Self-Started Kerr-Lens Mode-Locked Femtosecond Thin-Disk Vortex Laser Oscillator with an Integrated Sagnac Interferometer

High-power femtosecond optical vortices directly generated from lasers will advance their applications in material processing, optical manipulation, and communication, but the average power achieved so far has been limited. In this work, we apply for the first time a Sagnac interferometer to directly output high-power femtosecond vortices from a Kerr-lens mode-locked thin-disk oscillator. By varying the parameters of the Sagnac interferometric structure, we can also alternate between the Laguerre–Gaussian vortex and Hermite–Gaussian output modes. The average power and pulse width of these modes are above 10 W and below 300 fs, respectively. This work introduces a new approach for generating high-power femtosecond vortices by extending mode-locking technologies at fundamental modes to high-order modes.