Large-Area Field Enhancement via Plasmonic Hot-Grid in Nanocube Arrays

Abstract

Plasmonic nanoparticles have attracted considerable attention due to their ability to amplify local electric fields and generate hot-spots. These hot-spots are highly desirable for enhancing scattering and non-linear processes. Rough surfaces and sharp edges have been previously used for such applications. However, small hot-spot volume and inherent randomness limit their reliability and effectiveness. Here, we propose a design that utilizes interference of surface plasmon polaritons using array of nanocubes. We numerically study the analytical solutions of the metal-insulator-metal (MIM) geometry and conduct finite difference time domain simulations to investigate the optical response of the proposed design. The design offers over 1000-fold local field intensity enhancement which corresponds to over 10⁶-fold Raman enhancement. We demonstrate field enhancement over a large area that we term the “hot-grid”. The design uses the propagating odd surface plasmon polariton mode of MIM geometry produced by an array of nanocubes. The extremely small gap of 1 nm produces significant field enhancement, which is further amplified by constructive interference achieved by multiple reflections, similar to a Fabry-Perot cavity. These results highlight the promise of nanocube arrays for applications that demand significant electric field enhancement, including nonlinear optics, photonics, spectroscopy, sensing, and imaging.