Reduced transport velocity of multiply scattered light due to resonant scattering

The transport properties of photons traveling through random media are of great fundamental and applied importance. For instance the dwell time due to resonant Mie scattering can lead to a significant reduction in transport velocity. Here, we have measured directly the energy-transport velocity of photons in strongly scattering media using a combination of time resolved transmission, measuring the diffusion coefficient, and angular resolved backscattering, yielding the transport mean free path. We find that the transport velocity is strongly reduced when the effective diameter of the scattering particles is a multiple of half the wavelength. This is consistent with the occurrence of resonant Mie scattering in the samples. We compare our data to previous theoretical calculations of the transport velocity as a function of scatterer size.