Absorption saturation in optically excited graphene

We investigate the saturation of the optical absorption in graphene induced by ultrafast optical pulses. Within a microscopic theory, we study the momentum-, angle-, and time-resolved interplay of anisotropic excitation, carrier-carrier, and carrier-phonon scattering, and its influence on the saturation of absorption and transmission. In agreement with performed experiments, we observe a linear regime for the intensity-dependence of the transmission at low pump fluences and a nonlinear saturation in the high excitation regime. Applying 10 fs-pulses, we obtain a saturation fluence of approximately 0: 65 mJ/cm(2). We demonstrate how the interplay of Pauli-blocking and intensity-dependent relaxation determines the saturation behavior. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768780]