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28 November 2012

Manipulating nanoscale ‘rainbows’ for solar cells and TV screens

The manipulation of light is a core photonics activity performed in numerous ways for numerous practical effects. For example, consider the design of lasers for purposes as diverse as repairing a retina to restore vision and downloading a movie over the internet onto a tablet for viewing.

Anatoly Zayats and his team at King's College
London have created artificial "rainbows" at
the nanoscale. The technology has potential
for use in solar energy generation, optical
computing, and more.
Amazing as those human-scale applications are, imagine manipulating multiple colors of light on a structure about 100 times smaller than the width of a human hair -- and then applying that for the very practical effects of sensing toxins, improving solar cell efficiency, enabling optical circuits for tele- and data communications, and improving flat-screen display.

A team of researchers led by Anatoly Zayats in the Biophysics and Nanotechnology Group at King’s College London reported recently in Nature’s Scientific Reports that they had demonstrated how to separate and even rearrange a spectrum of colors and create artificial “rainbows” using nanoscale structures on a metal surface.

The researchers trapped light of different colors at different positions at a dimension on the order of a few micrometers, an unprecedented scale in previous research, on a gold film.

"Nanostructures of various kinds are being considered for solar cell applications to boost light absorption efficiency," Zayats said in a King’s College press release. "Our results mean that we do not need to keep solar cells illuminated at a fixed angle without compromising the efficiency of light coupling in a wide range of wavelengths. When used in reverse for screens and displays, this will lead to wider viewing angles for all possible colors.”

The group’s nanoscale rainbows differ from actual rainbows in the sense that researchers were able to manipulate where the colors would appear by controlling the nanostructure’s parameters. They also discovered the possibility of separating colors on different sides of the nanostructures.

The effects demonstrated could also provide color sensitivity in infrared imaging systems for security and product control and enable construction of microscale spectrometers for sensing applications.

Zayats, who is a Fellow of SPIE, told about other applications of plasmonic effects and nanostructured metals in a recent SPIE Newsroom video interview. He will have further updates in an invited paper titled “Integrated nanophotonic devices based on plasmonics” to be presented next February at SPIE Photonics West in San Francisco.

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