Optical properties of coupled silicon nanowires and unusual mechanical inductions

Abstract

A recent study of the photonic coupling between metallic nanowires has revealed new degrees of freedom in the system. Unexpected spin torques were induced on dimers when illuminated with linearly polarized plane waves. As near-field observables, the spectra of torques showed more resolved resonances than the peaks in typical far-field spectra. Here, the study is extended to silicon dimers. The optical properties of high-dielectric systems are governed by volume resonances, not by surface resonances as is the case in plasmonic arrangements. Differently from plasmonic systems, which show strong mechanical inductions only for p-polarized light, high-dielectric systems experience the action of strong forces and torques for both polarizations s and p. The asymmetry in strong near-fields is responsible for the unusual mechanics of the system. Some consequences of this may include the breaking of the action-reaction principle or the appearance of pulling forces. This numerical study is based on an exact method. The work provides ideas for the design of nanorotators and nanodetectors. It suggests a new viewpoint about optical forces: the resultant dynamics of topological variations of electromagnetic fields.