Wave Propagation and Localization in Random Structures

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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. ***