Creation of tunable longitudinally polarized terahertz pulse carrying orbital angular momentum

There is a growing interest to the longitudinal electric field because of its applications in the particle acceleration, metallic particle trapping and optical data storage. When the longitudinal electric field is added by the vorticity at terahertz domain, this unique property can be have more potential for many applications. Here by applying two optical vortices through plasma, a scheme to produce the terahertz pulse carrying orbital angular momentum with the longitudinal polarized electric field is proposed. To excite the helicity of the terahertz pulse, the twisted input lasers are employed. Input pulses with the perpendicular polarization to the propagation path can generate a combined longitudinal and transversal polarized terahertz pulse. To separate the longitudinal polarized component of the radiated terahertz electric field, one can use the two orthogonal polarizers. Furthermore, the electric field components, radiation pattern and spectrum of emitted terahertz are analytically derived.