Influence of finite coherence length of incoming light on enhanced backscattering

We have investigated the effects of the finite coherence length of the incoming light on multiple scattering in a random medium. Large optical fluctuations observed with coherent light gradually decrease their intensity as the coherence length of the incoming light is shortened. When the coherence length is shortened below the elastic mean free path, the enhanced backscattering peak is revealed without ensemble average of the fluctuations. This variation of the fluctuations as a function of the coherence length of the incoming light has been analyzed on the basis of the diffusion approximation.