Analysis of asymmetry of Fano resonance in plasmonic metal-insulator-metal waveguide

A Fano resonance has stimulated interests due to its asymmetrical resonance profile. Fano resonance generally emerges due to coupling and destructive interference between two resonating modes having disparate quality factors. This coupling between modes leads to an asymmetrical resonance profile which makes Fano resonance quite distinct from the traditional Lorentzian profile. Asymmetry is a key feature of Fano resonance. It is examined using Complex plane analysis and redefined using Reflection Argand diagram. The newly defined parameter named as Argand Asymmetric ratio (ρ) is in line with the previously defined asymmetrical factor of Fano resonance. This newly defined parameter (ρ) is also studied against coupling and frequency detuning between resonating modes. The parameter is also numerically investigated by exciting Fano resonance in a pair of resonators coupled MIM (Metal-Insulator-Metal) waveguide using the OptiFDTD tool. The newly defined parameter can find its way in analyzing different Fano resonance based applications like as optical buffers, sign reversal Fano tuning, switches, modulators, etc.