Tailoring Second-Harmonic Generation in Plasmonic Radial Trimers using Cylindrical Vector Beams

Collective effects in assemblies of plasmonic nanostructures are attracting widespread interest. Such effects are governed by the interactions among the constituents of the overall structure, providing an alternative path to modify plasmon resonances [1]. A particularly interesting collective effect in these structures is the so-called dark plasmon mode, which has a net zero dipole moment and cannot be accessed using plane waves or linearly polarized light under normal incidence. An emerging way to excite collective dark modes in such structures is through the use of cylindrical vector beams (CVB) that exhibit inhomogeneous states of polarization such as azimuthal or radial polarizations [2,3]. The use of CVBs to excite collective nonlinear optical effects such as second-harmonic generation (SHG) in oligomers has started only recently [4]. Here, we demonstrate a similar possibility by tailoring SHG in plasmonic radial trimers using CVBs.