Optical Computers: Nanoantenna That Directs Light Could Help Development Of New Systems

An unconventional silicon nanoantenna developed by researchers could help in the development of optical computers that will work much faster than conventional computers. Optical information processing relies on photons — the particles that make up light — as opposed to conventional computing that uses electrons.

Developed by researchers from ITMO University in St. Petersburg, Russia, the Moscow Institute of Physics and Technology (MIPT) and the University of Texas at Austin, the nanoantenna can be used to reflect light in a specific direction that will vary depending on the intensity of the light. This ability to dynamically tune the property of the antenna is what makes it important for optoelectronics.

The antenna is not only capable of flexible information processing, but can also operate at an astonishing 250 gigabits per second since photons travel pretty fast, or at least as fast as light, which is the fastest thing we know. But that creates its own complications. Photons have no charge or mass, making them relatively hard to control compared to other particles that have charge or mass.

In their approach, the researchers used silicon nanoparticles to achieve nonlinear and ultrafast control over light. The nanoantenna is made of two silicon nanospheres of unequal diameters. When irradiated with a weak laser beam, it scatters light sideways due to its asymmetric shape. By choosing the diameter of one of the nanospheres to resonate with the wavelength of the laser beam, electron plasma is generated, which changes the optical properties of that sphere. By carefully controlling the various factors involved, it is possible to make the antenna scatter the light forward instead of sideways.

“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. 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,” Denis Baranov, a postgraduate student at MIPT and the lead author of the paper, said in a statement.

While modern optic fiber cables can transfer data at speeds of hundreds of gigabits per second, current electronic devices can only process a few gigabits per element at a time. If optical computing were to become a reality, this speed could go up exponentially.

The study was published in the journal Laser & Photonics Review.