Achieving Strong Field Enhancement and Light Absorption Simultaneously with Plasmonic Nanoantennas Exploiting Film-Coupled Triangular Nanodisks

5 years ago

Achieving Strong Field Enhancement and Light Absorption Simultaneously with Plasmonic Nanoantennas Exploiting Film-Coupled Triangular Nanodisks

Cheng Chi, Dezhao Li, Baoling Huang, Yang Li

Plasmonic nanoantennas (PNs) comprised of film-coupled or in-plane coupled nanoparticles have been exploited for light confinement or field enhancement. However, achieving strong local electric field enhancements (|E_loc|/|E₀| > 100) and near-perfect absorption (>95%) simultaneously remains a challenge, although it will benefit a wide range of applications. Here Ag/Al₂O₃/Au PNs are proposed by introducing high-density triangular nanodisks into film-coupled systems, which can produce dense “hot spots” with a large |E_loc|/|E₀| of 211 and a near-unity absorbance. Due to the combination of the strong lightning rod effect and the out-of-plane coupling, the MIM structure combined with the triangular nanodisks effectively enhances the coupling strength and thereby the electric field confinements along the x-, y-, and z-directions in film-coupled PNs, showing a lateral resolution as small as 4 nm. The highest |E_loc|/|E₀| is more than three times higher than for their circular and square counterparts and more than four times higher than for isolated triangular nanodisks. The near-perfect absorption results from the magnetic resonance induced by plasmonic coupling. Compared to the bowtie-shaped PNs based on the in-plane coupling, the developed PNs here offer more desired advantages including the polarization-independent near-perfect absorption, much larger field enhancements, and greater potential for large-scale production.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b03956

DOI: 10.1021/acs.jpcc.7b03956