Nonlinear excitation of the Mie resonance in a laser-irradiated cluster

The nonlinear collective electron dynamics inside a large heated cluster irradiated by a strong linearly polarized short laser pulse are considered in the approximation of an incompressible medium. When the incident radiation frequency is near three-photon resonance with the Mie frequency, the field inside the cluster exhibits a third harmonic with an amplitude comparable with that of the fundamental. In the same parameter range, due to shielding, the field inside the cluster at the fundamental frequency is strongly reduced with respect to the incident field. The presence of the third harmonic can lead to a strong enhancement of the production of multiply charged ions. Third-harmonic generation by a cluster under the same conditions is analyzed, too. (C) 2003 Optical Society of America.