Stark, H.H.StarkBuldt, J.J.BuldtMüller, M.M.MüllerKlenke, A.A.KlenkeLimpert, J.J.Limpert2022-03-062022-03-062021https://publica.fraunhofer.de/handle/publica/26902110.1364/OL.417032An ultrafast fiber chirped-pulse amplification laser system based on a coherent combination of 16 ytterbium-doped rod-type amplifiers is presented. It generates 10 mJ pulse energy at 1 kW average power and 120 fs pulse duration. A partially helium-protected, two-staged chirped-pulse amplification grating compressor is implemented to maintain the close to diffraction-limited beam quality by avoiding nonlinear absorption in air.en620535journal article