非周期多层膜Kirkpatrick-Baez显微镜成像

从光线传播的角度分析了非周期多层膜Kirkpatrick-Baez(KB)显微镜的成像性能,并与单层膜KB显微镜、周期多层膜KB显微镜进行了对比。与单层膜KB显微镜相比,多层膜KB显微镜提高了工作掠入射角度,在同样分辨力和集光效率要求下具有更大的视场。周期多层膜KB显微镜的反射率和能量分辨本领高于非周期多层膜KB显微镜,但非周期多层膜元件具有较大的角度带宽和均一的反射率,克服了周期多层膜KB显微镜视场范围和像场均匀性的不足。在此基础上,制备了中心角度1.133 0°的非周期多层膜反射镜元件,以8 keV能量的X射线光管为背光源进行了KB显微镜成像实验,实验结果与理论分析一致。     

Modeling and optimization of non-periodic grating couplers

The higher degree of freedom available for non-periodic gratings (as compared with their periodic counterparts) is investigated. These non-periodic structures may be employed to design novel light couplers with increased functionality. Optimizing such devices requires a complex search in a huge parameter space. The success in the solution of this task depends on the availability of a fast forward solver and a reliable search algorithm. Here, a fast forward solver based on the multiple multipole (MMP) method together with a near-to-far field transformation and a multiple scattering calculation is presented. Thanks to the efficiency of our approach, non-periodic gratings are evaluated with a speed comparable to commonly used periodic grating approximations. This allows our solver to be combined with a heuristic global search scheme, namely an evolutionary algorithm. The procedure is demonstrated with the optimization of a non-periodic grating output coupler that suppresses an unwanted second diffracted order.     

Miniaturisation of High-NA Objectives for Optical Recording

High-NA objectives for optical recording have received a lot of attention due to the investigation of the Blu-ray Disc system. More recently to enable optical storage in portable devices, small building height optical drives have been studied requiring miniaturised high-NA objectives. Previously reported miniaturised objectives consist of two elements and are, therefore, less suited for mass production. In this paper the design and manufacturing of a miniaturised single element high-NA objective is reported. Furthermore, with the aid of non-periodic phase structures the tolerances of the objectives can be further expanded.     

Extinction,periodicity and multistability in a Ricker model of stage-structured populations

We study the dynamics of a second-order difference equation that is derived from a planar Ricker model of two-stage (adult-juvenile) biological populations. We obtain sufficient conditions for global convergence to zero in the non-autonomous case yielding general conditions for extinction in the biological context. We also study the dynamics of an autonomous special case of the equation that generates multistable periodic and non-periodic orbits in the positive quadrant of the plane.     

应用于VCSEL的宽角度光束控制非周期性高对比度光栅阵列

设计了特定周期和占空比的非周期性高对比度光栅来实现光束的波前相位控制,进而实现对光束的多角度控制.在研究中,采用有限时域差分法模拟了特殊排列的非周期高对比度光栅,并获得了-10.644°,-21.176°,-28.307°,10.644°,21.447°和28.418°的光束控制角度.基于这种多角度控制的高对比度光栅阵列,提出了一种具有多角度光束控制的VCSEL光源,这种尺寸极小的宽角发射VCSEL光源系统能使激光雷达系统的结构紧凑化和微型化.     

非周期多层膜Kirkpatrick-Baez显微镜成像

从光线传播的角度分析了非周期多层膜Kirkpatrick-Baez（KB）显微镜的成像性能,并与单层膜KB显微镜、周期多层膜KB显微镜进行了对比。与单层膜KB显微镜相比,多层膜KB显微镜提高了工作掠入射角度,在同样分辨力和集光效率要求下具有更大的视场。周期多层膜KB显微镜的反射率和能量分辨本领高于非周期多层膜KB显微镜,但非周期多层膜元件具有较大的角度带宽和均一的反射率,克服了周期多层膜KB显微镜视场范围和像场均匀性的不足。在此基础上,制备了中心角度1.133 0°的非周期多层膜反射镜元件,以8 keV能量的X射线光管为背光源进行了KB显微镜成像实验,实验结果与理论分析一致。     

Homogenization of the Maxwell Equations: Case II. Nonlinear Conductivity

The Maxwell equations with uniformly monotone nonlinear electric conductivity in a heterogeneous medium, which may be non-periodic, are homogenized by two-scale convergence. We introduce a new set of function spaces appropriate for the nonlinear Maxwell system. New compactness results, of two-scale type, are proved for these function spaces. We prove existence of a unique solution for the heterogeneous system as well as for the homogenized system. We also prove that the solutions of the heterogeneous system converge weakly to the solution of the homogenized system. Furthermore, we prove corrector results, important for numerical implementations.     

Non-periodic motions of a Jeffcott rotor with non-linear elastic restoring forces

The conditions that give rise to non-periodic motions of a Jeffcott rotor in the presence of non-linear elastic restoring forces are examined. It is well known that non-periodic behaviours that characterise the dynamics of a rotor are fundamentally a consequence of two aspects: the non-linearity of the hydrodynamic forces in the lubricated bearings of the supports and the non-linearity that affects the elastic restoring forces in the shaft of the rotor. In the present research the analysis was restricted to the influence of the non-linearity that characterises the elastic restoring forces in the shaft, adopting a system that was selected the simplest as possible. This system was represented by a Jeffcott rotor with a shaft of mass that was negligible respect to the one of the disk, and supported with ball bearings. In order to check in a straightforward manner the non-linearity of the system and to confirm the results obtained through theoretical analysis, an investigation was carried out using an experimental model consisting of a rotating disk fitted in the middle of a piano wire pulled taut at its ends but leaving the tension adjustable. The adopted length/diameter ratio was high enough to assume the wire itself was perfectly flexible while its mass was negligible compared to that of the disk. Under such hypotheses the motion of the disk centre can be expressed by means of two ordinary, non-linear and coupled differential equations. The conditions that make the above motion non-periodic or chaotic were found through numerical integration of the equations of motion. A number of numerical trials were carried out using a 4th order Runge-Kutta routine with adaptive stepsize control. This procedure made it possible to plot the trajectories of the disk centre and the phase diagrams of the component motions, taken along two orthogonal coordinate axes, with their projections of the Poincaré sections. On the basis of the theoretical results obtained, the conditions that give rise to non-periodic motions of the experimental rotor were identified.     

非周期长码直扩信号的伪随机码盲估计

研究了m序列三阶相关函数特性,证明了不同周期m序列三阶相关函数存在共同峰,推导得到共同峰的特性以及共同峰坐标与m序列本原多项式之间对应关系,基于上述理论提出了非合作通信下的非周期长码直扩信号伪随机码估计方法。加性高斯白噪声下的仿真结果表明,本方法仅需1/4倍长码周期长度信号和4 dB信噪比,估计非周期长码直扩信号的扩频码和长扰码的正确概率就可达到99%以上。     

Quasi-periodic and Non-periodic Waves in (2+1)-Dimensional Nonlinear Systems

New exact quasi-periodic and non-periodic solutions for the (2 1)-dimensional nonlinear systems are studied by means of the multi-linear variable separation approach (MLVSA) and the Jacobi elliptic functions with the space-time-dependent modulus. Though the result is valid for all the MLVSA solvable models, it is explicitly shown for the long-wave and short-wave interaction model.