White-light-seeded, CEP-stable, 4.5-W, 4-micron KTA parametric amplifier driven by a 1.4-ps Yb:YAG thin disk laser

Abstract: We demonstrate a robust, carrier envelope phase (CEP)-stable, potassium titanyl arsenate (KTA)-based optical parametric amplifier (OPA) delivering 6-cycle (79 fs), 3.8-$\mu$m pulses at a 100-kHz repetition rate with an average power of 4.5 W. The pivotal achievement is stable generation of supercontinuum (SC) seed pulses in a YAG crystal with a rather long pulse of 1.4 ps; to our knowledge, this is the longest duration for SC generation (SCG). This technology offers a robust and simplified OPA architecture with characteristics of passively-stabilized CEP, simplified dispersion management with bulk materials, wavelength tunability of the output pulses from 1.3-4.5 $\mu$m, and the future power scaling up to kW-class based on Yb:YAG thin disk amplifiers. The total output power of 17 W (signal plus idler) is achieved and the capability of this high photon flux aspect is successively demonstrated by its application to high harmonic generation (HHG) in ZnSe crystals, with which faint yet novel signals above their bandgap are clearly observed.