A metallic nanocross geometry sustaining broad dipole and
sharp higher order localized surface plasmon resonances is investigated.
Spectral tunability is achieved by changing the cross arm length and the
angle between the arms. The degree of rotational symmetry of the nanocross
is varied by adding extra arms, changing the arm angle and shifting the
arm intersection point. The particle’s symmetry is shown to have a crucial
influence on the plasmon coupling to incident radiation. Pronounced dipole,
quadrupole, octupole and Fano resonances are observed in individual cross
structures. Furthermore, the nanocross geometry proves to be a useful
building block for coherently coupled plasmonic dimers and trimers where
the reduced symmetry results in hybridized subradiant and superradiant
modes and multiple Fano interferences. Finite difference time domain
calculations of absorption and scattering cross-sections as well as charge
density profiles are used to reveal the nature of the different plasmon modes.
Experimental spectra for the discussed geometries support the calculations.