Sub 25 fs pulses from solid-core nonlinear compression stage at 250 W of average power

We report on a highpower femtosecond fiber chirped-pulse amplification system with an excellent beam quality (M(2)=1.2) operating at 250 MHz repetition rate. We demonstrate nonlinear compression in a solid-core photonic crystal fiber at unprecedented average power levels. By exploiting self-phase modulation with subsequent chirped-mirror compression we achieve pulse shortening by more than one order of magnitude to 23 fs pulses. The use of circular polarization allows higher than usual peak powers in the broadening fiber resulting in compressed 0.9 μJ pulse energy and a peak power of 34 MW at 250 W of average power (M(2)=1.3). This system is well suited for driving cavity-enhanced high-repetition rate high-harmonic generation.