As the hardware in communications systems has progressed from copper wires to fibre optic cables, the acceleration of data transfer speed has been profound. No one with access to fibre would ever want to go back to copper connections, but there is still one place we are stuck with them — in the chips that drive our electronic devices.
Zubin Jacob, an electrical engineering professor at the University of Alberta, wants to bring this same advantage to those chips by enabling them to cast off their copper and employ light as the primary carrier of bits of information. “The holy grail is to bring some of this technology inside your computer,” Jacob says. “Can we get the information to flow much faster by having such cables on the chip?”
This challenge, however, amounts to more than just installing fibre optic connections where the copper used to go. The wiring found in the latest generation of computer chips is much finer than any conventional fibre optic cable, which operate effectively at diameters no smaller than one-thousandth of a millimetre. Below that limit, such cables tend to be overly “lossy,” meaning data carried by light waves becomes incoherent and disappears, says Jacob.
Jacob and U of A graduate student Saman Jahani have designed fibre-optic cables that operate successfully at sizes a full order of magnitude smaller, which raises the practical possibility of using them within a computer chip. The key to this breakthrough was the development of a non-metallic metamaterial that compresses and contains light waves without generating heat and without compromising signal integrity. “We have introduced a paradigm shift in light confinement strategy that rests on transforming the momentum of evanescent waves,” the pair wrote in the journal Optica. “Our transformations can be achieved by all-dielectric media fundamentally overcoming the foremost challenge in the field of plasmonics and metamaterials: optical absorption.”
Jacob is confident that the advantages offered by photonic circuitry within computer chips will motivate manufacturers to introduce this innovation into their products. “This is the last frontier for fibre optics,” he says.