Nonlinear plasmonics at high temperatures

We solve the Maxwell and heat equations self-consistently for metal nanoparticles under intense continuous wave (CW) illumination. Unlike previous studies, we rely on {\em experimentally}-measured data for the metal permittivity for increasing temperature and for the visible spectral range. We show that the thermal nonlinearity of the metal can lead to substantial deviations from the predictions of the linear model for the temperature and field distribution, and thus, can explain qualitatively the strong nonlinear scattering from such configurations observed experimentally. We also show that the incompleteness of existing data of the temperature dependence of the thermal properties of the system prevents reaching a quantitative agreement between the measured and calculated scattering data. This modelling approach is essential for the identification of the underlying physical mechanism responsible for the thermo-optical nonlinearity of the metal and should be adopted in all applications of high temperature nonlinear plasmonics, especially for refractory metals, both for CW and pulsed illumination

The photothermal nonlinearity in plasmon-assisted photocatalysis

We show that the temperature rise in large ensembles of metal nanoparticles under intense illumination is dominated by the temperature dependence of the thermal conductivity of the host, rather than by the optical properties of the metal or the host. This dependence typically causes the temperature rise to become sublinear, with this photothermal nonlinear effect becoming unusually strong, reaching even several tens of percent. We then show that this can explain experimental observations in several recent plasmon-assisted photocatalysis experiments. This shows that any claim for dominance of non-thermal electrons in plasmon-assisted photocatalysis must account for this photothermal nonlinear mechanism