Generation of terahertz annular vector beams with arbitrary order from gas-plasma induced by few-cycle vector beams

A method for the generation of annular vector beams (AVBs) with arbitrary order in the THz regime is proposed and numerically confirmed based on the photocurrent model from gas-plasma induced by a near-infrared few-cycle laser driver. Moreover, the variance of its radius R with its azimuthal order L follows a simple rule, i.e., R∼L1∕2, the same as that for the few-cycle laser driver. In contrast, as for the width of spatial intensity annual rings, that of few-cycle laser driver increases with the increase of L, whereas that of THz AVBs decreases.