Fig.1
Subcellular FDTD modeling of graphene sheet in the Yee cell (i,j,k) based on specific updating equations for tangential components of and under influence of .
Fig. 2
The real part of the conductivity of graphene is illustrated in (a), its imaginary part in (b) and λSPP in (c), for B = 0 T, as functions of the chemical potential μc.
Fig. 3
Geometry of the FSS of [1010 [10] L. Lin, L. S. Wu, W. Y. Yin, and J. F. Mao, “Modeling of magnetically biased graphene patch frequency selective surface (FSS),” in 2015 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP), Jul. 2015, pp. 1-3.] (perspective view of part of the periodic structure).
Fig. 4
Validation of the developed FDTD methodology: co-polarization transmission coefficient.
Fig. 5
The unit cell of the FSS proposed in this work for dynamic change of the state of operation and smart tuning of rejection band(s).
Fig. 6
Comparison between FDTD and HFSS results: FSS co-polarization transmission coefficient for the graphene ring with rectangular aperture with dimensions d = 0.25 μm and l = 2.25 μm, without the internal graphene sheet. For the graphene ring, μce is set to 1 eV.
Fig. 7
(A/m2) for the following FSSs: (a) square ring only, μce = 1 eV and d = l = 2.25 μm at f = 3.29 THz and (b) square ring with the graphene sheet in its aperture, μce = 0.75 eV, μci = 1 meV and a = 100 nm, for f = 2.65 THz (first resonance).
Fig. 8
for the FSSs configured with μce = 1 eV and with the following parameters: (a) d = 0.25 μm and l = 2.25 μm for f = 3.39 THz (first resonance, with no graphene sheet in the ring aperture), (b) d = 0.25 μm and l = 2.25 μm for f = 6.93 THz (second resonance, with no graphene sheet in the ring aperture) (c) μci = 1 eV and a = 100 nm, for f = 2.78 THz (first resonance of the proposed FSS), (d) μci = 1 eV and a = 100 nm, for f = 6.21 THz (second resonance of the proposed FSS).
Fig. 9
Mesh generated in HFSS for modeling the FSS with a = 100 nm. Mesh details are highlighted.
Fig. 10
Co-polarization transmission coefficient for a = 100 nm: (a) the two proposed FSS operation configurations, (b) validation of FDTD model for the off mode and (c) validation of FDTD model for the on mode.
Fig. 11
Transmission coefficient for the analyzed configurations.
Fig. 12
Distribution of surface current density for the μce = μci = 1 eV configuration: (a) at the first resonance (2.78 THz) and (b) at the second resonance (6.21 THz).
Fig. 13
Distribution of for μce = 1 eV / μci = 0.6 eV configuration at: (a) 2.73THz and (b) 5.09 THz.
Fig. 14
Transmission coefficients illustrating the shift of both rejection bands of mode on due to regulation of μce.
Fig. 15
Transmission coefficients for the two illustrative initial configurations, displaying shifting of both bands.
Fig. 16
Transmission coefficient for the configurations analyzed, illustrating controlled shifting of the lower rejection band.
Fig. 17
Distribution of surface current density for the μce = 1 eV / μci = 0.55 eV configuration: (a) at the first resonance (2.71THz) (a) and (b) at the second resonance (4.91 THz).
Fig. 18
Distribution of surface current density for the μce = 0.55 eV / μci = 0.65 eV configuration: (a) at the first resonance (2.07 THz) (a) and (b) at the second resonance (4.88 THz).
Fig. 19
Transmission coefficient illustrating the shifting of the rejection band of mode off by tuning μce.
Fig. 6
Comparison between FDTD and HFSS results: FSS co-polarization transmission coefficient for the graphene ring with rectangular aperture with dimensions d = 0.25 μm and l = 2.25 μm, without the internal graphene sheet. For the graphene ring, μce is set to 1 eV.
Fig. 7
(A/m2) for the following FSSs: (a) square ring only, μce = 1 eV and d = l = 2.25 μm at f = 3.29 THz and (b) square ring with the graphene sheet in its aperture, μce = 0.75 eV, μci = 1 meV and a = 100 nm, for f = 2.65 THz (first resonance).
Fig. 8
for the FSSs configured with μce = 1 eV and with the following parameters: (a) d = 0.25 μm and l = 2.25 μm for f = 3.39 THz (first resonance, with no graphene sheet in the ring aperture), (b) d = 0.25 μm and l = 2.25 μm for f = 6.93 THz (second resonance, with no graphene sheet in the ring aperture) (c) μci = 1 eV and a = 100 nm, for f = 2.78 THz (first resonance of the proposed FSS), (d) μci = 1 eV and a = 100 nm, for f = 6.21 THz (second resonance of the proposed FSS).
Fig. 9
Mesh generated in HFSS for modeling the FSS with a = 100 nm. Mesh details are highlighted.
Fig. 10
Co-polarization transmission coefficient for a = 100 nm: (a) the two proposed FSS operation configurations, (b) validation of FDTD model for the off mode and (c) validation of FDTD model for the on mode.
Fig. 11
Transmission coefficient for the analyzed configurations.
Fig. 12
Distribution of surface current density for the μce = μci = 1 eV configuration: (a) at the first resonance (2.78 THz) and (b) at the second resonance (6.21 THz).
Fig. 13
Distribution of for μce = 1 eV / μci = 0.6 eV configuration at: (a) 2.73THz and (b) 5.09 THz.
Fig. 14
Transmission coefficients illustrating the shift of both rejection bands of mode on due to regulation of μce.
Fig. 15
Transmission coefficients for the two illustrative initial configurations, displaying shifting of both bands.
Fig. 16
Transmission coefficient for the configurations analyzed, illustrating controlled shifting of the lower rejection band.
Fig. 17
Distribution of surface current density for the μce = 1 eV / μci = 0.55 eV configuration: (a) at the first resonance (2.71THz) (a) and (b) at the second resonance (4.91 THz).
Fig. 18
Distribution of surface current density for the μce = 0.55 eV / μci = 0.65 eV configuration: (a) at the first resonance (2.07 THz) (a) and (b) at the second resonance (4.88 THz).
Fig. 19
Transmission coefficient illustrating the shifting of the rejection band of mode off by tuning μce.
Fig. 20
Schematic diagram of the experiment conducted in [1212 [12] A. C. Tasolamprou, A. D. Koulouklidis, C. Daskalaki, C. P. Mavidis, G. Kenanakis, G. Deligeorgis, Z. Viskadourakis, P. Kuzhir, S. Tzortzakis, M. Kafesaki, E. N. Economou and C. M. Soukoulis, “Experimental demonstration of ultrafast THz modulation in a graphene-based thin film absorber through negative photoinduced conductivity,” ACS photonics, vol. 6, no. 3, pp. 720-727, 2019.] for measuring graphene absorption of THz incident wave.
Fig. 21
Comparison among absorption spectra obtained experimentally and numerically in [1212 [12] A. C. Tasolamprou, A. D. Koulouklidis, C. Daskalaki, C. P. Mavidis, G. Kenanakis, G. Deligeorgis, Z. Viskadourakis, P. Kuzhir, S. Tzortzakis, M. Kafesaki, E. N. Economou and C. M. Soukoulis, “Experimental demonstration of ultrafast THz modulation in a graphene-based thin film absorber through negative photoinduced conductivity,” ACS photonics, vol. 6, no. 3, pp. 720-727, 2019.] and the spectra calculated in this work using CST and COMSOL.