Solitons and intrinsic localized modes in a one-dimensional antiferromagnetic chain

By use of the Hartree approximation and the method of multiple scales, we investigate quantum solitons and intrinsic localized modes in a one-dimensional antiferromagnetic chain. It is shown that there exist solitons of two different quantum frequency bands: i.e., magnetic optical solitons and acoustic solitons. At the boundary of the Brillouin zone, these solitons become quantum intrinsic localized modes: their quantum eigenfrequencies are below the bottom of the harmonic optical frequency band and above the top of the harmonic acoustic frequency band.     

基于模糊神经网络的自适应PID控制器

提出了一种应用于自适应PID控制器的神经网络与模糊控制相结合的算法,该算法可以有效地解决普通PID控制器依赖于对象的数学模型的缺点,可实现控制系统的在线自适应调整,可满足实时控制的要求。仿真结果表明,基于模糊神经网络整定的PID控制器具有较好的自学习和自适应性,具有较快的响应速度。     

Nonlinear polarization rotation-induced pulse shaping in a stretched-pulse ytterbium-doped fiber laser

We report on controllable pulse shaping in a Yb-doped stretched-pulse fiber laser followed by a high-power chirped pulse amplifier. We demonstrate that the pulses after an extra-cavity grating pair change their intensity profile from Lorentz to Gaussian and then to sech2 shapes by adjusting the intra-cavity polarization through a quarter-wave plate inside the fiber laser cavity. The laser pulses with different pulse shapes exhibit pulse-to-pulse amplitude fluctuation of -- 1.02%, while the sech2-shaped pulse train is provided with a more stable free-running repetition rate as a result of the stronger self-phase modulation in the fiber laser cavity than Lorentz- and Gaussian-shaped pulse trains.     

理论研究电流注入对垂直腔面发射激光器多横模行为的影响

从包含时空变量的速率方程出发,针对弱折射率导引垂直腔面发射激光器(VCSELs),利用空间积分法分析了典型电注入参数对VCSELs多横模行为的影响,在不降低模型准确性的前提下提高了仿真效率。仿真结果表明,注入盘孔径和注入环越小、注入强度越低以及电流扩散越弱时,VCSELs更易实现单横模工作;反之,VCSELs高阶横模开始出现并呈现较强的模式竞争,引发了载流子空间烧孔效应,并导致基模强度降低。进一步得出,在环形注入方式下,高阶模式更容易出现且彼此间的竞争较盘形注入时强。     

基于边缘估计的自适应各向异性扩散的医学超声图像降噪算法

提出了一种针对医学超声图像的自适应各向异性扩散算法;该算法充分利用图像本身的边缘信息以及图像水平和垂直方向梯度的差异,用GHAD方法在两个方向设置不同的梯度门限,避免了传统的常数及单一梯度门限带来的鲁棒性差等问题;改进的扩散系数改善了传统扩散系数收敛过快及边界平滑的问题;经过多组仿真实验,综合峰值信噪比(PSNR)和边缘保持度(FOM)等指标,表明该算法相比同类算法有更好的降噪和边缘保持效果。     

Intracavity phase interferometry: frequency combs sensor inside a laser cavity

In traditional interferometric measurements, a physical quantity that changes the phase of a resonator is monitored through a change of its transmission. Interferometry inside a laser exploits the ultimate Q‐factor of that resonator, and converts the phase to be measured into a frequency. A mode‐locked laser with two intracavity pulses emits two frequency combs of the same repetition rate. The quantity to be measured (a sub‐nano displacement, a nonlinear index, an acceleration or rotation, a magnetic or electric field) produces a minute phase change ( rad) in one of the two intracavity pulses, which is converted into a frequency, measured by beating the two pulse trains emitted by the laser. This paper presents methods of operating mode‐locked lasers in which two independent pulses circulate, producing two frequency combs of the same repetition rate. Various examples of physical quantities that can be measured through this technique are presented.     

Laser diode pumped LNYAB self-frequency-doubling lasers

The LNYAB self-doubling laser pumped by (LD) has been developed for the first time. The properties of the lasers are much better than those of NYAB self-doubling lasers pumped by LD. The LNYAB self-doubling laser pumped by LD can be operated in TEM_(00) mode with threshold pumping power of 3.6mW which is lower than that of LD pumped NYAB self-doubling lasers by 74%. The output power is 29mW at 0.531μm in green region with optical-to-optical efficiency of 4.8% which is higher than that of NYAB self-doubling laser by 20%.     

局域模、简正模的李代数表示

本文介绍李代数的非简谐振子的表示。运用这样的表示可以方便地讨论局域模与简正模之关系及其半经典图象。     

二次型复折射率介质中的光导现象

本文讨论了n(z,r)=n_0(z)+n_2(z)r~2/r_e~2型复折射率介质中的激光传输问题,给出了激光传输参数(光束半径和波阵面曲率)的演化公式。指出只要存在一定大小的n_(21),在传输过一段特征距离z_c之后,将出现完全光导(即自相似模的传播),而且自相似模是激光体系的特征模式。其传输参数只与n_2有关,而与激光初始参数无关。自相似模必定是高斯球面波,而不是高斯平面波。     

Synchronization between two different noise-perturbed chaotic systems with unknown parameters

In this paper, a general method of synchronizing noise-perturbed chaotic systems with unknown parameters is proposed. Based on the LaSalle-type invariance principle for stochastic differential equations and by employing a combination of feedback control and adaptive control, some sufficient conditions of chaos synchronization between these noise-perturbed systems with unknown parameters are established. The model used in the research is the chaotic system, but the method is also applicable to the hyperchaotic systems. Unified system and noise-perturbed RSssler system, hyperchaotic Chen system and nolse-perturbed hyperchaotic RSssler system are taken for illustrative examples to demonstrate this technique.[第一段]