一新型金属有机化合物在皮秒激光下的三阶非线性光学性质研究

利用皮秒激光光源,采用z扫描技术研究了一种新型金属有机化合物的三阶非线性光学性质以及光限幅特性.z扫描研究结果表明,这种化合物在1064 nm波长激光激发下的三阶非线性极化率χ(3)为3.8×１０-14 esu,并且存在双光子吸收.光限幅实验结果显示双光子吸收和非线性折射两种不同机制决定了该化合物的光限幅特性.     

基于虚拟仪器的高精度Z扫描实验系统设计

设计了一个表征样品非线性特性的基于虚拟仪器的z扫描实验系统。利用Labview控制数字示波器TDS3012采集两路光强信号，并结合对微位移平台的控制实现Z扫描。以Nd：YAG飞秒放大器产生的800nm的飞秒激光作为探测光，经透镜聚焦后通过薄介质样品；用数字示波器测量样品在透镜焦点附近的透射光强，经过数据处理得到样品的非线性折射率和非线性吸收系数。利用该实验系统，对标准非线性吸收样品Rhodamine 6B进行了测量，计算得到其双光子吸收截面为σ^2=6．8GM（GM：10^-50cm4s photon^-1 molecule^-1），该结果与其他文献利用不同测量方法得到的结果接近，证明该实验系统的测量结果是正确的，可满足非线性测量的精度要求。     

大非线性相移下光学非线性Z扫描特性的研究

采用高斯分解法(GD)对大非线性相移下的Z扫描特性进行了分析，通过对数值算法的优化，将GD推广到对脉冲入射激光下大非线性相移下的Z扫描理论分析.对不同条件下大非线性相移Z扫描曲线峰谷结构的比较，发现在大非线性相移的情况下，Z扫描曲线的峰和谷随透过光阑或入射光强变化表现出某些新的特性.随着透过光阑孔径的增加，Z扫描曲线峰的变化要明显快于谷的变化，而且在谷明显存在的情况下，峰很快消失.采用皮秒脉冲激光下的纯二硫化碳实验对理论结果加以验证，实验结果和理论分析相一致.我们的分析结果对大非线性相移下Z扫描测量有一定的指导性意义，避免在大非线性相移下对Z扫描结果产生错误的分析. 关键词： 大非线性相移 高斯分解法 Z扫描     

Z—扫描技术及其应用

文章介绍了Ｚ－扫描技术的原理、特点及其应用，分析了单色Ｚ－扫描法测量非线性折射系数和非线性吸收系数，以及双色Ｚ－扫描法研究非简并非线性光学效应．     

基于图像处理的条纹相机扫描非线性修正

为了使条纹相机输出图像达到更高的测量准确度,提出一种基于图像处理的扫描非线性修正算法. 该算法根据给出的标称扫描速度拟合出扫描速度曲线,求出每道的扫描速度,取其算术平均值作为一个标准,根据每道的扫描速度与该标准的大小关系来修正像素的位置和亮度. 实验结果表明,可以将测量非线性由原来的8%减小到2%以下.     

厚光学非线性介质Z扫描理论分析

采用高斯分解方法，对厚光学非线性材料的Ｚ扫描进行了理论分析，得到了对于实验工作者寻找优良的光学非线性材料和合理设计光学限制器时较有用的结果。 关键词：     

以衍射理论为基础考虑双光子吸收的Z-扫描理论

以菲涅尔-基尔霍夫衍射理论为基础,建立了非线性介质对高斯光束的衍射模型,对高斯光束通过非线性介质后的传输行为进行了详细的理论推导和数值计算,从一种新的角度解释了Z-扫描现象.理论推导出了考虑双光子吸收的闭孔和开孔Z-扫描曲线的统一公式,是计算非线性折射率和双光子吸收系数的一种新方法.数值模拟计算表明,对于考虑双光子吸收的闭孔Z-扫描曲线,其结果与经典的Z-扫描理论完全一致.而对于已给定的开孔Z-扫描曲线,用该理论计算出的双光子吸收系数是经典开孔Z-扫描理论计算值的1/3,其它结论与传统Z-扫描理论完全吻合.该理论的近似条件只要求薄样品和小非线性吸收,比传统理论具有更好的准确性.     

克尔介质中瞬态热光非线性效应的作用

研究了介质中瞬态热光非线性效应对于克尔效应Z扫描测量结果的影响，观察到了Z扫描峰谷特性的转变，相应的数值模拟结果与实验结果很好地吻合.实验也发现，克尔效应和瞬态热光非线性效应相互抵消时Z扫描曲线呈现出新奇的单峰或平台状曲线.对于用纳秒脉冲激光进行的Z扫描测量结果的正确分析具有重要意义. 关键词： 瞬态热光非线性效应 克尔效应 Z扫描     

双臂相位Z扫描测量稀溶液中溶质光学非线性

基于相位Z扫描技术提出了双臂相位Z扫描技术,在相位Z扫描技术的光路中并联一个相同的光路。与传统的Z扫描技术相比,相位Z扫描可区分溶液的三阶非线性折射和瞬态热致非线性,且可实现单脉冲测量,系统灵敏度也要比Z扫描技术高。以往的方法都不能很好地测量稀溶剂中纯溶质的光学非线性,采用双臂相位Z扫描技术可极大提高系统测量信噪比,从而可准确地测量出稀溶剂中纯溶质的光学非线性。     

测量慢弛豫介质的非线性折射率Z扫描方法

对非线性折射率慢弛豫介质的Z扫描理论进行了详细推导,得到了透射光场的表达式.分析表明:对于慢弛豫介质,其Z扫描过程也是非线性折射的累积过程.实验结果与理论分析一致. 关键词：     

三维形貌测量的扫描相移法研究

物体三维形貌测量中常用的光切法的主要优点是易于实现扫描测量大型物体表面,缺点是光刀中心位置难以精确确定;相移法的主要优点是可以用较宽的光栅提高测量的灵敏度与准确度,具有测量速度快和较好的抗静态噪声的能力,缺点是当待测范围较大时,采集图像的像差较大,不利于大型物面的测量.将这两种方法有机地结合起来,取长补短,提出了一种扫描相移法.实验结果表明,这个方法不但适用于长形大物面的形貌检测,而且又大大地减少了图像采集系统畸变误差的影响,从而提高了检测准确度.     

A calibration method of lens distortion for line scan cameras

We present a practical method to calibrate the lens distortion in line scan cameras. The distortion correction software based on this method has been designed and implemented in the digital protection of cultural relics. In this paper, a lens distortion model which applies to line scan cameras is derived from the widely used array camera distortion model. Then, a new calibration method which utilizes the imaging characteristic of equidistant collinear feature points is proposed to calibrate the model. Experiment results show the proposed calibration method is stable and effective.     

A study on the evaluation of usefulness depending on the image reconstruction method in bone SPECT scan

The recent advances in image-processing techniques have led to the development of many methods to reduce the scan time without degrading the image quality. In particular, tomography has improved image reconstruction methods with the concomitant improvement of high-quality images. In this study, PRECEDENCE 16 was used to reconstruct images using the filtered back projection method, which is generally used, and the Astonish method and three-dimensional ordered-subsets expectation maximization method, which are based on repetition techniques. In qualitative and quantitative analysis of the reconstructed images, a comparison was made between images with different acquisition times and between images with the same acquisition time, which aimed at determining the optimal method for reconstructing high-quality images. A blind test for qualitative analysis confirmed almost no difference in image quality depending on the image acquisition time. Furthermore, in quantitative analysis, there was no significant difference in image quality depending on the image acquisition time. On the other hand, the results of the analysis in the image reconstruction method with the same acquisition time demonstrated a significant difference. The images reconstructed by the Astonish method, which uses a repetition technique, are believed to be excellent because they have high resolution and provide clinical diagnostic information. This study confirmed that the reconstruction method with a repetition technique could be used to improve image quality and reduce the scan time, despite not being in general use until recently due to the lengthy time needed for image reconstruction and lack of storage space.     

New Periodic Wave Solutions to Generalized Klein-Gordon and Benjamin Equations

By making use of extended mapping method and auxiliary equation for finding new periodic wave solu tions of nonlinear evolution equations in mathematical physics, we obtain some new periodic wave solutions for generalized Klein-Cordon equation and Benjamin equation, which cannot be found in previous work. This method also can be used to find new periodic wave solutions of other nonlinear evolution equations.     

Extended Hyperbola Function Method and Its Application to Nonlinear Equations

An extended hyperbola function method is proposed to construct exact solitary wave solutions to nonlinear wave equation based upon a coupled Riccati equation. It is shown that more new solitary wave solutions can be found by this new method, which include kink-shaped soliton solutions, bell-shaped soliton solutions and new solitary wave.The new method can be applied to other nonlinear equations in mathematical physics.     

A Direct Algebraic Method in Finding Particular Solutions to Some Nonlinear Evolution Equations

Firstly, a direct algebraic method and a routine way in finding traveling wave solutions to nonlinear evolution equations are explained. And then some new exact solutions for some evolution equations are obtained by using the method.     

具5次强非线性项的波方程新的孤波解

提出一种新的函数变换法，并与直接积分法相结合简便地求出了Lienard方程、广义PC方程以及力学中重要的一类非线性波方程等几类具5次强非线性项的波方程的四类显示精确孤波解.本方法同样适用于求解其他具有更高次非线性项的非线性方程. 关键词： 函数变换法 孤波解 直接积分法 非线性波方程     

路径积分Monte Carlo方法与非线性随机振动

给出了一种求解非线性随机振动问题的新方法-基于路径积分表述的Monte Carlo方法。受白噪声激励的非线性系统的各响应统计值被表成路径积分形式,并采用Monte Carlo方法进行计算。讨论了应用方面的问题,并计算了两个实例。     

Study of absorption spectrum and dynamics evaluation of the indocyanine‐green first singlet excited state

Excited state absorption and excited state dynamics of indocyanine‐green (ICG) dissolved in dymethyl sulfoxide were measured using white‐light continuum Z‐scan (WLCZScan) and white‐light continuum pump–probe (WLCPP) techniques. The excited state absorption spectrum, obtained through Z‐scan measurements, revealed saturable absorption (SA) for wavelengths longer than 630 nm, while reverse saturable absorption (RSA) appeared, as indicated by a band at approximately 570 nm. Both processes were modeled by a three‐energy‐level diagram, from which the excited state cross‐section values were determined. SA and RSA were also observed in pump–probe experiments, with a recovery time in the hundreds of picoseconds time scale due to the long lifetime of the first excited state of ICG. Such results contribute to the understanding of ICG optical properties, allowing application in photonics and medicine. Copyright © 2010 John Wiley & Sons, Ltd.     

A Direct Algebraic Method in Finding Particular Solutions to Some Nonlinear Evolution Equations

Firstly, a direct algebraic method and a routine way in finding traveling wave solutions to nonlinear evolution equations are explained. And then some new exact solutions for some evolution equations are obtained by using the method.