Influences of CO2 laser modification on the surface morphology and optical absorption of graphene thin films

Abnormal optical absorption phenomena were observed in as-modified few-layer graphene thin films by 10.6-μm CO2 laser under ambient conditions. Saturable absorption (SA) responses were measured using z-scan technology. The graphene samples showed SA before laser modification, whereas they exhibited reverse SA behavior after laser modification due to the effects of thinning and damage to samples. The shift of 2D peak and appearance of D peak from Raman scattering spectra further confirm the effects of laser irradiation on graphene.