Scattering delay time of Mie scatterers determined from steady-state and time-resolved optical spectroscopy

We have determined the scattering delay time of Mie scatterers (r = 255 nm quartz spheres in polyester resin) from a combination of steady-state (inte grating-sphere) and time-resolved (frequency-domain) measurements performed in the multiple-scattering regime. The effective transport velocity of lig ht was derived from intensity and phase measurements at four different wave lengths by using the time-integrated microscopic Beer-Lambert law. We could demonstrate a systematic underestimation of the effective transport veloci ty compared with the phase velocity in the medium. Assuming that this discr epancy was caused entirely by the transient nature of a single-scattering p rocess, the data presented resulted in time delays of between 18 fs (lambda = 678 nm) and 177 fs (lambda = 1064 nm) per scattering event. For three ou t of four wavelengths investigated, the measured values are in excellent ag reement with values predicted by a theoretical model for the scattering del ay time has ed on Mie theory. (C) 2000 Optical Society of America [S0740-32 32(00)01404-6] OCIS codes: 290.7050, 290.4210, 290.4020, 120.3150, 300.6500 .