Abstract
We develop a quasi-normal mode theory (QNMT) to calculate a system's scattering matrix, simultaneously satisfying both energy conservation and reciprocity even for a small truncated set of resonances. It is a practical reduced-order (few-parameter) model based on the resonant frequencies and constant mode-to-port coupling coefficients, easily computed from an eigensolver without the need for QNM normalization. Furthermore, we show how low- modes can be separated into an effective slowly varying background response , giving an additional approximate formula for , which is useful to describe general Fano-resonant phenomena. We demonstrate our formulation for both normal and fixed-angle oblique plane-wave incidence on various electromagnetic metasurfaces.
- Received 6 May 2021
- Revised 26 June 2021
- Accepted 15 July 2021
DOI:https://doi.org/10.1103/PhysRevResearch.3.033228
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Published by the American Physical Society