Sketch of the electrodynamics of the bare magnetic permalloy disk (Py-DI) generating an electric dipole (pO) triggered by the electric field Ei of an incident linearly polarized electromagnetic radiation and a magneto-optically activated electric dipole (pMO) by a magnetic field H. pO and pMO of the Py nanoantenna inside the Non-Concentric Ring Disk nanocavity (NRCD) are enhanced (by a factor of ~5) with respect to a bare Py disk by hybridization with the dark mode of the gold ring (Au-RI). This is qualitatively depicted by the relative size of electric dipoles pO and pMO in the Py-DI, and in the NCRD. In the NCRD nanocavity, hybridization generates a hybrid multipolar mode with a weak dipolar dipolar component pO'. In the Py-DI system both pO and pMO are generated by radiant (bright) LPR modes and the resulting H-induced polarization change in the reflected radiation, Er, is determined by their ratio (MOA ? |pMO|/|pO|). The large enhancement of the H-induced polarization change in the NCDR system is a consequence of the low-radiant character of the hybrid multipolar mode due to the weak dipolar component pO', whilst pMO is strongly enhanced and has a radiant character.
by Alberto López-Ortega, Mario Zapata-Herrera, Nicolò Maccaferri, Matteo Pancaldi, Mikel Garcia, Andrey Chuvilin, and Paolo Vavassori