'Metalens' could disrupt the vacuum UV market

‘Metalens’ could disrupt the vacuum UV market

By etching hundreds of precisely triangular-shaped nanometers into precisely-formed concentric circles on a microscopic film of zinc oxide, Rice University photonics researchers have created “Metalence,” a solid, transparent device thinner than a sheet of paper that bends light like a conventional lens. Rice Minerals converts 394 nm of ultraviolet light (blue) into 197 nm “vacuum UV” (pink) while simultaneously focusing the VUV output onto a small spot less than 2 millionths of a meter in diameter. Credit: M. Semmlinger/Rice University

Photonics researchers at Rice University have created a potentially disruptive technology for the ultraviolet optics market.

By carefully etching hundreds of tiny triangles onto the surface of a microscopic film of zinc oxide, nanophotonic pioneer Naomi Hallas and her colleagues have created “metalins” that convert incoming long-wave ultraviolet (UV-A) radiation into a concentrated output of vacuum ultraviolet (UV-A) radiation ( VUV ) radiation. VUV is used in semiconductor manufacturing, photochemistry and materials science, and has historically been expensive to work with, in part because it is absorbed by nearly all types of glass used to make conventional lenses.

“This work is particularly promising in light of recent demonstrations that chip manufacturers can increase the production of surfactants using CMOS-compatible processes,” said Halas, co-author of a cross-sectional study of metallic minerals published in science progress. “This is a basic study, but it clearly indicates a new strategy for the high-throughput manufacturing of integrated VUV optical components and devices.”

Halas’ team showed that the microscopic metals can convert 394 nm UV radiation into a concentrated output of 197 nm VUV. The disc-shaped mineral is a translucent sheet of zinc oxide that is thinner than a sheet of paper and has a diameter of 45 millionths of a meter. In the demonstration, a 394-nm UV-A laser was shone at the back of the disc, and the researchers measured the light coming from the other side.

The metal’s main feature is its facade, a front surface studded with concentric circles of small triangles, said study co-author Katherine Arndt, a graduate student in applied physics in the Halas research group.

“The interface is where all the physics happens,” she said. “We are actually transmitting a phase shift, changing the speed at which the light travels and the direction it travels. We don’t have to collect the light’s output because we use electrodynamics to redirect it to the interface where we generate it.”

Violet light has the lowest wavelength visible to humans. UV rays have lower wavelengths, which range from 400 nm to 10 nm. Vacuum UV rays, with wavelengths between 100-200 nanometers, are so named because they are strongly absorbed by oxygen. The use of VUV light today requires a vacuum chamber or other specialized environment, as well as machines to generate and concentrate VUV.

“Conventional materials usually don’t generate VUV,” Arendt said. “It is made today of nonlinear crystals, which is bulky, expensive and often export-controlled. The result is that VUV is very expensive.”

In previous work, Halas, Rice physicist Peter Nordlander, and former Rice PhD. Student Michael Semmlinger et al. showed that they could convert 394 nm UV light into 197 nm VUV with a zinc oxide-free surface. Like the metal, the penetrating surface was a transparent film of zinc oxide with an embossed surface. Arendt said the pattern needed was not complicated because it didn’t need to focus the light output.

“Minerals benefit from the fact that the properties of light change when it hits a surface,” she said. “For example, light travels through air faster than it does through water. That is why you get reflections on the surface of a pond. The surface of the water is the facade, and when sunlight hits the facade, little of it is reflected.”

Previous work showed that the superficial can produce VUV by transforming long-wavelength ultraviolet radiation via a frequency-doubling process called second harmonic generation. But VUV is expensive, in part, because it’s expensive to rig after it’s been produced. Commercially available systems therefore can fill large cabinets such as refrigerators or compact cars and cost tens of thousands of dollars, she said.

“For metal, you’re trying to generate and manipulate light,” Arendt said. “In the visible wavelength system, metalens technology has become very effective. Virtual reality headsets use that. Metalens lenses have also been shown in recent years for visible and infrared wavelengths, but no one has done so at shorter wavelengths. And they absorb a lot of VUV materials.” So it was just a blanket challenge for us to see, “Can we do this?”

To fabricate the metals, Arendt worked with corresponding author Din Bing Tsai of City University of Hong Kong, who helped produce the complex Metalens surface, and with three co-authors: Simlinger, who graduated from Rice in 2020, Ming Zhang, who graduated from Rice in 2021 and Ming Lun Zeng, associate professor at National Yang Ming Chiao Tung University in Taiwan.

Tests at Rice showed that the metal could focus its 197-nanometer output on a spot with a diameter of 1.7 microns, increasing the energy density of the light by 21 times.

Arendt said it’s too early to say if the technology can rival the latest VUV systems.

“It’s really key at this point,” she said. “But it has a lot of potential. It can be made a lot more efficient. With this first study, the question was, ‘Does it work?'” In the next stage, we will ask, “How better can we make it?”

Record-breaking minerals could revolutionize photonic technologies

more information:
Ming Lun Tseng et al, Ultraviolet Nonlinear Metal Vacuum, science progress (2022). DOI: 10.1126 / sciadv.abn5644 Michael

Semmlinger et al., UV-free surface for light generation, nano messages (2018). DOI: 10.1021 / acs.nanolett.8b02346

Presented by Rice University

the quote: Metalens Can Disrupt Vacuum UV Market (2022, May 5) Retrieved May 5, 2022 from https://phys.org/news/2022-05-metalens-disrupt-vacuum-uv.html

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2022-05-05 17:30:23

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