Spectral-domain low-coherence dynamic light scattering and its application to measurement of the air-liquid interface effect

The Brownian motion of particles close to the interface between air and liquid will be affected by the hydrodynamic interaction due to Stokes drag force. The particles in this region move slower than those in the free diffusive region far from the fluid surface. The new low-coherence dynamic light scattering (LC-DLS) technique based on the spectral-domain optical coherence tomography (SD-OCT) is proposed to analyze simultaneously the dynamics of the Brownian particles from the far region to the near region. The hydrodynamic interaction between the Brownian particles and the fluid surface is experimentally investigated in diffusion coefficient of particles.