2017 03 Electrically Tunable Metasurfaces Pave Dynamic | Holography

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2017 03 Electrically Tunable Metasurfaces Pave Dynamic
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    Electrically tunable metasurfaces pave theway toward dynamic holograms 2 March 2017, by Lisa Zyga  A new metasurface composed of silicon nanodisksintegrated into a liquid crystal can be electrically tunedby turning a voltage “on” and “off.” The change involtage changes the orientation of the liquid crystalmolecules, which in turn changes the opticaltransmission of the metasurface. Credit: Komar et al.Published by AIP Publishing (Phys.org)—Dynamic holograms allow three-dimensional images to change over time like amovie, but so far these holograms are still beingdeveloped. The development of dynamicholograms may now get a boost from recentresearch on optical metasurfaces, a type ofphotonic surface with tunable optical properties. In a new study published in Applied Physics Letters  , a team of scientists at The AustralianNational University in Canberra, Australia;Friedrich Schiller University Jena in Jena,Germany; and Sandia National Laboratories inAlbuquerque, New Mexico, US, has demonstrateda new way to tune optical metasurfaces.A metasurface is a thin sheet consisting of aperiodic array of nanoscale elements. The exactdimensions of these elements is critical, since theyare specifically designed to manipulate certainwavelengths of light in particular ways that enhancetheir electric and magnetic properties. Here, the scientists demonstrated how tomanipulate a metasurface by applying an electricalvoltage. By switching the control voltage on and off, the researchers could change the opticaltransmission of the metasurface. For instance, theycould tune the transmission from opaque to thetransparent regime for certain wavelengths,achieving a transmittance change of up to 75%.The voltage switch could also change the phase ofcertain wavelengths by up to 180°. We demonstrate a new technology platform thatenables tuning of optical metasurfaces with largecontrast by simple application of a voltage, Dragomir Neshev, a physics professor at TheAustralian National University, told Phys.org  . Froman application perspective, it adds to thesignificance that our tuning concept is based on asimilar technology as used in commercial liquidcrystal displays, which would largely facilitate thetranslation of our concept to real-world applicationsof tunable metasurfaces. The way this tuning works is that the voltagephysically changes the elements of themetasurface. The metasurface is made of a squarelattice of 600-nm-diameter silicon nanodisksembedded into a liquid crystal. When the voltage is off, the elongated molecules of the liquid crystallie parallel to the metasurface. Turning the voltage on reorients the liquid crystal molecules so thatthey stand up perpendicular to the metasurface.Light waves interact with the metasurfacedifferently depending on the orientation of the liquidcrystal.While other methods of metasurface tuning havebeen suggested, these have various drawbacks,such as that they work slowly and requireassistance that makes them impractical forimmediate applications. Since the new electrically  1 / 3    tunable metasurface works quickly and simply, theresearchers expect that the method could have awide variety of applications, including dynamicholograms, tunable imaging, and active beamsteering. Regarding a long-term vision or inspiration for thedevelopment of dynamic holographic devices, wecan watch almost any science fiction movie, Neshev said. Most of them feature holographicman-machine interaction devices for visualizationand communication purposes, where the hologrammoves and changes in time based on user input. While we are still far from this goal, a realisticmedium-term application of our metasurfaces aretunable lenses for laser microscopy applicationsand beam shapers with enhanced functionalities,such as polarization selective response. Activebeam steering or beam shaping could be applied incommunications or as components in opticallaboratory setups. More information:  Andrei Komar et al. Electrically tunable all-dielectric opticalmetasurfaces based on liquid crystals. Applied Physics Letters  . DOI: 10.1063/1.4976504 ABSTRACT We demonstrate electrical tuning of the spectralresponse of a Mie-resonant dielectric metasurfaceconsisting of silicon nanodisks embedded into liquidcrystals. We use the reorientation of nematic liquidcrystals in a moderate applied electric field to alterthe anisotropic permittivity tensor around themetasurface. By switching a control voltage on and off, we induce a large spectral shift of themetasurface resonances, resulting in an absolutetransmission modulation of up to 75%. Ourexperimental demonstration of voltage control ofdielectric metasurfaces paves the way for newtypes of electrically tunable metadevices, includingdynamic displays and holograms. © 2017 Phys.orgAPA citation: Electrically tunable metasurfaces pave the way toward dynamic holograms (2017, March 2)retrieved 3 March 2017 from https://phys.org/news/2017-03-electrically-tunable-metasurfaces-pave-dynamic.html  2 / 3    This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Pwred byTCPD wwwtcpdf.org)  3 / 3
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