Enhanced Light Emission by Magnetic and Electric Resonances in Dielectric Metasurfaces

Abstract

An enhanced emission of high quantum yield molecules coupled to dielectric metasurfaces formed by periodic arrays of polycrystalline silicon nanoparticles is demonstrated. Radiative coupling of the nanoparticles, mediated by in‐plane diffraction, leads to the formation of collective Mie scattering resonances or Mie surface lattice resonances (M‐SLRs), with remarkable narrow line widths. These narrow line widths and the intrinsic electric and magnetic dipole moments of the individual Si nanoparticles allow resolving electric and magnetic M‐SLRs. Incidence angle‐ and polarization‐dependent extinction measurements and high‐accuracy surface integral simulations show unambiguously that magnetic M‐SLRs arise from in‐ and out‐of‐plane magnetic dipoles, while electric M‐SLRs are due to in‐plane electric dipoles. Pronounced changes in the emission spectrum of the molecules are observed, with almost a 20‐fold enhancement of the emission in defined directions of molecules coupled to electric M‐SLRs, and a fivefold enhancement of the emission of molecules coupled to magnetic M‐SLRs. These measurements demonstrate the potential of dielectric metasurfaces for emission control and enhancement, and open new opportunities to induce asymmetric scattering and emission using collective electric and magnetic resonances.

Low‐Index‐Contrast Dielectric Lattices on Metal for Refractometric Sensing

“…For our hybrid system, nanopillar arrays are on an optically thick metal film, which blocks the transmission of light completely, and the issue of symmetric dielectric environment between the substrate and the upper cladding does not exist, in contrast to the requirement of a symmetric environment for achieving sharp lattice resonances in all-plasmonic [14,16] and alldielectric systems. [15,17] In this work, we show that dielectric nanopillar arrays on metal can be an efficient platform for refractometric sensing. We fabricate TiO 2 nanopillar arrays on gold by reactive ion etching (RIE) combined with a large-area soft lithography technique.…”

“…The collective lattice resonance stemming from the diffractive coupling in a periodic array of either metal [ 10–12 ] or high‐index dielectric nanoparticles [ 13 ] requires a symmetric refractive‐index environment between the bottom substrate and the upper cladding (e.g., aqueous buffers in sensing). [ 14–17 ] An asymmetric environment can inhibit long‐range coupling between nanoparticles and suppress lattice resonances. In optical sensing, a periodic array of either metal or high‐index dielectric nanoparticles is usually fabricated on a transparent substrate and exposed to solutions with different refractive indices.…”

“…For our hybrid system, nanopillar arrays are on an optically thick metal film, which blocks the transmission of light completely, and the issue of symmetric dielectric environment between the substrate and the upper cladding does not exist, in contrast to the requirement of a symmetric environment for achieving sharp lattice resonances in all‐plasmonic [ 14,16 ] and all‐dielectric systems. [ 15,17 ]…”

Coherent Networks of Si Nanocrystals: Tunable Collective Resonances with Narrow Spectral Widths

“…This is aligned with previous reports that showed that in periodic arrays of Si nanoparticles, SLR occurs more efficiently in homogeneous media. [ 33,34 ] In fact under this condition, the first‐order RA wavelength, given by ( or ), influences the wavelength of the sharp peak. Therefore, to tune the wavelength of SLR, one needs to change and consistently.…”

“…Recent studies have shown the possibility of hybridization of magnetic and electric dipoles of Si nanoparticles with the lattice modes, forming SLRs associated with diffractive coupling of such dipoles with the Rayleigh anomaly (RA). [ 26,32–34 ]…”