Scientists invent an ultra-fine flat lens capable of color imaging – Xinhua

WASHINGTON, Oct. 3 (Xinhua) – Think of a pair of glasses of thinner thickness than a sheet of paper. American researchers have made this possible with the first flat lens capable of properly focusing a wide range of colors on the same focus.

The study published Wednesday in the journal Light: Science & Applications describes flat lenses, very micro-thick, consisting of pixels or "meta-atoms", which can significantly reduce the size and weight of any optical device used for the purpose. imaging. .

A conventional lens carries all the light falling on it by stacking multiple lenses so that different colors, which are never sharp at the same time, arrive at the same time at the focal point, thus increasing weight and cost. And that is why a conventional lens is thicker in its center than in its edge.

Scientists led by Yu Nanfang with Columbia University have developed two-dimensional structures to control the propagation of light, using meta-atoms representing only a fraction of the wavelength of light and retarding the light that passes through it in a different quantity.

According to the study, the researchers were able to achieve the same function as a much thicker and thicker conventional lens system by creating a very thin, flat layer of nanostructures on a substrate as thin as a human hair.

Yu's team manufactured the meta-lenses using standard 2D planar fabrication techniques similar to those used for computer chip manufacturing, but this is simpler because they do not have to define that a layer of nanostructures.

The advantage of flat meta-lenses is that, unlike conventional lenses, they do not require long and expensive grinding and polishing processes, according to the researchers.

"So we can send our lens designs to semiconductor foundries for mass production and benefit from industry-wide economies of scale," said Sajan Shrestha, a PhD student in the group. Yu who was co-author of the study.

In addition, the lens can focus light on any arbitrary polarization state, so that it works not only in the laboratory, where the polarization can be well controlled, but also in applications of the real world, where ambient light has a random polarization.