Coherent backscattering of Raman light

Coherent backscattering of light is observed when electromagnetic waves undergo multiple scattering within a disordered optical medium. So far, coherent backscattering of light has been studied extensively for elastic (or Rayleigh) light scattering. The occurrence of inelastic scattering affects the visibility of the backscattering effect by reducing the degree of optical coherence in the diffusion process. Here, we discuss the first experimental observation of a constructive interference effect in the inelastically backscattered Raman radiation from strongly diffusing silicon nanowire random media. The observed phenomenon originates from the coherent nature of the Raman scattering process, which typically occurs on a scale given by the phonon coherence length. We interpret our results in the context of a theoretical model of mixed Rayleigh-Raman random walks to shed light on the role of phase coherence in multiple scattering phenomena.