Drift and Diffusion in Periodically Driven Renewal Processes

We consider the drift and diffusion properties of periodically driven renewal processes. These processes are defined by a periodically time dependent waiting time distribution, which governs the interval between subsequent events. We show that the growth of the cumulants of the number of events is asymptotically periodic and develop a theory which relates these periodic growth coefficients to the waiting time distribution defining the periodic renewal process. The first two coefficients, which are the mean frequency and effective diffusion coefficient of the number of events are considered in greater detail. They may be used to quantify stochastic synchronization.     

周期极化LiNbO3晶体中电极布置对反转畴扩张的影响

利用外加电场极化的方法,分别研究了三种不同方式布置的极化电极对C向切割LiNbO_{3< /sub>晶体极化反转畴扩张的影响.实验结果表明在相同极化条件下，当极化电极长度方向与六边 形反转畴一对边呈90°和0°角时，极化扩张速度分别为0.089μm/ms和0.011μm/ms.实验结果揭示，为了有效地控制极化占空比，在制备一维准相位匹配LiNbO3晶体时应 避免极化电极与六边形反转畴壁中一对边呈90°的情况. 关键词： 周期极化 极化扩张 准相位匹配}     

准相位匹配扇形光栅铌酸锂光波导倍频绿光输出

采用外加电场极化方式对具有扇形光栅的 0 .5mm厚Z切铌酸锂晶体进行极化反转 ,制成了退火质子交换光波导。极化反转周期为 5 .8μm～ 6 .2 μm ,采用Nd∶YAG激光器输出的 1.0 6 4 μm连续激光为基频光波 ,实现了0 .5 32 μm倍频绿光输出 ,相互作用长度为 4mm ,耦入波导的基频光波功率为 10mW ,获得了 2 0 μW的绿色倍频光输出 ,归一化转换效率为 12 5 % (W·cm2 )。     

To the Theory of Quasi-Phase-Matched Parametric Amplification in Periodically Poled Optical Nonlinear Crystals

A theory of optical parametric amplification at high-frequency pumping in crystals with regular space modulation of the sign of the nonlinear coupling coefficient of interacting waves is developed. By applying the matrix method, the theory is based on a step-by-step approach. It is shown that, in the case where the pumping intensity is less than some critical value, the spatial dynamics of the signal intensity inside a separate layer with a constant nonlinear coefficient has an oscillatory behavior and the change of the signal intensity from layer to layer is defined, in general, by a polynomial dependence. The same law is valid for the change of variance of the signal's quadrature components. With a large number of layers, these dependences can be reduced to the well-known ones for homogeneous nonlinear optical crystals.     

光孤子传输模型及其应用

从周期性集中放大系统孤子传输的基本方程出发，建立了比平均孤子模型适用范围更广、更精确的传输模型，运用微扰方法对孤子到达时间抖动作了研究，并与平均孤子模型给出的结果作了比较。     

Five‐cycle pulses near λ = 3 μm produced in a subharmonic optical parametric oscillator via fine dispersion management

Five‐cycle (50 fs) mid‐IR pulses at 80‐MHz repetition rate are produced using a degenerate (subharmonic) optical parametric oscillator (OPO), synchronously pumped by an ultrafast 1560‐nm fiber laser. The effects of cavity dispersion and the length of a periodically poled lithium niobate (PPLN) gain element on the output spectrum and pulse duration are investigated by taking advantage of a very broad (∼ 1000 cm⁻¹) gain bandwidth near the 3.1‐μm OPO degeneracy point. A new method of assessing the total OPO group delay dispersion across its entire spectrum is proposed, based on measuring spectral signatures of trace amounts of molecular gases injected into the OPO cavity.     

基于周期性极化铌酸锂倍频的光学电压传感方法

从光学电压传感器的原理出发,在周期性极化铌酸锂(PPLN)晶体倍频(SHG)效应基础上,提出了一种新的光学电压传感方法,讨论了周期性极化铌酸锂不同长度、不同占空比对该电压传感性能的影响,并给出了图示。结果表明：当周期性极化铌酸锂长度一定,在占空比为0．3或0．7时,灵敏度最高;在占空比趋于0．5,但不等于0．5时,电压测量范围最大;长度增加,灵敏度提高,但测量范围变小。这些结果为制作此类传感器提供了可靠的理论依据。     

一类周期线性时变切换系统的稳定性

讨论一类包含一组线性时变子系统和一个周期切换信号的切换系统的稳定性.在系统满足一定条件的情况下,利用Floquet定理,给出了周期线性时变切换系统指数稳定的充分必要条件.     

铌酸锂晶体紫外激光诱导畴反转实验研究

报道了在铌酸锂晶体中实现紫外激光诱导畴反转的实验。在一定外加均匀电场下,铌酸锂晶体中通过波长365nm的紫外激光,由于紫外光的照射降低了矫顽电场只在通光区实现畴反转。研究表明,该方案可用于周期性极化铌酸锂的制备,并有望成为制作精细周期性畴结构的有效技术方案。     

基于周期极化KTiOPO$lt;sub$gt;4$lt;/sub$gt;晶体的高亮度纠缠源研制

量子纠缠是量子信息领域的核心资源,目前利用β型硼酸钡（BBO）晶体参量下转换制备的纠缠光子对的亮度较低,它直接制约了量子通信的最远距离,已无法满足星地实用化量子通信的发展需求.利用周期极化KTiOPO₄晶体,采用准相位匹配技术设计产生了一种后选择的纠缠源,测得的符合计数达到了16×10³s^-1 mW^-1,极化对比度达到27∶1,在亮度上比基于BBO的量子纠缠光源提高了一个数量级以上.这一高亮度的纠缠源可以广泛应用于量子密钥分发、量子隐形传态以及量子计算等新兴量子信息领域,为实现全球化量子通信提供了有力的保障. 关键词： 纠缠态 准相位匹配 4晶体')" href="#">周期极化KTiOPO₄晶体