Polarization switching between parallel and orthogonal collective resonances in arrays of metal nanoparticles

In this work, we discuss excitation of orthogonal and parallel collective resonances in rectangular arrays of aluminum nanoparticles and switch between them with a change of array dimensions or polarization. We demonstrate that in the case of the substrate, scattered fields from nanoparticles can interact with each other in directions both parallel and orthogonal to the external electric field, which results in manifestation of the parallel coupling when localized plasmon resonance is near its spectral position. In this work, the parallel diffraction waves couple with in-plane quadrupolar mode excited with a scattered field coming from the neighboring nanoparticles. The rate of the parallel coupling depends on the interparticle distance, which allows us to control the intensity of the coupled mode. (C) 2019 Optical Society of America