Fibre-optic cables are the backbone of today’s data infrastructure, carrying data around the world in form of light-signals. Researchers have been working on integrating this same technology inside computer chips, with the goal of increasing processing speeds and capabilities manifold. However, the diffraction limit of light — a 400-year old conception of total internal reflection inside fibres — theoretically precludes shrinking fibre optic cables to nanoscale.
Not so fast, thought electrical engineering researchers at the University of Alberta in Edmonton, Alberta (Canada), and designed nano-optical cables that are 10 times smaller than existing fibre-optic cables, and thus small enough to replace the copper wiring on computer chips. “We revisited the phenomenon of total internal reflection discovered over 400 years ago that governs the reflection of light inside fibres,” says electrical engineering professor Zubin Jacob. In a groundbreaking discovery, his team showed that the diffraction limit of light can be fundamentally modified with transparent metamaterials. “Using these transparent nonmetallic metamaterials, we were able to theoretically propose a new class of light-guiding structures, called ‘extreme skin-depth waveguides’."
These extreme skin-depth waveguides solve a critical problem with conventional fibre-optic cables, which is the large penetration depth of electromagnetic waves outside the core of the cable, by fundamentally changing the penetration depth of the electromagnetic waves using transparent metamaterials.
Could this pioneering step achieved at the public research university in Canada be a game-changer for photonic circuits, the holy grail of nanophotonics? “Our work presents a milestone, since it shows that electromagnetic waves can be controlled outside the core in ways previously not imagined,” says Jacob. The work also represents a major advance in the field of metamaterials, as this is the first proposal for a transparent metamaterial device. “Previously,” says the expert, “lossy metallic components were considered a necessity for metamaterial devices.”
Hence, the transparent metamaterial could lead to a new approach to confining light to nanoscale without using metals and without creating heat, slowing the signal or losing data. “This is achieved by redefining the fundamental phenomenon of total internal reflection, where rays of light are 100% reflected at the interface between glass and air,” Jacob says.
The team is now building such extreme skin depth waveguides on a silicon platform.
The findings are published in The Optical Society’s (OSA) journal Optica, in the article “Transparent subdiffraction optics: nanoscale light confinement without metal.”
Written by Sandra Henderson, Research Editor Novus Light Technologies Today