Atomic‐Layer Graphene as a Saturable Absorber for Ultrafast Pulsed Lasers

Abstract The optical conductance of monolayer graphene is defined solely by the fine structure constant, α = $e^2 /\hbar c$ (where e is the electron charge, $\hbar $ is Dirac's constant and c is the speed of light). The absorbance has been predicted to be independent of frequency. In principle, the interband optical absorption in zero‐gap graphene could be saturated readily under strong excitation due to Pauli blocking. Here, use of atomic layer graphene as saturable absorber in a mode‐locked fiber laser for the generation of ultrashort soliton pulses (756 fs) at the telecommunication band is demonstrated. The modulation depth can be tuned in a wide range from 66.5% to 6.2% by varying the graphene thickness.…