The secret to twisting light
Scientists from the Australian National University (ANU) have uncovered the secret to twisting light at will - the latest step in the development of photonics. Their research has been published in the journal Nature Communications.
Photonics has been described as the faster, more compact and less carbon-intensive successor to electronics. Light carried by fibre optics has already replaced electricity for carrying signals over long distances; the next step is to develop photonic analogs of electronic computer chips by actively controlling the properties of light, such as its polarisation.
The ability of a material to rotate polarisation springs from the asymmetry of a molecule. This occurs in natural minerals and substances, such as sugar, but the researchers created their own metamaterial which rotates the polarisation of light “orders of magnitude more strongly than natural materials”, according to lead author Mingkai Liu from the ANU Research School of Physics and Engineering (RSPE).
The metamaterial is formed from a pattern of tiny metal shapes, dubbed ‘meta-atoms’. Liu and his colleagues used pairs of C-shaped meta-atoms, one suspended above the other by a fine wire, to achieve optical rotation. When light is shined onto the pair of meta-atoms the top one rotates, making the system asymmetric.
“Because light affects the symmetry of our system, you can tune your material’s response simply by shining a light beam on it,” said Liu.
“The high responsiveness of the system comes because it is very easy to make something hanging rotate.”
Liu added that the ability to tune the metamaterial is an important step towards building devices based on such materials. According to co-author Dr David Powell, also from RSPE, such devices could be put to use in the photonics industry.
“Thin slices of these materials can replace bulky collections of lenses and mirrors,” said Dr Powell. “This miniaturisation could lead to the creation of more compact optoelectronic devices, such as a light-based version of the electronic transistor.”
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