The invention of fiber optics revolutionized the way we share information, allowing us to transmit data at volumes and speeds we'd only previously dreamed of, and now are breaking another barrier, designing nano-optical cables small enough to replace the copper wiring on computer chips.
This could result in radical increases in computing speeds and reduced energy use by electronic devices.
"We're already transmitting data from continent to continent using fiber optics, but the killer application is using this inside chips for interconnects—that is the Holy Grail," says Zubin Jacob, an electrical engineering professor leading the research. "What we've done is come up with a fundamentally new way of confining light to the nano scale."
Normalized tangential electric field of the TM mode for a glass slab waveguide with a size of 0.1λ surrounded with all-dielectric metamaterial cladding. The metamaterial has dielectric constants of εx=1.1 and εz=15. On comparison with a conventional mode that has air as the surrounding medium, a rapid decay of the evanescent fields is observed. The plots are normalized to the same input electric energy. Inset: as the anisotropy of the cladding is increased, the mode length decreases significantly below the diffraction limit with completely transparent media. This can be achieved with a cladding size (width b) three times that of the core size (width a). Credit: DOI:10.1364/OPTICA.1.000096
At present, the diameter of fiber optic cables is limited to about 1/1000th of a millimeter. Cables designed by graduate student Saman Jahani and Jacob are 10 times smaller—small enough to replace copper wiring still used on computer chips. Put into perspective, a dime is about 1 mm thick.
Researchers around the world have been stymied in their efforts to develop effective fiber optics at smaller sizes. One popular solution has been reflective metallic claddings that keep light waves inside the cables.
But the biggest hurdle is increased temperatures: metal causes problems after a certain point.
“If you use metal, a lot of light gets converted to heat. That has been the major stumbling block. Light gets converted to heat and the information literally burns up—it’s lost.”
Jahani and Jacob have invented a new, non-metallic metamaterial that enables them to "compress" and contain light waves in smaller cables without creating heat, slowing the signal or losing data.