Generation of THz vortex beam by infrared vector beam rectification

We report on the conversion of an infrared vector beam into THz vortex beams using a ZnTe cubic crystal. We provide a theoretical analysis demonstrating how an infrared vector beam with the azimuthal order ℓ can be transformed into a THz beam endowed with an orbital angular moment content that consists of optical vortices with topological charge ±2ℓ. Experimentally, quasi-monochromatic THz vortex beams with topological charges +2 and -2 are produced and characterized both in amplitude and phase using real-time two-dimensional imaging of the terahertz electric field.