Abstract
Multipolar analysis of the scattered radiation from nanostructures is a useful technique for understanding their optical scattering properties and designing new novel structures and metamaterials. Traditionally, these modes are excited by linearly or circularly polarized light sources. Here, we utilize more complex beams constructed from Hermite-Gaussian modes to excite these optical modes. In particular, beams with a radial polarization state (RP beams) and an azimuthal polarization state (AP beams) are used. These novel light sources can be used to selectively drive certain modes of the system.
In this talk, I will discuss the methods used to produce these vector beams and perform a multipole expansion of the scattered radiation in Finite-Difference Time-Domain (FDTD) simulations. These methods will be demonstrated on several different experimentally realized nanoscale structures: a dielectric sphere, a core-shell structure, and a core-satellite structure (a SiO2 spherical core whose surface is decorated with silver nanoparticles). RP and AP beams are demonstrated to selectively excite certain optical modes of these structures. In particular, the AP beam is shown to selectively excite a magnetic dipole mode of the core-satellite structure in the visible that does not appear in the similar core-shell structure. An extension to non-spherically symmetric structures, such as monolayers, will also be discussed.