Active Control over the Interplay between the Dark and Hidden Sides of Plasmonics Using Metallodielectric Au–Ge2Sb2Te5 Unit Cells

We present a systematic study for a metallodielectric nanoplasmonic unit cell to support both Fano and toroidal resonances in the near-infrared region. Using full electromagnetic computations, we show that a combination of phase-changing and metallic materials allows for designing a unit cell with different spectral responses at different phases of the phase-changing material (here Ge2Sb2Te5 or simply GST). This phenomenon of switching between toroidal response and Fano resonant mode is confirmed using both finite-element and finite-difference time-domain methods. Having active control over the interplay between narrow and tunable Fano and toroidal modes at different wavelengths with fast transition would allow for developing efficient and practical photonic devices for communication and imaging applications.