Abstract

Nondegenerate two-wave mixing (NDTWM) has been previously used to measure the relaxation time of solid-state systems. In an artificial Kerr medium, the relaxation time is the time for a particle to diffuse a portion of the index grating induced by radiation-pressure forces. This time is proportional to the viscosity of the medium. Our work demonstrates the use of NDTWM as a viscometer for picoliter volumes. Experiments were performed to measure the viscosity of suspensions of 0.090 µm diameter polystyrene microspheres titrated with known quantities of water and glycerol. Good quantitative agreement with tabulated values was found for the viscosity of water-glycerol solutions. Unlike viscometer techniques, which typically require large volumes of fluid, this technique can be implemented with fewer than 50 pL of sample volume, making it ideal for biological work.

© 1990 Optical Society of America