Terahertz generation from laser filaments in the presence of a static electric field in a plasma

Abstract

Two femtosecond laser pulses with frequencies ω1 and ω2 that undergo filamentation in a plasma couple nonlinearly in the presence of a transverse, static electric field to generate terahertz wave at the frequency ω1-ω2. The coupling is enhanced in the presence of the static electric field. We develop a theoretical model and observe over 30 times increase in the magnitude of normalized terahertz amplitude by applying a dc electric field ~50kV/cm.