Visible Range Plasmonic Modes on Topological Insulator Nanostructures

Phase-resolved real-space imaging of localized plasmons in Bi1.5Sb0.5Te1.8Se1.2 topological insulator nanostructures is performed by scattering-type scanning near-field optical microscopy. Dipolar and higher order surface plasmon modes with well-defined field amplitude and phase profiles are detected in the visible part of the spectrum.MOE (Min. of Education, S’pore)Accepted versio

Germanium-on-carborundum surface phonon-polariton infrared metamaterial

Surface phonon-polaritons in thin layers of high-index dielectric structures are emerging as promising excitations for exploitation in high-density photonic devices. Here, a mid-infrared phononic–dielectric metamaterial, a 2D periodic array of germanium discs on silicon carbide (carborundum) is demonstrated. It is shown that the metamaterial can support sharp resonances at the free space wavelength that is at least ten times larger than lattice parameter of the array. With germanium discs of thickness 120 nm and diameter 1 µm, a metamaterial resonance at the wavelength of 11 µm is observed. A blueshift of the resonant frequency observed upon increase of the disk size is related to the anomalous dispersion of surface polaritons at germanium carborundum interface. It is argued that such surface phonon-polariton metamaterial is a promising platform for applications where enhanced homogeneity of optical response is required, such as imaging, holography, and cloaking.Agency for Science, Technology and Research (A*STAR)Ministry of Education (MOE)National Research Foundation (NRF)Accepted versionThis research was supported by the Singapore Ministry of Education (Academic Research Fund MOE2016-T3-1-006 (S) and Grant No. MOE2018-T2-1-176), by Advanced Manufacturing and Engineering Grant from the Agency for Science, Technology and Research (A*STAR) (Award No. A18A7b0058), by the National Research Foundation Singapore programs NRF-CRP18-2017-02 and NRF-CRP19-2017-01, and by the UK Engineering and Physical Sciences Research Council (Grant No. EP/M009122/1)

Plasmonics of topological insulators at optical frequencies

We show that topological insulator crystals are an excellent plasmonic platform in the UV to near-IR part of the spectrum, thanks to the interplay of interband transitions and Drude-like response of metallic surface states. This opens up exciting opportunities for the integration of plasmonic, electronic and spintronic devices