Fano resonances in vertically and horizontally coupled micro-resonators

Fano resonances are desirable lineshapes for numerous applications in diverse fields, due to their small bandwidth and potentially high extinction ratio. In this paper we propose and analyze two configurations of optical add-drop filters exhibiting Fano resonances. The first approach is based on a planar structure add drop filter comprising concentric racetrack resonators. The second approach is based on a multi-layer structure comprising two micro-rings located in different layers which are coupled via I/O waveguides located in a middle layer. Analytic models for these structures are developed and studied and compared to three dimensional finite difference time domain simulations.