An international team of researchers from Moscow State University (Russia), Sandia National Laboratories in Albuquerque (USA), and Friedrich-Schiller University in Jena (Germany) have devised an ultrafast tunable metamaterial based on GaAs nanoparticles.
The researchers think that the new optical metamaterial could pave the way to ultrafast information transfer on the nanoscale.
For almost twenty years, researchers have been designing metamaterial-based devices, however, the properties of these materials have remain fixed. In this latest work, published by Nature Communications, the team of physicists and engineers have found a way to turn the metamaterials ‘on’ and ‘off’ at more than 100 billion times per second.
They made the metamaterial from a thin GaAs film using electron-beam lithography with subsequent plasma etching. The material consists of an array of semiconductor nanoparticles, which can resonantly concentrate and ‘hold’ light on the nanoscale. In other words, when the light illuminates the metamaterial, it is ‘trapped’ inside the nanoparticles and interacts more efficiently with them.
The working principle of the ultrafast tunable metamaterial lies in generation of electron-hole pairs. In the steady state, the metamaterial is reflective. Then, researchers illuminate the metamaterial with an ultrashort laser pulse, whose energy is used to generate electrons and electron vacancies – ‘holes’ – in the material. The presence of electrons and holes changes the properties of the material: now, the metamaterial is not reflective anymore.
In a split second, electrons and holes disappear by meeting each other, and the metamaterial is reflective again. This way, it is possible to construct optical logic elements, opening the possibility of creating ultrafast optical computers.
In 2015, a part of the same collaboration reported a similar device based on silicon nanostructures. In their new study, GaAs was used instead of silicon, which increased the efficiency of controlling light with light in metamaterials by an order of magnitude.
Prospectively, the research will allow creating devices for information transfer and processing at speeds of tens and hundreds of terabits per second. The demonstration of highly efficient tunable semiconductor metamaterials is a significant step towards such information processing speeds.
