Remote RF generation from ultrafast laser plasmas

Ultrashort pulse (USP) lasers provide a novel approach to microwave production for remote applications. In this scheme, the plasma produced in the interaction of a USP with a material surface at a distance serves as a localized source of radio frequency (RF) radiation. Ultrashort pulses allow for the long-range projection of high-intensity light (∼1013 W/cm2), through the phenomenon of laser filamentation, thereby enabling the efficient generation of transient plasmas on remote material surfaces. In this paper, the mechanism of RF production in the laser–matter interaction is discussed and experimental characterization of the RF emission in a variety of target geometries is presented. Both transient dipole radiation and resonance absorption are discussed as theoretical mechanisms of RF generation. Furthermore, spectral composition of the RF emission, angular distribution of the emission, and dependence of the RF on laser focusing conditions are all characterized for a number of target materials in the single to tens of GHz range, using microwave horn antennas in conjunction with heterodyning electronics.