Monte Carlo simulations are widely considered to be the gold standard for studying the propagation of light in turbid media. However, traditional Monte Carlo methods fail to account for diffraction because they treat light as a particle. This results in converging beams focusing to a point instead of a diffraction limited spot, greatly effecting the accuracy of Monte Carlo simulations near the focal plane. Here, we present a technique capable of simulating a focusing beam in accordance to the rules of Gaussian optics, resulting in a diffraction limited focal spot. This technique can be easily implemented into any traditional Monte Carlo simulation allowing existing models to be converted to include accurate focusing geometries with minimal effort. We will present results for a focusing beam in a layered tissue model, demonstrating that for different scenarios the region of highest intensity, thus the greatest heating, can change from the surface to the focus. The ability to simulate accurate focusing geometries will greatly enhance the usefulness of Monte Carlo for countless applications, including studying laser tissue interactions in medical applications and light propagation through turbid media.
Brett H. Hokr, Aidan Winblad, Joel N. Bixler, Gabriel Elpers, Byron Zollars, Marlan O. Scully, Vladislav V. Yakovlev, and Robert J. Thomas, "Accurately modeling Gaussian beam propagation in the context of Monte Carlo techniques," Proc. SPIE 9706, Optical Interactions with Tissue and Cells XXVII, 970614 (Presented at SPIE BiOS: February 16, 2016; Published: 7 March 2016); https://doi.org/10.1117/12.2213653.
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