Total internal reflection scattering

We show that the wave front of a total internal reflected beam is perturbed by fluctuations in the region probed by the evanescent wave, and light is scattered both above and below the critical angle. While singly scattered light is related to the two-dimensional Fourier transform at the boundary, multiply scattered light originating from very turbid samples can appear only below the critical angle. We show that the very weak scattered light above the critical angle is due to a double tunnel effect, and it is solely due to single scattering at the surface. Applications are discussed.