Saturable absorption in multilayer epitaxial graphene driven by mid-infrared quantum cascade lasers

We report saturable absorption in multilayer epitaxial graphene at 4.7 μm wavelength using mid-infrared quantum cascade laser. From z-scan and differential transmittance measurements, we demonstrate an enhancement of the transmittance of 9 %, attributed to the Pauli blocking effect in the graphene layers. We found that the saturation intensity is in the range of MW/cm
²
. Our results show the potential of graphene for ultrafast optical modulation in compact mid-infrared platforms as well as for assisting ultrashort pulse generation in quantum cascade lasers.