Silicon Nanoantennas Turn Light Around

Light is rather hard to control, as photons have neither mass nor electric charge. Devices such as nanoantennas can control the propagation of electromagnetic waves, but only to a certain degree.

A proposed nonlinear optical nanoantenna that can be manipulated will operate at 250 Gbps, shining light, so to speak, on the development of optical computers where information is carried by photons, rather than electrons, greatly increasing the speed of transmitting and processing of information.

An artist's rendering of nonlinear light scattering by a dimer of two silicon particles with a variable radiation pattern. Courtesy of the MIPT press office.

Physicists from ITMO University in Saint Petersburg, Russia, the Moscow Institute of Physics and Technology (MIPT) and the University of Texas at Austin have developed an unconventional nanoantenna of sorts that can scatter light in a particular direction depending on the intensity of incident radiation.

Using silicon nanoparticles, which generate electron plasma under harsh laser radiation, researchers demonstrated the possibilities of using these nanoparticles for nonlinear and ultrafast control of light. They were initially successful in manipulating the scattered light radiation both forward and backward. Now, they have found that by changing the intensity of incident light they can turn the scattered light beam in a desired direction.

Researcher and MIPT postgraduate student Denis Baranov said their nanoantenna is different than existing optical nanoantennas that can control light in a fairly wide range.

“This ability is usually embedded in their geometry and the materials they are made of, so it is not possible to configure these characteristics at any time,” said Baranov. “The properties of our nanoantenna, however, can be dynamically modified. When we illuminate it with a weak laser impulse, we get one result, but with a strong impulse, the outcome is completely different.”

With the weak laser pulse, the scientists found that the light scattered sideways. When the nanoantenna was illuminated with an intense laser impulse, leading to the production of electron plasma within the device, the scattering pattern rotated by twenty degrees.

To rotate the radiation pattern of the nanoantenna, the researchers used the mechanism of plasma excitation in silicon. They used two silicon nanospheres of unequal diameters; one particle is resonant at the wavelength of the laser light and the other remains nonresonant.

Sergey Makarov, a senior researcher at the Department of Nanophotonics and Metamaterials at ITMO University said their focus leans toward the development of a nanoscale optical chip measuring much less than the wavelength of a photon at less than 200 X 200 X 500 nanometers.

The simulation results of nonlinear light scattering by a nanoantenna of two silicon particles. Courtesy of MIPT press office.

“The new device will allow us to change the direction of light propagation at a much better rate compared to electronic analogues,” said Makarov. “Our device will be able to distribute a signal into two optical channels within a very short space of time, which is extremely important for modern telecommunication systems.”

This type of advanced light manipulation via the proposed nanoantenna is crucial for the development of optical computers.

The research was published in Laser & Photonics Reviews (doi: 10.1002/lpor.201600164).