Funhouse mirrors just got a whole lot wackier. Reflective surfaces built using the principles behind invisibility cloaks could bounce light at strange angles, or make a mirror that turns into a window depending on the light in the room.
Invisibility cloaks, capable of hiding objects by bending light around them, are just one of the fantastic-sounding promises of metamaterials 鈥� which have complex internal structures that allow them to manipulate light. Viktar Asadchy of Aalto University in Finland and his colleagues realised they could apply the principles to mirrors, creating a metamirror.
Building metamaterials that manipulate visible light is tricky because of its short wavelength, so the team worked with microwaves at a wavelength of 6 centimetres instead. They embedded loops of copper wire in plastic foam to create the necessary metamaterial structure.
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While a normal mirror reflects light at the same angle it hits, their metamirror bounces face-on microwaves back at a 45 degree angle. 鈥淲e have small antennas in our device and they reflect the wave differently. We can change the wavefront of the light, which means you can change the direction,鈥� says Asadchy.
What鈥檚 more, because the metamirror is tuned to work at a certain wavelength, it is transparent to all others. Making a visible light version would mean having a surface that was mirrored under red light, for instance, but see-through for other colours.
The team hopes to extend the work to visible light, but have applications in mind for other wavelengths. For example, a radio metamirror coating on the surface of a satellite鈥檚 solar panels would let sunlight through, but also act as an antenna to communicate with the ground, saving room on the spacecraft.
Journal reference: Physical Review Letters, DOI:
