Time-domain Characteristics of Twisted Pulses based on Spiral Phase Plate at Terahertz Frequencies

Abstract A twisted terahertz (THz) pulse is presented, and the time-domain characteristics of the twisted THz pulse are discussed. For this purpose, the generation and propagation of single-frequency vortex THz beam based on spiral phase plate (SPP) are studied at THz frequencies firstly, and the characteristics of the vortex THz beam are analyzed. The twisted THz pulse is more useful and attractive than the single-frequency vortex THz beam given that it can be considered as superposition of the single-frequency vortex THz beam at a certain frequency range. A fractional bandwidth 8 GHz at center frequency 199 GHz has been applied to obtain the twisted THz pulse by inverse Fourier transform, a uniform frequency spectrum is considered. Theoretical simulations and experimental measurements of the twisted THz pulse are carried out, the results are extremely consistent the proposed theory.