Enhanced magnetic modulation of light polarization exploiting hybridization with multipolar dark plasmons in magnetoplasmonic nanocavities

in Light: Science and Applications (2020), 9

Enhancing magneto-optical effects is crucial for size reduction of key photonic devices based on non-reciprocal propagation of light and to enable active nanophotonics. Here, we disclose a so far ... [more ▼]

Enhancing magneto-optical effects is crucial for size reduction of key photonic devices based on non-reciprocal propagation of light and to enable active nanophotonics. Here, we disclose a so far unexplored approach that exploits hybridization with multipolar dark modes in specially designed magnetoplasmonic nanocavities to achieve a large enhancement of the magneto-optically induced modulation of light polarization. The broken geometrical symmetry of the design enables coupling with free-space light and hybridization of multipolar dark modes of a plasmonic ring nanoresonator with the dipolar localized plasmon resonance of the ferromagnetic disk placed inside the ring. Such hybridization results in a low-radiant multipolar Fano resonance that drives a strongly enhanced magneto-optically induced localized plasmon. The large amplification of the magneto-optical response of the nanocavity is the result of the large magneto-optically induced change of light polarization produced by the strongly enhanced radiant magneto-optical dipole, which is achieved avoiding the simultaneous enhancement of re-emitted light with the incident polarization by the driving multipolar Fano resonance. The partial compensation of the magneto-optically induced polarization change caused by the large re-emission of light with the original polarization is a critical limitation of magnetoplasmonic designs explored so far. [less ▲]

Anisotropic Nanoantenna-Based Magnetoplasmonic Crystals for Highly Enhanced and Tunable Magneto-Optical Activity

in Nano Letters (2016), 16(4), 2533-2542

We present a novel concept of a magnetically tunable plasmonic crystal based on the excitation of Fano lattice surface modes in periodic arrays of magnetic and optically anisotropic nanoantennas. We show ... [more ▼]

We present a novel concept of a magnetically tunable plasmonic crystal based on the excitation of Fano lattice surface modes in periodic arrays of magnetic and optically anisotropic nanoantennas. We show how coherent diffractive far-field coupling between elliptical nickel nanoantennas is governed by the two in-plane, orthogonal and spectrally detuned plasmonic responses of the individual building block, one directly induced by the incident radiation and the other induced by the application of an external magnetic field. The consequent excitation of magnetic field-induced Fano lattice surface modes leads to highly tunable and amplified magneto-optical effects as compared to a continuous film or metasurfaces made of disordered noninteracting magnetoplasmonic anisotropic nanoantennas. The concepts presented here can be exploited to design novel magnetoplasmonic sensors based on coupled localized plasmonic resonances, and nanoscale metamaterials for precise control and magnetically driven tunability of light polarization states. [less ▲]