High field broadband THz pulses by ultrashort laser-plasma interaction

Broadband THz radiation with electric field up to hundreds of MV/cm is achieved using femtosecond laser interaction with solid target. Particle-in-cell simulations reveal that the THz pulses are coherent transition radiation (CTR) of hot electrons produced in laser-plasma interaction. Due to the square law dependence of CTR energy on the electron number, laser-plasma based strong THz sources can reach unprecedented intensity comparing to other methods. Besides planar targets, nano-grating targets have also been investigated, which improve the THz sources both in intensity and directionality. Theory model and simulations agree very well with experimental observations.