What a Twist: Silicon Nanoantennas Turn Light Around
November 16, 2016 | MIPTEstimated reading time: 4 minutes

A team of physicists from ITMO University, Moscow Institute of Physics and Technology (MIPT) and University of Texas at Austin have developed an unconventional nanoantenna that scatters light in a particular direction depending on the intensity of incident radiation. The research findings will help with the development of flexible optical information processing in telecommunication systems.
Fig. 1. An artist’s rendering of nonlinear light scattering by a dimer of two silicon particles with a variable radiation pattern.
Photons—the carriers of electromagnetic radiation—have neither mass nor electric charge. This means that light is relatively hard to control, unlike, for example, electrons: their flow in electronic circuits can be controlled by applying a constant electric field. However, such devices as nanoantennas enable a certain degree of control over the propagation of electromagnetic waves.
One area that requires the “advanced” light manipulation is the development of optical computers. In these devices, the information is carried not by electrons, but by photons. Using light instead of charged particles has the potential to greatly improve the speed of transmitting and processing information. To make these computers a reality, we need specific nanoantennas with characteristics that can be manipulated in some way—by applying a constant electric or magnetic field, for instance, or by varying the intensity of incident light.
In the paper published in Laser & Photonics Reviews ("Tuning of near- and far-field properties of all-dielectric dimer nanoantennas via ultrafast electron-hole plasma photoexcitation"), the researchers designed a novel nonlinear nanoantenna that can change the direction of light scattering depending on the intensity of the incident wave (Fig. 1). At the heart of the proposed nanoantenna are silicon nanoparticles, which generate electron plasma under harsh laser radiation.
The authors previously demonstrated the possibilities of using these nanoparticles for the nonlinear and ultrafast control of light (ACS Photonics, "Nonlinear Transient Dynamics of Photoexcited Resonant Silicon Nanostructures"). The researchers then managed to manipulate portions of light radiation scattered forward and backward. Now, by changing the intensity of incident light, they have found a way to turn a scattered light beam in the desired direction.
To rotate the radiation pattern of the nanoantenna, the authors used the mechanism of plasma excitation in silicon. The nanoantenna is a dimer—two silicon nanospheres of unequal diameters. Irradiated with a weak laser beam, this antenna scatters the light sideways due to its asymmetric shape (blue diagram in Fig. 2A). The diameters of the two nanoparticles are chosen so that one particle is resonant at the wavelength of the laser light. Irradiated with an intense laser pulse, electron plasma is generated in the resonant particle which causes changes in the optical properties of the particle. The other particle remains nonresonant, and the powerful laser field has little effect on it.
Generally speaking, by accurately choosing the relative size of both particles in combination with the parameters of the incident beam (duration and intensity), it is possible to make the size of the particles virtually the same, which enables the antenna to bounce the light beam forward (red diagram in Fig. 2a).
Fig. 2. The simulation results of nonlinear light scattering by a nanoantenna of two silicon particles.
“Existing optical nanoantennas can control light in a fairly wide range. However, 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,” says Denis Baranov, a postgraduate student at MIPT and the lead author of the paper. “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.”
The scientists performed numerical modeling of the light scattering mechanism, Fig. 2b. The simulation showed that when the nanoantenna is illuminated with a weak laser beam, the light scatters sideways. However, if the nanoantenna is illuminated with an intense laser impulse, that leads to the generation of electron plasma within the device and the scattering pattern rotates by 20 degrees (red line). This provides an opportunity to deflect weak and strong incident impulses in different directions.
Sergey Makarov, a senior researcher at the Department of Nanophotonics and Metamaterials at ITMO University concludes: “In this study, we focused on the development of a nanoscale optical chip measuring less than 200×200×500 nanometers. This is much less than the wavelength of a photon, which carries the information. The new device will allow us to change the direction of light propagation at a much better rate compared to electronic analogues. 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.”
Today, information is transmitted via optical fibers at speeds of up to hundreds of Gbit/s. However, even modern electronic devices process these signals quite slowly: at speeds of only a few Gbit/s for a single element. The proposed nonlinear optical nanoantenna can solve this problem, as it operates at 250 Gbit/s. This paves the way for ultrafast processing of optical information. The nonlinear antenna developed by the researchers provides more opportunities to control light at nanoscale, which is what is required in order to successfully develop photonic computers and other similar devices.
Suggested Items
DARPA Selects Cerebras to Deliver Next Generation, Real-Time Compute Platform for Advanced Military and Commercial Applications
04/08/2025 | RanovusCerebras Systems, the pioneer in accelerating generative AI, has been awarded a new contract from the Defense Advanced Research Projects Agency (DARPA), for the development of a state-of-the-art high-performance computing system. The Cerebras system will combine the power of Cerebras’ wafer scale technology and Ranovus’ wafer scale co-packaged optics to deliver several orders of magnitude better compute performance at a fraction of the power draw.
Altair, JetZero Join Forces to Propel Aerospace Innovation
03/26/2025 | AltairAltair, a global leader in computational intelligence, and JetZero, a company dedicated to developing the world’s first commercial blended wing airplane, have joined forces to drive next-generation aerospace innovation.
RTX's Raytheon Receives Follow-on Contract from U.S. Army for Advanced Defense Analysis Solution
03/25/2025 | RTXRaytheon, an RTX business, has been awarded a follow-on contract from the U.S. Army Futures Command, Futures and Concepts Center to continue to utilize its Rapid Campaign Analysis and Demonstration Environment, or RCADE, modeling and simulation capability.
Ansys to Integrate NVIDIA Omniverse
03/20/2025 | ANSYSAnsys announced it will offer advanced data processing and visualization capabilities, powered by integrations with NVIDIA Omniverse within select products, starting with Fluent and AVxcelerate Sensors.
Altair Releases Altair HyperWorks 2025
02/19/2025 | AltairAltair, a global leader in computational intelligence, is thrilled to announce the release of Altair® HyperWorks® 2025, a best-in-class design and simulation platform for solving the world's most complex engineering challenges.