100 W average power femtosecond UV laser for ultra-high photon flux XUV sources

We present a femtosecond laser system delivering up to 100 W of average power at 343 nm. The laser system employs an Yb-based femtosecond fiber laser and subsequent secondand third harmonic generation in BBO. Thermal gradients within the BBO crystals are reduced due to sapphire heat spreaders directly bonded to the front and back surface of the crystals. Thus a nearly diffraction-limited beam quality (M2<1.5) is achieved despite the high thermal load to the nonlinear crystals. This laser source is expected to generate XUV radiation with ultra-high photon flux in the near future.