A novel method to design flexible URAs

Aperture patterns play a vital role in coded aperture imaging ( CAI) applications. In recent years, many approaches were presented to design optimum or near-optimum aperture patterns. Uniformly redundant arrays (URAs) are, undoubtedly, the most successful for constant sidelobe of their periodic autocorrelation function. Unfortunately, the existing methods can only be used to design URAs with a limited number of array sizes and fixed autocorrelation sidelobe-to-peak ratios. In this paper, we present a novel method to design more flexible URAs. Our approach is based on a searching program driven by DIRECT, a global optimization algorithm. We transform the design question to a mathematical model, based on the DIRECT algorithm, which is advantageous for computer implementation. By changing determinative conditions, we obtain two kinds of types of URAs, including the filled URAs which can be constructed by existing methods and the sparse URAs which have never been mentioned by other authors as far as we know. Finally, we carry out an experiment to demonstrate the imaging performance of the sparse URAs.

Weighted least-squares phase unwrapping algorithm based on derivative variance correlation map

Among different phase unwrapping approaches, the weighted least-squares minimization methods are gaining attention. In these algorithms, weighting coefficient is generated from a quality map. The intrinsic drawbacks of existing quality maps constrain the application of these algorithms. They often fail to handle wrapped phase data contains error sources, such as phase discontinuities, noise and undersampling. In order to deal with those intractable wrapped phase data, a new weighted least-squares phase unwrapping algorithm based on derivative variance correlation map is proposed. In the algorithm, derivative variance correlation map, a novel quality map, can truly reflect wrapped phase quality, ensuring a more reliable unwrapped result. The definition of the derivative variance correlation map and the principle of the proposed algorithm are present in detail. The performance of the new algorithm has been tested by use of a simulated spherical surface wrapped data and an experimental interferometric synthetic aperture radar (IFSAR) wrapped data. Computer simulation and experimental results have verified that the proposed algorithm can work effectively even when a wrapped phase map contains intractable error sources. (c) 2006 Elsevier GmbH. All rights reserved.

Numerical simulation of wavefronts diffracted by apertures with circular symmetry

The numerical simulation of the wavefronts diffracted by apertures with circular symmetry is realized by a numerical method. It is based on the angular spectrum of plane waves, which ignored the vector nature of light. The on-axial irradiance distributions of plane wavefront and Gauss wavefront diffracted by the circular aperture have been calculated along the propagation direction. Comparisons of the simulation results with the analytical results and the experimental results tell us that it is a feasible method to calculate the diffraction of apertures. (c) 2006 Published by Elsevier GmbH.

光纤激光阵列锁相和孔径装填技术研究进展

介绍了几种典型的激光阵列锁相和孔径装填技术,重点综述了国内外光纤激光阵列锁相和孔径装填技术的研究进展,最后对高功率高光束质量激光光源的应用和发展前景进行了展望。

Impact of polarized illumination on high NA imaging in ArF immersion lithography at 45 nm node

Immersion lithography has been considered as the mainstream technology to extend the feasibility of optical lithography to further technology nodes. Using proper polarized illumination in an immersion lithographic tool is a powerful means to enhance the image quality and process capability for high numerical aperture (NA) imaging. In this paper, the impact of polarized illumination on high NA imaging in ArF immersion lithography for 45 nm dense lines and semi-dense lines is studied by PROLITH simulation. The normalized image log slope (NILS) and exposure defocus (ED) window are simulated under various polarized illumination modes, and the impact of polarized illumination on image quality and process latitude is analyzed. (C) 2007 Elsevier GmbH. All rights reserved.

大口径干涉仪装置的调整及支承机构

采用蜗轮蜗杆驱动调整机构、使用同步带安装标准镜片方式、正交十字导轨支撑等可有效提高光学精密检测系统中大口径干涉仪装置的镜面面形质量、稳定性和调节准确度，从理论上介绍了蜗轮蜗杆驱动机构等设计原理及其基本公式，并从实验上验证了这些机构对光学精密检测系统稳定性的影响．

Core size scaling of helical-core optical fibres

The mode-area, scaling properties of helical-core optical fibres are numerically studied and the limit of core size for achievable single-mode operation is explored. By appropriate design, helical-core fibres can operate in a single mode with possible scaling up to 300 mu m in core diameter with numerical aperture 0.1.

Influence of the chirp on the intensity distributions of an apertured pulse

Starting from the Huygens-Fresnel diffraction integral and the Fourier transform, the propagation expression of a chirped pulse passing through a hard-edged aperture is derived. Using the obtained expression, the intensity distributions of the pulse with different chirp in the near and far fields are analyzed in detail. Due to the modulation of the aperture, many intensity peaks emerge in the intensity distributions of the chirped pulse in the near field. However, the amplitudes of the intensity peaks decrease on increasing the chirp, which results in the smoothing effect in the intensity distributions. The beam smoothing brought by increasing the chirp is explained physically. Also, it is found that the radius of the intensity distribution of the chirped pulse decreases when the chirp increases in the far field. (c) 2005 Elsevier GmbH. All rights reserved.

ICF靶场中光束口径与列阵间隔的研究

从靶场反射镜架模块的机械结构设计布局所需几何空间的角度出发，根据大口径、列阵器件的特殊要求，给出符合“神光Ⅲ”装置总体技术要求的ICF靶场光束口径与列阵间隔之间的关系，得出靶场△纵、△横应满足的公式．

基于孔径耦合带状线的激光脉冲整形系统

实现了一种新型的激光脉冲整形系统，该系统使用了一个由孔径耦合带状线（ACSL）电脉冲整形器驱动的电光调制器。一个电脉冲整形器由两条通过其公共接地板上的耦合孔径发生耦合作用的带状传输线所组成的四端口装置。更换具有不同耦合孔径的公共接地板，该电脉冲整形发生器可以具有150ps时间结构的任意整形电脉冲。将任意整形的电脉冲输入到电光调制器上，就可以得到任意整形的激光脉冲。利用该系统，激光脉冲整形系统能够产生具有150ps前后沿，1～3ns脉冲宽度可调、高对比度、光滑过渡以及任意整形的激光脉冲。

Design and control of an ultraprecision stage used in grating tiling

In petawatt laser system, the gratings used to compose pulse compressor are very large in size which can be only acquired currently by arraying small aperture gratings to form a large one instead, an approach referred to as grating tiling. Theory and experiments have demonstrated that the coherent addition of multiple small gratings to form a larger grating is viable, the key technology of which is to control the relative position and orientation of each grating with high precision. According to the main factors that affect the performance of the grating tiling, a 5-DOF ultraprecision stage is developed for the grating tiling experiment. The mechanism is formed by serial structures. The motion of the mechanism is guided by flexure hinges and driven by piezoelectric actuators and the movement resolution of which can achieve nanometer level. To keep the stability of the mechanism, capacitive position sensors with nanometer accuracy are fixed on it to provide feedback signals with which to realize closed-loop control, thus the positioning precision of the mechanism is within several nanometers range through voltage control and digital PID algorithm. Results of experiments indicate that the performance of the mechanism can meet the requirement of precision for grating tiling.}

高功率激光装置前端系统激光脉冲的时间整形及修正技术

针对激光惯性约束聚变实验研究对高功率激光驱动器前端系统复杂时间形状种子激光脉冲的需求, 应用孔径耦合带状线集成波导整形系统设计了满足需要的前端整形激光脉冲。用一种新方法精确计算了孔径耦合带状线电脉冲整形器的耦合系数和孔径宽度的数值关系, 并针对高衬比度整形激光脉冲的需求, 提出了高衬比度双极型集成波导整形系统方案。由该系统可以得到100 ps脉冲前沿、1～3 ns脉冲宽度可调、高衬比度(大于100∶1)、光滑无纹波调制、可精确满足神光II八路及第九路装置需求的前端整形激光脉冲。

拼接光栅压缩器的时域特性

在拼接光栅和拼接光栅压缩器的设计中,子光栅调节偏差不可避免,各维偏差与拼接光栅的时间特性之间的关系很关键。通过脉冲压缩理论分析得到各维偏差和聚焦脉冲时间宽度展宽之间的解析关系,从数值计算结果分析,面平行左右偏差对脉冲的时间宽度影响较大,必须控制在21.08 μrad内；条纹密度差异对脉冲宽度的影响很显著,相对条纹密度的比值应控制在10-5以内；从消除角色散的角度分析,面平行俯仰偏差和条纹平行度偏差可以相互补偿,条纹密度差异和面平行左右偏差也可以相互补偿。

阵列光栅压缩器的空域特性

引入角度偏差、位移偏差作为拼接光栅系统的物理参数，定义了拼接光栅的孔径函数，利用傅里叶角谱理论研究了高斯脉冲入射拼接光栅压缩器后的远场分布特性。研究表明；出射脉冲仍然是高斯型脉冲，但包络中心发生偏移，偏移量由角度偏差量和光束口径决定；位移偏差引入的相位随着拼接光栅压缩器传递，其对远场焦斑的影响，取决于每片子光栅的非整数倍光栅常数的横向位移偏差和纵向位移偏差的综合作用。通过数值计算得到了各维偏差对阵列光栅压缩器空域特性的影响，计算表明：光栅面外角度偏差（俯仰左右）和条纹平行度偏差都必须控制在1μrad以内，

大口径八边形钕玻璃片支撑系统的光机集成分析

控制由机械装夹方式所引入的波前畸变以提高惯性约束聚变(ICF)输出光束的质量，是在大口径钕玻璃片主放大器结构设计中必须考虑的。提出了一种新的有限元变形结果与光学元件面形畸变之间的数据处理方式，并与传统方式进行了对比。基于新的数据处理接口，利用光机集成分析方法对大口径八边形钕玻璃片的支撑系统结构设计参数进行优化。优化的结果保证了由支撑系统引起的透过波前畸变小于十分之一波长，同时波前畸变与设计参数变动的相关性最小。