Switchable dual-band generation of femtosecond pulses in a mode-locked Erbium-doped fiber laser based on monolayer graphene

This work presents a stable and switchable dual-band generation from a polarization-dependent Erbium-doped fiber laser mode-locked by monolayer graphene as a saturable absorber. The ultrashort generated pulses at single band exhibit spectral (temporal) widths of 8.8 nm (305 fs) and 9 nm (384 fs) at 1536 nm and 1557 nm, respectively, while the simultaneous dual-band state ensured a spectral width of 5 and 6 nm for both wavelengths, which are the best dual-band mode-locked performances of the literature obtained from an EDFL. Also, its dual-band spectral evolution was analyzed by changing the pumping power and the intracavity polarization state via a motorized polarization controller. Finally, our simulation provided an excellent qualitative explanation of the laser switching as a function of pumping power due to the change in EDF gain. We found a relative percentage error between experimental results and simulation of $22.7\%$ , $13.3\%$ , $9\%$ , and $8.3\%$ for 1530 nm, 1556 nm, and dual-band left and right central wavelength, respectively.