Surface Plasmonic Resonance: The Underlying Fano Resonance Mechanism for the Attenuated Total Internal Reflection (ATIR)

We demonstrate with both theoretical formulism and experimental verification a new Fano resonance based mechanism for surface plasmonic resonance (SPR) in the attenuated total internal reflection (ATIR) configurations. Based on the characteristic asymmetric response profile of the reflectance under SPR ATIR, we propose that the nature of the SPR ATIR is that of a Fano resonance, which involves the interference between two pathways, one continuous in nature and the other discrete in nature. We further note that the discrete nature of the pathway in SPR ATIR response is related to the excitations of the surface plasmons (SPs) and its corresponding surface plasmonic polaritons (SPPs), while the continuous pathway is that of the normal Fresnel total internal reflection in nature. The proposed Fano resonance mechanism for SPR ATIR is in sharp contrast to the current understanding and interpretations of the SPR phenomena, which are based on the multipath interference where all pathways are Fresnel reflections in nature. The proposed Fano resonance model explains the asymmetric SPR responses naturally and provides new insights to the nature of the underlying SPP as well as the SPR excitations.