Realization of Fanolike Resonance Due to Diffraction Coupling of Localized Surface Plasmon Resonances in Embedded Nanoantenna Arrays

We present a straightforward method to realize Fanolike resonance due to diffraction coupling of localized surface plasmon (SP) resonances by embedding the nanoantenna arrays into the substrate. Light transmission spectra of the embedded nanoantenna arrays are theoretically studied and show a Fanolike resonance resulting from the interference between localized SP resonances excited on individual plasmonic nanoantennas and an in-plane propagating collective surface mode arising from the array periodicity. The effect can be attributed to the fact that our approach, by embedding the nanoantenna arrays into the substrate, offers a more homogeneous dielectric background allowing stronger diffraction coupling among nanoantennas leading to the Fanolike resonance. Upon the excitation of this Fanolike resonance, a nearly 110 times enhancement of electric fields was achieved as compared with the purely resonance. More importantly, we also found that in addition to the above requirement of homogeneous dielectric background, only a collective surface mode with its electric field parallel to the array plane can mediate the excitation of such a Fanolike resonance. The steep dispersion of the Fano resonance profile and enhanced electric fields obtained in these structures could be attractive for biosensing and nonlinear photonics applications.