Abstract
AbstractWe introduce a novel magnetoplasmonic sensor concept for sensitive detection of refractive index changes. The sensor consists of a periodic array of Ni/SiO2/Au dimer nanodisks. Combined effects of near-field interactions between the Ni and Au disks within the individual dimers and far-field diffractive coupling between the dimers of the array produce narrow linewidth features in the magneto-optical Faraday spectrum. We associate these features with the excitation of surface lattice resonances and show that they exhibit a spectral shift when the refractive index of the surrounding environment is varied. Because the resonances are sharp, refractive index changes are accurately detected by tracking the wavelength where the Faraday signal crosses 0. Compared to random distributions of pure Ni nanodisks or Ni/SiO2/Au dimers or periodic arrays of Ni nanodisks, the sensing figure of merit of the hybrid magnetoplasmonic array is more than one order of magnitude larger.
Highlights
IntroductionFerromagnetic metals support the excitation of surface plasmon resonances [10,11,12]
Label-free plasmonic biosensors exploit surface plasmon polaritons (SPPs) at metal/dielectric interfaces or localizedFerromagnetic metals support the excitation of surface plasmon resonances [10,11,12]
We introduce a novel magnetoplasmonic sensor concept for sensitive detection of refractive index changes
Summary
Ferromagnetic metals support the excitation of surface plasmon resonances [10,11,12]. Spin-orbit coupling results in the excitation of two LSPRs, one along the direction of the incident electric field and the second induced orthogonally to the first and the direction of magnetization [13]. The amplitude and phase relations of these two LSPRs determine the magneto-optical response of a ferromagnetic nanoparticle, i.e. the rotation and ellipticity of light polarization upon transmission or reflection. Ordering of plasmonic nanoparticles into a regular array can improve the FoM. In this geometry, hybridization between LSPRs and the diffracted order of the array
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