Passively mode-locked Yb-doped fiber laser based on CNT-film sandwiched between the multimode fiber connectors

We propose and demonstrate a saturable absorber (SA) of composite mode-locked mechanisms based on the Carbon nanotube (CNT) film sandwiched between the multimode fiber (MMF) connectors (CNT-MMF) for achieving passively mode-locked fiber laser. Compared with that CNT-film sandwiched between the single-mode fiber (SMF) connectors (CNT-SMF), the modulation depth is increased 1.48% and the saturation intensity decreases, which is the main reason that the fiber laser based on CNT-MMF-SA can achieve full mode-locked and work for a long time at higher pump power. However, the fiber laser based on the CNT-SMF-SA can only occur the Q -switched mode-locked state and the CNT-film is easily burned out. Further, the structure of the CNT-MMF provides an effective way for obtaining high damage threshold and improving the performance of the fiber laser based on various nanomaterial films. Our work dramatically broadens the design possibilities in terms of technology and provides convenient architectures for the nanomaterial-based mode-locked fiber laser.