Monte Carlo simulation of photon transport in a scattering-dominated medium with a refractive index gradient for acoustic light-guiding

Abstract

Acoustic light waveguides use a technology that employs acoustic waves to create pressure-dependent refractive index distribution and guide light deep into biological tissue similar to an optical fiber. The method by which acoustic optical waveguides increase light transmission in biological tissues occurring inside scattering-dominated medium has not been clarified. To understand the phenomena occurring inside the scattering-dominated medium, we performed Monte Carlo simulations of photon transport in acoustic optical waveguides. The findings indicate that the larger the change in the refractive index in the scattering-dominated media, the greater the effect of photon confinement. In addition, as the refractive index gradient was increased, the near-field internal fluence was found to be greatly enhanced. The transition depth, which indicates the region where the internal fluence is enhanced by the refractive index gradient, was determined as a function of the radius at which the refractive index change is given.