Sub‐100 Fs Vortex Beams Generated from a Yb:CALGO Laser

Abstract Direct intracavity generation of vortex beams with pulse durations below 100 fs based on Yb:CALGO vortex laser oscillator is proposed and investigated experimentally. The oscillator integrated semiconductor saturable absorber mirror (SESAM)‐assisted Kerr mode‐locking with spot‐defect mirror technology. The SESAM‐assisted Kerr mode‐locking mechanism enabled phase locking between different longitudinal modes to obtain short pulses. Meanwhile, the spot‐defect mirror regulated transverse mode characteristics, optimizing the intracavity optical field distribution under longitudinal mode phase‐locking conditions. This synergistic approach enhanced nonlinear spatiotemporal mode coupling. By precisely adjusting the position of the spot‐defect mirror, a well‐defined Laguerre‐Gaussian (LG) mode profile is obtained when the defect is aligned with the cavity axis. Under these conditions, the Yb:CALGO vortex laser oscillator achieved a pulse duration as short as 75.7 fs, a spectral bandwidth of up to 18.2 nm, and a maximum output power of 3.2 W. To the best of the knowledge, this represents the shortest pulse duration for an ultrafast vortex beam generated directly from an oscillator.