News | August 24, 2020

Researchers Develop Flat Lens A Thousand Times Thinner Than A Hair

A lens a thousand times thinner than a hair was developed by researchers at the São Carlos School of Engineering at the University of São Paulo (EESC-USP). The piece can be used as a photographic lens on smartphones or used in other devices that depend on sensors. "In the current technological context, its applications are almost unlimited", says Emiliano Rezende Martins , a professor in the Department of Electrical and Computer Engineering at EESC-USP and one of the research coordinators to FAPESP Agency.

The research was published in the magazine ACS Photonics , with the title “ On Metalenses with Arbitrarily Wide Field of View ”. The study was supported by FAPESP through a research internship scholarship abroad awarded to doctoral student Augusto Martins , the main author of the article.

The lens consists of a single layer of silicon, of nanometric thickness, equipped with nanopost that interact with light. This structure is printed using lithography - a technique already well known and used in the manufacture of transistors.

According to Rezende Martins, the so-called metalentes emerged about 10 years ago and allow the maximum resolution physically possible. The problem is that his viewing angle is extremely closed, less than a degree of circumference. “One way to solve the problem is to compose metal elements, forming complex structures”, he informs.

The authors realized that, in a conventional lens, the field of view increases when the refractive index also increases as the lens becomes flatter. What they did, then, was to design a metallizer to mimic a completely flat lens, which would have an infinite refractive index - something impossible to achieve in the case of a conventional lens.

“Our lens has an arbitrary field of view, which ideally can reach 180 degrees without distortion of the image. We have already tested its effectiveness at an angle of 110 degrees. From that opening, the light energy decreases due to the shadow effect. But this can be corrected through post-processing ”, says Rezende Martins.

The composition compromises the super resolution of the metals, however the obtained resolution is sufficient for all conventional applications. With a camera built using 3D printing, doctoral student Augusto Martins tested the lens. And obtained high-resolution images in a wide field of view. “For now, we can only shoot in green. But, in the coming months, we will improve the lens, so that all colors are made possible ”, he says.

Source: FAPESP Agency