Femtosecond optical responses of disordered clusters, composites, and rough surfaces: The ninth wave effect

We predict that in the course of femtosecond excitation of random clusters, composites, or rough surfaces in the optically linear regime, ultrafast giant fluctuations of local fields occur. These fluctuations cause transient (on a femtosecond scale) formation of highly enhanced fields localized in nanometer-size regions (the ninth wave effect). The spatial distribution of those fields is dramatically different from the case of steady-state excitation. We discuss manifestations of this effect and possible experiments.