Gigahertz Repetition Rate Kerr-Lens Mode-Locked Oscillator With Above 7-W Average Power

We present a soft-aperture Kerr-lens mode-locked Yb:KGW oscillator capable of generating multi-watt average output power at gigahertz repetition rate. Using a dual-confocal ring cavity design, the laser waist inside the Yb:KGW crystal matched well with a multi-mode fiber-coupled laser diode. At the pump power of 42 W, double-pulse modelocking is observed due to high-power operation, and the transition from double-pulse operation to single-pulse operation is realized when increasing the negative intracavity group delay dispersion. The stable single-pulse modelocking with 7.73-W average output power and 189-fs pulse duration at 1.68-GHz is achieved. This is the highest average output power ever reported from any soft-aperture Kerr-lens mode-locked (KLM) oscillators operating at GHz repetition rate, as far as we are aware.