Plasmon hybridization in nanoapertures for development of an efficient nanoantenna array

Abstract

Extraordinary optical transmission through nanoholes has recently taken much interest for its promise to a wide range of applications. Enhancement of non-linear optical phenomena and the development of sensitive biosensors are among the leading ones. As a result of recent studies on the subject, it is now widely accepted that either the non-trivial interaction of the localized and extended surface plasmons or only the localized surface plasmons (for direct transmissions) are responsible from the extra-ordinary light transmission effect. On the other hand, there is little conceptual understanding for controlling the localized surface plasmonic behavior of the individual apertures and their coupling to the extended surface plasmons. In this letter, an intuitive and straightforward picture of the extra-ordinary light transmission phenomena is developed using basic antenna principles for the elementary plasmonic excitations and hybridization of these plasmonic excitations in complex nano-apertures. As an example, the model is successfully applied to explain the experimentally observed plasmonic response of the complex rectangular coaxial apertures. Experimentally measured red-shifting of the plasmonic resonances of the rectangular coaxial-apertures with respect to those of the simple rectangular aperture arrays are successfully described and the asymmetric nature of the plasmonic resonances are explained in relation to strong shape anisotropies. Further enhancement of the extra-ordinary light transmission is also predicted by the model and experimentally demonstrated by using rectangular coaxial aperture arrays as a result of significantly larger net dipole moment in the apertures. Model is also verified by rigorous 3D-FDTD calculations.