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Belle Dumé writing in physicsworld.com reports that a new device that collects and focuses light before converting it into a current of electrons has been developed by researchers at Rice University in the US. The nano-optical antenna and photodiode – the first device of its kind – could potentially be used in a variety of applications such as photosensing, energy harvesting and imaging.
Conventional antennas, which are widely used to transmit radio or TV signals, can be used at optical frequencies as long as the device is shrunk to the nanoscale. Such optical nano-antennas work by exploiting “plasmonic modes”, which increase the coupling between light emitted by neighbouring molecules and the antenna.
Naomi Halas and colleagues have now taken advantage of these plasmonic modes to make the first optical nano-antenna that also works as a photodiode – a type of photodetector capable of converting light into either current or voltage. Halas’s team made its device by growing rod-like arrays of gold nano-antennas directly onto a silicon surface – so creating a metal–semiconductor (or Schottky) barrier formed at the antenna–semiconductor interface.
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