Light spectra in the near field of random media

The spectrum of light in close proximity to a highly scattering, randomly inhomogeneous medium is investigated. We find differences between the far- and near-field spectra that are due to evanescent wave contributions. We show that these spectral modifications depend on the coherence properties of an equivalent planar source, which, in turn, relates to the statistical characteristics of the interface. (C) 2004 Optical Society of America