Two regimes of wavelength tunable noise-like pulse in a figure-eight fiber laser based on a nonlinear amplifying loop mirror: continuous-wave mode locking and Q-switched mode locking

We experimentally demonstrate wavelength tuning of a continuous-wave mode-locking noise-like pulse (CMLNLP) and a Q-switched mode-locking noise-like pulse (QMLNLP) in a passively mode-locked figure-eight fiber lasers based on a nonlinear amplifying loop mirror (NALM). The NALM simultaneously functions as an artificial saturable absorber (SA) and a tunable spectral filter. By carefully tuning pump power and polarization controllers (PCs), wavelength tunable CMLNLP and QMLNLP can be alternately generated. Results show continuous central wavelength tuning exceeding 20 nm for both pulse types: CMLNLP from 1544.5 nm to 1564.6 nm, and QMLNLP from 1543.7 nm to 1563.9 nm. The variation of characteristic pulse parameters with wavelength is systematically analyzed. These tunable wavelength outputs have great potential in laser micromachining and so on.