A random find in a washing basket has led a team of scientists at Australian National University ( ANU) to uncover the secret to twisting light at will.
The discovery is being hailed as the latest step in the development of photonics, the faster, more compact and less carbon- hungry successor to electronics. It is also hoped it will prove useful in medicine, such as the area of diabetes research.
Mingkai Liu, a PhD student at the ANU Research School of Physics and Engineering (RSPE), was moved to research the idea after he found a piece of wire in his washing one day.
That led him, and his team at ANU, to begin a series of experiments shining a light on objects hanging from a fine wire. This helped create the latest in a new breed of materials known as metamaterials. These artificial materials show extraordinary properties not seen in natural materials.
"Our material can put a twist into light -- that is, rotate its polarisation -- orders of magnitude more strongly than natural materials," said Liu, the project's lead author. "And we can switch the effect on and off directly with light."
Electronics is estimated to account for 2 percent of the global carbon footprint, a figure which photonics has the potential to reduce significantly. Already light carried by fibre optics, has replaced electricity for carrying signals over long distances. The next step is to develop photonic analogues of electronic computer chips, by actively controlling the properties of light, such as its polarisation.
The ability of a material to rotate polarisation, as in this experiment, springs from the asymmetry of a molecule. It occurs in natural minerals and substances: for example, sugar is asymmetric and so polarisation rotation can be used to measure sugar concentrations, which is useful in diabetes research.
However, the remarkable properties of this artificial material might first be put to use in the budding photonics industry, suggested co-author Dr. David Powell, also from RSPE.
"It's another completely new tool in the toolbox for processing light," he said. "Thin slices of these materials can replace bulky collections of lenses and mirrors. This miniaturisation could lead to the creation of more compact opto-electronic devices, such as a light-based version of the electronic transistor."
The metamaterials 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 on to 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," said Liu. "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. Tunability of a metamaterial is an important step towards building devices based on these artificial materials."