Femtosecond microjoule pulses with 15.8 W average power from a passively mode-locked diode-pumped Yb:YAG thin-disk laser

Abstract

Summary form only given. Femtosecond laser sources with multi-watt average powers and multi-kW peak powers are required for many applications. We have found a power-scalable concept to achieve this kind of performance directly with a diode-pumped passively mode-locked laser oscillator, not requiring any amplification stages. The concept is based on a Yb:YAG thin-disk laser, which in continuous wave (CW) operation has delivered output powers of up to /spl ap/100 W in a diffraction-limited beam. We have now for the first time to our knowledge passively mode-locked such a laser using a semiconductor saturable absorber mirror (SESAM). The laser head, which had generated 20 W CW near-room-temperature produced 680-fs pulses at 1030 nm with 15.8 W of average power in two nearly transform-limited beams (time-bandwidth product 0.33). This is to our knowledge the highest average power reported for a laser oscillator (without amplifier) in the subpicosecond regime. The pulse repetition rate was 15 MHz. Pulse energies of 2/spl times/0.5 /spl mu/J and peak powers as high as 2 X 680 kW were achieved. Autocorrelation and optical spectrum are given. To obtain subpicosecond pulse durations, we operated the laser in the soliton mode-locked regime using a Gires-Tournois Interferometer (GTI). The high tendency of Yb:YAG for Q-switched mode-locking was strongly suppressed by the small laser mode size in the thin-disk laser head, the low repetition rate, and a stabilizing effect resulting from soliton mode-locking.