Above 100 nJ all-normal-dispersion femtosecond pulse generation from a large-core multi-mode fiber laser

Abstract

We demonstrate an all-normal-dispersion mode-locked fiber laser based on a piece of large-core Yb-doped multi-mode fiber. High order modes are suppressed by coiling the gain fiber to produce large loss for the high modes but low loss for the fundamental mode. Mode-locking is self-starting by exploiting a combination of a grating-aperture based spectral filter with a nonlinear polarization evolution effect. The laser directly delivers 1.1 ps, 107 nJ pulses at a repetition rate of 76.7 MHz, with an average power of up to 8.2 W. The pulses can be compressed externally to 210 fs with a peak power of up to 350 kW.