Colloquium on December 11th, 2006


Georg Maret
Universität Konstanz

Anderson-localization of light

Wave propagation in disordered media such as light propagation in a cloud can be roughly described by diffusive transport of the wave intensity. This description which is well known from the Drude model for electronic transport totally ignores the wave nature and hence fails to describe interference effects such as optical speckles which are fingerprints of the disorder. The particular interference of waves traveling along reciprocal multiple scattering paths is always constructive in the backscattering direction, even after averaging over many speckles, and thus gives rise to enhanced backscattering and (weak) wave localization. P.W. Anderson predicted in 1958 a breakdown of the wave transport on macroscopic length scales which should occur when the scattering strength of the medium becomes very high, i.e. when the transport mean free path becomes smaller than the wavelength. I shall discuss recent experiments which provide first clear evidence for the transition from weak to strong localization of visible light and allow a quantitative analysis of the localization transition.