Plasmonic EIT switching in ellipsoid tripod structures

We have numerically investigated the plasmon properties supported by dark–bright resonator and dark–bright–dark resonators compose of elliptical dolmen structures. The transmission spectrum shows a single transparency window for the symmetric coupling, an additional transparency window appears when introducing asymmetry. The constructive interference strengthens the coupling between the bright and dark resonators, leading to a more prominent EIT-like transparency window. Based on the magnetic field distribution, we find that the magnetic field are strongly localized inside the cavities, the new existing peaks can be results from the first- or second-order magnetic resonance, and only negative or positive and negative field can enhance in both cavities, while for the transmission dips, the magnetic localize in one cavity. The spectra are highly sensitive to the refractive-index fluctuation of the surrounding medium. The resonator design strategy opens up a rich pathway for the implementation of optimized optical properties for specific applications.

► Additional transparency windows appear in the spectra when introducing asymmetry.
► The interference strengths the coupling and leads to a prominent transparency window.
► The magnetic field localized in both cavities or only in one relying on wavelength.
► The spectra are highly sensitive to the refractive-index fluctuation of the medium.