Topological-Insulator-Based Gap-Surface Plasmon Metasurfaces

Abstract

Topological insulators (TIs) have unique highly conducting symmetry-protected surface states while the bulk is insulating, making them attractive for various applications in condensed matter physics. Recently, topological insulator materials have been tentatively applied for both near- and far-field wavefront manipulation of electromagnetic waves, yielding superior plasmonic properties in the ultraviolet (UV)-to-visible wavelength range. However, previous reports have only demonstrated inefficient wavefront control based on binary metasurfaces that were digitalized on a TI thin film or non-directional surface plasmon polariton (SPP) excitation. Here, we numerically demonstrated the plasmonic capabilities of the TI Bi2Te3 as a material for gap–surface plasmon (GSP) metasurfaces. By employing the principle of the geometric phase, a far-field beam-steering metasurface was designed for the visible spectrum, yielding a cross-polarization efficiency of 34% at 500 nm while suppressing the co-polarization to 0.08%. Furthermore, a birefringent GSP metasurface design was studied and found to be capable of directionally exciting SPPs depending on the incident polarization. Our work forms the basis for accurately controlling the far- and near-field responses of TI-based GSP metasurfaces in the visible spectral range.

Topological Insulator Metamaterials

“…Aigner and co-workers recently predicted that the superior plasmonic figure of merit of Bi 2 Te 3 topological insulator can be utilized to create gap plasmon metasurfaces and designed a far-field beam-steering metasurface for the visible spectrum, yielding a cross-polarization efficiency of 34% at 500 nm while suppressing the copolarization to 0.08%. 200…”

“…Nanometric topological insulator thin films were shown to act as an intrinsic optical resonant cavity due to the unequal refractive indices in their metallic surfaces and bulk, leading to enhancement of phase shifts and realization of holographic imaging. Aigner and co-workers recently predicted that the superior plasmonic figure of merit of Bi 2 Te 3 topological insulator can be utilized to create gap plasmon metasurfaces and designed a far-field beam-steering metasurface for the visible spectrum, yielding a cross-polarization efficiency of 34% at 500 nm while suppressing the copolarization to 0.08% …”

Plasmon Resonances in 1D Nanowire Arrays and 3D Nanowire Networks of Topological Insulators and Metals

“…On the other hand, inter-band transitions are responsible for the visible and UV optical responses [ 6 , 19 , 20 ] with spectral regions where the real part of the dielectric constant has negative values (see Figure 1 a). In these spectral regions, these compounds may present plasmonic behavior, and several works have shown plasmon resonances in the visible and UV spectral ranges in nanostructures made of them [ 21 , 22 , 23 , 24 , 25 ]. Moreover, due to the high negative values of the real part of the dielectric constant, they have been proposed as alternative materials for the development of UV devices based on UV plasmonics [ 6 ], and for infrared photonic applications [ 26 ].…”