Hybrid hollow-Gaussian and Laguerre–Gaussian terahertz beam generated by optical rectification in β-barium borate

Optical vortex beams attract much attention due to their versatile applications. Various methodologies have been developed to generate and manipulate optical vortex beams. In contrast, the generation of THz vortex beams is still in its infancy. Nonlinear optical processes have the potential to help develop novel methods to generate THz vortex beams. This work investigates the optical rectification in β-barium borate pumped with optical vector beams. The results show that the generated THz beam is hybrid, composed of a hollow-Gaussian mode and two Laguerre–Gaussian modes bearing opposite topological charges. The hollow-Gaussian mode is independent of the optical pump’s polarization state. On the contrary, the Laguerre–Gaussian modes’ orientations depend on the optical pump’s polarization state.