Generation of pulse bursts with controllable number of pulses and of spectral broadening directly at the laser output from a km-long Yb-doped all-fiber laser

In this work, we study the pulse burst regime of a fiber laser, which allows generating packets of multiple pulses whose number can be precisely controlled by modifying the polarization state by means of two retarder plates (QWR, HWR). The proposed experimental scheme is a highly energetic Yb-doped all-fiber ring pulsed laser operating in the 1064 nm wavelength region and using a nonlinear polarization rotation (NPR)-based passive mode locking technique. Raman scattering effects can be found by increasing pump power to achieve the formation of up to four Stokes, resulting in a spectral broadening over more than 200 nm.