Diffusing-wave spectroscopy

Diffusing-wave spectroscopy (DWS) is an optical technique derived from dynamic light scattering (DLS) that studies the dynamics of scattered light in the limit of strong multiple scattering. It has been widely used in the past to study colloidal suspensions, emulsions, foams, gels, biological media and other forms of soft matter. If carefully calibrated, DWS allows the quantitative measurement of microscopic motion in a soft material, from which the rheological properties of the complex medium can be extracted via the microrheology approach.

Laser light is sent to the sample and the outcoming transmitted or backscattered light is detected by an optoelectric sensor. The light intensity detected is the result of the interference of all the optical waves coming from the different light paths.

Typical setup of diffusing-wave spectroscopy

The signal is analysed by calculating the intensity function called g₂. ${\displaystyle g_{2}(\tau )={\frac {\langle I(t)I(t+\tau )\rangle _{t}}{\langle I(t)\rangle _{t}^{2}}}}$

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