Revealing the Photothermal Behavior of Plasmonic Gap Modes: Toward Thermostable Nanocavities

Abstract

AbstractPlasmonic nanocavities based on nanoparticle‐on‐mirror geometries draw widespread interest due to their easy‐fabricated structures and highly confined plasmon modes, enabling light–matter interaction for developing state‐of‐the‐art photonic devices. To truly be ideal building blocks for practical nanophotonic devices, the nanoparticle‐on‐mirror nanocavities are expected to be simultaneously spectral tunable and thermostable under the focused laser irradiation. Here, the in‐situ optical tuning of the nanocavity mode is achieved in the nanocube‐on‐mirror nanocavities by continuous laser irradiation. Through the photothermal‐assisted morphology changes, the in‐situ shifting of the plasmon resonances to the lower and higher energies is accomplished by the deformation of the surfactant covering the silver nanocube and reshaping the rounding curvature of the nanocubes, respectively. Furthermore, it is found that the alumina‐encapsulated nanocube on mirrors constructed by surfactant‐eliminated nanocubes are capable of enduring more intense irradiation than the normal ones. On this basis, the factors affecting the plasmonic heating effect are also systematically investigated, and the internal relationship among light absorption, temperature increases, and plasmonic resonance shifts is established. In general, these results provide ideas for designing novel stable nanocavities, and the surfactant‐eliminated nanocube‐on‐mirror nanocavities presented here are a promising platform for future applications in boosting light–matter interaction.