We have studied the influence of absorption, scattering, and refractive index of a phantom medium in conjunction with various beam diameters on the penetration depth of light at 633nm. We used mixtures of Intralipid 10% (scattering medium) and Evans blue (absorbing medium). Measurements were performed in media with a scattering coefficient of 1/mm, an anisotropy factor of 0.71, absorption coefficients of 0.0013, 0.01, and 0.05/mm, and a refractive index of 1.33. The experimental results were compared with an analytical solution of the fluence rate based on diffusion theory. We found good agreement (deviations of <10%) between theory and experiment for incident beam diameters between 10 and 60mm.
C. J. M. Moes, M. J. C. van Gemert, W. M. Star, J. P. A. Marijnissen, and S. A. Prahl. Measurements and calculations of the energy fluence rate in a scattering and absorbing phantom at 633 nm. Appl. Opt., 28:2292-2296, 1989.