Quasi-bound states in the continuum induced by supercell coupling

Area of Science:

• * Metasurface physics
• * Nanophotonics
• * Optical metamaterials

Background:

• * Metasurfaces offer unique light-matter interactions.
• * Quasi-bound states in the continuum (quasi-BICs) are crucial for enhancing light-matter interactions and enabling novel optical functionalities.
• * Generating quasi-BICs in symmetrical metasurfaces typically requires complex designs or external perturbations.

Purpose of the Study:

• * To propose a novel coupling mechanism for generating quasi-BICs in symmetrical metasurface structures.
• * To theoretically demonstrate that supercell coupling can induce quasi-BICs.
• * To analyze the underlying physical mechanism of quasi-BIC generation via sub-cell coupling within supercells.

Main Methods:

• * Coupled mode theory (CMT) was employed to analyze the coupling mechanism.
• * Supercell structures with coupled sub-cells were theoretically investigated.
• * Full-wave simulations and experimental verification were conducted.

Main Results:

• * A novel supercell coupling mechanism for quasi-BIC generation in symmetrical metasurfaces was theoretically predicted.
• * The study demonstrates for the first time that supercell coupling can induce quasi-BICs.
• * The physical mechanism of quasi-BIC generation was elucidated through CMT analysis of sub-cell coupling.

Conclusions:

• * The proposed supercell coupling mechanism provides a new pathway for generating quasi-BICs in symmetrical metasurfaces.
• * The findings are validated by both theoretical predictions and experimental results.
• * This work contributes to the understanding and design of advanced metasurface functionalities.