Generation of all-fiber femtosecond vortex laser based on NPR mode-locking and mechanical LPG

An all-fiber femtosecond vortex laser based on common fiber components is constructed. It can produce femtosecond orbital angular momentum modes whose time pulse width is 398 fs. The topological charge of output orbital angular momentum (OAM) modes from this laser can be adjusted among 0, +1, and −1 easily while it is also easy to convert between continuous OAM modes and pulse OAM modes.