Femtosecond Mamyshev oscillator at 920 nm

A femtosecond all-PM-fiber Mamyshev oscillator (MO) at 920 nm is presented. It is based on a neodymium-doped fiber with a W-type index profile that effectively suppresses the emission around 1064 nm. The linear cavity is bounded by two near-zero dispersion fiber Bragg gratings with Gaussian reflectivity profiles. The laser is self-starting and generates up to 10-nJ pulses at a repetition rate of 41 MHz. The pulses can be compressed to 53 fs with a grating-pair compressor. To our knowledge, this is the first Mamyshev oscillator and also the highest energy femtosecond fiber oscillator demonstrated in this spectral region.