Ultra-high-order Laguerre–Gaussian field generated directly from a laser cavity with spherical aberration

Pursuing higher topological charge—larger angular indices m of high-order Laguerre–Gaussian (LG) beams—is not only important for frontier applications like optical/quantum communication, optical tweezers, and super-resolution imaging, but also involves a novel laser cavity and beam dynamics. Active methods to directly generate high-order-mode vortex beams from a laser cavity have excellent power handling and conversion efficiency, but struggle to achieve hundred-level ultra-high-order LG modes. Here, the generation of ultra-high-order LG beams with m beyond 300 is demonstrated, utilizing the spherical aberration of a lens in the cavity of a simple end-pumped Nd:YVO₄ laser at 1064 nm. LG_0,±m modes with m up to 317, selectable across a large range, are generated. With a simple model, how the mode selection relates to the cavity parameters is explained, and it is predicted that even higher order mode output can be expected by appropriate management of the elements’ aperture and laser gain. The approach provides a simple and flexible method to convert a wide range of lasers to generate ultra-high-order LG modes.