开放的三能级系统中无粒子数反转激光的瞬态分析

本文分析了在一个开放的简单三能级系统中的无粒子数反转激光的瞬态性质,研究了这个系统从瞬态无粒子数反转激光到定态无粒子数反转激光的演化.从原子相干和布居数分布的时间演化,我们阐明了系统产生无粒子数反转激光增益的机制.     

原子初态对双频场作用的三能级原子动力学行为的影响

求得双频场作用下串接型三能级原子系统哈密顿量的本征函数和本征值。从而得到原子初态任意、偏调任意情况下原子随时间的演化。给出了原子布居数和原子极化与初始原子状态的关系和与偏调的关系公式。研究了原子动力学行为与入射光强、偏调、二入射光场的相对相位以及原子初始状态的关系。揭示了原子初始相位和光场相位对原子光相互作用大小的影响。当相对相位为π时,原子与场耦合最小,在特殊情况下原子与场耦合为零,即原子与场无相互作用。     

相干量子拍频三能级系统的稳态脉冲

本文研究光脉冲与初始处在叠加态的量子拍频三能级系统相互作用的动力学过程，导出稳态脉冲的波形函数，并讨论稳态脉冲波形与初始态的关系。     

相干量子拍频三能级系统的稳态脉冲

本文研究光脉冲与初始处在叠加态的量子拍频三能级系统相互作用的动力学过程，导出稳态脉冲的波形函数，并讨论稳态光脉冲波形与初始态的关系．     

单模真空场与型三能级原子相互作用系统中光场的相位特性

运用Pegg－Barnett理论，得到了初始处于真空态的单模场与型三能级原子耦合系统中光场的相位特性，着重讨论了原子相干性和单光子失谐量对相位的时间演化和统计性质的影响．     

利用V型三能级原子玻色-爱因斯坦凝聚体与双模压缩光场相互作用制备双模原子激光

研究了Ⅴ型三能级原子的玻色-爱因斯坦凝聚体(BEC)与双模压缩相干态光场相互作用系统的量子动力学行为，分析了利用Ⅴ型三能级原子BEC与双模压缩相干态光场相互作用制备双模原子激光的可能性。结果表明：在光场作用下，Ⅴ型三能级原子BEC中被激发到非俘获态的原子，仍保持其相干态的特性，从而在理论上证明了利用Ⅴ型三能级原子BEC与双模压缩相干态光场相互作用可以产生双模原子激光。     

非马尔可夫玻色库对单个三能级原子量子隐形传态的影响

利用量子态扩散方法研究了耦合到多模非马尔可夫玻色库的单个三能级原子的量子隐形传态保真度的动力学演化特性,并分析了不同参数对保真度的影响.结果 表明,当三能级原子与强非马尔可夫环境耦合并且三能级原子初始状态处于激发态或亚稳态时,三能级原子量子隐形传态保真度拥有较长的弛豫时间及较好的鲁棒性.此外,利用外加磁场控制三能级原子的量子隐形传态,可以使得三能级原子拥有鲁棒性较好的保真度.     

三能级原子同时存在辐射和吸收时的量子相干性

量子位和环境的相互作用,将引起量子位能量耗散或相对位相改变,最终导致量子位由相干叠加态退化为混合态或纯态,这种现象被称为量子消相干.针对三能级原子同时存在辐射和吸收时的情况,基于量子力学和Kraus算子理论,利用约化密度矩阵方法,分析了三能级原子密度矩阵元的演化规律,从而研究该系统的量子相干特性.结果表明:初态处于相干叠加态的三能级原子,由于辐射和吸收,可能演化成相干叠加态、未完全混合态、完全混合态、纯态.     

三能级系统中多波混频过程的缀饰态处理

我们采用全量子力学方法推导了在V型三能级系统中存在两个强入射光场时的缀饰态,利用缀饰变换求出了相应于此系统的密度矩阵运动方程的稳态解及增益表达式,讨论了增益表达式随失谐量、两个入射光场强度等参量的变化关系,利用这一结果,对三能级系统中的多波混频过程作了讨论。     

准三能级系统自由感应衰变(FID)中的干涉

本文从三能级布洛赫方程出发,导出了用斯塔克开关的有限脉冲预制下准三能级系统自由感应衰变的宏观极化公式     

Markovian场中级联三能级系统的五阶非线性效应

运用高阶关联函数理论研究了级联三能系统Markovian场的五阶非线性效应(FPBCTMS)。通过对Markovian场混沌场模型、相散场模型及实高斯场模型的分析,得到了五阶极化拍频信号的强度在Markovian场中随时间变化的规律。讨论了Markovian场中幅度、相位涨落对测量原子能级分裂精度的影响。     

Heavy-hole and light-hole quantum beats in the polarization stateof coherent emission from quantum wells

Dual-channel spectral interferometry is used to measure the vectorial dynamics of the the four-wave-mixing signal from a GaAs-AlGaAs multiple quantum well when both heavy-and light-hole excitons are excited. The ellipticity, the orientation, and the sense of rotation of the polarization ellipse associated with this emission are observed to oscillate dramatically at the heavy-hole-light-hole quantum beat frequency. The qualitative nature of the beating can be described by a simple model based on the density matrix equations for two independent three-level systems without the inclusion of many body effects; however, these beats are superposed on a polarization that is dominated by many-body effects     

开放的三能级系统中无粒子数反转激光的非线性理论

本文给出了开放的简单三能级原子系统无粒子数反转激光的非线性理论 ,研究了探测场和驱动场的 Rabi频率、原子注入速率、原子退出速率及能级间衰变速率对系统无粒子数反转激光增益、布居数差以及相干项的影响 ,讨论了无粒子数反转激光增益的稳定性     

Complex finite-element method applied to the analysis of opticalwaveguide amplifiers

A complex finite-element method and a three-level model for erbium ions are applied to obtain gain and propagation constants for erbium-doped waveguide amplifiers (EDWA's). The complex refractive index profile includes the effect of the dopant polarization induced by the pump field. The method allows to consider arbitrary dopant density profile as well as the modal structure of the pump field. For different waveguide geometries we obtain gain curves as function of pump intensity as well as slight variations in the modal propagation constants. The threshold pump power is shown to be a function of the waveguide geometry, which agrees qualitatively with experimental results,     

随机偏振光学加密算法的加密及解密特性分析

为了阐明随机偏振模板在光学加密系统中的作用,采用理论分析与数值模拟相结合的方法,进行了在双随机偏振光学加密系统中偏振模板的特性参量对系统加密效果及解密误差的影响的理论和仿真分析;对比了随机相位模板和随机偏振模板对光学加密系统加密效果及解密误差的不同影响。结果表明,加密方面,采用随机偏振模板或随机相位模板均能生成平稳白噪声分布的密文,但是偏振模板有两个构造参量,密钥空间更大;解密方面,系统对相位模板以及偏振模板中不同参量的解密敏感性有一定差异,随机偏振加密具有更高的应用灵活性。该结果对理解相位及偏振编码光学加密系统的本质属性及设计安全性更高的光学加密系统有一定的帮助。     

啁啾Gauss飞秒脉冲驱动三能级系统的超快布居转移

利用不含旋波近似(RWA)的Schrdinger方程的数值解,研究了线性极化的啁啾Gauss飞秒激光脉冲驱动Ξ型三能级原子系统的超快粒子布居转移。研究结果表明,粒子布居转移主要决定于驱动激光场的Rabi频率(强度)和啁啾率,两跃迁偶极距的比值和脉宽对粒子布居转移也有明显的影响。通过适当选择以上参量的取值,可以实现粒子布居99.6%的转移。     

Optically pumped CW dimer lasers

Bound-bound electronic transitions in simple molecules are generally suited to realize efficient multiline laser oscillation in the visible and ultraviolet spectral region. By means of optical excitation with argon and krypton lasers, CW laser oscillation could be obtained for various homonuclear diatomic (dimer) molecules such as Li2, Na2, K2, Bi2, S2, Te2, and I2, with emission of several hundred laser lines in the spectral range of about 400-1350 nm. The principles of these lasers and the general dependence of threshold and output power on temperature, pressure, length of vapor zone, and some other parameters is discussed. To achieve satisfactory CW operation, low quenching losses for the upper laser level population and a sufficiently fast relaxation of the population of the lower laser level are necessary. Under optimum operation conditions, efficiencies up to 15 percent, multiline output powers up to 400 mW, and single line-single frequency output powers up to 200 mW were achieved. These dimer lasers are three-level laser systems. In case of coherent optical excitation, two-photon or Raman-type processes contribute to the amplification process. Due to these mechanisms the forward direction is strongly favored and in a ring laser system spontaneous unidirectional oscillation is obtained. By means of a suitable three-level model, analytical and numerical calculations of gain profiles are performed and compared with experiments. These optically pumped molecular lasers are suited for various spectroscopic and kinetic investigations, for frequency standards or as simple and efficient systems to convert pump laser radiation into other spectral regions.     

三电平PWM整流器的SVPWM算法研究

本文提出了一种三电平PWM整流器的SVPWM算法。这种算法是将参考电压矢量转换到60°坐标系,然后再经过简单的算术运算即可计算出各基本矢量作用时间,避免了大量三角函数的运算。通过Matlab建立了三相三电平PWM整流器的电压定向控制系统的仿真模型,对该算法进行了仿真研究,结果验证了该算法的有效性。     

Three-Phase Photovoltaic System With Three-Level Boosting MPPT Control

This paper proposes a three-phase photovoltaic (PV) system with three-level boosting maximum power point tracking (MPPT) control. A simple MPPT control using a power hysteresis tracks the maximum power point (MPP), giving direct duty control for the three-level boost converter. The three-level boost converter reduces the reverse recovery losses of the diodes. Also, a weighted-error proportional and integral (PI) controller is suggested to control the dc link voltage faster. All algorithms and controllers were implemented on a single-chip microprocessor. Experimental results obtained on a 10-kW prototype show high performance, such as an MPPT efficiency (MPPT effectiveness) of 99.6%, a near-unity power factor, and a power conversion efficiency of 96.2%.