共查询到20条相似文献,搜索用时 781 毫秒
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通过双探针近场光学扫描显微镜在银纳米线上实现近场激发和近场收集表面等离子体,用一个探针在银纳米线的一端近场激发表面等离子体,另一个探针近场探测银纳米线上的表面等离子体强度分布,得到强度分布图.强度分布图显示表面等离子体在银纳米线的一端被有效激发并且有一部分表面等离子体沿着银纳米线和基底的界面传播到了另一端.用有限元法对银纳米线内的传播模式进行数值模拟,结果显示银纳米线内存在两种表面等离子体传播模式,分别为基模和高阶模.沿着银纳米线和基底介质之间传输的基模表面等离子体由于传输环境稳定,散射损耗小,实际传输长度接近模式传输长度,达10μm以上;而高阶模表面等离子体由于部分裸露在空气中受表面缺陷散射的影响,散射损耗大,实际传输长度远小于模式传输长度.研究表明:以能量高度束缚的基模表面等离子体作为载体,不仅可以实现低损耗传输,还可以减小集成器件之间的信号串扰,有效提高信息传输的安全性,在集成光学中具有重要应用. 相似文献
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新型特殊模式激光柬的传播是激光应用研究的基础和重要课题.利用柯林(Collins)积分公式研究了广义超几何光束在ABCD近轴光学系统中的传播行为,得到了光束在输出平面复振幅的解析表达式.结果表明,其传播后的复振幅分布与库默尔(Kummer)函数成正比.通过将Kummer函数展开成级数,获得了光束在输出平面复振幅的模的级数形式,从该级数町以看出,广义超几何光束在ABCD近轴光学系统中传播时的模式结构一般是要发生变化的.作为特殊光学系统,讨论了自由空间传播时近场和远场衍射近似表达式,它们均为一系列同心圆环,空间频率随径向坐标增加而增加,近场衍射时横向模式结构保持不变,而远场衍射时则发生变化.给出了光束的归一化系数,分析了该光束一些简化模式与高斯光束的关系. 相似文献
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二维正方晶格光子晶体平板的近场成像特性 总被引:1,自引:1,他引:0
光子晶体是由两种或两种以卜不同介电函数的材料周期性排列组成的一种人工晶体.由于介电甬数的周期性分布对入射光的调制作用,使得特定频率区域的人射光在光子晶体中传播时的群速度方向和相速度方向相反,因而使得光子晶体平板表现出负折射特性.系统研究了介质柱的形状对二维正方品格光子品体近场成像特性的影响.通过对分别由正方形、三角形、椭网形、长方形等形状介质柱组成的二维正方品格光子晶体平板近场成像特性的理论分析,发现当介质柱形状的对称性降低到一定程度后可以实现光子晶体近场成像的纵向平移.进一步通过对相应等频率曲线形状的分析,明确了光子晶体近场成像是由于自准直效应和负折射效应的共同作用形成的. 相似文献
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在原有的平面循环平稳近场声全息基础上,提出一种基于波叠加法的循环平稳近场声全息技术,可以对具有复杂表面的声源进行全息重建,重建的声源表面声压谱相关密度函数能反映出调制信号的信息.声源表面声压谱相关密度函数全息图形象地反映了调制信号在表面的强弱分布情况,可由此确定调制信号源的产生位置.仿真分析和实验验证表明,基于波叠加法的循环平稳近场声全息技术可以更准确地反映循环平稳声场的调制特性.该方法继承了波叠加法的优点,无需计算边界奇异积分,计算效率高、精度好.
关键词:
近场声全息
循环平稳信号
波叠加 相似文献
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耦合径向基函数与多项式基函数的无网格方法 总被引:3,自引:1,他引:2
耦合径向基函数和多项式基函数,形成一种新的近似函数.该近似函数对散乱分布的离散数据点进行逼近时,只需节点信息,不需要划分网格.详细描述了耦合近似函数的建立、属性、插值行为及其形函数和形函数导数的性质.最后引入修正变分原理和单位分解积分技术求解边值问题,并给出了计算实例,表明耦合径向基函数和多项式基函数是一种非常有效的方法. 相似文献
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在原有的平面循环平稳近场声全息基础上,提出一种基于波叠加法的循环平稳近场声全息技术,可以对具有复杂表面的声源进行全息重建,重建的声源表面声压谱相关密度函数能反映出调制信号的信息.声源表面声压谱相关密度函数全息图形象地反映了调制信号在表面的强弱分布情况,可由此确定调制信号源的产生位置.仿真分析和实验验证表明,基于波叠加法的循环平稳近场声全息技术可以更准确地反映循环平稳声场的调制特性.该方法继承了波叠加法的优点,无需计算边界奇异积分,计算效率高、精度好. 相似文献
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Statistics of coherent radiation propagating in a random medium is analyzed in the framework of diagram technique. The distribution function for radiation intensity is calculated and it is shown, that only for small values of the argument the distribution function is a simple exponential, as predicted by Rayleigh statistics. For larger values of intensity the distribution function differs drastically from the simple exponential, and the asymptotical behavior is a stretched exponential. The results obtained are confirmed by numerical simulations. 相似文献
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OFLID: Simple method of overlap factor calculation with laser intensity distribution for biaxial lidar 总被引:1,自引:0,他引:1
We proposed a simple overlap factor calculation method based on laser intensity distribution (OFLID), which is simple, practical and can be applied to any specific laser intensity distribution. In order to obtain the laser intensity distribution and parameters of our laser system, we designed a simple experiment to measure them, and then simulated an ideal Gaussian and uniform laser intensity distribution with the measured parameters. The OFLID calculation results indicated that the overlap factor of the measured distribution has approximately half the relative error of that of the ideal Gaussian distribution in the increasing range field for our lidar. Specifically, the laser intensity distribution should be regarded in the overlap correction of the lidar signal. Theoretically, the OFLID method can reduce the error caused by the hypothesis of ideal uniform or Gaussian intensity distributions in the analytical method. In addition, the method is easy to implement for overlap correction, signal simulation and system configuration optimization for biaxial lidar. 相似文献
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Edward B. Manoukian 《General Relativity and Gravitation》1990,22(5):501-505
A simple quantum viewpoint of gravitational radiation is given. The starting point is the definition of the amplitude that a given source distribution of matter emits a graviton of goven momentum and helicity. From the corresponding probability distribution of the number of gravitons of a given energy, the classic slow motion expression for the power loss follows in a simple and lucid manner. Special attention is also given to the gauge terms in the analysis. 相似文献
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焦距法测试自聚焦透镜折射率分布常数 总被引:1,自引:0,他引:1
本文介绍了一种测量自聚焦透镜折射率分布常数的方法─—焦距法,并进行了原理公式推导,和精度分析,其测量不确定度为±1×10 ̄(-3);其次,简要地介绍了实验方法。实验结果证明了焦距法是测量自聚焦透镜折射率分布常数的简单实用的方法,它具有装置简单、数据处理也不复杂的特点,是一种非破坏性的测试方法。 相似文献
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Klaus Petermann 《Optical and Quantum Electronics》1981,13(4):323-333
Simple relations for the phase distribution of the fundamental mode of gain-guided lasers are derived, yielding simple, approximate analytic expressions for the far-field distribution parallel to the junction in the case of strong astigmatism. It is shown that the shape of the far-field distribution is essentially determined solely by the distribution of the effective refractive index parallel to the active layer. The relations may be used for any shape of the effective refractive index distribution to yield simple arguments as to why there are lasers which exhibit far-field distributions with double as well as triple maxima. Because of the simplicity of the expressions for the far-field distribution it is also possible to make an estimate of the shape of the carrier profile, once the near-field and far-field intensity distributions are known. In addition, a general relation between the normalized fundamental mode gain and the shape of the far-field distribution is given. 相似文献
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Let F be a probability distribution with support on the non-negative integers. Four methods for generating a simple undirected graph with (approximate) degree distribution F are described and compared. Two methods are based on the so called configuration model with modifications ensuring a simple graph, one method is an extension of the classical Erdös-Rényi graph where the edge probabilities are random variables, and the last method starts with a directed random graph which is then modified to a simple undirected graph. All methods are shown to give the correct distribution in the limit of large graph size, but under different assumptions on the degree distribution F and also using different order of operations. 相似文献
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It is shown experimentally that the scattering of sound by sound can be observed outside the region of interaction between primary waves and that it carries information on the spatial distribution of the scatterer’s nonlinear characteristics. Based on this effect, a simple method for reconstructing the distribution of the nonlinear parameter by using complex-modulated broadband primary signals and a small number of transmit and receive transducers is implemented. The possibility of reconstructing a two-dimensional distribution of a nonlinear parameter inhomogeneity with the use of only three transducers (two transmitters and one receiver) without additional scanning in the aspect angle is demonstrated. This simple scheme loses information on the low-frequency components of the scatterer’s spatial spectrum and reconstructs the distribution of only the spatial variations of the nonlinear parameter. 相似文献
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O.A. Goroshko V.A. Ivanov I.V. Soppa 《Journal of magnetism and magnetic materials》2010,322(21):3385-3390
A simple method is proposed for the observation of interaction in the assembly of single domain particles based on registration of anhysteretic remanent magnetization. In contrast to established methods relied on isothermal magnetization, the proposed method is more sensitive to the weak interaction and helps to find the distribution of the particles in the interaction fields. The method is very simple: a differentiating of a single experimental curve is enough to obtain the distribution. Verification of the method was performed on the samples of different origins and proved a good correlation of experimental results and numerical estimations. 相似文献
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U. Garibaldi E. Scalas P. Viarengo 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(2):241-246
We propose a simple stochastic exchange game mimicking
taxation and redistribution. There are g agents and n coins;
taxation is modeled by randomly extracting some coins; then, these
coins are redistributed to agents following Polya's scheme. The
individual wealth equilibrium distribution for the resulting Markov
chain is the multivariate symmetric Polya distribution. In the
continuum limit, the wealth distribution converges to a Gamma
distribution, whose form factor is just the initial redistribution
weight. The relationship between this taxation-and-redistribution
scheme and other simple conservative stochastic exchange games (such
as the BDY game) is discussed. 相似文献
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Bershadskii A 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》1999,59(6):7216-7219
It is shown that multifractality of large deposition probabilities observed in a simple model of crystal growth (the Das Sarma model with neglected surface diffusion, desorption, and hop) corresponds to another type of statistical distribution: multifractal Bernoulli distribution. Lognormal distribution is also discussed in this context. 相似文献