Generation of pulse bursts and broadband spectrum in a hundred-meter-long Yb-doped fiber laser

We report an experimental investigation into the generation and control of multi-pulse bursts in a passively mode-locked Yb-doped fiber laser based on nonlinear polarization rotation (NPR). By systematically adjusting the polarization controller (PC) at a fixed pump power, we successfully realize controllable pulse bursts with varying pulse numbers and intervals. Notably, distinct pulse interval distributions are observed in the output configurations ranging from 1 to 5 pulses. Additionally, a broadband spectrum with a 20 dB bandwidth extending up to 66 nm is achieved, attributed to the interplay between Raman scattering and polarization state modulation within the laser cavity. These findings demonstrate the potential for precise pulse control and broad spectral generation in NPR based fiber lasers.