# Quasi-Bound State in the Continuum of the Intracoupled All-Dielectric Coherent Metasurface

## TL;DR

This paper introduces a new dielectric metasurface design that enhances light-matter interactions with high efficiency and minimal loss.

## Contribution

A novel metasurface design using biradial circular resonators to achieve quasi-bound states in the continuum with a high Q factor.

## Key findings

- The metasurface achieves a Q factor of 650 through interference of electric dipole and magnetic quadrupole.
- The design provides 4-fold photoluminescence enhancement and strong photonic confinement.
- The approach simplifies fabrication and enhances robustness while maintaining high tunability.

## Abstract

Metasurfaces have
transformed the landscape of nanophotonics by
enabling the precise control of light–matter interactions across
a wide spectral range. Recently, dielectric metasurfaces have garnered
significant attention due to their potential for low nonradiative
loss. In this study, we introduce a novel metasurface design that
employs biradial circular resonators to induce quasi-bound states
in the continuum (q-BIC) through minimal symmetry breaking, demonstrating
resonance with a Q factor of 650. It is predominantly
driven by the interference of the electric dipole and the magnetic
quadrupole. This approach addresses key limitations by simplifying
fabrication and enhancing robustness while delivering high tunability,
strong photonic confinement, and a 4-fold photoluminescence enhancement
experimentally. The proposed strategy not only provides a new pathway
for emission enhancement but also underscores the broader utility
of q-BIC metasurfaces in light–matter interaction. Through
a detailed analysis of the symmetry, resonance tuning, and field distribution,
we elucidate the fundamental physics underlying our design.