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Electromagnetically induced transparency and controllable group velocity in a five-level atomic system

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Chinese Optics Letters 2006年第5期4卷 252-254页

作者：金黎慧龚尚庆钮月萍金石琦 State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800

The optical properties of a five-level atomic system composed of a A-type four-level atomic and a tripod four-level atomic systems are investigated. It is found that the behaviors of electromagnetically induced transparency （EIT） and group velocity can be controlled by choosing appropriate parameters with the interacting dark resonances. In particular, when all the fields are on resonance, the slow light at the symmetric transparency windows with a much broader EIT width is obtained by tuning the intensity of the coupling field in comparison with its sub-system, which provides potential applications in quantum storage and retrieval of light,

关键词： couplings Electromagnetic field effects Optical properties Quantum optics Resonance Velocity Windows

Improved layer peeling algorithm for strongly reflecting fiber gratings

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Chinese Optics Letters 2006年第9期4卷 505-507页

作者：黄力群黄卫平汪晋宽杨光 Department of Computer Engineering Northeastern University at Qinhuangdao Department of Electrical Engineering McMaster University Hamilton

An improved algorithm based on the layer peeling （LP） method is proposed and demonstrated. The new method is shown to be effective for mitigating the impact of numerical errors on reconstruction of coupling function for strongly reflecting Bragg gratings. As examples, a flat-top dispersion-free fiber grating and a fiber-grating dispersion compensator are designed by the improved LP method. For a chirp grating, more accurate results are demonstrated in comparison with those obtained by the integral layer peeling （ILP） method.

关键词： Algorithms couplings Dispersions Errors Functions Optical fibers

A novel NOLM structure with nonreciprocal phase shift bias for power fluctuation reduction of pulse trains

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Chinese Optics Letters 2006年第8期4卷 449-452页

作者：郭力为冯雪刘越刘小明 Department of Electronic Engineering Tsinghua University

A novel nonlinear optical loop mirror （NOLM） with a nonreciprocal phase shift bias （NPSB）, called power equalization NOLM （PE-NOLM）, is proposed for reducing the power fluctuation of pulse trains. NPSB provides part of the nonreciprocal phase difference so that the required input power is reduced, and nonsymmetrical coupling ratio of coupler can adjust the transmission curve to improve the equalization range. It has been shown theoretically that compared with earlier PE-NOLM, about 1.6 dB of equalization power reduction and about 2.2 dB of equalization demonstrated that the output power fluctuation peak power range is 4.5 dBm （15.6-20.1 dBm）.

关键词： couplings Phase shift Power transmission

Discrete elliptic solitons in two-dimensional waveguide arrays

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Chinese Optics Letters 2005年第4期3卷 227-229页

作者：叶芳伟董亮伟王建东蔡田李永平 Department of PhysicsUniversity of Science and Technology of China Hefei 230026

The fundamental properties of discrete elliptic solitons (DESs) in the two-dimensional waveguide arrays were studied. The DESs show nontrivial spatial structures in their parameters space due to the introduction of the new freedom of ellipticity, and their stability is closely linked to their propagation directions in the transverse plane.

关键词： Arrays couplings Lattice constants Nonlinear equations Stability Two dimensional Wave propagation Waveguides

Tunable CW Tm,Ho:YLF laser at 2μm

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Chinese Optics Letters 2006年第8期4卷 470-471页

作者：李玉峰姚宝权王振国王月珠鞠有伦 Laboratory of Tunable Laser Technology Harbin Institute of Technology

A tunable continuous wave （CW） low temperature operating Tm （6 at.-%）,Ho （0.6 at.-%）：YLF laser pumped by fiber-coupled diode laser is reported. The maximum output power is 4.16 W at 2073 nm by use of 30% output coupling, the slope efficiency is 33%. A tuning range from 2049 to 2081 nm is achieved with a birefringent filter （BF）. The factors that contribute to the output power and tuning range are discussed.

关键词： Birefringence couplings Optical filters Semiconductor lasers

Diode-pumped CW Tm:GdVO_4 laser at 1.9 μm

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Chinese Optics Letters 2006年第3期4卷 175-176页

作者：李玉峰姚宝权王月珠 Laboratory of Tunable Laser Technology Harbin Institute of Technology Harbin 150001

A high power cryogenic cooling Tin-doped （2%） GdVO4 laser double-end-pumped by fiber-coupled-diode： with the center wavelength of 804.5 nm at 21 ℃ is reported. The highest continuous-wave （CW） power of 2.35 W at 1903 nm is attained at pump power of 24 W. The slope efficiency is 12.5% and the tt, reshoht is 3.2 W. Single- and double-end-pumped types are investigated.

关键词： Cooling couplings Cryogenics Diodes Efficiency Fibers Gadolinium High power lasers Pumping (laser) Rare earth additions Thulium

Application of two-mode fiber in voltage sensor

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Chinese Optics Letters 2006年第11期4卷 631-632页

作者：王河林毕卫红杨爱军刘丰 College of Information and Engineering Yanshan University Qinhuangdao 066004 College of Mathematics and Information Science Hebei Normal University Shijiazhuang 050016

A new mode patter＇s demodulation technique is put forward. Researches of experiment and theory show that the coupling efficiency of two kinds of different fibers depends on the relative offset between the two fibers when the core diameter of the information pick-up fiber is a little smaller than the major semi-axes of the elliptical-core two-mode fiber. Especially, when the relative offset δ≈1, fusing splice coupling efficiency reaches peak value. Furthermore, based on the new demodulation scheme, the sine voltage signal applied on the piezoelectric lead zirconate titanate （PZT） is obtained and the detection precision of the system is within ±0.2% when the voltage changes between 0.1 and 20 V. OCIS codes： 060.2370, 070.5010, 070.6020, 120.4570.

关键词： couplings Demodulation Electric potential Sensors

3.6-W cryogenic Tm,Ho:YLF laser pumped by fiber-coupled diodes module

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Chinese Optics Letters 2005年第4期3卷 210-211页

作者：姚宝权鞠有伦王月珠贺万骏李玉峰 National Key Laboratory of Tunable Laser TechnologyHarbin Institute of Technology Harbin 150001

In this paper, we report a high power cryogenic cooling Tm(6 at.-%),Ho(0.5 at.-%):YLF laser end-pumped by a 19-fiber-coupled-diodes module with the central wavelength of 792 nm at 20°. The highest continuous-wave power of 3.6 W at 2.051 μm is attained under pumping power of 13.6 W, corresponding to optical-optical conversion efficiency of 26%, and the slope efficiency is larger than 30%. The threshold power is only about 0.16 W because of the long lifetime, large effective emission cross section, and low re-absorption in Tm,Ho:YLF crystal.

关键词： couplings Cryogenics Diodes Doping (additives) Holmium Laser applications Optical fibers Pumping (laser) Thulium

Estimation of Spectral Gap for Markov Chains

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Acta Mathematica Sinica,English Series 1996年第4期12卷 337-360页

作者： Chen Mufa Department of Mathematics Beijing Normal University Beijing, 100875 China Department of Mathematics Beijing Normal University Beijing China

The study of the convergent rate (spectra gap) in the L^2-sense is motivated from several different fields: probability statistics, mathematical physics, computer science and so on and it is now an artive research topic. Based on a new approach (the coupling technique) introduced in [7] for the estimate of the convergent rate and as a continuation of [4],[5],[7-9],[23] and [24], this paper studies the estimate of the rate for time-continuous Markov chains. Two variational formulas for the rate are presented here for the first time for birth-death processes. For diffusions, similar results are presented in an accompany paper [10]. The new formulas enable us to recover or improve the main known results. The connection between the sharp estimate and the corresponding eigenfunction is explored and illustrated by various examples. A previous result on optimal Markovian couplings is also extended in the paper.

关键词： Markov chains Spectral gap couplings