Vortex beam generation via total angular momentum addition in flat optical elements

Shaping light with flat optical devices has enabled advancements in fields such as microscopy, quantum information, and optical communication. However, structured light in the nonlinear regime remains challenging. This study demonstrates the structuring of third-harmonic light by leveraging total angular momentum (TAM) projection addition in a thin amorphous silicon film. Experimental results reveal the critical role of TAM projection, supported by numerical simulations. These findings highlight the sensitivity of third-harmonic patterns to pump polarization, offering applications in circularly polarized light detection and advancing nonlinear flat optics