Complete light absorption in graphene-metamaterial corrugated structures

We show that surface-plasmon polaritons excited in negative permittivity metamaterials having shallow periodic surface corrugation profiles can be explored to push the absorption of single and continuous sheets of graphene up to 100$\%$. In the relaxation regime, the position of the plasmonic resonances of the hybrid system is determined by the plasma frequency of the metamaterial, allowing the frequency range for enhanced absorption to be set without the need of engineering graphene.

Figure 1

Schematic picture showing transverse magnetic light impinging on graphene placed on a periodically structured conducting substrate. The light is converted into surface plasmonic waves and subsequently absorbed in graphene.

Figure 2

The SPP spectrum for a flat-surface interface $\Sigma$ with $\hslash {\omega }_p=0.5$ eV and $\gamma =0$ (solid line in the left panel). Its intersection with the displaced incident photon line ($k_x\to k_x+G_n)$ gives an estimate of the frequency of SPPs in the $n$th band [e.g., $\hslash \Omega \left(G_1\right)\simeq 0.147$ eV]. Absorption at normal incidence near the first SPP resonance (right top panel), and the scattering function $S\left(\omega \right)$ for a wider frequency interval (right bottom panel). Dashed lines in the right panels refer to the bare interface (in the absence of graphene).

Figure 3

Dependence of the absorption at resonance on the corrugation height (left panel) for different graphene Fermi energies $E_F$, and relative absorption for a nonzero metamaterial relaxation's rate $\gamma$ (right panel) with $\gamma /{\omega }_p=\{{10}^{-4},5\times {10}^{-4},{10}^{-3}\}$ (magnitude increasing as indicated by the arrow). (Left panel) The fast change in $A\left(G_1\right)$ as $E_F$ varies from $0.07$ to $0.08$ eV results from a suppression of interband transitions in graphene as $2E_F\gtrsim \hslash \Omega \left(G_1\right)$. (Right panel) Appearance of two peaks for the highest values of $\gamma$ witnesses a considerable shift of the resonant position of $A\left(G_1\right)$ relative to $A_{\mathrm{bare}}\left(G_1\right)$. Other parameters as in Fig. 2.

Figure 4

Contour plot for the magnetic field modulus in the hybrid graphene-metal corrugated interface (top) and for the same structure in the absence of graphene (bottom). The field modulus is periodic in $x$ and thus only the restricted interval $\left|x\right|⩽a/2$ is shown. The corrugation height is ${\zeta }_0=85$ nm and the impinging light has $\hslash \omega =0.1474$ eV. The bar indicates the scale of the oscillation resulting from interference of the incident field and the reflected field, $2{\lambda }_{\mathrm{in}}=4\pi c/\omega$.