Nanoantennas on glass: the path to full photonic night vision?

December 13, 2016 // By Julien Happich
In a paper published in Nano Letters, a team of researchers from the Australian National University (ANU) are revealing a new way to fabricate nanoantennas so as to be able to lay them evenly on top of a transparent glass substrate.

This new feat, they explain in the paper "Nonlinear Generation of Vector Beams From AlGaAs Nanoantennas", makes it possible to observe and characterize the nanoantennas' behaviour with respect to different light frequencies shone at them, from any direction. And what they found was that when lit at infrared frequencies, the embedded nanophotonic components (AlGaAs nanodisks tested with various diameters from 340 to 690nm and 300nm thick, laid out periodically 5μm apart) were capable of manipulating light locally and spatially.

The nanoantennas were emitting second harmonics in a preferential direction with a backward-to-forward ratio of up to five. By tuning the nanodisks, the researchers were able to shape the second harmonic radiation pattern in forward and backward directions as well as its polarization state.

Although this research was rather fundamental, Prof. Dragomir Neshev from ANU later envisaged that one application could be the direct conversion of infrared light (or other frequencies non visible to the human eye) to visible frequencies, directly in line of sight. Instead of designing bulky optoelectrical conversion apparatuses relying on sensors and displays, this may be done by embedding the right combination of nanodisks onto the lens surface of conventional glasses. Due to its obvious military applications, the team has put in a proposal to DARPA, seeking funds to develop such a technology in the next 5 years. Other applications could include anti-counterfeit markings only detectable under specific lighting.

"It is still too early stage for patenting or a start-up, but I hope we can secure the funding to get closer to a real product" commented Neshev.

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