Photon propagation and the statistics of electromagnetic modes in random media

We argue that the statistical character of wave propagation in random media can be described in terms of two universal parameters which are average properties of eigenmodes of the field. We show that the width and spacing of electromagnetic modes can be determined from the measurement of the intensity correlation function with frequency shift. The ratio δ of the typical level width to the spacing of modes, which is essentially the Thouless number, gives the proximity to the localization threshold. Its inverse δ-1 gives the degree of long range intensity correlation in the sample.