Transition Metal Dichalcogenide Dimer Nanoantennas for Tailored Light–Matter Interactions

Abstract

Transition metal dichalcogenides have emerged as promising materials for nanophotonic resonators because of their large refractive index, low absorption within a large portion of the visible spectrum, and compatibility with a wide range of substrates. Herein, we use these properties to fabricate WS 2 double-pillar nanoantennas in a variety of geometries enabled by the anisotropy in the crystal structure. Using dark-field spectroscopy, we reveal multiple Mie resonances, to which we couple WSe 2 monolayer photoluminescence and achieve Purcell enhancement and an increased fluorescence by factors up to 240 for dimer gaps of 150 nm. We introduce postfabrication atomic force microscope repositioning and rotation of dimer nanoantennas, achieving gaps as small as 10 ± 5 nm, which enables a host of potential applications, including strong Purcell enhancement of single-photon emitters and optical trapping, which we study in simulations. Our findings highlight the advantages of using transition metal dichalcogenides for nanophotonics by exploring applications enabled by their properties.

Optical Constants of Several Multilayer Transition Metal Dichalcogenides Measured by Spectroscopic Ellipsometry in the 300–1700 nm Range: High Index, Anisotropy, and Hyperbolicity

“…This interest has grown even more after publication of several nanopatterning methods of TMDs and studies of optical phenomena in resulting TMD nanostructures. 14,15 Recent observations include high-index Mie resonances and anapole states in WS 2 nanodisks, 14 optical anisotropy in TMD slabs 7,9 and nanocones, 16 self-hybridization in TMD slabs 17,18 and nanotubes, 19 optical modes in lattices of TMD nanostructures, 20 improved second-harmonic generation in WS 2 and MoS 2 nanodisks, 21,22 high-index metamaterials, 23 nanoholes down to ∼20 nm, 24 dimer nanoantennas, 25 and TMD metamaterials with atomically sharp edges. 26 Theoretical predictions of large values of dielectric functions of TMDs and related vdW materials include density functional theory (DFT) studies, which confirm exceptionally high values and the anisotropic nature of permittivity tensors in these materials.…”

“…These observations have led to a recently renewed interest in TMD optics and nanophotonics. This interest has grown even more after publication of several nanopatterning methods of TMDs and studies of optical phenomena in resulting TMD nanostructures. , Recent observations include high-index Mie resonances and anapole states in WS 2 nanodisks, optical anisotropy in TMD slabs , and nanocones, self-hybridization in TMD slabs , and nanotubes, optical modes in lattices of TMD nanostructures, improved second-harmonic generation in WS 2 and MoS 2 nanodisks, , high-index metamaterials, nanoholes down to ∼20 nm, dimer nanoantennas, and TMD metamaterials with atomically sharp edges …”

Tunable optical properties of transition metal dichalcogenide nanoparticles synthesized by femtosecond laser ablation and fragmentation

“…12,33 It inspired researchers to shift their attention to their bulk counterparts 34 since they preserve the advantages of monolayers, namely, large optical constants, 6 an asymmetrical optical response, 23,35 and excitonic dielectric function, 36 thanks to weak vdW bonding between layers. As a result, layered materials have already demonstrated great results in subdiffractional guiding, 23,37 integrated circuits, 38 strong light-matter coupling, [39][40][41] resonance nonlinear processes, 28,42 polaritonic transport, 23,43 anisotropic metasurfaces, 31,44 and photothermal conversion, 45 especially, in the case of transition metal dichalcogenides (TMDCs). In addition, recent works 40,[45][46][47][48] establish the fabrication processes of TMDC nanostructures that are compatible with widespread complementary metal oxide technologies.…”

Optical Metasurfaces for Energy Conversion

“…The intrinsic layered nature of TMD crystals further provides record high optical anisotropy, 165 with advantages for the development of photonic components and devices. Recent reports have demonstrated that single disks of TMD crystals (Figure 7h), owing to their large refractive index, exhibit optical Mie resonances and anapole states 166 and can be fabricated with atomic precision in dimer nanoantennas 167 and optical metasurfaces (Figure 7i,j). 168 The versatility in the fabrication of TMD structures for photonic applications enables the generation of exciton plasmon polaritons in hybrid metal-TMD photonic gratings 169 or unidirectional nonlinear emission in metasurfaces 170 made entirely from bulk TMD crystals.…”