Wave Propagation and Localization in Random Structures

这个提议的目的是给出微波和光辐射从扩散传播到局域传播转变的清晰图像。利用可调谐的单频源、短脉冲和亚波长空间分辨率，确定了随机散射体系综中波传播的关键统计特性和微观散射参数。测量了局域波的强度、透射率、电导和飞行时间分布的概率分布、相关函数和平均值的标度。利用散射参数、样品几何形状和边界条件的适当组合，将传播描述转化为一种通用形式。经典波传播是通信的载体，为发现非均匀系统的结构提供了一种手段。此外，它还可以作为超小型系统中电子输运的模型。这个项目的目的是找到从扩散状态（从许多中心随机散射，如原子和分子）到“局部”状态（光不再能够通过介质传播）转变的通用描述。这是一种微妙而复杂的效应，在半导体世界中以电子而闻名，但现在正在探索通过宏观介质传播的光学和微波辐射。该研究对紧凑滤波器和开关等光子材料的开发和技术应用具有重要意义。＊＊＊

9311605 Genack The aim of this proposal is to give a clear picture of the transition from diffusive to localized propagation for microwave and optical radiation. Using tunable single frequency sources, short pulses and subwavelength spatial resolution, the key statistical characteristic of wave propagation and the microscopic scattering parameters are determined in an ensemble of random scatterers. Measurements are made of the scaling of the probability distributions, correlation function and average value of the intensity, transmission and conductance as well as time of flight distribution of localized waves. The description of propagation is cast into a universal form using appropriate combinations of scattering parameters, sample geometry and boundary conditions. %%% Classical wave propagation is the vehicle for communication and provides a measure for discovering the structure of inhomogenous systems. Moreover, it serves as a model for electronic transport in ultrasmall systems. The aim of this project is to find a universal description of the transition from diffusive regime (random scattering from many centers, like atoms and molecules) to a "localized" regime where the light is no longer able to propagate through the medium. This is a subtle and complicated effect that is known for electrons in the semiconductor world, but is just now being explored for optical and mircrowave radiation propagating through macroscopic media. The research has important implications for photonic materials development and technological applications such as compact filters and switches. ***