Experimental Evidence for Recurrent Multiple Scattering Events of Light in Disordered Media

The coherent backscattering of light from disordered samples was studied with a new technique, which allowed for a very accurate determination of the enhancement factor in exact backscattering. Using circularly polarized light, the enhancement factor in the polarization conserving channel was found to be $2.00\pm 0.01$ in the weak scattering regime and was found to drop gradually below this value for stronger scattering. We argue that this behavior of the enhancement factor is the first direct experimental manifestation of recurrent multiple scattering events.