Bound states in the continuum supported by silicon oligomer metasurfaces

Oligomer metasurfaces have attracted a lot of attention in recent years because of their ability to drive strong resonance effects. In this work, by perturbing the symmetry of the structure, we find that there are a large number of resonance modes in the oligomer metasurfaces associated with the optical bound states in the continuum (BICs) near the communication wavelength. When the positions of two nanodisks of the hexamer oligomers are moved along the x- or y-directions at the same time, the mirror symmetry is broken, and an electric quadrupole BIC and three magnetic dipole BICs are excited. The results of near-field distribution of three-dimensional nanodisks and far-field scattering of multiple dipoles in each quasi-BIC reveal that the four BICs present different optical characteristics. It is noted that the method of symmetry breaking by moving the position of nanodisks can accurately control the asymmetric parameter of symmetry-protected BICs, which provides a route for the realization of ultrahigh quality (Q)-factor oligomer meta- surfaces in experiment. (C) 2022 Optica Publishing Group

Automated summary

This study investigates oligomer metasurfaces and their resonance modes. The researchers find that by perturbing the structure's symmetry, multiple resonance modes associated with optical bound states in the continuum (BICs) can be excited. By moving the positions of nanodisks, different optical characteristics can be controlled, providing a route for realizing high-quality oligomer metasurfaces in experiments.