Parabolic Mirror Focusing of Spatiotemporally Coupled Ultrashort Terahertz Pulses

Abstract

Ultrashort terahertz (THz) beam is often affected by spatio-temporal distortion due to its long wavelength, and this spatio-temporal coupling will degrade the focusing effect. Here, we develop a numerical model for calculating the vector focusing of ultrashort pulses with arbitrary spatial and temporal distribution, which adopt the vector diffraction integral and coherent spectrum superposition methods. Leveraging it, the focusing of a broadband pulse can be characterized together with its vector characteristics and we explore the influences of multifarious spatio-temporal couplings on the focusing of ultrashort THz pulses. In addition, the possibility of focusing the ultrashort THz radiation from an undulator to 1 GV/m is also discussed. This will provide further guidance for the non-equilibrium state of matter induced by ultrashort strong-field THz pulses.