Time-domain characteristics of twisted pulses based on spiral phase plate at terahertz frequencies

•The twisted THz pulse can be considered as superposition of the vortex THz beam at a certain frequency range.•The generation of twisted THz pulse are studied based on vortex THz beam, and the analytic expression is deduced.•The characteristics of the vortex THz beam are analyzed.•The time-domain characteristics of twisted THz pulse are analyzed.•Simulations and measurements are extremely consistent the proposed theory.