[20p-C304-1~14] 4.1 Plasmonics and Nanophotonics

▲ [20p-C304-14] Tailoring bound states in the continuum with Bravais/non-Bravais lattices

〇Shunsuke Murai¹, Diego R Abujetas², Libei Liu¹, Gabriel W. Castellanos³, Vincenzo Giannini⁴, Jose A Sanchez-Gil⁴, Katsuhisa Tanaka¹, Jaime Gomez Rivas³ (1.Kyoto Univ., 2.Fribourg U., 3.Eindhoven U.Tech., 4.IEM-CSIC)

Keywords:silicon, Surface Lattice Resonance

We design and experimentally demonstrate optical BICs using a subdiffraction Bravais lattice of Si nanodisks. The out-of-plane magnetic dipole resonance in the dielectric nanodisks couples with the subdiffraction lattice and defines a symmetry-protected BIC at the Γ point. We also prepare three non-Bravais lattices by detuning size and position of the second disk in the unit cell. Diffraction-induced coupling excites magnetic/electric dipoles in each nanodisk, producing two surface lattice resonances at the Γ point with a band gap in between. The high/low energy branch becomes a BIC for the size/position-detuned array, respectively, while both branches are bright (or leaky) when both size and position are detuned simultaneously. The role of magnetic and electric resonances in dielectric nanoparticles and the change of BIC to bright character of the modes is explained by the two different origins of BICs in the detuned arrays, which is further discussed with the aid of a coupled electric and magnetic dipole model.