Generation of picoseconds stimulated Raman scattering in a BaWO4 crystal and frequency up-conversion by difference-frequency generation in BBO

The characters of stimulated Raman scattering of BaWO₄ crystal excited by a picoseconds laser at 1064 nm are studied based on optical parametric amplification (OPA). Up to six-order Stokes components and five-order anti-Stokes components are observed. The SRS components are amplified by an OPA and the wavelength tunable range from 411 to 2594 nm is achieved with a maximum conversion efficiency of 38% using the OPA stage.     

Optical properties of the Au–Ag alloy nanowire coated with an anisotropic shell

The optical properties of the Au–Ag alloy nanowire coated with a cylindrical shell with radial dielectric anisotropy are investigated based on quasistatic theory. Numerical results show that the surface plasmon resonance (SPR) peak is redshifted with increasing the component ratio of Au in the alloy, while the intensity of extinction section at the SPR increases with increasing the component ratio of Ag in the alloy. In addition, as the extent of anisotropy of the shell increases, the extinction section at SPR wavelength decreases and the SPR wavelength is redshifted, but compared with the isotropic shell consisting of comparable dielectric constant materials, the SPR has a distinct blueshift for anisotropic shell. We also find that the field enhancement can be completely concentrated inside the anisotropic shell and the electromagnetic transparency can be exhibited.     

Slowly rotating neutron stars and hadronic stars in the chiral SU(3) quark mean-field model

The equations of state for neutron matter, strange and non-strange hadronic matter in the chiral SU(3) quark mean-field model are applied in the study of slowly rotating neutron stars and hadronic stars. The radius, mass, moment of inertia, and other physical quantities are carefully examined. The effect of the nucleon crust for the strange hadronic star is exhibited. Our results show that the rotation can increase the maximum mass of compact stars significantly. For a big enough mass of pulsars which cannot be explained as strange hadronic stars, theoretical approaches to increase the maximum mass are addressed.     

Conductively cooled 250-Hz single frequency Nd：YAG laser

A conductively cooled, laser diode （LD） end-pumped, injection-seeded single frequency Nd：YAG laser is designed and impleinented. The laser utilizes Nd：YAG rod as gain medium and compact dual-endpumping arrangement using two fiber-coupled LDs with a maximum output of 150 W. The optimized ramp-fire technique is applied to build reliable single longitudinal mode oscillating. The laser is capable of producing a 10-raJ Q-switched pulse with 13-ns pulse width at 1064 nm at a pulse repetition rate of 250 Hz. The output beam qualities M2 of approximately 1.19 and 1.22 in horizontal and vertical directions are detected, respectively.     

离子注入ZnO薄膜的拉曼光谱研究

室温下,用80 keV N⁺和400 keV Xe⁺离子注入ZnO薄膜,注入剂量分别为5.0×10¹⁴—1.0×10¹⁷/cm²和2.0×10¹⁴—5.0×10¹⁵/cm².利用拉曼散射技术对注入前后的ZnO薄膜进行光谱测量和分析,研究了样品的拉曼光谱随离子注入剂量的变化规律.实验结果发现,未进行离子注入的样品在99,435 cm<     

LD双端泵浦U型腔Nd∶YVO4激光器稳定性研究

 基于传输矩阵理论,针对端面抽运的U型腔Nd∶YVO4固体激光器谐振腔的稳定性进行了理论分析和数值模拟。通过改变“U”型腔各个臂长得到不同腔臂长条件下谐振腔的稳区范围和晶体中心处的振荡光斑,比较稳区范围以及振荡光斑,找出一组腔参数值使谐振腔能够在较高泵浦功率下保持稳定且振荡光斑足够理想。按照确定的腔参数值进行了具体实验,实验结果表明:按选定参数设计的谐振腔在调Q重复频率为100kHz,泵浦功率为60W时,激光器能够稳定工作并输出21.6W的高重频激光,谐振腔稳区范围的变化规律与理论计算基本吻合。     

Euler-Voigt方程组的全局适定性

利用Galerkin逼近研究得到具Dirichlet边界条件的Euler-Voigt方程的弱解以及强解全局存在性,在此基础上也得到了唯一性与连续依赖性和高阶正则性结果.     

Exact solutions for a Wick-type stochastic 2D KdV equation

A Wick-type stochastic 2D KdV equation with variable coefficients is investigated. The exact solutions are showed by using the homogeneous balance principle and the Herimite transform in the white noise space.     

多输入多输出不确定非线性系统的输出反馈自适应机动控制

输出机动控制问题通常由几何任务和动态任务两部分组成.对具有参数不确定性的多输入多输出非线性系统,研究了其基于输出反馈的自适应机动控制问题.通过引入滤波器和观测器来实现对不可量测系统状态的虚拟估计.利用向量形式的Backstepping反推方法,构造出了输出反馈自适应控制器,并给出了三种路径变量自适应律设计方案.所提出的控制方案保证了闭环系统的全局渐近稳定性,使得系统同时完成几何任务和动态任务.最后的仿真结果验证了本方法的有效性. 关键词： 输出反馈 非线性系统 输出机动 反推