640 nm High-Order Laguerre-Gaussian Modes with Controllable Topological Charge up to 42 from a Pr:YLF Laser with Intracavity Spherical Aberration

In this work, we demonstrate the generation of 640 nm high-order Laguerre-Gaussian (LG) modes with controllable order up to 42 from a Pr:YLF laser utilizing intracavity spherical aberration (SA). To the best of our knowledge, these constitute the highest order vortex beams in the visible spectral region, obtained from a simple laser cavity with strict SA management. By precisely adjusting the on-axis displacement of the laser output coupler, the angular index m of the generated LG modes could be varied in the range of 12–42. This work provides a flexible and robust method of generating visible vortex beams with tunable, high-index topological charge, which have potential use in spatial measurement, fluid dynamics and active debris removal applications.