Highly stable thin-disk multipass amplifier delivering 1kW of average output power with excellent beam quality

Ultrafast lasers have become essential for many fields of material processing such as precise ablation, drilling of micro-holes or surface structuring [1] - [3] . Among other power amplifier schemes, thin-disk multipass amplifiers (TDMPA) are known to deliver both high average power and high pulse energy. However, compared to fibre amplifiers they may be limited in stability due to the long propagation length and may suffer from thermo-mechanically induced beam degradation. In this contribution we address the main limitations observed in previous TDMPAs [4] , [5] , to achieve excellent beam quality as compared to what is typically achieved with fiber amplifiers at the same power levels.