Graphene mode-locked and Q-switched 2 - μ m Tm/Ho codoped fiber lasers using 1212-nm high-efficient pumping

Abstract

We report graphene mode-locked or Q-switched Tm/Ho-codoped fiber laser pumped by a 1212-nm phosphorus-doped fiber Raman laser. First, comparison experiments were performed for a continuous-wave 2 μm Tm/Ho-codoped fiber laser pumped by a 1565-nm laser or a 1212-nm laser, verifying that the 1212- nm pumping is more efficient than the conventional ∼1560-nm pumping. Then, we further realized 1212-nm highly efficient pumped Tm/Ho-codoped fiber lasers mode-locked and Q-switched by a graphene saturable absorber, respectively. Using only 30-cm Tm-Ho gain fiber under the 1212-nm pumping, the passive Q-switching at a center wavelength of 1976 nm was efficiently generated with tunable repetition rate between 32.2 and 43.0 kHz and shortest pulse width of 1.41 μs. Moreover, the passive mode-locking at 1913.7 nm was stably achieved with a fundamental repetition rate of 19.978 MHz and pulse energy of ∼20 pJ. To the best of our knowl- edge, it is the first demonstration of 2-μm pulsed fiber lasers high efficiently pumped by a 1212-nm laser. © 2016