Spectral Shift From Near to Far-Field Radiation in Metallic Nanoparticles

The interaction between light and metallic nanoparticles, driven by potential applications, requires a comprehensive understanding of the intensity and spectral shift from near-field to far-field radiation. The far-field spectra have received extensive attention, yet significant peak shifts in the near-field are often overlooked by Mie solutions, necessitating full-wave numerical solvers for accurate analysis and thus limiting a deeper understanding of near-field behavior. This work proposes an impedance-based compact solution that harnesses the fundamental relationship of voltage-current and the analogy between a series resonant circuit and the near-field to develop compact models uniquely identifying the fundamental mode near and far-field spectral shifts. The results align closely with Mie solutions in the far-field and full-wave solvers in the near-field, demonstrating a strong agreement highlighting the distance-dependent spectral shift dominating the overall response. The compact, parameter-dependent model offers valuable insights, enabling the exploitation of the distinctive near-field interactions of nanoparticles to design and develop extraordinary solutions.