Measurement of low optical absorption in highly scattering media using the thermal lens effect

In this work we show that the thermal lens effect can be applied to highly scattering and weakly absorbing materials. We apply the thermal lens effect and the z-scan technique to estimate the effective absorption coefficient of a suspension of TiO 2 particles with a mean diameter of 220 nm at two wavelengths: 488 nm and 514 nm. From the effective absorption coefficient we estimate the absorption cross section of the particles.