Controlled stacking of graphene monolayer saturable absorbers for ultrashort pulse generation in erbium-doped fiber lasers

Stacked chemical-vapour deposited (CVD) graphene monolayer samples were fabricated and applied as saturable absorbers in erbium-doped fiber laser (EDFL). Transient absorption experiments show that at the saturation absorption regime, and regardless the number of stacked layers (from 1 to 5 layers), samples present 1 ps recovery time. Pulses with duration from 0.60 to 1.17 ps were generated in an EDFL, depending on the number of graphene layers (i.e., the linear optical absorption) used. The results show that it is possible to increase the linear optical absorption of a graphene stacking without affecting its nonlinear optical behavior and ultrafast response time. Therefore, by stacking individual CVD-monolayer graphene samples it is possible to control the optical properties in graphene-based EDFLs and simultaneously tune their ultra-short pulse generation.