Optical fiber carries nearly all of the internet's traffic almost losslessly — but shrinking that same performance onto a computer chip has been a decades-long engineering problem. Caltech researchers say they've now closed most of that gap.

The team built light-guiding channels on standard silicon wafers using germano-silicate, the exact glass optical fiber is made from, and achieved visible-light signal loss 20 times lower than the previous best silicon nitride technology. The work was published in the journal Nature.

  • 20x improvement over the previous visible-light loss record for silicon nitride waveguides
  • 8- and 12-inch standard computer-chip wafers used for fabrication — no exotic materials required
  • Performance at near-infrared wavelengths already matches leading silicon nitride tech
  • Applications span optical clocks, gyroscopes, AI data-center links and quantum computing

Why shrinking fiber onto a chip is so hard

Optical fiber works because it's made of exceptionally pure, smooth glass: light bounces down its length with almost nothing absorbed or scattered along the way. Photonic chips need that same quality, but squeezed into nanoscale structures etched onto a flat wafer instead of a cylindrical strand of glass.

The Caltech team, led by applied physics professor Kerry Vahala, shaped germano-silicate into spiral-patterned waveguides using a lithography-based fabrication process — effectively coiling fiber-like material into a space small enough to fit on a chip, the same way a coiled fiber lengthens the path light can travel without needing more room.

"We have developed a method to print optical circuits, made from the same material as optical fiber, directly onto the same 8- and 12-inch wafers used for computer chips," said Kerry Vahala, the Ted and Ginger Jenkins Professor of Information Science and Technology and Applied Physics at Caltech.

Where the performance jump matters most

At near-infrared wavelengths — the range used in most telecom applications — the new platform performs on par with existing silicon nitride technology. But at visible wavelengths, it pulls decisively ahead, which matters for a specific set of next-generation tools.

Lower optical loss at visible wavelengths translates into more coherent lasers, which in turn improves the precision of atomic clocks used for timekeeping and gyroscopes used to measure rotation in navigation systems. It also reduces the energy cost of shuttling light between fiber-optic cables and the semiconductor lasers used in data centers and quantum computing hardware.

"Germano-silicate waveguides demonstrate extremely low loss and are also readily adaptable to efficiently transfer light between optical fibers and semiconductor lasers, which is of paramount importance in reducing the overall energy cost of server infrastructure," said Henry Blauvelt, a visiting associate in applied physics at Caltech and chief technology officer at photonics company Emcore.

A manufacturing shortcut, not just a lab trick

What makes this approach notable isn't just the loss numbers — it's that the fabrication happens on the same standard-sized wafers the chip industry already uses. That matters for how quickly a lab breakthrough can turn into something manufacturable at scale, since it sidesteps the need for new, specialized production lines.

The paper's lead authors, Caltech postdoctoral scholar Hao-Jing Chen and graduate student Kellan Colburn, conducted the work in Vahala's lab. As AI data centers push harder on energy efficiency and quantum computing systems demand ever more precise light sources, a chip-scale platform that gets this close to fiber-optic performance is the kind of unglamorous materials advance that tends to show up quietly in a lot of other technologies a few years later.

Full technical details are available from Caltech and a plain-language summary from SciTechDaily.