Sub-20 femtosecond, 100  kHz repetition rate, microjoule pulse generation in a high-pressure hollow-core fiber

We present the 10-fold spectral broadening of laser pulses with tens-of-microjoules pulse energy via self-phase modulation in an argon-filled 200 µm diameter hollow-core fiber at 49% transmission. After broadening, the initially 160 fs long pulses from a commercially available 1030 nm wavelength Yb:KGW laser, operated at repetition rates of 100-200 kHz, are compressed with high-anomalous-dispersion mirrors. Transient-grating frequency-resolved optical gating of the final pulses demonstrates pulse durations down to 16.5 fs. Our results are well reproduced by generalized nonlinear Schrödinger equation modeling, suggesting they are readily transferable to similar laser systems. The broadened beam has excellent position and pointing stability, suggesting it as an ideal source for nonlinear or frequency-upconverted time-resolved angle-resolved photoemission spectroscopy or similar measurements requiring intermediate intensities, long integration times, and elevated repetition rates.