An All‐Dielectric Metasurface Building Block for the Kerker Effect between Excitons and Nanocavities: Germanium Nanogroove

Abstract Coupling between light and matter has many infusive physical effects and potential applications. Large Rabi splitting energy is achieved in many plasmonic nanostructures; however, these noble metallic materials generally suffer from a high level of Joule heating losses at optical frequencies. As an alternative strategy, all‐dielectric materials for manipulating light at the subwavelength scale have attracted enormous interest. However, the understanding of the interactions between all‐dielectric nanostructures and molecular excitons remains limited to date. Here, the use of a germanium nanogroove as a new all‐dielectric metasurface building block is demonstrated for the Kerker effect between molecular excitons and nanocavities. A distinct dip in the backward scattering spectra is observed, indicating relatively strong light–matter interaction due to the cavity magnetic resonance mode in the grooves. Germanium with a large real part and nonnegligible imaginary part of the refractive index in the visible region provides magnetic field enhancement similar to that of other all‐dielectric nanostructures; this phenomenon is theoretically explained by simulating the magnetic field distribution in the grooves. These findings may help researchers to better understand the interactions between all‐dielectric nanostructures and molecular excitons and indicate that germanium nanogrooves can potentially be used as metasurface building blocks in nanophotonic devices.