The ability of two nearly-touching plasmonic nanoparticles to squeeze light into a nanometer gap has provided a myriad of fundamental insights into light–matter interaction. In this work, we construct a nanoelectromechanical system (NEMS) that capitalizes on the unique, singular behavior that arises at sub-nanometer particle-spacings to create an electro-optical modulator. Using in situ electron energy loss spectroscopy in a transmission electron microscope, we map the spectral and spatial changes in the plasmonic modes as they hybridize and evolve from a weak to a strong coupling regime. In the strongly-coupled regime, we observe a very large mechanical tunability (~250 meV/nm) of the bonding-dipole plasmon resonance of the dimer at ~1 nm gap spacing, right before detrimental quantum effects set in. We leverage our findings to realize a prototype NEMS light-intensity modulator operating at ~10 MHz and with a power consumption of only 4 fJ/bit.
Bibliographical noteFunding Information:
This work was supported by a Multi University Research Initiative funded by the US Air Force (grant FA9550-17-1-0002) and an individual investigator grant from the AFOSR (grant FA9550-18-1-0323). JHS also acknowledges support from the Basic Science Research Program funded through the “National Research Foundation of Korea (NRF)” (NRF-2016R1A6A3A03012480). JvdG is supported by a Rubicon Fellowship from the “Nederlandse organisatie voor Wetenschappelijk Onderzoek (NWO).” SR acknowledges support by the Independent Research Funding Denmark (7026-00117B). Part of this work was performed at the Nano@Stanford labs, supported by the National Science Foundation under award ECCS-1542152.
© 2021, The Author(s).