Second-harmonic vortex beam generation via parallel continuous-wave all-optical domain structuring

We report the generation of second-harmonic vortex beams using nonlinear pitchfork holograms directly induced via a parallel all-optical domain structuring technique in lithium niobate. The method employs a single-step exposure with amplitude-modulated visible continuous-wave laser light to induce ferroelectric domains through a photovoltaic field-assisted process. Subsequent second-harmonic generation from pulsed infrared excitation reveals well-defined vortex beam profiles with tunable topological charge, verified by far-field diffraction and Fourier analysis of the domain structures. These results demonstrate the scalability and versatility of the approach for the parallel fabrication of nonlinear photonic elements tailored for structured light generation.