Role of Static Modes in Quasinormal Modes Expansions: When and How to Take Them into Account?

The scattering of electromagnetic waves by a resonator is determined the excitation eigenmodes system. In case open resonators made absorbing materials, system non-Hermitian, and are quasinormal modes. Among whole set modes, static modes (modes with zero eigenfrequency) occupy specific place. We study role in expansions calculated numerical solver implemented finite-element method. show that, dielectric permittivity described Lorentz model, markedly contribute to field reconstruction but incorrectly designed compute non-zero eigenfrequencies. propose solve this issue adding separate, computation