Tamm plasmon photonic crystals: From bandgap engineering to defect cavity

Abstract

Photonic bandgap engineering plays a key role in modern photonics since it allows for an ultimate control of photon propagation in periodic dielectric or metallic media. Tamm plasmon structures are a particularly attractive platform since the electromagnetic field can be completely controlled by patterning the thin metal layer. Up to now, only macroscopic patterning (larger than the operation wavelength) has been experimentally demonstrated, leading to 3D confinement of light but suffering from a lack of fine control of the dispersion properties of Tamm plasmons. Here, we report for the first time the opening of a bandgap in Tamm plasmon structures via subwavelength-periodic patterning of the metallic layer. By adopting a “double period” design, we experimentally put into evidence a photonic bandgap for the TE polarization up to 150 nm wide in the telecom wavelength range. Moreover, such a design offers a great flexibility to tailor on-demand, and independently, the bandgap size from 30 nm to 150 nm and its spectral position within a range of 50 nm. Finally, by implementing a defect cavity within the Tamm plasmon photonic crystal, a 1.6 μm cavity supporting a single highly confined Tamm mode is experimentally demonstrated. All experimental results are in perfect agreement with numerical calculations. Our results demonstrate the possibility to engineer novel band dispersion with surface modes of hybrid metallic/dielectric structures, thus opening the way to applications in topological photonics, metamaterials, and parity-time symmetry physics.