Dipole Mechanism Generation of Terahertz Waves under Laser-Cluster Interaction

The feasibility of dipole radiation of terahertz waves under the action of a femtosecond laser pulse on a cluster is demonstrated theoretically. It is shown that the dipole mechanism of terahertz radiation generation plays a decisive role in the interaction of a laser pulse with small-size clusters with a sufficiently high electron collision frequency. The dependences of the spectral, angular, energetic, and spatiotemporal characteristics of the terahertz signal on the density of free electrons in the cluster plasma under the conditions in which dipole radiation is dominant are investigated. It is shown that the energy of terahertz radiation is maximal under the resonance conditions, when the laser frequency coincides with the eigenfrequency of a spherical cluster.