High-Peak-Power Femtosecond Pulse Generation by Nonlinear Compression in a Yb-Doped Hybrid Fiber

We demonstrate a Yb-doped hybrid fiber with anomalous dispersion in the 1 μm spectral range, where asymptotically single-mode behavior is achieved with a differential mode amplification technique. The fiber has a dispersion of 70-100 ps/(nm·km) in the spectral range from 1.020 μm to 1.055 μm and a sharp dispersion peak (approximately 400 ps/(nm·km) near 1.064 μm) caused by the modes anti-crossing. The relatively large hybrid mode field diameter (8 μm) allows us to demonstrate high-peak-power femtosecond pulse generation via nonlinear chirped pulse compression in both dispersion regimes. Operation near 1.064 μm allows us to compress narrowband (3 dB spectral width of 2 nm) 6 ps pulses down to a duration of 250 fs with a peak power of 3.3 kW. Operation in the spectral region with a nearly constant anomalous dispersion is found to be optimal for the compression of wideband pulses. In particular, 1 ps pulses centered at 1.03 μm with a spectral width of approximately 11 nm are compressed down to 90 fs with a peak power of approximately 10 kW, which to the best of our knowledge is the best result for all-fiber (i.e., without external bulk compressors) systems operating near 1 μm.