New directions in antenna-assisted switches and optical memory read more at here www.spinonews.com/index.php/item/1375-new-directions-in-antenna-assisted-switches-and-optical-memory

University of Southampton scientists have developed a fast nanoscale optical transistor using gold nanoantenna assisted phase transition.

The work opens up new directions in antenna-assisted switches and optical memory.

Nanoantennas are designed to have strong optical resonances where energy is concentrated far below the diffraction limit, the smallest scale possible using conventional optics.

Such extreme concentration of light can be used to enhance all kinds of effects related to localized energy conversion and harvesting, coupling of light to small molecules and quantum dots, and generating new frequencies of light through nonlinear optics.

Next to precise tuning of these antennas by design, an ability to actively tune their properties is of great interest.

Professor Otto Muskens, from the University of Southampton, said, if we are able to actively tune a nanoantenna using an electrical or optical signal, we could achieve transistor-type switches for light with nanometer-scale footprint for data communication.

Such active devices could also be used to tune the antenna’s light-concentration effects leading to new applications in switchable and tunable antenna-assisted processes.

The Southampton research team used the properties of the antenna itself to achieve low energy optical switching of a phase-change material. The material used to achieve this effect was vanadium dioxide.

Vanadium dioxide is a special material with properties that can be switched from an insulator to a metal by increasing the temperature above the phase transition point (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.

Professor Muskens explained, the nanoantenna assists the phase transition of the vanadium dioxide by locally concentrating energy near the tips of the antenna. It is like a lightning-rod effect. Antenna-assisted switching thus results a large effect while requiring only a small amount of energy.