Tunable ytterbium fiber laser mode-locked with a nonlinear amplifying loop mirror

Abstract

We present a widely tunable ytterbium fiber laser mode-locked with a nonlinear amplifying loop mirror (NALM). By introducing a transmission grating pair and a collimator into the cavity, which work as both a wavelength selector and a dispersion compensator, continuous wavelength tunable mode-locked operation from 1020.8 nm to 1059.5 nm is achieved. At the typical wavelength of 1030 nm, the laser delivers laser pulses with a pulse duration of 1.36 ps and a time-bandwidth product of 0.71 by assuming a Gaussian pulse envelope. By altering dispersion of the grating pair, the transition between two distinct pulse-shaping regimes in a figure eight NALM laser is demonstrated for the first time, to the best of our knowledge. When the laser enters the dissipative-soliton regime, chirped pulses with 24.9-nm spectral bandwidth are generated and the pulses can be dechirped to 88.7 fs which is a new pulse-duration record for figure eight ytterbium fiber lasers.