A universal Fano type scattering model and its experimental tests

Abstract Fano-type scatterings, with the spectra being deviated manifestly from the usual symmetric Lorentzian profiles, have being widely observed experimentally. While their physical mechanisms have not been completely resolved. Here, with a typical kind of the Fano-type devices, i.e., the distributed resonators, we propose a universal physical model beyond the usual electric-dipole approximation (EDA), to well explain the observed Fano-type scatterings. Specifically, by introducing a low-Q cavity to describe the practically-existing non-EDA effects for the scatterings of a distributed resonator, we provide a universal scattering spectral formula to well explain the Fano-type scattering spectra observed in various experiments. With the fabricated and measured superconducting λ/2 Coplanar waveguide resonators, we demonstrate that the proposed model can provide an effective approach to accurately extract the loaded quality factors of the loaded resonators. Therefore, the model presented here can be used to conventionally design various Fano-type devices for precisely manipulating the transport of electromagnetic waves in various frequency bands.