High-efficiency ultra-high-order OAM fiber lasers with intracavity cascaded geometric phase manipulation

Lasers with orbital angular momentum (OAM) are crucial for quantum detection, quantum entanglement and related research. However, achieving efficient generation of high-topological-helicity vortex beams in these lasers remains challenging. The resolution of diffraction elements and the divergence of higher-order modes are the main limiting factors. Here, we introduce a fiber-free-space hybrid laser design, with a vortex half-wave plate (VHP) serving as a higher-order mode converter, and cascaded VHPs to reduce the resolution limit of the device, enabling the generation of vortex beams with topological charge up to 264. The slope efficiency of the vortex laser is as high as 24 %. This method provides an expandable solution for the development of high-power, arbitrary-high-order vortex lasers.