Hollow fiber pulse compression of multi-millijoule, 200-fs pulses from a cw-diode-pumped single-stage Yb:CaF2 MOPA

In this contribution we show encouraging results for the spectral broadening and pulse recompression at a multi-mJ energy level of pulses from a novel broadband single-stage regenerative Yb:CaF₂ amplifier, which provides 200 fs, 1 kHz, 6 mJ pulses at 1030 nm wavelength and holds the potential for a robust, compact and cheap alternative to kHz Ti:sapphire amplifiers, because no additional pump lasers for the seeder and the amplifier are required. The output beam of a near diffraction-limited quality was coupled into a 300-μm diameter, 1-m-long fused silica hollow-core fiber. Spectrally broadened pulses from the capillary output were compressed by a pair of Brewster-angled prisms. To avoid accumulation of additional nonlinear phase in air and prisms we collimated the beam after the hollow-core fiber filled by Ar at the diameter-1.5 cm and ~3cm for the Ne-filled fiber. Lack of nonlinear distortions in the prism compressor was confirmed by measurements of the spectrum at the hollow-core fiber output and after the prism compressor. The compressed pulses after the prisms pair were measured using SHG FROG apparatus with 50 μm I-type BBO crystal.