  Optical properties of a plasmonic nano-antenna made of two metallic
nanospheroids (prolate or oblate) are investigated analytically in quasistatic
approximation. It is shown that in clusters of two nanospheroids, three types
of plasmonic modes can be present. Two of them can be effectively excited by a
plane electromagnetic wave, while the third one can be effectively excited only
by a nanolocalized light source (an atom, a molecule, a quantum dot) placed in
the gap between the nanoparticles. Analytical expressions for absorption and
scattering cross-sections, enhancement of a local field, and radiative decay
rate of a dipole source placed near such a nano-antenna are presented and
analyzed.
