Transition metal dichalcogenide nanodisks as high-index dielectric Mie nanoresonators

Abstract

Monolayer transition metal dichalcogenides (TMDCs) have recently been proposed as a unique excitonic platform for advanced optical and electronic functionalities. However, in spite of intense research efforts, it has been largely overlooked that, in addition to displaying rich exciton physics, TMDCs also possess a very high refractive index. This opens a possibility to utilize these materials for constructing resonant nanoantennas based on subwavelength geometrical modes. Here we show that nanodisks fabricated from exfoliated multilayer WS 2 support distinct Mie resonances and so-called anapole states that can be easily tuned in wavelength over the visible and near-infrared spectral range by varying the nanodisks' size and aspect ratio. We argue that the TMDC material anisotropy and the presence of excitons substantially enrich nanophotonics by complementing traditional approaches based on plasmonics and well-known high-index materials such as silicon. As a proof-of-concept, we demonstrate a novel regime of light-matter interaction, anapole-exciton polaritons, which we realize within a single WS 2 nanodisk. Our results thus suggest that nanopatterned TMDCs are promising materials for high-index nanophotonics applications with enriched functionalities and superior prospects.

Integration of two-dimensional transition metal dichalcogenides with Mie-resonant dielectric nanostructures

“…Patterning of TMDs provides an opportunity to hybridize inelastic excitonic properties with elastic scattering properties, e.g. by featuring Mie-type resonances supported by their high refractive index, as very recently demonstrated by Verre and coworkers [105]. The authors fabricated nanodisk-shaped Mie-resonators by electron-beam lithography starting from exfoliated multilayer WS 2 .…”

“…A recently demonstrated approach to realize the strong coupling condition in TMDs is to directly fabricate the nanoresonators from the TMD material [105]. A corresponding recent work will be discussed in section 4.4 below.…”

Metasurfaces: Subwavelength nanostructure arrays for ultrathin flat optics and photonics

“…WS 2 , a TMDC material, has anisotropic properties with in-plane n ≥ 4, which is much higher than its out-of-plane n (Figure 1e). 20 Realization of metadevices has been attempted, and one of the most important goals is the development of technology to actively control metasurfaces. 21 One approach is to exploit the electrical gating method by modulating the free-carrier density; examples include metasurfaces based on transparent conducting oxides (e.g., indium tin oxide) 22 or highly doped semiconductors (e.g., gallium arsenide).…”

Ultrafast nonequilibrium dynamics of strongly coupled resonances in the intrinsic cavity of WS2 nanotubes

“…Besides the two-dimensional platelets, TMDs also form fullerenelike structures and nanotubes (NTs) [28][29][30][31][32][33][34][35][36][37][38][39][40][41]. In a suitable geometry the high refractive index of TMDs provides an intrinsic optical cavity mode (CMR) that strongly couples to the excitonic resonance of nanotubes [42,43] and nanodisks [44].…”