Interaction between ultra short pulses and a dense scattering medium by Monte Carlo simulation:: consideration of particle size effect

With an enough short-pulse incident to an individual particle, elementary scattering modes can be observed: internal or external reflection, refraction and diffraction. Simulation of pulse propagation in dense scattering medium is usually computed for large observation time, so that time delays of pulse interaction with the particles are negligible compared to propagation times between particle. A Monte Carlo method is proposed to compute the propagation of an incident 100 fs laser pulse in dense medium taking into account time-dependent scattering characteristics of particle: observation time of scattered light is less than 5000 fs. Two extreme cases are exemplified: predominance of direct and single-scattered photons appears in a thin time window for small particles (1 mum). On the contrary multiple scattering is always predominant and scrambles the transmitted signal for large particles (100 mum). (C) 2003 Elsevier Science B.V. All rights reserved.