Quasinormal mode theory for multiresonant metasurfaces with superwavelength periodicity involving two-dimensional materials

Contemporary photonic resonant systems are non-Hermitian, exhibiting radiation leakage and loss. By specifying the quasinormal modes (QNMs) that they support, one can obtain physical insight into the light-matter interaction processes and construct modal analysis tools that allow for the efficient calculation of their spectral response. The authors develop here a QNM framework for non-Hermitian periodic resonant systems that involves bulk and two-dimensional materials. It is employed to study multiresonant metasurfaces with superwavelength periodicity and is proven highly efficient and accurate.