High-power coherently combined femtosecond laser based on InnoSlab amplifiers

We report a high-power, ultrafast coherent beam combination system featuring two InnoSlab CPAs based on Yb: YAG crystals. 306 W average power and 1.53 mJ pulse energy are delivered at 200 kHz, with a power fluctuation of 0.52% RMS. The combined beam quality is optimized from <i>M</i>² = 1.24 × 1.41 to <i>M</i>² = 1.1 × 1.18, due to the filtering effect of spatial mode. The combined beam is compressed to 460 fs by a grating compressor with close to the diffraction-limited spatial beam quality. Both excellent spatiotemporal performance and long-time stability are achieved, representing a novel, to the best of our knowledge, kilowatt-class average power amplifier which will greatly benefit the applications.