THz plasmonic metasurface based on a periodic array of InSb metamolecules with narrow resonances

Abstract

We propose an indium antimonide (InSb) THz plasmonic metasurface featuring a surface lattice resonance (SLR) with the quality factor of Q ∼ 375 and theoretically investigate the plasmonic response of the ensemble of InSb metamolecules. The localized surface plasmon resonances (LSPRs) of individual metamolecules couple together through Rayleigh Anomaly (RA) diffraction, leading to the appearance of the SLR at 0.75THz , suitable for biophotonic applications. The major advantage of the proposed metasurface over metal-based ones in the THz regime is the tunability of SLR frequency by changing the carrier concentration. Apart from SLR, it is possible to achieve additional resonances by tuning the superstrate thickness exploiting Fabry–Perot (FP)-like cavity effects. Achieving a narrow-linewidth SLR and the resultant remarkable local-field enhancement in the InSb-based metasurface opens the door to a wide range of applications. Conducive to optical manipulation and sensing, the capability of the proposed metasurface is examined in plasmonic tweezing and medium-perturbation sensing fields.