Brian Roxworthy and Vladimir Aksyuk from the National Institute of Standards and Technology, USA, have now demonstrated a plasmomechanical system that can localize optothermomechanical interactions to subdiffraction volumes. Their approach is based on electrically tunable localized-gap plasmon resonators (LGPRs) that use electrostatic actuation. A point-like LGPR is embedded into a fully functional nanoelectromechanical system that is a simple silicon nitride cantilever design. The cantilever is approximately 165 nm thick and has on top an approximately 15-nm-thick gold layer. The cantilever is suspended above, with a nominal gap of 20 nm, an underlying stationary gold pad and can be electrostatically actuated by applying a voltage between the top gold layer and the pad. The LGPR is defined by a 40-nm-thick gold cuboid embedded in the cantilever’s underside, the gold pad and the gap, and it mediates both optomechanical and thermomechanical coupling via its spatial location. The team shows that the thermomechanical coupling can induce self-oscillation of the nanomechanical device and can be injection-locked to a small-amplitude mechanical stimulus. Changing the plasmonic gap tunes the coupling and controls the threshold power of the oscillator. The findings will be of use for facile electro-optic modulation, nanomechanical sensing and reconfigurable metasurfaces.
About this article
Cite this article
Won, R. Versatile plasmomechanical systems. Nature Photon 12, 123 (2018). https://doi.org/10.1038/s41566-018-0124-5