Figure 5.

Absorption enhancement with controllable spectral and polarization selectivity. (a) The absorption in the absorptive layer with the Fermi energy of graphene ranging from 0.5 to 0.7 eV under the illumination of a TM mode at normal incidence is shown; (b) The absorption in the absorptive layer with the Fermi energy of graphene ranging from 0.6 to 0.8 eV under the illumination of TE mode at normal incidence is shown; (c) Electrically tunable polarization selectivity of absorption. The red, blue, and green curves show the dependence of polarization absorption ratio (defined as 20log$(A_{TM}^{\prime }/A_{TE}^{\prime })$) on the variation of graphene’s Fermi energy at $13.5\mathsf{\mu }$m, $12.9\mathsf{\mu }$m, and $12.5\mathsf{\mu }$m, respectively.