Diffusing Wave Spectroscopy (DWS) is a technique which allows to perform light scattering experiments on highly turbid samples, the latest characteristic being actually one of the requirement of the technique, whose analysis is based on a diffusion equation [1]. DWS is nowadays a widely used multiple light scattering technique, having the ability to probe the dynamics of scattering particles over an unrivaled time range. While many applications are found in the visco-elastic characterization of soft materials by probing the motion of embedded tracer particles (microrheology), DWS allows as well the study of the internal dynamics of colloidal dispersions in the concentrated range when the turbidity is too large for classic light scattering techniques.

We have one home-built setup which is designed as depicted in the figure below, and combines both the two-cell technique [2] and the echo-technique such as detailed in [3]. The laser is a 50mW single longitudinal mode red laser (lambda 662nm) from CrystaLaser. We have different cell holders for cell width ranging from 0.5 to 20mm, with one cell holder being temperature regulated by a water bath, and a second one (Peltier based) with a temperature stability less than 0.01K. The scattered light can be detected either in transmission or reflection, by a mono-mode fiber, and subsequently analyzed by a single photon counter and a correlator. The setup is designed in order to fulfill all requirements for a correct DWS measurement, in particular for non-ergodic samples.