New algorithm paves the way for light-based computers
An inverse design algorithm developed by Stanford engineersenables the design of silicon interconnects capable of transmitting data between computer chips via light. The newprocess replaces the wire circuitry used to relay information electronically, whichcould lead to the development of highly efficient, light-based computers.
While the heavy lifting in computer processingtakes place inside the chips, an analysis by Stanford professor of electricalengineering, David Miller, showed that up to 80 percent of a microprocessor’spower is eaten up by the transmitting of data as a stream of electrons overwire interconnects. Basically, shipping requires far more energy thanproduction, and chewing through all that power is the reason laptops heat up.
Inspired by the optical technology of the internet, theresearchers sought to move data between chips over fiber optic threads beamingphotons of light. Besides using far less energy than traditional wire interconnects,chip-scale optic interconnects can carry more than 20 times more data.
The majority of fiber optics are made from silicon, which istransparent to infrared light the same way glass is to visible light. Thus,using optical interconnects made from silicon was an obvious choice. “Siliconworks,” said Tom Abate, Stanford Engineering communications director. “The whole industry knows howto work with silicon.”
But optical interconnects need to bedesigned one at a time, making the switch to the technology impractical forcomputers since such a system requires thousands of such links. That’s wherethe inverse design algorithm comes in.
Thesoftware provides the engineers with details on how the siliconstructures need to be designed for performing tasks specific to their opticalcircuitry. The group designed a working optical circuit in the lab, copieswere made, and all worked flawlessly despite being constructed on less than ideal equipment. The researchers cite this as proof of the commercialviability of their optical circuitry, since typical commercial fabricationplants use highly precise, state-of-the-art manufacturing equipment.
Whiledetails of the algorithm’s functions is a tad complex, it basically works by designing silicon structures that are able tobend infrared light in various and useful ways, much like a prism bends visiblelight into a rainbow. When light is beamed at the silicon link, two wavelengths, or colors, of light split off at right angles in a T shape. Eachsilicon thread is miniscule – 20 could sit side-by-side within a humanhair.
Theoptical interconnects can be constructed to direct specific frequencies ofinfrared light to specific locations. And it’s the algorithm that instructs howto create these silicon prisms with just the right amount and bend of infraredlight. Once the calculation is made as to the proper shape for each specifictask, a tiny barcode pattern is etched onto a slice of silicon.
Building an actual computer that uses the optical interconnects has yet to be realized, but the algorithm is a first big step. Other potential uses for the algorithm include designing compact microscopy systems, ultra-secure quantum communications, and high bandwidth optical communications.
The team describes their work in the journal Nature Photonics.
Source: Stanford University