May 18 2017
Nature Communications has recently published a report on the development of an ultrafast tunable metamaterial, based on gallium arsenide nanoparticles, by an international team of Researchers from Moscow State University (Russia), Sandia National Laboratories in Albuquerque (USA) and Friedrich-Schiller University in Jena (Germany).
This new optical metamaterial makes room for ultrafast information transfer on the nanoscale.
A semiconductor-based metamaterial tuned by ultrashort laser pulses. (CREDIT: Maxim Shcherbakov)
Optical metamaterials are man-made media that attain unusual optical properties because of nanostructuring. For almost twenty years, Researchers succeeded in designing a plethora of metamaterial-based devices, ranging from those hiding objects to those sensitive to minute concentrations of substances. However, upon fabrication, metamaterial properties remain fixed. The team of Engineers and Physicists have devised a way to turn metamaterials "on" and "off," and do it extremely fast, more than 100 billion times per second.
The metamaterial was fabricated by the team from a thin gallium arsenide film by electron-beam lithography with subsequent plasma etching. The material is made up of an array of semiconductor nanoparticles capable of resonantly concentrating and holding light on the nanoscale. This also means that when the light illuminates the metamaterial, it gets trapped inside the nanoparticles and interacts in a more efficient manner with them.
The working principle of the ultrafast tunable metamaterial is present in the generation of electron-hole pairs. The metamaterial is reflective in the steady state. The material is then illuminated by the team with the help of an ultrashort laser pulse, whose energy is used to produce electrons and electron vacancies- "holes"- in the material. The properties of the material are changed by the presence of holes and electrons: the metamaterial is thus no longer reflective. Within a split second, holes and electrons disappear by coming in contact with each other, and the metamaterial again becomes reflective. In this manner, it is possible to develop optical logic elements, thus making way for the development of ultrafast optical computers.
A part of the same collaboration provided details about a similar device based on silicon nanostructures in 2015. In their recent study, gallium arsenide was employed instead of silicon, which increased the effectiveness of controlling light with light in metamaterials by an order of magnitude.
The team’s work belongs to photonics, which deals with light and its usage in different applications. For example, in electronics electric currents help transmit signals, but in photonics, this is performed by light quanta. The research proves to be promising for the future as it will allow developing devices for information transfer and processing at speeds of tens and hundreds of terabits per second. The demonstration of extremely efficient tunable semiconductor metamaterials is considered to be a major step towards such information processing speeds.