Abstract
With advances in nanofabrication techniques, extreme-scale nanophotonic devices with critical gap dimensions of just 1-2 nm have been realized. The plasmonic response in these extreme-scale gaps is significantly affected by nonlocal electrodynamics, quenching field enhancement and blue-shifting the resonance with respect to a purely local behavior. The extreme mismatch in lengthscales, ranging from millimeter-long wavelengths to atomic-scale charge distributions, poses a daunting computational challenge. In this paper, we perform computations of a single nanoslit using the hybridizable discontinuous Galerkin method to solve Maxwell's equations augmented with the hydrodynamic model for the conduction-band electrons in noble metals. This method enables the efficient simulation of the slit while accounting for the nonlocal interactions between electrons and the incident light. We study the impact of gap width, film thickness and electron motion model on the plasmon resonances of the slit for two different frequency regimes: (1) terahertz frequencies, which lead to 1000-fold field amplitude enhancements that saturate as the gap shrinks; and (2) the near- and mid-infrared regime, where we show that narrow gaps and thick films cluster Fabry-Pérot (FP) resonances towards lower frequencies, derive a dispersion relation for the first FP resonance, in addition to observing that nonlocality boosts transmittance and reduces enhancement.
Highlights
A nanometer-scale slit in a metal film is one of basic building blocks to construct plasmonic waveguides [1,2,3,4], sensors [5,6,7], metasurfaces [8], nanolasers [9], and nanoelectrodes [10]
We study the impact of gap width, film thickness and electron motion model on the plasmon resonances of the slit for two different frequency regimes: (1) terahertz frequencies, which lead to 1000-fold field amplitude enhancements that saturate as the gap shrinks; and (2) the near- and mid-infrared regime, where we show that narrow gaps and thick films cluster Fabry-Pérot (FP) resonances towards lower frequencies, derive a dispersion relation for the first FP resonance, in addition to observing that nonlocality boosts transmittance and reduces enhancement
The hybridizable discontinuous Galerkin (HDG) method belongs to the class of discontinuous Galerkin (DG) methods, which are unstructured, high accurate, locally conservative, exhibit low dissipation and dispersion and are high-order, meaning the numerical error in the approximation can be made insensitive to the mesh discretization, as opposed to other finite-difference time-domain (FDTD) or finite element method (FEM) commercial solvers
Summary
A nanometer-scale slit in a metal film is one of basic building blocks to construct plasmonic waveguides [1,2,3,4], sensors [5,6,7], metasurfaces [8], nanolasers [9], and nanoelectrodes [10]. As electromagnetic waves pass through narrow slits, their local field intensity can be significantly enhanced. Such high field energy density in the slit, in turn, can lead to interesting effects such as enhanced optical transmission [16], nonlinear phenomena [17,18], and surface-enhanced infrared absorption [19,20], among others. As the slit width is reduced to few nanometers and below, quantum mechanical effects [21,22,23,24,25,26], in particular the nonlocal smearing of conduction electrons characterized by the Thomas-Fermi screening length (∼0.1 nm in gold) cannot be ignored [22,27,28,29,30,31,32]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
