First-principles nanocircuit model of open electromagnetic resonators

We derive from first principles a general circuit model for open, frequency dispersive electromagnetic resonators in the full-wave regime. This model extends the concepts of radiation impedance to the polarization current-density modes induced in open resonators by an arbitrary external excitation. Its physics-based elements offer physical insights into the scattering problem and enable efficient modeling of the resonance frequency and associated bandwidth for arbitrary scattering resonances, establishing a powerful platform for the design and optimization of nanophotonic circuits. Our findings offer compelling prospects for electromagnetic scattering and ultrafast nanophotonics, streamlining the analysis and design of nanoresonators with enhanced operational speeds, and outlining a physics-based model of their temporal dynamics.