• 'Metalens' could disrupt vacuum UV marke

    From ScienceDaily@1:317/3 to All on Thu May 5 22:30:40 2022
    'Metalens' could disrupt vacuum UV market

    Date:
    May 5, 2022
    Source:
    Rice University
    Summary:
    Photonics researchers have created a potentially disruptive
    technology for the ultraviolet optics market. Solid-state
    'metalens' transform long- wave UV into focused 'vacuum UV,' a
    type of light used in semiconductor manufacturing that is costly,
    in part because it is absorbed by almost all types of glass used
    to make conventional lenses.



    FULL STORY ==========================================================================
    Rice University photonics researchers have created a potentially
    disruptive technology for the ultraviolet optics market.


    ==========================================================================
    By precisely etching hundreds of tiny triangles on the surface of a
    microscopic film of zinc oxide, nanophotonics pioneer Naomi Halas and colleagues created a "metalens" that transforms incoming long-wave UV
    (UV-A) into a focused output of vacuum UV (VUV) radiation. VUV is used
    in semiconductor manufacturing, photochemistry and materials science
    and has historically been costly to work with, in part because it is
    absorbed by almost all types of glass used to make conventional lenses.

    "This work is particularly promising in light of recent demonstrations
    that chip manufacturers can scale up the production of metasurfaces
    with CMOS- compatible processes," said Halas, co-corresponding author
    of a metalens demonstration study published in Science Advances. "This
    is a fundamental study, but it clearly points to a new strategy for high-throughput manufacturing of compact VUV optical components and
    devices." Halas' team showed its microscopic metalens could convert 394-nanometer UV into a focused output of 197-nanometer VUV. The
    disc-shaped metalens is a transparent sheet of zinc oxide that is thinner
    than a sheet of paper and just 45 millionths of a meter in diameter. In
    the demonstration, a 394-nanometer UV- A laser was shined at the back
    of the disc, and researchers measured the light that emerged from the
    other side.

    Study co-first author Catherine Arndt, an applied physics graduate student
    in Halas' research group, said the key feature of the metalens is its interface, a front surface that is studded with concentric circles of
    tiny triangles.

    "The interface is where all of the physics is happening," she said. "We're actually imparting a phase shift, changing both how quickly the light
    is moving and the direction it's traveling. We don't have to collect
    the light output because we use electrodynamics to redirect it at the
    interface where we generate it." Violet light has the lowest wavelength visible to humans. Ultraviolet has even lower wavelengths, which
    range from 400 nanometers to 10 nanometers. Vacuum UV, with wavelengths
    between 100-200 nanometers, is so-named because it is strongly absorbed by oxygen. Using VUV light today typically requires a vacuum chamber or other specialized environment, as well as machinery to generate and focus VUV.



    ========================================================================== "Conventional materials usually don't generate VUV," Arndt said. "It's
    made today with nonlinear crystals, which are bulky, expensive and
    often export- controlled. The upshot is that VUV is quite expensive."
    In previous work, Halas, Rice physicist Peter Nordlander, former Rice
    Ph.D.

    student Michael Semmlinger and others demonstrated they could
    transform 394- nanometer UV into 197-nanometer VUV with a zinc oxide metasurface. Like the metalens, the metasurface was a transparent film
    of zinc oxide with a patterned surface. But the required pattern wasn't
    as complex since it didn't need to focus the light output, Arndt said.

    "Metalenses take advantage of the fact that the properties of light change
    when it hits a surface," she said. "For example, light travels faster
    through air than it does through water. That's why you get reflections
    on the surface of a pond. The surface of the water is the interface,
    and when sunlight hits the interface, a little of it reflects off."
    The prior work showed a metasurface could produce VUV by upconverting
    long-wave UV via a frequency-doubling process called second-harmonic generation. But VUV is costly, in part, because it is expensive to
    manipulate after it's produced.

    Commercially available systems for that can fill cabinets as large as refrigerators or compact cars and cost tens of thousands of dollars,
    she said.

    "For a metalens, you're trying to both generate the light and manipulate
    it," Arndt said. "In the visible wavelength regime, metalens technology
    has become very efficient. Virtual reality headsets use that. Metalenses
    have also been demonstrated in recent years for visible and infrared wavelengths, but no one had done it at shorter wavelengths. And a lot
    of materials absorb VUV. So for us it was just an overall challenge
    to see, 'Can we do this?'" To make the metalens, Arndt worked with co-corresponding author Din Ping Tsai of City University of Hong Kong,
    who helped produce the intricate metalens surface, and with three co-first authors: Semmlinger, who graduated from Rice in 2020,Ming Zhang, who
    graduated from Rice in 2021, and Ming Lun Tseng, an assistant professor
    at Taiwan's National Yang Ming Chiao Tung University.



    ========================================================================== Tests at Rice showed the metalens could focus its 197-nanometer output
    onto a spot measuring 1.7 microns in diameter, increasing the power
    density of the light output by 21 times.

    Arndt said it's too early to say whether the technology can compete with
    state- of-the-art VUV systems.

    "It's really fundamental at this stage," she said. "But it has a lot of potential. It could be made far more efficient. With this first study,
    the question was, 'Does it work?' In the next phase, we'll be asking, 'How
    much better can we make it?'" Halas is Rice's Stanley C. Moore Professor
    of Electrical and Computer Engineering, director of Rice's Smalley-Curl Institute and a professor of chemistry, bioengineering, physics and
    astronomy, and materials science and nanoengineering. Nordlander,
    a co-author of the study, is the Wiess Chair and Professor of Physics
    and Astronomy, and professor of electrical and computer engineering,
    and materials science and nanoengineering.

    Additional study co-authors include Benjamin Cerjan and Jian Yang of
    Rice; Tzu- Ting Huang and Cheng Hung Chu of Academia Sinica in Taiwan;
    Hsin Yu Kuo of National Taiwan University; Vin-Cent Su of National United University in Taiwan; and Mu Ku Chen of City University of Hong Kong.

    The research was funded by Taiwan's Ministry of Science and
    Technology (107- 2311-B-002-022-MY3, 108-2221-E-002-168-MY4, 110-2636-M-A49-001), National Taiwan University (107-L7728, 107-L7807, YIH-08HZT49001), the Shenzhen Science and Technology Innovation Commission (SGDX2019081623281169), the University Grants Committee/Research Grants
    Council of China's Hong Kong Special Administrative Region (AoE/P-502/20),
    the Department of Science and Technology of China's Guangdong Province (2020B1515120073), the Department of Electrical Engineering of City
    University of Hong Kong (9380131), the Taiwan Ministry of Education's
    Yushan Young Scholar Program, the Research Center for Applied Sciences
    at Taiwan's Academia Sinica, the Robert A. Welch Foundation (C-1220,
    C-1222), the National Science Foundation (1610229, 1842494), the Air
    Force Office of Scientific Research (MURI FA9550-15-1-0022) and the
    Defense Threat Reduction Agency (HDTRA1-16-1-0042).


    ========================================================================== Story Source: Materials provided by Rice_University. Original written
    by Jade Boyd. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Ming Lun Tseng, Michael Semmlinger, Ming Zhang, Catherine Arndt,
    Tzu-Ting
    Huang, Jian Yang, Hsin Yu Kuo, Vin-Cent Su, Mu Ku Chen, Cheng
    Hung Chu, Benjamin Cerjan, Din Ping Tsai, Peter Nordlander, Naomi
    J. Halas. Vacuum ultraviolet nonlinear metalens. Science Advances,
    2022; 8 (16) DOI: 10.1126/sciadv.abn5644 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/05/220505143812.htm

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