Fig. 2: Analytical models of optical resonators.
a One-mode resonators with the same radiative decay rates with respect to two ports (\({\gamma }_{{\rm{r}}1}={\gamma }_{{\rm{r}}2}\)). The maximum absorptance is 50%, and the reflection or transmission can have Fano line shape due to the interference between the mode and the background. b One-mode resonators with different radiative decay rates with respect to two ports (\({\gamma }_{{\rm{r}}1}\,\ne \,{\gamma }_{{\rm{r}}2}\)) due to structure asymmetry. The absorption of light incident from Port 1 (solid line) and Port 2 (dashed line) are asymmetric. c One-mode resonators with a reflective background that prohibits the transmission of light (\({\gamma }_{{\rm{r}}2}=0\)). Perfect absorption can be achieved when light is incident from Port 1. d Two-mode resonators where a bright mode with a large radiative decay rate couples with a dark mode with a negligible radiative decay rate. EIT can happen due to the mode coupling. e Two-mode resonators where two modes with different symmetry properties reside in the same resonator. Super absorption with the maximum absorptance larger than 50% can be achieved. For convenience, in (d) and (e), resonators with mirror symmetry with respect to the middle plane are chosen (\({\gamma }_{{\rm{r}}1}={\gamma }_{{\rm{r}}2}\))
