Strong Enhancement of Terahertz Radiation from Laser Filaments in Air by a Static Electric Field

Abstract

We observe a 3 order of magnitude enhancement of the terahertz energy radiated by a femtosecond pulse undergoing filamentation in air in the presence of a static electric field. Measurements of terahertz pulse duration, spectrum, polarization, and radiation pattern elucidate the physical processes responsible for this radiation. A theoretical model explains the results and predicts another 3 orders of magnitude enhancement with a terawatt laser pulse.