

Researchers from King’s College London have developed a detailed process to separate colors and create ‘rainbows’ on a metal surface by utilizing nanoscale structures. This method will likely lead to improved solar cells and LED displays, according to the researchers.

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The modern discovery of how to separate and project different colors was actually also made at King’s College, more than 150 years ago. This discovery led to the development of color televisions and other displays. In modern research, the primary goal has been for the manipulation of color on the nanoscale. When this capability is further developed it will lead to great changes in imaging and spectroscopy, the sensing of chemical and biological agents, and also (likely) to better solar cells, LED displays, and TV screens.

In the new research, light of different colors was ‘trapped’ at different positions of a nanostructured area, by using nanostructures designed specifically for this function. Specific to the nanostructure’s geometry, a ‘trapped’ rainbow “could be created on a gold film that has the dimension on the order of a few micrometers — about 100 times smaller than the width of a human hair.”

Professor Anatoly Zayats explains: “Nanostructures of various kinds are being considered for solar cell applications to boost light absorption efficiency. 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 primary difference between natural rainbows and these artificial rainbows is that the researchers can actually control where and in what order the colors appear, simply by altering the nanostructures’ parameters. And in addition to this, they can also separate colors to appear on different sides of the nanostructures.

Co-author Dr Jean-Sebastien Bouillard says: “The effects demonstrated here will be important to provide ‘color’ sensitivity in infrared imaging systems for security and product control. It will also enable the construction of microscale spectrometers for sensing applications.”

“The ability to couple light to nanostructures with multicolour characteristics will be of major importance for light capturing devices in a huge range of applications, from light sources, displays, photo detectors and solar cells to sensing and light manipulation in optical circuits for tele and data communications.”

The new research is published in Nature’s Scientific Reports.

Source: King’s College London

Image Credits: Dr. Jean-Sebastien Bouillard, Dr. Ryan McCarron