CW passive mode-locking evolved from Q-switched mode-locking in erbium doped fiber lasers

Summary form only given. We report a new mode-locking mechanism, where the use of a two-photon absorber in addition to a saturable absorber allows for CW mode-locking to reliably evolve from Q-switched mode locking. An optimal design of the two-photon absorber limits the peak power of the Q-switched pulses via optical limiting and thus aids in preventing damage to the saturable absorber. Moreover, the threshold for optical limiting is chosen to set an optimum stability point for CW mode-locked operation.