Rare-Earth Monopnictide Alloys for Tunable, Epitaxial, Designer Plasmonics

We demonstrate that plasmonic response can be tuned spectrally via the alloy composition of an epitaxial semimetallic film. Specifically, attenuated total reflectance studies show that the surface plasmon resonance of rare-earth monopnictide La_<i>x</i>Lu_1–<i>x</i>As alloy films can be tuned across the mid-IR, while lattice-matching to technologically important substrates. The electrical properties are a strong function of the composition, which, in turn, manifests as tunability of the optical properties. The ability to produce tunable (semi)­metals that can be epitaxially integrated with III–V emitters and absorbers is expected to enable a new generation of novel nanophotonic device architectures and functionality