Tunable Geometric Fano Resonances in a Metal/Insulator Stack

We present a theoretical analysis of surface-plasmon-mediated mode-coupling in a planar thin film metal/insulator stack. Solving for the modes of this structure, we obtain an avoided crossing in the angular domain that is tunable using the system's materials and geometrical parameters. The computed reflectance of the metal/insulator stack exhibits a lineshape that is modeled as a geometric Fano resonance, accompanied by a response function characteristic of an induced coherence, albeit in the angular domain. We also observe a reversal of the Fano lineshape asymmetry as the system's parameters are varied. We attribute this \emph{q}-reversal to an interloping background radiation field comprising the surface plasmon polariton mode.