Fig. 1. Schematic of the proposed graphene stratified slab cladded by the prism and another semi-infinite dielectric medium. Double GSP resonances can be excited by Otto configuration under TM-wave incidence.

Fig. 2. (a) Optical responses of the proposed graphene stratified slab with respect to the incident angle θ at frequency f=1  THz, (b) schematic diagram depicting the phase-matching mechanism for double resonant excitations of GSP modes. The three dotted lines indicate three critical angles for ATRs occurring at interfaces of np−n1, n1−n2, and n2−na, respectively. (c) Electric field distributions along the z direction for light with varying incident angle θ. The white solid lines denote two graphene sheets placed at the interfaces of the dielectric layers. The prism occupies the region z<0. (d) Electric field distributions in the absence of graphene sheets. The white dashed lines indicate the interfaces of dielectric layers, except for the np−n1 one, which is located at z=0.

Fig. 3. (a) Angular reflection spectra with various Fermi levels on each graphene layer. The black dotted line indicates the independence of resonant excitation I on Fermi level EFB, while the black dashed line indicates the invariance of resonance II with respect to EFA. (b) Independent excitation and tuning of double resonant excitations with frequency f=3  THz and τ=1  ps.

Fig. 4. (a) Dependence of resonant angles on their corresponding Fermi level. Theoretically estimated results are also presented. (b) Dependence of FWHMs and FHs of both resonances on the corresponding Fermi level.

Fig. 5. Dependence of the resonant angle and FH on (a) the refractive index and (b) the thickness of dielectric layer 1. Both resonant excitations are presented.

Fig. 6. Dependence of the resonant angle and FH on (a) the refractive index and (b) the thickness of dielectric layer 2. Both resonant excitations are presented.

Fig. 7. (a) Angular reflection spectrum with triple resonant excitations. The inset shows the schematic of the graphene stratified slab with three graphene sheets. (b) Electric field distributions of triple resonant excitations. Light is selectively coupled into three different GSP modes by varying the incident angle. The white solid lines denote the three graphene sheets placed at the interfaces of the dielectric layers. The prism occupies the region z<0.

Fig. 8. (a) Angular reflection spectra with various Fermi levels on each graphene layer. The black dot-dashed, dotted, and dashed lines indicate the starting resonant angles of the three GSP modes with EFA=EFB=EFC=0.30  eV, respectively. (b) Angular reflection spectra with quintuple resonant excitations and their independent tuning via the Fermi level of graphene A.

Fig. 9. Validation of (a) angular spectra and (b) electromagnetic distributions comparing results obtained by the TMM-SCBC method and by commercial software COMSOL Multiphysics. An SCBC boundary condition is also employed in the COMSOL simulation. Markers are specific data points to better demonstrate the comparison.