Wave Propagation and Localization in Random Structures

9311605 Genack这项提议的目的是清楚地描述微波和光学辐射从扩散传播到局域传播的转变。利用可调谐的单频光源、短脉冲和亚波长空间分辨率，在随机散射体集合中确定了波传播的关键统计特性和微观散射参数。测量了局域波强度、透射率和电导的概率分布、关联函数和平均值以及飞行时间分布的标度。使用散射参数、样本几何和边界条件的适当组合，将传播描述转换为通用形式。经典波传播是交流的载体，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传输的模型。这个项目的目的是找到从扩散模式(从许多中心，如原子和分子的随机散射)向光不再能够通过介质传播的“局域”模式转变的普遍描述。这是一种微妙而复杂的效应，对于半导体世界中的电子来说是众所周知的，但对于通过宏观介质传播的光学和微波辐射来说，这一效应才刚刚被探索出来。该研究对紧凑型滤光片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. ***