Diffraction effects in Monte Carlo simulations

Abstract

In modeling image acquisition of objects beneath turbid media, the Monte Carlo (MC) protocol holds many significant advantages over diffusion-based models because of the ease with which different imaging parameters can be incorporated. Using this approach, two-photon fluorescence imaging through turbid media is analyzed resulting to contrast enhancement of the scattered image. The analysis is then extended to the temporal domain where the broadening behavior of a femtosecond pulse propagating through a scattering layer is investigated. The MC model utilized in the preceding applications simulates photon transport by assuming incoherent illumination. For coherent light focused by lenses, diffraction and interference effects influence the intensity distribution at the focal volume. In order to simulate real focused imaging systems, diffraction effects must be incorporated in the model.
This paper proposes a modification of the MC model that allows diffraction and interference effects to be taken into account. Results of the modified procedure are shown to be consistent with theoretical calculations for single and double-slit diffraction when there is no scattering medium present. We then investigate how the diffraction pattern deteriorates in the presence of scattering.