Tripartite phonon–magnon–plasmon coupling, parametric amplification, and formation of a phonon–magnon–plasmon polariton in a two-dimensional periodic array of magnetostrictive/plasmonic bilayered nanodots

Coupling between spin waves (SWs) and other types of waves in nanostructured magnetic media has attracted increased attention in recent years because of the rich physics and the potential to spawn disruptive technologies. Among this family of intriguing phenomena, we recently reported a new one: coupling between SWs and hybridized phonon–plasmon waves, resulting in tripartite coupling of magnons, phonons, and plasmons. Here, this acousto-plasmo-magnonic phenomenon is studied in a two-dimensional periodic array of bilayered Co/Al nanodots on a silicon substrate, where Co is a magnetostrictive constituent responsive to magnetoelastic coupling and Al acts as a source of surface plasmons. Time-resolved magneto-optical-Kerr-effect microscopy revealed parametric amplification and strong coupling between two SW modes mediated by a hybrid phonon–plasmon mode. The strong coupling forms a new quasi-particle: the phonon–plasmon–magnon polariton.