Thin-disk multipass amplifier delivering sub-400 fs pulses with excellent beam quality at an average power of 1 kW

We present an improved multipass amplifier design, enabling the amplification of ultrashort pulses with excellent beam quality to more than 1 kW of average output power. 260 fs short pulses at an average power of 105 W and a repetition rate of 1 MHz were directly amplified up to an average power of 1033 W. The pulse duration at this power level was measured to be 388 fs assuming a Gaussian temporal shape. This corresponds to a peak power of 2.5 GW. The power stability was measured to be 0.16% RMS over a duration of more than two hours at a sampling rate of 2 Hz. High beam quality is proven with measured values of M x 2 = 1 .16 in the horizontal and M y 2 = 1 .19 in the vertical plane according to ISO Standard 11146.