2.04 µm harmonic noise-like pulses generation from a mode-locked fiber laser based on nonlinear polarization rotation

We report the generation of harmonic noise-like mode-locked pulses in a thulium-doped fiber laser. In this laser, mode-locking can be realized through nonlinear polarization rotation (NPR) technique. The ring cavity configuration uses 5 m Tm-doped dual-cladding fiber, as gain medium, pumped by 793 nm diode couple controllers (PCs) and polarization-dependent isolator to form polarization-rotating saturable absorber. By carefully adjusting PCs, laser generates at 2.04 µm band. With increase pump power, harmonics fundamental repetition frequency 6.88 MHz, from which we obtain second controlled mode. obtained results may useful for enhancing understanding mechanism characteristics pulse 2