Understanding Resonances in Metasurfaces and Nanoresonators

Because all systems are either absorptive, open, or both, their resonance modes correspond to the eigenstates of a non-Hermitian operator and therefore have complex frequencies. These modes, known as quasinormal modes (QNMs), extend well beyond the electromagnetic context I will discuss in the seminar. They have gained significant interest in recent years, particularly in relation to key topics in quantum mechanics, black hole theory, hydrodynamics, and turbulence. Over the past decade, substantial progress has been made in the theory of electromagnetic QNMs. This theory is now mature and ready for application. I will illustrate how it can be used to analyze the electromagnetic density of states of complex systems, such as disordered metasurfaces [1], or to engineer the dissipative coupling between two nanoresonators, well beyond the weak-coupling, high-Q regime where classical temporal coupled-mode theory (CMT) applies.

Speaker: Philippe Lalanne, Centre National de la Recherche Scientifique, France