Thin-disk multipass amplifier delivering 10 GW of peak power

Summary form only given. Recent development of thin-disk multipass amplifiers has resulted in several breakthroughs in average power and pulse energy of both ps- and fs-amplifiers [1-3]. These results confirm the suitability of this laser architecture for amplification of ultrafast pulses with high energy and at high average powers thanks to low nonlinearities in the thin-disk and to an efficient cooling scheme. However, as peak powers are reaching or exceeding the GW, even nonlinearities induced by propagation in air become relevant in terms of spectral broadening due to self-phase modulation (SPM).In this work we investigate possible exploitation of spectral broadening occurring in a 400 W thin-disk multipass amplifier seeded by a TruMicro 5050 Femto Edition delivering 805 fs pulses. The seed laser can be used at either 800 kHz or 200 kHz repetition-rate, yielding 2 mJ and 0.5 mJ respectively at the output of the multipass amplifier [3]. Marginal spectral broadening occured at 0.5 mJ (800 kHz), whereas strong spectral broadening due to SPM in air during propagation of the beam in the amplifier was observed at 2 mJ (200 kHz). Therefore these spectrally broadened pulses can be sub-sequently compressed. We estimated the amount of negative group delay dispersion (GDD) to compress the output pulses to be in the range of -20000 fs2. Several reflections at highly dispersive mirrors (with a GDD of about -3000 fs2 per bounce) were used to compress the output pulses.