Switchable Dual-Wavelength Synchronously Q-Switched Erbium-Doped Fiber Laser Based on Graphene Saturable Absorber

We demonstrate a switchable dual-wavelength synchronously pulsed fiber laser Q-switched by graphene saturable absorber. Wavelength-resolved studies on the output Q-switched pulses show that despite of large wavelength spacing up to 26 nm, the two Q-switched pulses at each individual wavelength can be temporally synchronized with per-pulse energy up to similar to 70 nJ. Further experiments show that by adjusting the intracavity birefringence, dual-wavelength emission can be switched to another dual-wavelength operation regime with wavelength separation of 5.7 nm. Our experimental results are also qualitatively supported by the cavity linear transmission characteristics of the ring cavity.