Australasian Science: Australia's authority on science since 1938

New Material Twists Light

Research published in Nature Communications has described a new material with the ability to twist light, with potential applications in fibre optic communications.

“Our material can put a twist into light – that is, rotate its polarisation – orders of magnitude more strongly than natural materials,” said lead author Mingkai Liu, a PhD student at The Australian National University. “And we can switch the effect on and off directly with light.”

The ability of a material to rotate its polarisation springs from the asymmetry of a molecule. For example, sugar is asymmetric, so rotations of its polarisation can be used by diabetes researchers to measure sugar concentrations.

Co-author Dr David Powell said that the remarkable properties of the team’s artificial material might be put to use by the photonics industry. “Thin slices of these materials can replace bulky collections of lenses and mirrors,” he said. “This miniaturisation could lead to the creation of more compact opto-electronic devices, such as a light-based version of the electronic transistor.”

The materials are formed from a pattern of tiny metal shapes dubbed meta-atoms. To obtain optical rotation, Liu and his colleagues used pairs of C-shaped meta-atoms, one suspended above the other by a fine wire. When light is shined onto the pair of meta-atoms, the top one rotates, making the system asymmetric. “The high responsiveness of the system comes because it is very easy to make something hanging rotate,” Liu said.

The fact that the team’s meta-atoms move when light shines on them adds a new dimension. “Because light affects the symmetry of our system, you can tune your material’s response simply by shining a light beam on it,” Liu said.