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Absorption saturation in optically excited graphene
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View: Figures


Image of FIG. 1.
FIG. 1.

(a) Schematic illustration of optical pumping (red arrow) and competing effects due to carrier scattering (green arrows) and Pauli-blocking. (b) Temporal evolution of the pump-induced change in occupation in the most efficiently excited state for several pump fluences. The maximum is studied, respectively, to determine the saturation behavior. The dashed line indicates the temporal location of the maximum.

Image of FIG. 2.
FIG. 2.

(a) Saturation behavior in consideration of (i) all scattering channels (red solid line), (ii) pure carrier-carrier scattering (green dotted line), and (iii) pure carrier-phonon scattering (blue dashed-dotted line). The phonon-induced dynamics saturates at , which is much lower than in the Coulomb-induced () or in the full-dynamics case (). The thin vertical lines indicate the saturation fluence, respectively. (b) Full logarithmic plot of the full-dynamics shows a linear range for pump fluences of up to approximately . (c) The temporal location of the maximum with respect to the center of the Gaussian pulse indicates two different regimes for the full-dynamics: (i) at low pump intensities, the saturation resembles the purely phonon-driven dynamics, (ii) at higher intensities, the saturation reflects the purely Coulomb-driven dynamics.

Image of FIG. 3.
FIG. 3.

(a) Pump-induced change of occupation at the photon energy for the angle-averaged carrier distribution (solid red line) and for the states perpendicular (dotted blue line) and parallel (dashed green line) with respect to the polarization of the exciting pulse. (b) Maximal change of the corresponding carrier occupation averaged over all directions (red squares), perpendicular (blue triangles), and (iii) parallel (green circles) with respect to the polarization of the exciting field. The black lines are obtained by fitting the data with Eq. (4).

Image of FIG. 4.
FIG. 4.

Experimentally determined saturation of transmission: Using a 60-layer sample and a 56 fs-pulse with a photon energy of we obtain a saturation fluence of (blue). A direct comparison to the corresponding microscopic calculation (red) shows an excellent agreement.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Absorption saturation in optically excited graphene