Propagation of a femtosecond pulse in a scattering medium: theoretical analysis and numerical simulation

The time profile of a femtosecond pulse propagating in media with a high scattering anisotropy (g≥0.9) is studied in detail. The iteration method based on the expansion of the light field in a series in photon scattering orders with the account for the multiply scattered component is proposed to study analytically the structure of a scattered radiation pulse. The small-angle approximation of the radiation transfer theory used for calculations of low-order scatterings is modified to take into account the spread in the photon delay times. The shape of a scattered ultrashort pulse calculated theoretically well agrees with the shape obtained by the Monte-Carlo simulation. It is shown that the pulse profile in a scattering medium depends on the shape of the scattering phase function with the conservation of the anisotropy factor. A comparative analysis of contributions from different scattering orders to the pulse structure is performed depending on the optical properties of a scattering medium.