High Q Hybrid Mie–Plasmonic Resonances in van der Waals Nanoantennas on Gold Substrate

Dielectric nanoresonators have been shown to circumvent the heavy optical losses associated with plasmonic devices; however, they suffer from less confined resonances.By constructing a hybrid system of both dielectric and metallic materials, one can retain low losses, while achieving stronger mode confinement.Here, we use a high refractive index multilayer transition-metal dichalcogenide WS 2 exfoliated on gold to fabricate and optically characterize a hybrid nanoantenna-on-gold system.We experimentally observe a hybridization of Mie resonances, Fabry-Perot modes, and surface plasmon-polaritons launched from the nanoantennas into the substrate.We measure the experimental quality factors of hybridized Mie-plasmonic (MP) modes to be up to 33 times that of standard Mie resonances in the nanoantennas on silica.We then tune the nanoantenna geometries to observe signatures of a supercavity mode with a further increased Q factor of over 260 in experiment.We show that this quasi-bound state in the continuum results from strong coupling between a Mie resonance and Fabry-Perot-plasmonic mode in the vicinity of the higher-order anapole condition.We further simulate WS 2 nanoantennas on gold with a 5 nm thick hBN spacer in between.By placing a dipole within this spacer, we calculate the overall light extraction enhancement of over 10 7 , resulting from the strong, subwavelength confinement of the incident light, a Purcell factor of over 700, and high directivity of the emitted light of up to 50%.We thus show that multilayer TMDs can be used to realize simple-to-fabricate, hybrid dielectricon-metal nanophotonic devices granting access to high-Q, strongly confined, MP resonances, along with a large enhancement for emitters in the TMD-gold gap.