Collective Resonances of a Twisted Plasmonic Array Pair

Plasmonic SLR (surface lattice resonance) has sharp and intense extinction or absorption peaks, which facilitates a variety of optical and spectral applications, e.g., optical filters, absorbers, reflectors, sensors, etc. In this work, we propose a plasmonic array pair structure composed of two stacked finite square array panels. By twisting it, its plasmonic SLR changes, since the break of periodicity alters the inter-layer plasmonic coupling. Numerical simulation is carried out using the DDA (discrete dipole approximation) method. Simulation results show that its optical properties such as extinction spectra/absorption spectra change dramatically when the two-layer structure is twisted by only a small angle. More interestingly, two resonance peaks at different wavelengths show an inverse trend while twisting, one gets lower and broader, while the other gets higher and narrower. Dipole mapping of amplitude and phase is checked to reveal the plasmonic coupling under twist. The influence of environment/material permittivity on spectra is also examined. Results introduced in this work may work as a scientific tool to reveal more properties of plasmonic SLR and can serve as an angle sensor, tunable optical filter, chiral sensor, etc.