Blocking-assisted infrared transmission of subwavelength metallic gratings by graphene

The transmittance of simple one-dimensional gratings and two-dimensional pillar arrays is usually broadband with poor selectivity in the infrared region. In this paper, it is demonstrated that covering graphene on top of a Ag grating will improve both the magnitude and coherence of the transmitted infrared radiation. The underlying mechanism of this anomalous blocking-assisted transmission is attributed to the excitation of localized magnetic resonances. Quantitative predictions of the resonance wavelength for different geometric parameters and graphene chemical potentials are provided based on the equivalent-circuit model. The enhancement is alignment-free and actively tunable. Such graphene-covered gratings may help improve the performance and robustness of optical devices, such as polarizers, color filters, lab-on-chip sensors, and transparent conductors.