Multiple-scattering-free light scattering spectroscopy with mode selectivity.

Seeing through the dynamics of turbid media is often demanded in both science and technology. Dynamic light scattering is one of the most powerful means to study the dynamics of various condensed matter systems, in particular, soft matter systems, in a nondestructive manner. However, its applicability is often limited by multiple scattering of light, which severely distorts the signal. To overcome this problem, cross correlation spectroscopy has been developed. Here, we propose another physical principle by which we can avoid the effects of multiple scattering. We demonstrate that this method allows not only Rayleigh but also Brillouin scattering measurements even in very turbid colloidal suspensions. This method opens a possibility of optically characterizing the dynamics (translational and rotational diffusion, thermal diffusion, and acoustic phonon dynamics) of turbid materials with mode selectivity.