Fluctuating Forces Induced by Nonequilibrium and Coherent Light Flow

We show that mesoscopic coherent fluctuations of light propagating in random media induce fluctuating radiation forces. A hydrodynamic Langevin approach is used to describe the coherent light fluctuations, whose noise term accounts for mesoscopic coherent effects. This description-generalizable to other quantum or classical wave problems-allows us to understand coherent fluctuations as a nonequilibrium light flow, characterized by the diffusion coefficient D and the mobility sigma, otherwise related by a Einstein relation. The strength of these fluctuating forces is determined by a single dimensionless and tunable parameter, the conductance g(L). Orders of magnitude of these fluctuation forces are offered that show experimental feasibility.