Measurements of optical properties of high-density media

Measurements of optical properties ?scattering coefficient ?s, absorption coefficient ?a, reduced scattering coefficient ?s?, and asymmetry factor g? have been carried out up to a volume particle concentration of ? ? 0.227. The results for ?s and ?s? show significant deviations from the linear dependence on ? as expected when the independent scattering assumption is fulfilled. The asymmetry factor also changed signifi- cantly. In contrast, the dependence of ?a remained linear even at the largest concentration investigated. The simple linear dependence of absorption on the chromophore concentration expected from the inde- pendent scattering assumption is thus applicable also to spectroscopic measurements of dense media. A comparison with an approximate theoretical model based on the Foldy-Twersky equation is also re- ported. The model provides a good description of the dependence of ?s on particle concentration.