, and about 5.6Å expansion at the c direction compared to pure FePS3. The Mössbauer spectra indicate that there are three kinds of divalent irons with high spin state in the intercalation compound, which implies that charge transfer from guest to the Fe-S e*g anti-bonding orbits of host lattice. No cationic vacancies are formed in the intercalation compound. The ferromagnetism at low temperature originates from the spin canting of divalent irons.
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Structure, Electrical, and Optical Properties of Nb-doped BaTiO3 Thin Films Grown by Laser Molecular Beam Epitaxy
GUO Hai-Zhong, LIU Li-Feng, LU Hui-Bin, FEI Yi-Yan, XIANG Wen-Feng, ZHOU Yue-Liang, CHEN Zheng-Hao
Chin. Phys. Lett. 2004, 21 (2):
396-399
.
Structure, electrical, and optical properties of Nb-doped BaTiO3 (Nb:BTO) thin films on MgO substrates grown by laser molecular beam epitaxy with the increasing Nb content were investigated. The Nb:BTO thin films with high crystallinity are epitaxially grown on MgO substrates. With more Nb-doped content, the impurity phases are found in Nb:BTO thin films. Hall measurement at room temperature confirms that the charge carriers of the Nb:BTO thin films are n-type. When the Nb-doped content increases, the carrier concentration and carrier mobility increase. Meanwhile the optical transmittance decreases with the increase of the Nb-doping, and the width of the forbidden band in each group is not affected by the presence of Nb in the samples. Raman spectra show that the structural phase transition may occur with the increase of the Nb-doping content, in the meantime more defects and impurities exist in the Nb:BTO thin films.
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Induced Nucleation of Diamond Films on ZnS Substrates Precoated with Ceramic Interlayer
GAO Xu-Hui, LU Fan-Xiu, TONG Yu-Mei, GUO Hui-Bin, TANG Wei-Zhong, LI Cheng-Ming, CHEN Guang-Chao, YU Huai-Zhi, CHENG Hong-Fan, YANG Hai
Chin. Phys. Lett. 2004, 21 (2):
406-409
.
We attempt to coat a multi-spectrum chemical-vapor-deposition ZnS substrate with smooth crystalline diamond films on the top of properly designed ceramic interlayer, which provides protection for ZnS against corrosion by the H2-CH4 microwave plasma and mitigates the thermal expansion coefficient mismatching between diamond and ZnS. However, difficulties in the homogenous diamond nucleation on a ceramic interlayer were encountered. It was found that high rate nucleation of diamond could be induced by a metal or semiconductor mask placed on the top of ZnS.
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Two-Step Growth of MgO Films on Sapphire (0001) Substrates by Radio Frequency Plasma-Assisted Molecular Beam Epitaxy
MEI Zeng-Xia, DU Xiao-Long, ZENG Zhao-Quan, GUO Yang, WANG Jian, JIA Jin-Feng, XUE Qi-Kun
Chin. Phys. Lett. 2004, 21 (2):
410-413
.
We report on the growth of rock salt MgO films on sapphire (0001) substrates by rf plasma-assisted molecular beam epitaxy. A two-step method, i.e., high temperature epilayer growth after low-temperature buffer layer growth, was adopted to obtain the single crystal MgO film. The epitaxial orientationship between the MgO epilayer and the sapphire (0001) substrate was studied by using in-situ reflection high energy electron diffraction and ex-situ x-ray diffraction, and it is found that the MgO film grows with [111] orientation. The role of the low temperature buffer layer in the improvement of crystal quality of the MgO epilayer is discussed based on the cross-sectional scanning electron microscopy.
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57 articles
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