High-Q Localized Phonon Polaritons in Thin hBN Discs with Omnidirectional Strong Light Absorptions.

Based on numerical calculations, we have found that thin hexagonal boron nitride nanodiscs support high-quality localized phonon polariton modes in the upper Reststrahlen band. Near the resonances, single disc can be phenomenologically considered as an electric dipole. By arranging discs into a square lattice, strong light absorptions can be achieved. Modeling such periodic systems as dipole lattices, simple reflecting substrates can be designed which lead to omnidirectional strong, even nearly perfect, light absorptions. Under the condition of nearly total absorption, the electric fields at the hexagonal boron nitride surfaces are largely enhanced due to low-loss localized phonon polaritons. Our investigations might be useful for phonon polariton–based nanophotonic devices, such as sensors. [ABSTRACT FROM AUTHOR]