Few-layer graphitic carbon nitride (g-C₃N₄) nanosheets were fabricated and utilized as a saturable absorber for mode-locking in an Er-doped fiber laser with net normal dispersion. The g-C₃N₄/polyvinyl alcohol (PVA) hybrid-film-based saturable absorber has a modulation depth of 4.01% and a saturation intensity of 7.5 MW/cm². By integrating g-C₃N₄-PVA mode-locker into the laser cavity, a mode-locked operation could be obtained. The achieved mode-locking pulse centered at 1530.3 nm has a pulse width of 530 ps. Its repetition rate is 40.8 MHz, and the corresponding signal-to-noise ratio is about 55 dB.

We experimentally demonstrate a cascaded Raman scattering continuum, utilizing a compact mode-locked Yb-doped fiber laser based on a nonlinear polarization rotation technique in the all normal dispersion regime. There is no physical filter or polarization controller in the oscillator, and a different mode-locked operation is achieved, corresponding to the extra fiber location in the oscillator. The broadband spectrum generation owes to the enhanced stimulated Raman scattering progress. The maximum output average power and peak power are 14.75 nJ and 18.0 W, and the short coherence light is suited for optical coherence tomography.