MSGID: 1:317/3 6274a4e2   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    '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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