Metallic nanoparticles exhibit unique plasmonic properties, enabling the confinement of electromagnetic fields at the nanoscale. In the nanoparticle-on-mirror (NPoM) geometry, nanoparticles vertically coupled to a metallic mirror across a dielectric spacer sustain tightly confined gap plasmons with limited direct far-field access. Combining these cavities with periodic arrays allows for the excitation of diffractively excited resonances that act as radiative gateways, enabling efficient far-field excitation and enhanced coupling to the gap modes.
However, preparing such hybrid metasurfaces remains challenging due to the disparate length scales involved and the reliance on poorly scalable top-down nanofabrication techniques. Here, these challenges are addressed by using a template-assisted self-assembly technique with metal colloids, resulting in a hybrid plasmonic metasurface: a periodic array of clustered metal nanoparticles separated from a metallic film by a dielectric spacer.
This nanostructure allows the interplay of grating-coupled Surface Plasmon Polaritons (SPP), the Surface Lattice Resonance (SLR), and the gap mode through a variety of geometrical parameters, enabling hybrid mode engineering and offering a route toward advanced photonic devices with tailored optical responses.
The research, titled "Hybridization of Gap Plasmons and Grating-Coupled Surface Plasmon Polaritons in Metal Nanoparticle Cluster Arrays on a Mirror", has been published in the journal Advanced Optical Materials.
