Infrared Plasmonic Resonators Based on Self-Assembled Core–Shell Particles

Abstract

Infrared resonators emerge as key elements of infrared optical devices demanded for widespread applications. Traditional resonators based solely on noble metals suffer from considerable ohmic losses, limited tunability, and low excitation efficiency of surface plasmons in the infrared region, while the alternatives made of high-refractive-index dielectrics encounter fabrication challenges and relatively weak optical coupling. This work presents the experimental demonstration of self-assembled plasmonic core–shell particle clusters exhibiting pronounced and spectrally tunable resonances at infrared, especially mid-infrared, wavelengths. It is shown that the reflection spectra of individual clusters are unique, which are determined by the number and configuration of the constituent particles. Simulation results confirm the measured data and further reveal the origin of the spectral features. These findings pave a new way for the development of complex resonators operating in the infrared region, leading to a substantial step toward reconfigurable plasmonics and metamaterials with potential applications in sensing, imaging, spectroscopy, surveillance, and energy harvesting.