Femtosecond energy concentration in nanosystems coherently controlled by excitation phase

We predict and quantitatively evaluate the unique possibility of concentrating the energy of an ultrafast excitation of a nanosystem in a small part of the whole system by means of coherent control (phase modulation of the exciting ultrashort pulse). Such concentration is due to dynamic properties of surface plasmons and leads to local fields enhanced by orders of magnitude. This effect exists for both engineered and random nanosystems. For linear processes, the coherent control affects the temporal distribution of the local fields, while the integrated energy of the local fields is not affected. For nonlinear processes, both the temporal distribution and integral energy are coherently controllable. We also discuss possible applications.