Induced transient gratings as a probe of the early-stage kinetics of phase-separating liquid mixtures

Because of the large number of nucleated domains and the polydispersity of the droplet distribution, the early-stage kinetics of a first-order phase transition remains difficult to explore. We investigate this issue by using laser-induced concentration variations to drive a transition locally in a liquid mixture with two intersecting pump beams whose interference pattern traps the nucleated droplets on the optical fringes. The time-resolved reflectivity of a third probe wave on the induced droplet grating allows us to characterize the droplet growth at its early stage, which illustrates the efficiency of transient grating methods in quantifying the kinetics of out-of-equilibrium processes. (C) 1998 Optical Society of America.