High-Efficiency Fiber Laser Generating up to 528th-Order Orbital Angular Momentum Light

Abstract

Structured light lasers carrying orbital angular momentum (OAM) have demonstrated considerable potential across diverse research fields and practical applications. Despite great progress in exploring this new degree of freedom of light, it remains challenging to achieve high-order OAM beam output directly from lasers with high efficiency. In this paper, we propose a promising scheme for generating ultrahigh-order OAM light via intracavity geometric phase manipulation within a nonpolarization-maintaining fiber laser. By symmetrically investigating the beam propagation in the laser cavity and optimizing the key parameters affecting the free-space-to-fiber coupling efficiency, we successfully designed a fiber laser supporting the generation of over 500th order OAM light. Finally, we experimentally demonstrate direct OAM beam output with a record quantum number as high as 528 and a slope efficiency of up to 54%. The laser exhibits a power stability better than 0.8% and a mode purity higher than 90%. The proposed scheme can be further extended to other working regimes and holds significant potential for generating extremely high-order OAM beams directly from laser sources.