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First Optical Rectenna Created for Converting Light Directly to DC

Category: Science & Technology
Posted: 06:14AM

The ability for antennas to convert radiation into electrical currents has been put to use for many decades now, but these systems have operated at radio and microwave frequencies. By moving up to optical frequencies though, antennas combined with rectifier diodes could be used to directly generate direct current. Now researchers at the Georgia Institute of Technology have finally achieved this with a rather ingenious design using carbon nanotubes.

To start the researchers grow conductive, vertically-aligned carbon nanotubes on a conducting substrate. The nanotubes are then coated with aluminum oxide, an insulator, and finally thin, transparent layers of calcium and aluminum are applied, forming a metal-insulator-metal diode. Bringing the antenna closer to the diode makes similar systems more efficient, so making the antenna one of the metals in the diode, as is the case here, is the ideal design. This efficiency is needed too, because the rectifier has to be able to switch on and off at femtosecond intervals in order for it to create a current from visible light.

Currently the proof-of-principle rectennas has an efficiency of have an efficiency of about one percent, but based on the work of others, the researchers are confident they could reach over 40% efficiency. Potential applications include photodetectors, and energy conversion systems that capture waste heat or light for generating electricity.



Source: Georgia Institute of Technology

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