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Experimental Study of Optical Nonlinearities in a Broadband Semiconductor Saturable Absorber Mirror
XING Qi-Rong, MAO Fang-Lin, LANG Li-Ying, WANG Zhuan, WANG Kai, LI Shu-Xin, CHAI Lu, ZHANG Zhi-Gang, WANG Qing-Yue
Chin. Phys. Lett. 2005, 22 (1):
40-42
.
The negative nonlinear index of a semiconductor saturable absorber mirror (SESAM) was investigated by using the reflection Z-scan technique. This is an experimental demonstration, for the first time to our knowledge, that the SESAM possesses comparable negative nonlinear index n2= -2.35×10-10,esu, which may have important implications in design and alignment of Kerr-lens mode-locking based on the self-focusing effect.
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Isoscaling of the Fission Fragments with Langevin Equation
WANG Kun, MA Yu-Gang, WEI Yi-Bin, CAI Xiang-Zhou, CHEN Jin-Gen, FANG De-Qing, GUO Wei, MA Guo-Liang, SHEN Wen-Qing, TIAN Wen-Dong, ZHONG Chen, ZHOU Xing-Fei
Chin. Phys. Lett. 2005, 22 (1):
53-56
.
The Langevin equation is used to simulate the fission process of 112Sn + 112Sn and 116Sn + 116Sn. The mass distribution of the fission fragments are given by assuming the process of symmetric fission or asymmetric fission with the Gaussian probability sampling. The isoscaling behaviour has been observed from the analysis of fission fragments of both the reactions, and the isoscaling parameter α seems to be sensitive to the width of fission probability and the beam energy.
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Parallel Momentum Distribution of 28Si Fragments from 29P
WEI Yi-Bin, MA Yu-Gang, CAI Xiang-Zhou, ZHONG Chen, CHEN Jin-Gen, ZHANG Hu-Yong, FANG De-Qing, WANG Kun, MA Guo-Liang, GUO Wei, TIAN Wen-Dong, SHEN Wen-Qing, ZHAN Wen-Long, XIAO Guo-Qing, XU Hu-Shan, SUN Zhi-Yu, Li Jia-Xing, GUO Zhong-Yan, WANG Meng, CHEN Zhi-Qiang, HU Zheng-Guo, CHEN Li-Xin, LI Chen, MAO Rui-Shi, BAI Jie
Chin. Phys. Lett. 2005, 22 (1):
61-64
.
Distribution of the parallel momentum of 28Si fragments from the breakup of 30.7MeV/nucleon 29P has been measured on C targets. The distribution has the FWHM with the value of 110.5±23.5MeV/c, which is quantitatively consistent with the Galuber model calculation assuming by a valence proton in 29P. The density distribution is also predicted by the Skyrme--Hartree--Fock calculation. The results show that the proton-skin structure may exist in 29P.
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Inter-relationship of Various Results in Analysis of (14.0MeV/U) Pb+Pb Reaction Using Mica and CN-85 Track Detectors
F. N. Khattak, E. U. Khan, Tabassum Nasir, J. J. Baluch, F. U. Khan
Chin. Phys. Lett. 2005, 22 (1):
69-71
.
Two detector materials mica and cellulose-nitrate(CN)-85 have been used to study (14.0MeV/u) Pb + Pb reaction. Events of different multiplicities were registered in mica and CN-85 detectors using the 2π-geometry technique of solid state nuclear track detection. After removing the target material from the detectors the damaged trails in the detectors were revealed as tracks by proper chemical etching. The irradiated area of each sample was scanned and events of different multiplicities were traced. The binary events were bifurcated into elastic and inelastic events. The elastic binary events and three prong events, observed in the reaction, have been used to search out coefficients Cμv in the presence of both the detectors, for the reaction under study. Using these coefficients 3- and 4-prong events have been analysed. From the detailed analysis of the results of (14.0MeV/u) Pb+Pb reaction, obtained from mica and CN-85 track detectors we observed a great resemblance of results obtained from the two detectors. Combining the results of both the detectors, we report some important outcomes.
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Optical Transition Probability of Nd3+ Ions Doped in Ferroelectric PLZT for Active Electro-Optical Applications
LI Bao-Zeng, ZHENG Zhi-Qiang, YANG Ji-Wen, LI Ke-Wen, Jiang Hua, CHEN Xue-Sheng, WANG An-Ting, XIE Jian-Ping, MING Hai
Chin. Phys. Lett. 2005, 22 (1):
80-82
.
The optical transition probability of Nd3+ (0.5mol%) doped lanthanum-modified lead zirconate titanate (PLZT) is investigated. The absolute intensities of its forced electric dipole transitions between 400nm and 1000nm were measured, from which we obtain three phenomenological parameters, Ω2= 0.787×10-20cm2, Ω4= 1.182×10-20cm2, and Ω6=1.042×10-20cm-20, according to the Judd--Ofelt theory. The radiation lifetime (346.9μs) of the 4F3/2 metastable state, the stimulated emission cross-section σij= (2.49×10-21cm2, 6.51×10-21cm2, 2.17×10-21cm2), and the fluorescence branch ratios are calculated. We also measured the fluorescence lifetime (155.84μs) and calculated the quantum efficiency (46.1%). The analysis reveals that Nd103+-doped PLZT, based on its large electro-optical effect, has potential applications in active optical devices.
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Trapping of Neutral Atoms with a Radio-Frequency Field
ZHANG Hai-Chao, ZHANG Peng-Fei, XU Xin-Ping, HAN Jiu-Rong, WANG Yu-Zhu
Chin. Phys. Lett. 2005, 22 (1):
83-86
.
Based on the dressed-atom approach, we discuss a two-dimensional (2D) radio-frequency trap for neutral atoms, in which the trap potential derives from the magnetic-dipole transitions among the hyperfine Zeeman sublevels. By adjusting the detuning of the radiation from resonance, the trapping states will be changed predominantly from the bare states of mF gF > 0 to other states of mF gF < 0, where mF and gF are the quantum numbers of Zeeman sublevels and the Landé factor, respectively. This character contrasts finely with that of a static magnetic trap that can only trap or guide the states of mF gF > 0. In comparison to the optical field, the radio-frequency trap eliminates the spontaneous emission heating of the atoms. Unlike other oscillating traps reported in the literature, the configuration of the radio frequency trap is suitable for realization of a miniature magnetic guide.
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Calculation of Electron-Impact 2s22p4 3P→ 2p33s3S0 Transition in Atomic Oxygen
WANG Yang, LI Yan-Hua, ZHOU Ya-Jun
Chin. Phys. Lett. 2005, 22 (1):
87-90
.
The inelastic scattering of electron from oxygen for the 2s22p4 3P→ 2p33s3S0 transition is studied using the momentum-space coupled channel optical method at 15, 17.5, 20, 22.5, 25, 27.5, 30, 50, and 100eV. Direct ionization cross sections, i.e. differential and integral cross sections, are reported. Important continuum states are included in the coupled channel calculation via a complex equivalent-local optical potential. The present results are compared with the available experimental data and other theoretical calculation results.
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Controllable Passively Q-Switched Laser
YANG Cheng-Wei, HUO Yu-Jing, HE Shu-Fang, YIN Xiao-Dong, ZHANG Bao-Shun
Chin. Phys. Lett. 2005, 22 (1):
117-119
.
We present a novel kind of pulsed laser named controllable passively Q-switched laser (CPQL). A CPQL of Nd:YVO4 with Cr:YAG as saturable absorber was demonstrated and studied as an example of the kind of pulsed lasers. In CPQL, as the actively controlling signal, a diode laser beam was focused onto the saturable absorber in the resonant cavity of the passively Q-switched laser (PQL) and was absorbed by the absorber to realize the active control of the CPQL. The characters of the CPQL output laser pulses, such as generation time, repetition rate, pulse width, peak power and energy per pulse, can be controlled by the operator. The CPQLs possess the advantages of both passively Q-switched laser and actively Q-switched laser. Because of their compactness, low cost and controllability, the CPQLs will find wide applications in many fields.
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A Room-Temperature Multiwavelength Erbium-Doped Fibre Laser by Exploiting Polarization Hole Burning
ZHANG Hao, XIONG Ling-Yun, DOU Qing-Ying, LI Yao, YU Ling, LIU Yan-Ge, LIU Li-Hui, YUAN Shu-Zhong, KAI Gui-Yun,
DONG Xiao-Yi
Chin. Phys. Lett. 2005, 22 (1):
122-124
.
Multiwavelength operation of a linear cavity erbium-doped fibre laser (EDFL) is proposed and demonstrated. A 3-dB fibre loop mirror and a high birefringence (HiBi) fibre loop mirror are utilized as the cavity reflectors. By utilizing the wavelength-dependent polarization rotation induced by the HiBi fibre loop mirror and by using a fibre polarizer to control the intracavity polarization state, the polarization states of different wavelengths are diversified. Therefore, the polarization hole burning (PHB) effect has been greatly enhanced and the homogeneous broadening of erbium-doped fibre is suppressed to a large extent. By simply tuning a polarization controller, we experimentally obtained simultaneous lasing of four and five wavelengths with wavelength spacing of ~1.8nm and less than 2\,nm at room temperature, respectively. The repeated scans show that all of these lasers have good stability.
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High Beam Quality Green Generation with Output 140W Based on a Thermally-Near-Unstable Flat--Flat Resonator
GENG Ai-Cong, BO Yong, BI Yong, SUN Zhi-Pei, YANG Xiao-Dong, PENG Qin-Jun, LI Hui-Qing, ZHOU Yi, LI Rui-Ning, CUI Da-Fu, XU Zu-Yan
Chin. Phys. Lett. 2005, 22 (1):
125-127
.
By using a diode-side-pumped Q-switched Nd:YAG rod laser based on a thermally-near-unstable flat--flat resonator, an intracavity-frequency-doubled green beam generation is investigated. Output power 140W is obtained at a repetition rate of 10kHz and a pulse width of 110ns. The green beam quality factors M2x and M2y, which are measured by a laser beam analyser, are 10.65 and 10.85, respectively, at output power of 124W.
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Luminescent Properties and Mechanism of Gd1-x-yAlO3Eux,REy
LUO Lan, LIU Qing-Feng, LIU Qian
Chin. Phys. Lett. 2005, 22 (1):
131-134
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GAP:Eu,Re(Gd1-x-yAlO3Eux,REy, RE=Pr or Ce) powders were prepared by a nitrate--citrate process. It is found that luminescent intensity decreases when GAP:Eu is co-doped with Pr or Ce. The phenomena of spectra prove that there is a resonant energy transfer between Eu and Pr, by the absorption and emission of lower-energy phonon, and also Ce sensitizer decreases the activator energy level from host→Eu. The two factors are considered to be the main reasons for decrease of the luminescent intensity for the co-doped GAP:Eu,Re.
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A Novel Reactive Gas Source and Its Application to Carbon Nanotube Film Deposition
JIANG Nan, CHEN Han-Yuan, QIAN Sheng-Fa
Chin. Phys. Lett. 2005, 22 (1):
161-163
.
Generally, gaseous discharge at pressure higher than 10kPa will collapse to filamentary form or streamer, which will produce a non-uniform treatment on the sample surface. Thus, atmospheric pressure glow discharge (APGD) is developed. However the realization of the APGD is not obvious, it needs special conditions. We propose a new concept to solve the non-uniformity problem. By using a grid electrode and putting the sample downstream of the discharge plasma, the streamers, instead of striking on sample surface, will strike on the grid, and the neutral active species produced in the discharge diffuse out to reach the sample surface uniformly. Finally, a carbon nanotube (CNT) film was produced to test this new concept.
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A Compact Magnetically Insulated Line Oscillator with New-Type Beam Dump
FAN Yu-Wei, SHU Ting, LIU Yong-Gui, ZHONG Hui-Huang, LI Zhi-Qiang, WANG Yong, ZHAO Yan-Song, LUO Ling
Chin. Phys. Lett. 2005, 22 (1):
164-167
.
We present a compact improved model of the magnetically insulated line oscillator with new-type beam dump and other novel features. In the experiments, high-power microwave of the TM01 mode is generated from the device with a frequency range of 1.73--1.78GHz and a peak power level of above 2GW, when the diode voltage is taken in the range 520--540kV, and the diode current is in the range 58--62kA. This confirms the simulation results.
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N-Doped LaAlO3/Si(100) Films with High-k, Low-Leakage Current and Good Thermal Stability
XIANG Wen-Feng, LU Hui-Bin, CHEN Zheng-Hao, HE Meng, LU Xu-Bing, LIU Li-Feng, GUO Hai-Zhong, ZHOU Yue-Liang
Chin. Phys. Lett. 2005, 22 (1):
182-184
.
High quality amorphous N-doped LaAlO3 (LaAlON) films have been deposited on Si (100) in nitrogen gas by laser molecular beam epitaxy. The chemical nature and physical distribution of N in LaAlON films has been performed by x-ray photoemission spectroscopy. Compared with LaAlO3, a significant improvement in the interfacial quality and leakage current density was obtained by nitrogen additive. At gate voltage +1V, the leakage current density of the LaAlON film with an equivalent oxide thickness as thin as 2nm is obtained to be 2.9× 10-6A/cm2, which decreases almost two orders of magnitude from that of LaAlO3 film with the same thickness. Moreover, high-resolution transmission electron microscope analysis show that the LaAlON sample is still amorphous with a very sharp interface between the LaAlON layer and the Si substrate after annealed at 900°C for 60s.
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Unusual Transport Properties near the Insulator--Metal Transition in Colossal Magnetoresistive Manganites
YUAN Song-Liu, ZHONG Qiang-Hua, DOYANANDA Debnath, CHEN Wei, ZHAO Li-Feng, MIAO JU-Hong, CAO Heng, LIU Sheng, XIA Zheng-Cai
Chin. Phys. Lett. 2005, 22 (1):
207-210
.
It is argued that a combination of the Griffiths theory and the double-exchange mechanism predicts the random distribution of ferromagnetic metallic clusters above the Curie temperature TC in colossal magnetoresistive manganites. Along this line, we propose a model for the temperature dependence of resistivity that yields a quantitative agreement with experimental data obtained in a typical manganite La2/3Ca1/3MnO3. Our result indicates that the formation and growth of ferromagnetic metallic clusters are responsible for the observation of unusual transport properties near the insulator--metal transition.
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Switching Behaviour of Magnetic Particles with Dipolar Interaction
XU Chen, HUI Pak-Ming, CHOW Chow-Wang, LI Zhen-Ya
Chin. Phys. Lett. 2005, 22 (1):
211-214
.
We study the switching in the magnetic moments of interacting magnetic particles. The dynamics of the magnetic moments is governed by a coupled set of Landau--Lifshitz--Gilbert equations. The magnetic particles are assumed to be spherical in shape, single domain, and have uniaxial anisotropy. Effects of dipolar interaction between the particles, anisotropy energy, an applied switching field with finite spatial extent and a small bias field are considered. When the separation between the particles is small, the dipolar field is significant and it affects the reversal of the magnetic moments. The final configuration attained depends sensitively on the decaying length of the switching field, the inter-particle separation, and the initial configuration. A bias field tends to suppress the effects of a spatially decaying switching field and dipolar interaction between neighbouring particles.
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Modified Photoluminescence by Silicon-Based One-Dimensional Photonic Crystal Microcavities
CHEN San, QIAN Bo, WEI Jun-Wei, CHEN Kun-Ji, XU Jun, LI Wei, HUANG Xin-Fan
Chin. Phys. Lett. 2005, 22 (1):
230-232
.
Photoluminescence (PL) from one-dimensional photonic band structures is investigated. The doped photonic crystal with microcavities are fabricated by using alternating hydrogenated amorphous silicon nitride (a-SiNx:H/a-SiNy:H) layers in a plasma enhanced chemical vapour deposition (PECVD) chamber. It is observed that microcavities strongly modify the PL spectra from active hydrogenated amorphous silicon nitride (a-SiNz:H) thin film. By comparison, the wide emission band width 208nm is strongly narrowed to 11\,nm, and the resonant enhancement of the peak PL intensity is about two orders of magnitude with respect to the emission of the λ/2-thick layer of a-SiNz:H. A linewidth of Δλ=11nm and a quality factor of Q=69 are achieved in our one-dimensional a-SiNz photonic crystal microcavities. Measurements of transmittance spectra of the as-grown samples show that the transmittance resonant peak of a cavity mode at 710nm is introduced into the band gap of one-dimensional photonic crystal distributed Bragg reflector (DBR), which further verifies the microcavity effects.
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Top-Emitting Organic Light-Emitting Devices Based on Silicon Substrate with High Luminance and Low Turn-on Voltage
WU Zhi-Jun, CHEN Shu-Fen, YANG Hui-Shan, ZHAO Yi, LI Chuan-Nan, HOU Jing-Ying, LIU Shi-Yong
Chin. Phys. Lett. 2005, 22 (1):
233-235
.
We have fabricated a top-emitting organic light-emitting device on silicon substrate with high yellow luminance based on 5,6,11,12-tetraphenylnaphthacene sub-monolayer. It consists of a thin layer of highly conductive silver as the semitransparent cathode and surfaced-modified Ag as the anode. The device turns on at 3V with the luminance of 8.4cd/m2. The maximum current efficiency is 1.3cd/A at 6V and the luminance reaches 14790cd/m2 at 14V. The performance of the device is excellent in top-emitting organic light-emitting devices according to our knowledge.
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Absorption Spectra and Ionic Conductivity of RbxCs1-xAg4I5 Superionic Conductors Thin Films
CAO Yang, SUN Jia-Lin, ZHANG Guo-Sheng, GUO Ji-Hua, WANG Zheng-Ping
Chin. Phys. Lett. 2005, 22 (1):
239-242
.
A series of RbxCs1-xAg4I5 (x=0--1) thin films were grown by vacuum evaporation on NaCl crystal substrates at 350K. The absorption spectra of these films were measured at 80K in the wavelength range from 240nm to 400nm. It is shown that superionic conductor thin films of quaternary compound Rb0.5Cs0.5Ag4I5 and ternary compound RbAg4I5 can be obtained at x=0.5--0.6 and x=0.7--1, respectively. At x=0.65, the combined compound film of the mixture of 30mol\% RbAg4I5 and 70mol% Rb0.5Cs0.5Ag4I5 is presented. Then, based on the spectral positions of the A1 and A2 peaks, we determined that the Rb0.5Cs0.5Ag4I5 exciton coupling energy Rex is 0.21eV, the forbidden zone width Eg is 3.82eV and the exciton radius aex is 0.70nm. Furthermore, the ionic conductivities of superionic conductor thin films of RbAg4I5 and Rb0.5Cs0.5Ag4I5 and their mixture film are investigated, respectively, in the temperature range 303K--393K.
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76 articles
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