We have determined the scattering delay time of Mie scatterers (r=255 nm quartz spheres in polyester resin) from a combination of steady-state (integrating-sphere) and time-resolved (frequency-domain) measurements performed in the multiple-scattering regime. The effective transport velocity of light was derived from intensity and phase measurements at four different wavelengths by using the time-integrated microscopic Beer–Lambert law. We could demonstrate a systematic underestimation of the effective transport velocity compared with the phase velocity in the medium. Assuming that this discrepancy was caused entirely by the transient nature of a single-scattering process, the data presented resulted in time delays of between 18 fs (λ=678 nm) and 177 fs (λ=1064 nm) per scattering event. For three out of four wavelengths investigated, the measured values are in excellent agreement with values predicted by a theoretical model for the scattering delay time based on Mie theory.
© 2000 Optical Society of America
(120.3150) Instrumentation, measurement, and metrology : Integrating spheres
(290.4020) Scattering : Mie theory
(290.4210) Scattering : Multiple scattering
(290.7050) Scattering : Turbid media
(300.6500) Spectroscopy : Spectroscopy, time-resolved
Stefan Willmann, Albert Terenji, Harald Busse, Ilya V. Yaroslavsky, Anna N. Yaroslavsky, Hans-Joachim Schwarzmaier, and Peter Hering, "Scattering delay time of Mie scatterers determined from steady-state and time-resolved optical spectroscopy," J. Opt. Soc. Am. A 17, 745-749 (2000)