Nanoscale control of light could revolutionise ICT
Electronics is about manipulating electrons so that they perform useful tasks. The miniaturisation of this technology has enabled computers today to contain billions of electronic transistors, carrying out numerous complex operations. “Photonics is based on a similar idea, but instead of electrons we are interested in photons – the elementary particle of light,” says Nanophotonics project investigator Sergey Kruk, currently at the Australian National University. “If we can control photons, these could be useful information carriers. Exchanging information with light instead of electricity is a lot faster and potentially more energy efficient.”
Miniaturising photonic technology
The project was coordinated by Paderborn University in Germany and supported by the Marie Skłodowska-Curie Actions programme. It focused on how to miniaturise a particular photonic technology – an optical isolator – in a similar way to how electronics has been miniaturised over the past century. Empowered by semiconductor technology, electronic systems can now include not just a handful, but millions and even billions of transistors. The Nanophotonics project wanted to do something similar with photonics. Instead of diodes and transistors, photonics uses these optical isolators, which perform broadly similar functions to their electronic analogues. “The technology behind optical isolators is roughly at the stage that electrical diodes were in the first half of the 20th century,” adds Kruk. “They are available commercially, but tend to be a few centimetres in size and can cost hundreds or even thousands of euro each.” It is therefore currently not feasible to put billions of these optical isolators into, say, a single photonic chip. Being able to fabricate optical isolators at the nanoscale, however, could revolutionise photonics, and open up the market for photonic information communication technologies.
Developing nanoscale optical isolators
Kruk wanted to show that this was possible. He began the project by designing nanoscale optical isolators using computer simulations. “You can think of these as road signs directing traffic,” he says. “Our nanoscale elements ensure that light flows in a particular direction, in a similar way to how road signs control traffic on a busy road.” These tiny components were then fabricated in a clean room, the kind of environment where computer chips are built. The components were then tested in a laser laboratory. “We shone a beam of light from a laser into these structures, to see what would happen,” explains Kruk. One interesting demonstration was a translucent slide structured at the nanoscale. As light passes through the slide, an encoded image can be seen, but when you flip the slide and look again, a completely different image is visible through it. “This pair of images was just one demonstration of an untapped number of possibilities,” notes Kruk.
The future of photonics
The Nanophotonics project has helped to demonstrate the potential of designing and fabricating optical isolators at the nanoscale. This is an important step forward towards the miniaturisation of photonic technology. “Photonics has already begun to replace electronics at the large scale,” adds Kruk. “For example, I’m currently talking to you from Australia via an optical fibre that runs under the ocean. Most long-range communication is almost exclusively achieved though electromagnetic waves such as infrared light, flowing through optical fibres.” The next logical step therefore is to refine and miniaturise photonic technology further, and bring optical elements into individual devices.
Keywords
Nanophotonics, nanoscale, photonic, electrons, computers, transistors, optical
