Numerical study of surface plasmon polaritons scattering at a planar metal−dielectric interface by an embedded dielectric nanocube

Abstract

Surface plasmon polaritons (SPPs) are localized electromagnetic waves propagating along a planar metal−dielectric interface. SPPs have drawn much attention in a variety of applications, such as light-emitting diodes, solar cells, Raman scattering, chemical or biological sensors, and integrated plasmonic circuits since they are localized electromagnetic waves on a metallic surface with higher local field density. As they have been applied in many applications, the in- and out-coupling of SPPs become important to efficiently excite SPP modes (in-coupling of SPPs), convert SPP modes into far-field radiating modes, electromagnetic waves propagating away from the metal surface to which SPPs are confined (out-coupling of SPPs), or manipulate SPPs (reflection or transmission). Particularly, efficient scattering of SPPs into the far-field radiating modes or reflected or transmitted SPPs is demanded in areas such as thin-film spectroscopy, integrated plasmonic devices, or organic light-emitting diodes (OLEDs). In this numerical study, it is investigated that how SPPs at a planar metal−dielectric interface are scattered by a dielectric nanocube embedded in the metal layer. The scattering properties of the embedded nanocube in terms of cross sections of scattering and absorption, scattering patterns, reflection, and transmission are numerically analyzed employing three-dimensional finite element method based simulations. It is confirmed that this embedded nanocube structural system is capable of wavelength-selective SPPs scattering dependent on the size of the nanocube due to the plasmonic resonant modes that are excited in the nanocube. Moreover, the correlation between the scattering properties of the embedded nanocube and the characteristics of the plasmonic resonant modes found in the embedded nanocube is discussed, showing that a specific plasmonic mode, which similarly appears in each of different-sized nanocubes, is responsible for strong scattering of SPPs. Along with the strong outcoupling of SPPs, the strong reflection also occurs when resonant modes of the embedded nanocube are excited, while the transmission decreases. In addition, the scattering patterns of the scattered waves out-coupled by the embedded nanocube are also discussed. With further development, this study would contribute to efficient scattering of SPPs at a planar interface, which can increase the performance of integrated plasmonic devices and, especially, the efficiency of OLEDs by outcoupling of SPPs into the far field radiating modes by collection of embedded dielectric nanocubes with an appropriately chosen size distribution.