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What do we see in a mirror?

New metasurfaces look 'bright' at one direction, while 'dark' for the opposite direction

Date:
December 21, 2018
Source:
Aalto University
Summary:
Researchers have developed metasurfaces with extreme angle-asymmetric response. The new device can be a good or bad reflector depending on the angle the light hits it.
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Researchers at Aalto University developed metasurfaces with extreme angle-asymmetric response. The new device can be a good or bad reflector depending on the angle the light hits it.

When we look at a mirror from an angle, we see the image of the object located at the opposite direction. This is because the scattering light of the object is reflected by the mirror and then perceived by observers' eyes. This process, known as specular reflection, is angle-symmetric: if the person stands on the left side of mirror can see the right person, then the right person can always see the left one with the same clearness. Conventional mirrors always have symmetric responses for light coming from both sides of the mirrors. Recently, researchers at Aalto University have successfully broken the angle-symmetric response of a mirror using the concept of gradient metasurfaces. The artificially synthesized surfaces can be designed to look "bright" at one direction, while "dark" for the observer at the opposite direction.

Metasurfaces are planar artificial materials, composed of periodic arranged meta-atoms at subwavelength scale. Meta-atoms are made of traditional materials but, if they are placed in a repeating patterns, the array can show many unusual effects which cannot be realized by the natural materials.. In their article Extreme Asymmetry in Metasurfaces via Evanescent Fields Engineering: Angular-Asymmetric Absorption published in Physical Review Letters, the team from Aalto use gradient metasurfaces to engineer the contrast ratio of brightness for waves coming from two oppositely tilted angles. "Our findings provide the first demonstration that a flat surface can realize extreme optical asymmetry in angle spectrum. This is an important milestone in both physics and engineering communities," says Xuchen Wang, who is currently a third-year doctoral student in Aalto University, and also the responsible person of this work. Xuchen studies electromagnetic metasurfaces under the supervision of Prof. Sergei Tretyakov. Xuchen explains.


Story Source:

Materials provided by Aalto University. Note: Content may be edited for style and length.


Journal Reference:

  1. Xuchen Wang, Ana Díaz-Rubio, Viktar S. Asadchy, Grigorii Ptitcyn, Andrey A. Generalov, Juha Ala-Laurinaho, Sergei A. Tretyakov. Extreme Asymmetry in Metasurfaces via Evanescent Fields Engineering: Angular-Asymmetric Absorption. Physical Review Letters, 2018; 121 (25) DOI: 10.1103/PhysRevLett.121.256802

Cite This Page:

Aalto University. "What do we see in a mirror?." ScienceDaily. ScienceDaily, 21 December 2018. <www.sciencedaily.com/releases/2018/12/181221123837.htm>.
Aalto University. (2018, December 21). What do we see in a mirror?. ScienceDaily. Retrieved July 22, 2024 from www.sciencedaily.com/releases/2018/12/181221123837.htm
Aalto University. "What do we see in a mirror?." ScienceDaily. www.sciencedaily.com/releases/2018/12/181221123837.htm (accessed July 22, 2024).

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