Introduction to Photon Correlation Techniques and Applications

Dynamic light scattering experiments on colloidal particles or similar systems typically use one of two optical systems which have been termed homodyne and heterodyne setups, respectively. The homodyne system uses a single illuminating laser beam. Light from the measurement volume is detected coherently, i. e. through a small detector aperture. As a result, fluctuating interference or light beats are observed due to relative motion of the scattering centers with respect to each other. For noninteracting particles, the coherence time of the detected light readily yields the coefficient of diffusion and hence the particle sizes - today the most important application of dynamic light scattering.