Strong-field control of the plasmonic response in core-shell nanoparticles

The strong-field control of plasmonic nanosystems indicates new perspectives for non-linear plasmonic spectroscopy and petahertz electronics. However, questions remain regarding the nature of non-linear light-matter interactions at sub-wavelength spatial and ultrafast temporal scales.  We investigated the non-linear plasmonic response of Au-nanoshells with a SiO₂-core to an intense laser pulse. Our measured strong-field-ionization photoelectron energy spectra from these core-shell nanoparticles display a striking transition between the weak-field (linear-response) to the strong-field (nonlinear-response) regime. This observed transition agrees with the prediction of our modified Mie–theory simulation that incorporates the non-linear dielectric nanoshell response. The demonstrated optical control of the non-linear plasmonic response in prototypical core-shell nanoparticles paves the way towards ultrafast switching and opto-electronic signal modulation with more complex nanostructures.