A group of Russian and American scientists from St. Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO), Moscow Institute of Physics and Technology (MIPT), and the University of Texas at Austin have developed a new technology that allows controlling the direction of light propagation without affecting the basic parameters of this light. The key point of this technology is a tiny nanoantenna, which in the future could become one of the standard units of optical computers or communication systems.
The principles of optical computing are based on replacing electrons with photons of light, which become information carriers. However, it is much harder to control the motion of photons than the motion of electrons, because the former have neither electric charge nor rest mass. And to implement full-fledged technologies of optical computing to control the flow of photons would require full analogues of electronic components, such as transistors, diodes, etc.
It is possible to control the propagation of light rays using traditional waveguides, but the new nanoantenna works in a completely different way. Instead of bending the trajectory of photons, it reflects the photons falling on it in a strictly defined direction, which is determined by the material and shape of the antenna. The antenna is a piece of silicon of a certain shape, measuring 200 by 200 and 500 nanometers. Its main feature is that its angle of light reflection depends on the intensity of the beam falling on it.
“All this will allow us to control the direction of light propagation in a much simpler way than any other methods based on the use of magnetic, electric fields and electronic control,” says Sergey Makarov, a senior researcher at the ITMO Institute.
The nanoantenna reflects light using surface plasmons, clouds of free electrons that arise on the surface of some materials under the influence of incident light. The intensity of the incident light determines the size and density of the electron clouds and, as a result, the antenna is able to reflect light at a certain angle, lying within 20 angular degrees. In addition, to increase the efficiency of light beam deflection, the plasmons must resonate at a certain frequency corresponding to the frequency of the incident light. This, in turn, is achieved by changing the size of the nanoantenna at the stage of its production.
According to available information, the new nanoantenna could be the basis of a device capable of data transmission at a speed of 250 gigabits per second. Thus, devices based on such antennas could become an intermediate link between optical systems, which allow transmission of data over cables at hundreds of gigabits per second, and electronic elements of computing systems, which can receive and process much smaller data flows.