Average power of 1.1 kW from spectrally combined, fiber-amplified, nanosecond-pulsed sources

We report on spectral combination of four high repetition rate 5 ns pulsed Yb-doped fiber amplifiers at 1 mu m wavelength. The output beam is spatially and temporally superposed by use of an all-reflective diffraction grating. 1.1 kW average power and 220 mu J pulse energy were extracted with a combining efficiency of 99%.