August 1, 2021

How to extract colors from black – La Provincia


Physicists have developed a way to extract a color palette richest spectrum available by taking advantage of messy patterns inspired by nature that would normally be seen as black.

The colors we see in nature often come from nanoscale patterns that reflect light in a particular way. A butterfly’s wing, for example, may appear blue because the small grooves on the wing’s surface cause only blue light to reflect.

However, when surfaces appear on black or whiteIt is often because the nanoscale structures are completely disordered, causing all light to be absorbed or reflected.

A team of researchers led by the Birmingham University He has found a way to control how light passes through these messy surfaces to produce vivid colors. They publish results in Nature Communications.

The team, which includes colleagues at Ludwig Maximilian University in Munich, Germany, and Nanjing University in China, has compared the method to techniques that artists have exploited for centuries. Among the most famous examples of this is the cup Roman Lycurgus of the 4th century, made of glass that looks green when the light shines from the front, but red when the light shines from behind.

In a modern advance, the research team demonstrated a way to finely control this effect to produce remarkably accurate color reproduction.

The different colors of the image are represented in different thicknesses of a transparent material, such as glass, on a lithographic plate. In addition to this, the researchers deposited the messy layer, in this case made of random clusters of gold nanoparticles. Finally, underneath this layer, the team placed a mirror to form a transparent cavity. The cavity can trap light particles, or photons, inside. Photons behave like waves within the cavity, resonating at different frequencies below the lithographic surface and releasing different colors depending on the length of each wave.

Using this technique, the team was able to reproduce a chinese watercolor painting with exquisite color accuracy.

The principal investigator, the professor Shuang ZhangHe explains: “The different ways in which nature can produce color are really fascinating. If we can take advantage of them effectively, we can open up a treasure of richer and more vivid colors than we have seen so far.”

Co-author Dr. Changxu Liu He adds: “In physics, we are used to thinking that randomness in nanofabrication is bad, but here we show that randomness can lead to being superior to an ordered structure in some specific applications. Also, light intensity within random structures that we produced is really strong, we can use that in other areas of physics, like new types of detection technologies. “

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