Full text loading...
General schematic of the structures considered in this paper. From bottom to top (increasing x direction) are dielectric of permittivity (occupying ), plasma substrate of permittivity and thickness , dielectric of permittivity and thickness , a sheet of monolayer graphene at a distance above the plasma layer, and dielectric of permittivity occupying the rest of the space above the graphene sheet.
(a) Coupled plasmon modes ( , , and , solid curves) of graphene 30 nm away from a semiconductor thin film of 50 nm thickness. The parameters used are , , , and for graphene, and for the doped semiconductor thin film. Decoupled modes, calculated with , are also plotted as dashed curves. Thin curves in the low-q region are the low-q approximation for each mode (Eqs. (7) – (9) and (11) ). The dotted curve represents the plasmon mode when the substrate is changed to a metal of with other parameters unchanged. The red dots mark the modes at and of which the electric field distributions are drawn in Fig. 3 . The crossing of the and modes around is enlarged in the inset. Colored areas are interband and intraband damping regions. (b) Coupled plasmon modes ( and , solid curves) of graphene 30 nm away from a semi-infinite semiconductor substrate ( ). Other parameters are the same as those used in (a). Decoupled modes, calculated with , are also plotted as dashed curves. Thin curves in the low-q region are the low-q approximation for each mode (Eqs. (9) , (12) , and (13) ). Inset: (black circles) and Eq. (29) of Ref. 10 (red circles) are plotted along with the numerical result (solid curve) with while other parameters remain unchanged. The solid curves and dashed curves in (b) are plotted again in (c) to be compared with the corresponding retarded mode (dotted curves). In (c), all the blue curves and the black curves are numerically calculated using and , respectively. The retarded mode is indistinguishable from the nonretarded mode. A waveguide mode appears between light lines and when .
Electric field magnitudes and directions of (a) mode (b) mode at , and (c) mode (d) mode at , which are marked by red dots in Fig. 2(a) . Darker and lighter shades depict higher and lower magnitudes of the electric field; the directions of the electric fieldsare given at , , and (see Fig. 1 ) by arrows, and z spans one period of the mode ( ). The right panel shows the x-component of the electric field ( ) corresponding to the field distribution at the center point ( ) of the left panel.
Tunability of the plasmon resonance of the mode at . The tuning parameter is marked next to each curve and the corresponding horizontal axis; the other parameters are fixed as those used for Fig. 2(a) . Asymptotes of , , and are also plotted as dashed lines.
Article metrics loading...