High-index dielectric nanostructures that support electric and magnetic resonances have emerged as potential nanophotonic building blocks for unique functions. The coherent interference between the localized Mie resonances of single nanostructures and the in-plane diffracted light can result in the so-called Mie surface lattice resonances by regularly arranging these nanostructures (SLRs). Researchers from the Chinese Academy of Sciences' Shenzhen Institute of Advanced Technology (SIAT) investigated periodic silicon nanodisks under oblique incidence with transverse magnetic polarization and discovered out-of-plane Mie electric dipole surface lattice resonance (ED-SLR) for the first time. On September 7, the work was published in Optics Express.
The researchers observed that under oblique incidence, the out-of-plane Mie ED-SLR may be activated alongside the in-plane electric dipole SLR (ED-SLR), magnetic dipole SLR (MD-SLR), and magnetic quadrupole SLR (MQ-SLR). Under the same conditions, they discovered that the out-of-plane Mie ED-SLR might have four times the quality factors as the in-plane one. Unlike the out-of-plane plasmonic ED-SLR, which is a subradiant or dark mode, the out-of-plane Mie ED-SLR may be considered as a bright mode with different near-field optical distributions and dispersion relationship, according to Li's team.
According to Dr. Li Guangyuan, the study's corresponding author, this is because the dipole field for Mie ED-SLRs is produced by displacement currents, whereas plasmonic ED-SLRs are driven by free electron gases.
The researchers also discovered that under normal incidence, the out-of-plane Mie ED-SLR may create a symmetry-protected bound state in the continuum. This is due to the fact that the out-of-plane Mie ED-SLR is not permitted to emit at normal incidence. The quality factor can even approach 104 for modest incidence angles.
According to Dr. Li, this study is a novel way to producing ultrahigh quality factors of Mie SLRs in dielectric metasurfaces. Furthermore, the occurrence of multipole SLRs opens up new possibilities for influencing light-matter interactions.
Journal Information: Xueqian Zhao et al, High-Q out-of-plane Mie electric dipole surface lattice resonances in silicon metasurfaces, Optics Express (2022). DOI: 10.1364/OE.471356