Pedro de Vries

INFLUENCE OF INTERNAL REFLECTION ON DIFFUSIVE TRANSPORT IN STRONGLY SCATTERING MEDIA

We treat the effect of internal reflection of the propagation of waves in strongly scattering media. The theory will be applied to the recently discovered phenomenon of coherent backscattering of light and to the time-dependent transport of light intensity in reflection and in transmission geometries. For backscattering and for transmission through relatively thin slabs the influence of internal reflection can be very strong. For transmission through relatively thick slabs the effect can be accounted for by renormalizing the diffusion coefficient with a length-scale dependent reduction factor.

Local-field effects on spontaneous emission of impurity atoms in homogeneous dielectrics

Abstract The local-field corrections to the spontaneous emission rate of an impurity atom in an otherwise homogeneous dielectric are calculated by making use of a macroscopic approach. An extension of a method introduced by Onsager and Bottcher is presented. By distinguishing between the substitutional and interstitial character of impurities, the well-known empty-cavity and Lorentz local-field factors are obtained, respectively. For fluids, the substitutional case is predicted to occur prevalently.

Simulation of two and three-dimensional disordered systems : Lifshitz tails and localization properties

Very large two and three-dimensional realizations of the Anderson model for localization are studied by solving the time-dependent Schrödinger equation. The density of states is calculated and Lifshitz tails extracted. Eigenstates at various energies are computed and analyzed. The localization length is determined as a function of the strength of the disorder and energy. For moderate disorder substantial deviations from results obtained by the strip-and-rod technique are found.

Wave localization in disordered and fractal systems

Abstract Numerical study of wave localization in systems with disorder and/or fractal characteristics is considered. Computational techniques employed entail solving the time-dependent Schrodinger equation for particular initial wave packets. Efficient and accurate numerical algorithms based on Trotter-Suzuki product formulas are presented. Propagation of light through a semi-infinite medium with disorder in the transverse directions is studied. It is shown that propagation of wave packets in one direction coexists with localization in the other two dimensions: We refer to this effect as transverse localization. Localization properties of quantum particles on fractal networks are investigated for two very well-known tight-binding models: The quantum percolation model and the fracton model. Spatial behavior of eigenstates is considered in connection with theoretical predictions of superlocalization. In disagreement with these predictions regular exponential behavior is found.