1.1 kW nanosecond fiber amplifier based on spectral beam combination

We report on scaling average power with the technique of spectral beam combining of four 5 MHz repetition rate 5 ns pulsed Yb-doped fiber amplifier systems operating around 1040 nm wavelength. Superposing the beams spatially and temporally by use of an all-reflective diffraction grating 1.1 kW average power and 220 µJ pulse energy were extracted with a combining efficiency of ∼99 %. At maximum output power the beam quality factor M 2 is 1.46 and 2.7, respectively. To our knowledge this represents the highest average output power and the most efficient combining process ever presented in a spectrally combined pulsed fiber amplifier configuration.