Monte Carlo analysis of focused Gaussian beam in scattering media: Curvature correction and Mie scattering

Abstract

We introduce curvature correction into the Monte Carlo (MC) technique to determine the suitable photon-step size and initial photon distribution in the focusing lens aperture, that can account for the effects of the radius of curvature on the axial intensity profile of a focused Gaussian beam that is propagated through a scattering medium. The scattering anisotropy of the medium is determined via the Mie scattering theory for given values of the scattering particle radius, density, and phase distribution values while optical ray tracing is used to determine the occurrence of scattering events. We evaluate the performance of the modified MC technique for random and periodic media by examining the axial intensity profiles of the propagating focused beam. Relative to the predictions of the scalar diffraction theory, curvature correction improves the accuracy of the MC results with decreasing step size s and increasing number of steps Ns. In the absence of scattering, the axial beam distribution approaches that of the scalar diffraction theory for a given numerical aperture (NA≤0.5), s, and Ns based on the Linfoot’s image quality criteria of fidelity, correlation quality and structural content.