# Bimodal Absorber Frequencies Shift Induced by the Coupling of Bright and Dark Modes

## TL;DR

This paper shows how the frequencies of a bimodal absorber change based on the coupling between bright and dark modes.

## Contribution

The study introduces a new analytical relationship linking absorption frequencies to coupling strength and losses in bimodal systems.

## Key findings

- Absorption frequencies shift as the coupling strength between bright and dark modes changes.
- Two absorption peaks move closer or farther apart depending on the coupling strength.
- Simulation with three metasurface structures confirms the theoretical predictions.

## Abstract

In this paper, we demonstrate that the absorption frequencies of the bimodal absorber shift with the coupling strength of the bright and dark modes. The coupling between the bright mode and the dark mode can acquire electromagnetically induced transparency, we obtain the analytical relationship between the absorbing frequencies, the resonant frequencies, losses of the bright mode and dark mode, and the coupling strength between two modes by combining the coupled mode theory with the interference theory. As the coupling strength between the bright mode and the dark mode decreases, the two absorption peaks gradually move closer to each other, inversely, they will move away from each other. The simulation employs three distinct metasurface structures with coupling of the bright and dark modes, thereby verifying the generality of the theoretical findings.