Enhancement of plasma nonlinearities and generation of a microwave–terahertz supercontinuum in the field of subterawatt mid-infrared pulses

The smallness of the velocity $v$ of laser-field-induced motion of electrons compared to the speed of light $c$ is one of the fundamental physical factors limiting the efficiency of nonlinear optical processes in plasma media. It has been shown in this work that the use of intense ultrashort mid-infrared pulses makes it possible to significantly enhance a wide class of $v/c$-weak plasma nonlinearities primarily related to plasma currents induced by the laser field. This allows implementing laser plasma schemes of the efficient generation of coherent broadband terahertz and microwave radiation, i.e., terahertz–microwave supercontinuum.