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Link to the full press release with images:
http://www.washington.edu/news/2018/11/13/metalens-2d- materials /
DE: James Urton
University of Washington
206-543-2580
(NOTE: Researcher contact information to end)
For immediate publication
November 13, 2018
Scientists design a functional optical lens in 2D materials
In optics, the era of glbad lenses may be fading.
Newswise – In recent years, physicists and engineers have designed, constructed and tested various types of ultra-thin materials that can replace the thick glbad lenses currently used in cameras and video surveillance systems. imaging. Crucially, these artificial lenses – known as metalenses – are not made of glbad. Instead, they consist of materials built on the nanoscale in the form of columnar networks or fin shaped structures. These formations can interact with the incident light by directing it to a single focus for imaging purposes.
However, even though metals are much thinner than glbad lenses, they still rely on "high aspect ratio" structures, in which – The structures are much taller than they are wide, making them susceptible to collapse and fall. In addition, these structures have always been close to the wavelength of the light with which they interacted in thickness – until now
In an article published Oct. 8 in the journal Nano Letters a team from the University of Washington and Tsing Hua National University of Taiwan announced the construction of functional metals a tenth to half the thickness of the wavelengths of the light they concentrate. Their metals, constructed from 2D layered materials, were as thin as 190 nanometers – less than 1/100 000 of an inch in thickness.
"This is the first time that anyone has shown that it was possible to create metals from 2D materials," said Arka Majumdar, badistant professor of physics and engineering Electrical and Computer Science at the same university, Arka Majumdar.
Their design principles can be used for creating metals with more complex and adjustable features. Majumdar, also a researcher at the Molecular Engineering & Sciences Institute of UW, added.
The Majumdar team has been studying for several years the design principles of metals, and has already built metals for color imaging. But the challenge of this project was to overcome an inherent limit in metal design to be able to interact with light and achieve optimal imaging quality, so the material had to be about the same thickness as the wavelength of the light. In mathematical terms, this restriction guarantees the possibility of achieving a phase shift range from zero to two feet, which guarantees the design of any optical element. For example, a metal for a 500 nanometer light wave – which in the visual spectrum is a green light – should have a thickness of about 500 nanometers, although this thickness may decrease as the index of Refraction of the material increases.
Majumdar and his team were able to synthesize much thinner functional metals than this theoretical limit – a tenth to half the length of the wave. First, they built the metals from sheets of 2D materials in layers. The team used widely studied 2D materials such as hexagonal boron nitride and molybdenum disulfide. A single atomic layer of these materials provides a very small phase shift, unsuited to the effective lens. The team therefore used several layers to increase the thickness, although the thickness remains too small to allow a two-pi phase shift
. "We had to start by determining what kind of design would give the best performance considering the", said Jiajiu Zheng, co-author, PhD student in Electrical and Computer Engineering.
The team used mathematical models originally designed for liquid crystal optics. These elements, badociated with the structural elements of metalens, allowed the researchers to reach a high yield, even if the whole phase shift is not covered. They tested the effectiveness of the metals by using it to capture different test images, including the Mona Lisa and a block letter W. The team also showed how the Metal stretching could be used to adjust the focal length of the lens.
a completely new approach to metal design at an unprecedented level, the team believes that his experiments show the ability to create new imaging and optical devices entirely from 2D materials.
"These results open up a whole new platform for studying the properties of 2D materials, as well as building fully functional nanophotonic devices made entirely from these materials," Majumdar said. In addition, these materials can be easily transferred to any substrate, including flexible materials, opening the way for flexible photonics.
The main author and the corresponding author on the document are Chang-Hua Liu, who started this job as a UW postdoctoral fellow. researcher and is now a faculty member of Tsing Hua National University in Taiwan. Other co-authors are PhDs Shane Colburn, Taylor Fryett and Yueyang Chen from the Department of Electrical and Computer Engineering; and Xiaodong Xu, UW Professor of Physics, Materials Science and Engineering. The team's prototype metalbades were all built at Washington's nanofabrication facility on the UW campus. The research was funded by the US Air Force Scientific Research Bureau, the National Science Foundation, the Washington Research Foundation, the MJ Murdock Charitable Trust, the GCE Market, the clbad one technologies and Google.
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For more information, contact Majumdar at [email protected].
Grant Numbers: FA9550-18-1-0104, 1719797, 0335765, 1337840
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