Controlled Generation of High-Purity Scalar Orbital Angular Momentum States from a High-Power Single-Crystal Fiber Laser

The orbital angular momentum (OAM) of light, which is associated with the rotation of the phase structure, gives rise to numerous novel physical phenomena inlight-matter interactions. However, the direct generation of scalar OAM lasers with power-handling capability and controllable states at the source remains challenging owing to mode degeneracy, handedness selection, and nonlinear thermal effects, which can even lead to topological charge splitting. This paper proposes a novel approach that allows spatial mode-conversion-controlled laser oscillation in a high-gain OAM laser cavity with an integrated spiral-face output coupler (SFOC). By adapting position-dependent resonant modes, scalar optical vortices with a record power level (>60 W), high purity (>90%), and controllable OAM states (h or -8h) are demonstrated. Further, the dynamic process of OAM generation and evolution in the cavity is revealed. The concept presented herein opens a new route for the generation of OAM laser sources toward high power levels and holds promise for advancing classical and quantum optics, particularly in the area of light-matter interactions.