A single-walled carbon nanotube wall paper as an absorber for simultaneously achieving passively mode-locked and Q-switched Yb-doped fiber lasers

We demonstrate a fiber ring laser based on a single-walled carbon nanotube (SWCNT) wall paper absorber. It is found that the proposed Yb-doped fiber laser can either be operated in the mode-locked states or Q-switched states. First, SWCNT wall paper acts as a mode locker when the pump power is below 80 mW. Self-started mode locking can be obtained when the pump power is about 47 mW. The proposed Yb-doped mode-locked fiber lasers can be operated in the dissipative soliton regime that the spectra have a narrow peak. Second, SWCNT wall paper acts as a Q switcher when the pump power is above 80 mW. The Yb-doped fiber laser can work in the Q-switched states at higher pump power which is quite different from the conventional pulse fiber lasers. The repetition rate increases from 30 kHz to 50 kHz and the pulse duration decreases from 2.7 μs to 1 μs with the increase of pump power. This is due to the SWCNT wall paper induced loss in the cavity which leads to Q-switched state at higher pump powers. The combination of the Q-switching and mode-locking in one fiber laser have potential application in the fields that require different pulse fiber lasers.