Finite-size effects in the spatial distribution of the intensity reflectedfrom disordered media

Statistical properties of the intensity of the field reflected speckle patt ern from a surface corrugated waveguide are presented. We have found strong finite-size effects due to a small number of propagating channels. We anal ytically deduce the intensity distributions in the localization regime usin g random matrix theory in the case of a two channel waveguide. We have also performed exact numerical calculations for the spatial intensity whose pro bability distribution remarkably agrees with the analytical predictions.