Femtosecond Carrier Dynamics and Saturable Absorption in Functionalized Epitaxial Graphene

We have measured carrier relaxation times and nonlinear optical properties in three functionalized epitaxial graphene layers grown on SiC wafers by using ultrafast optical pump-probe spectroscopy and open aperture z-scan at 780 nm. The results demonstrate that after different functionalization, the ratios of the slower relaxation in the range of 3.1-4.6 ps (related to carrier-phonon intraband and interband scattering) increase about 2-6 times compared to original graphene. These changes of relaxation obviously improved the nonlinear optical properties, making functionalized epitaxial graphene can be used as a tuneable saturable absorber.