MULTIPLE-SCATTERING OF LIGHT IN POROUS-GLASS

Two kinds of multiple-light-scattering measurements were performed for porous glass plates of several pore radii from 0.15 to 0.50 mum. One is the measurement of the angular dependence of the backscattered light intensity, and the other is the measurement of the temporal profile of light pulses transmitted through the sample. The measured curves were in very good agreement with the theoretical ones based on the diffusion model in uniform scattering media, and no features specific to the local geometry of porous glass were found. The pore radius dependence of the transport mean free path l* could be explained well by a Mie scattering calculation based on the independent scattering approximation. The transport velocity of light in the porous glasses in the measured range of the pore size calculated from the obtained values of l* and the diffusion constants was around 60% of the phase velocity in the bulk glass.