Plasmonic Nanostructures Analysis Using Characteristic Mode Method

With the development of nanoscale fabrication technology, nanomaterials have attracted more and more attention due to their unique optical properties. The plasmonic nanoantenna is a kind of optical antenna. When light and metal nanoparticles interact, their conduction electrons can be driven by the incident electric field, resulting in collective oscillation, forming a strong near-field enhancement. Meanwhile, characteristic mode theory has been widely applied in the design of various antennas. On the one hand, the characteristic mode can obtain the spectral resonances of various shaped antennas without the excitation source, on the other hand, the characteristic mode explains the radiation mechanism of antennas from the wave physics. Nowadays, in the radio frequency, the antenna designs with characteristic mode theory is well known and widely used, especially in metal characteristic mode theory. However, in the optical frequency, there are few studies on the characteristic mode, application of the characteristic mode to optical antennas and most of the time, we can’t get direct analysis from simulation software. In this paper, we develop the characteristic mode theory, with emphasis on the eigenmode analysis of Poggio-Miller-Chan-Harrington-Wu formula based on surface integral equation. By analyzing its scattering cross section and surface current distribution, we get its characteristics directly. Numerical experiments are performed to illustrate the effectiveness of the proposed method.