Active Plasmonics with Strong THz Fields

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Plasmonics treats the interaction of visible light with conduction band electrons in nanostructures of noble metal nanostructures.The resulting strongly localized electric field in the vicinity of metal nanoparticles has led to applications in fields ranging from high speed telecommunications to photovoltaics and biological sensing.Especially telecommunication and photonic applications rely on on a control and modulation of the plasmon properties, "active plasmonics".In principle, the plasmon properties depend on the properties of the conduction band electrons constituting the plasmon oscillation. Changing them changes the plasmon. Examples for approaches realizing active plasmonics try to, for exanple, modify the electron density by electrochemical doping. Still, the observed effects are not strong and, more importantly, the modulations are too slow for high-speed applications.We propose to use strong electric fields to modify the charge density within a nanoparticle.In our project, we aim at using strong electric fields of picosecond duration from THz pulses to perturb the electron cloud and to modify the plasmon properties. First experiments were promising and showed strong effects. We plan a systematic study to verify the effect and we want to develop a theory that allows texplaining and understanding the THz plasmon tuning.