Light scattering and diffuse light propagation in sintered porous silicon

The scattering coefficient and the refractive index of sintered porous silicon are deduced from measurements on 1-4 μm thick freestanding films. Mie's theory is applied to describe the light scattering by the spherical pores. Using a reduced effective refractive index for the host medium in Mie's theory accounts for the close spacing of the pores and results in an agreement between the measured and calculated scattering coefficients. A coherent calculation for the specular nonscattered radiation is combined with a model that describes the propagation of the scattered diffuse light flux. For this diffuse model two approaches, the Kubelka Munk theory and a Lambertian model developed in this work, are compared. The combined model reproduces both, the specular as well as the diffuse component of the measured reflection and transmission.