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We propose to achieve multi-band perfect plasmonic absorptions with peak absorptivity >99% via the excitation of standing-wave graphene surface plasmon polaritons using single-layer graphene-based rectangular gratings. For the case with continuous gratings, perfect absorptions are only allowed for even-order modes, while the absorptions are quite low for odd-order modes because the fields are out-of-phase. However, for gratings with bottom-open configuration, four-band perfect absorptions containing both the even- and odd-order modes can be realized, which are found to be highly sensitive to the incident angle. The simulated results agree very well with the theoretical analyses by considering the phase path of the plasmonic waves. This multi-band absorber is a promising candidate for future plasmonic devices.

To achieve plasmonically induced transparency (PIT), general near-field plasmonic systems based on couplings between localized plasmon resonances of nanostructures rely heavily on the well-designed interantenna separations. However, the implementation of such devices and techniques encounters great difficulties mainly to due to very small sized dimensions of the nanostructures and gaps between them. Here, we propose and numerically demonstrate that PIT can be achieved by using two graphene layers that are composed of a upper sinusoidally curved layer and a lower planar layer, avoiding any pattern of the graphene sheets. Both the analytical fitting and the Akaike Information Criterion (AIC) method are employed efficiently to distinguish the induced window, which is found to be more likely caused by Autler-Townes splitting (ATS) instead of electromagnetically induced transparency (EIT). Besides, our results show that the resonant modes cannot only be tuned dramatically by geometrically changing the grating amplitude and the interlayer spacing, but also by dynamically varying the Fermi energy of the graphene sheets. Potential applications of the proposed system could be expected on various photonic functional devices, including optical switches, plasmonic sensors.

By taking a graphene nanoribbon as a resonator, we have numerically and analytically investigated the spectral characteristics of plasmon-induced transparency in integrated graphene waveguides. For the indirect coupling, the formation and evolution of the transparency window are determined by the excitation of the super resonances, as well as by the destructive interference and the coupling strength between the two resonators, respectively, while for the indirect coupling, the peak transmission and corresponding quality factor can be dynamically tuned by adjusting the Fermi energy of graphene nanoribbons and the transparency peak shifts periodicity with the round-trip phase accumulated in the graphene waveguide region. Analytical results based on temporal coupled mode theory (CMT) show good consistence with the numerical calculations. Our findings may support the design of ultra-compact plasmonic devices for optical modulating.

Here we study the possibility to achieve polarization-independent optical absorption in stacked anisotropic 2D material nanostructures (NSs). Focusing on black phosphorus, we demonstrate that by crossly stacking even-layered NSs, surface plasmons resonant in the two lattice directions are complementary excited, leading to polarization-independent absorption at any layer distance. This property is numerically validated using full electromagnetic simulations and theoretically predicted by a two-particle model. Our proposal can open up the possibility of anisotropic 2D materials to develop polarization-independent plasmon devices such as sensors and absorbers.