The Role of Gas Dynamics on Laser Filamentation THz Sources Operating at High Repetition Rates

Nowadays, one of the most advantageous techniques for table-top terahertz (THz) generation is the two-color laser filamentation in gases, where an ultrashort laser pulse together with its second harmonic are focused into a gas medium, forming an ionized plasma channel, called filament, which emits THz radiation [1] . Typically, laser sources operating at pulse repetition rates from few Hz to several kHz are used for this generation scheme. Though, in case of high pulse repetition rates the dynamics of the gas medium become especially important, since the plasma channels act as a thermal source which generates density hole structures whose characteristic lifetime exceeds the time interval between two consecutive laser pulses [2] . Here we demonstrate that the THz emission from two-color laser filaments in gases is strongly affected by the pulse repetition rate of the driving laser [3] .