‘Lightning rod’ effect creates fast optical transistor

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A team of scientists, led by the University of Southampton, has produced a fast nanoscale optical transistor using gold nanoantenna assisted phase transition.

According to the team, nanostructures that can interact strongly with light are of interest for a range of emerging applications, including small optical circuits and metasurface flat optics.

Professor Otto Muskens, from the University of Southampton, said: “If we can actively tune a nanoantenna using an electrical or optical signal, we could achieve transistor-type switches for light with nanometre scale footprints. Such active devices could also be used to tune the antenna’s light-concentration effects, leading to new applications in switchable and tuneable antenna-assisted processes.”

The Southampton team used the properties of the antenna to achieve low energy optical switching of vanadium dioxide, whose properties switch from an insulator to a metal at temperatures of more than 68°C. Gold nanoantennas were fabricated on top of this thin film and were used to locally drive the phase transition of the vanadium dioxide.

Prof Muskens said: “The nanoantenna assists the phase transition of the vanadium dioxide by concentrating energy near the tips of the antenna. It is like a lightning-rod effect. These positions are also where the antenna resonances are the most sensitive to local perturbations. Antenna-assisted switching thus results a large effect while requiring only a small amount of energy.”