Strong magnetic resonance of coupled aluminum nanodisks on top of a silicon waveguide

We study the electromagnetic behavior of a structure consisting of coupled aluminum nanodisks on a silicon waveguide at telecom wavelengths. Numerical simulations show that the fundamental TE-like waveguide mode excites a localized magnetic plasmon resonance between adjacent nanodisks with suitable dimensions, leading to transmission dips. For a sufficient number of disks (periodically distributed along the propagation direction), the structure supports a magnetic mode arising from a magneto-inductive coupling between neighboring nanodisks, as revealed by an Eigenmode analysis. The transmission response of the samples was measured for both polarizations through an end-fire set-up, confirming that the strong resonances are only present for TE polarization. Measurements and simulations are in good agreement, showing that the resonances strength is maximized for three coupled nanodisks.