Fano resonance in concentric ring apertures.

ABSTRACT

We demonstrate a polarization-independent mid-infrared Fano resonance with extraordinary transmission when light passes through two concentric metallic ring apertures. A high-Q dark mode is indirectly excitated by coupling with a low-Q bright mode. A coupled optical resonator model is used to analyze the coupling process between the bright and dark modes. We find the Q of the dark mode is 3~6 times higher than that of the bright mode. We show that the dark mode can be selectively disabled without affecting the bright mode.