Picosecond pulsed flat-top beam in a mode-locking all-fiber laser

Ow7ing to the flat center and steep edge, the flat-top beam is widely used in the fields of micromachining and optical image processing. Here, we propose an efficient scheme to generate a picosecond pulsed flat-top beam in a mode-locking all-fiber laser. After utilizing an orthogonal polarization method for complete incoherence and a high-precision all-fiber optical delay line (ODL) for rigorous time synchronization, the pulsed fundamental mode (LP