Figure 2: Mechanisms behind the saturation.

Saturation behaviour according to the full numerical solution of the graphene Bloch equation (blue down triangles), equations (2 and 3), and to the quasi-stationary solution (red up triangles), equation (4), show excellent agreement for all pump fluences. Without the second term ∝(t)/γ_k(t) in equation (4), it has the same structure as the standard model and the corresponding saturation is depicted by the green squares showing a saturation in the μJ cm⁻² regime and at very low carrier occupations (see the inset).