High-energy ultrafast thin-disk oscillators

Abstract

We have studied experimentally and numerically the pulse shaping dynamics of a diode-pumped thin-disk laser oscillator with active multipass cell and large output coupling rates. We demonstrate the generation of high energy subpicosecond pulses with energies of up to 25.9 μJ and durations of 928 fs directly from a thin-disk laser oscillator without further amplification. We have achieved these results by employing a selfimaging active multipass geometry in order to increase the output coupling rate for a suppression of nonlinear optical effects. With this system we have obtained stable single pulse operation in ambient atmosphere with average output powers above 76W at a repetition rate of 2.93 MHz. A semiconductor saturable absorber mirror was used to start and stabilize passive soliton mode locking. The experimentally studied laser pulses show good agreement with numerical simulations including the appearance of Kelly sidebands. We present a modification to the soliton area theorem that is applicable for such a laser oscillator with active multiple pass cell and large output coupling rate. While numerically simulating the laser, we also investigated the intracavity pulse dynamics within one round-trip and limitations for power scaling. Furthermore, we demonstrate the laser's potential for micro machining applications by showing first examples of material processing, such as the determination of ablation thresholds and ablation rates for various materials.