84-fs 500-MHz Yb:Fiber-Based Laser Oscillator Mode Locked by Biased NALM

We demonstrate a 500-MHz repetition rate, self-starting Yb:fiber laser incorporated with a phase biased nonlinear amplifying loop mirror as an artificial saturable absorber. The laser has two output ports; the beam splitter port delivers pulses, which can be compressed to 84.4 fs at an average power of 51 mW and the polarization beam splitter port directly output 61-fs pulses at an average power of 197 mW. Although the fiber is non-polarization maintaining, the mode locking is environmentally stable.