Multipole analysis of meta-atoms

We determine the rigorously calculated scattered field of meta-atoms and decompose it into spherical harmonics with complex amplitudes. Transforming these spherical harmonics into a Cartesian base reveals all multipole moments in this coordinate system, i.e. all electric and magnetic dipole, quadrupole and any higher order moments can be completely determined. We show that these multipole moments provide a deeper understanding on how light interacts with the considered meta-atoms. After sketching the analytical framework, we investigate exemplarily two well-established meta-atoms and show the applicability of our approach.

► The scattering properties of meta-atoms are described in terms of electromagnetic multipoles.
► The multipoles in a Cartesian base are linked to those in a spherical base.
► A deep physical understanding of meta-atoms is provided based on excited multipoles.
► The assignment of effective parameters based on these multipoles is discussed.