Observation of coherent backscattering ‘factor of three’ in a numerical experiment

We study coherent backscattering of light by nonlinear scatterers in the weakly nonlinear regime. We compare full numerical calculations with a diagrammatic approach; the validity of the latter is demonstrated by the excellent agreement between these two approaches. Especially it emphasizes the fact that, in the weakly nonlinear regime, the coherent backscattering phenomenon originates, in general, from the interference between three different scattering amplitudes. This effect reveals itself in the first nonlinear correction of the backscattered intensity, which is enhanced by almost a factor three as compared to the diffuse background.