  We proposed multilayered graphene (Gr)-based surface plasmon
resonance-induced high-performance terahertz (THz) modulators with tunable
resonance frequencies. Several THz plasmonic modulators based on Gr
metamaterials were previously reported; however, these modulators had small
group delay, low extinction ratio (ER), and difficult-to-tune resonant
frequency without structural parameters in the THz range. A comprehensive
investigation employing the finite-difference time-domain (FDTD) simulation
technique revealed high group delay, broad tunability independent of structural
parameters, and large ER for our proposed quadband and pentaband plasmonic
modulators. We obtained tunable group delays with a maximum of 1.02 ps and 1.41
ps for our proposed quadband and pentaband plasmonic modulators, respectively,
which are substantially greater compared to previously reported Gr-based
metamaterial structures. The maximum ER of 22.3 dB was obtained which was
substantially high compared to previous reports. Our proposed modulators were
sensitive to the polarization angle of incident light; therefore, the
transmittance at resonant frequencies was increased while the polarization
angle varied from 0 to 180 degree. These high-performance plasmonic modulators
have emerging potential for the design of optical buffers, slow light devices,
multistop band filters, integrated photonic circuits, and various
optoelectronic systems.
