10-µJ-level femtosecond pulse generation in the erbium CPA fiber source with microstructured hollow-core fiber assisted delivery and nonlinear frequency conversion.

We report on the development of a chirped pulse amplification (CPA) designed erbium fiber source with a hybrid high-power amplifier, which is composed of erbium-doped and erbium/ytterbium-co-doped double-clad large-mode-area fibers. Stretched pulses from the high-power amplifier with up to 21.9 µJ energy and 198.5 kHz repetition rate are dechirped in the transmission grating pair-based compressor with 73% efficiency, yielding as short as 742 fs duration with 15.8 µJ energy and ≈13 peak power (maximum average power up to 3.14 W) at the central wavelength of 1.56 µm. Compressed pulses are coupled into microstructured negative-curvature hollow-core fibers with a single row capillary cladding and different core sizes of 34 µm and 75 µm in order to realize femtosecond pulse delivery with a diffraction-limited output beam ( ≤1.09) and demonstrate ∼200 Stokes pulse generation at 1712 nm via rotational SRS in pressurized hydrogen ( ). We believe that the developed system may be a prospect for high-precision material processing and other high-energy and high-peak-power laser applications.