Giant nonlinear optical activity in an aggregated silver nanocomposite

Nonlinear optical activity due to spatial dispersion is observed in a collo idal solution of silver. It is shown experimentally that the effect is subs tantially enhanced (by a factor of similar to 10(2)) when the silver partic les aggregate into fractal clusters. The self-rotation angle of the plane o f polarization is 2 mrad at an intensity of 2 MW/cm(2) for lambda = 0.532 m u m and a pulse duration of 11 ns. A method of separating the contributions of the local and nonlocal effects to the rotation of the plane of polariza tion is proposed and implemented. (C) 1998 American Institute of Physics. [ S0021-3640(98)00520-9].