Figure 1.

Plasmonic light trapping with graphene nanoribbon structure. (a) Schematic of the proposed structure. From the top to the bottom of the structure are a nanostructured graphene film with an array of periodical nanoribbons, an insulator layer with a thickness of s, an absorptive layer with a thickness of t, and a semi-infinite substrate, respectively. Incident light of transverse-magnetic (TM) (x-polarized) modes excites localized plasmons in the doped graphene layer, which trap light in the near-field and enhance the optical absorption in the light-absorbing layer underneath; (b) A graphene nanoribbon with geometric parameters. The period of the graphene nanoribbon is $P_x=400$ nm. The width is W; (c) Simulated spectra of reflection (R), transmission (T), total absorption (A), and absorption in the absorptive layer ($A^{\prime }$) for TM mode under normal incidence. The Fermi energy is $E_F=0.6$ eV. The enhancement of absorption in the absorptive layer is also shown; (d) Electric field distributions in the z-direction at the resonance wavelength of $14.0\mathsf{\mu }$m. The field is normalized to the field amplitude of the incident light ($E_0$) and plotted in the x–y plane that is 5 nm above the graphene nanoribbons.