Observation on the competition mechanism of terahertz wave generation from filament in bias electric field

Abstract Femtosecond laser pulse-generated terahertz (THz) wave that undergoes filamentation in air in the presence of a DC bias electric field is composed of ponderomotive force-generated and electric field-induced THz. A threshold for the bias electric field that determines the characteristics of the final THz wave is observed. When the bias electric field strength is lower than the threshold, the THz wave tends to be characterized by the ponderomotive force. Moreover, the property of THz wave is mostly determined by a relatively high bias electric field. A theoretical model based on electrical dynamics has been developed to clarify the competition mechanism of THz wave generation.