Combing through Streams of Light

Holly Evarts
January 15, 2016

After almost a decade of long-distance collaborations, Keren Bergman, Michal Lipson, and Alex Gaeta are working together in one place, here at Columbia Engineering. Lipson and Gaeta joined the School this summer as the Eugene Higgins Professor in Electrical Engineering (EE) and the David M. Rickey Professor of Applied Physics and of Materials Science, respectively. And now, together with Bergman, who is the Charles Batchelor Professor and EE chair, the trio is set to break new ground in nanophotonics, or, as Lipson, a preeminent leader in nanophotonic fabrication, puts it, “optics on a very, very small scale.”

“The emerging field of nanophotonics is revolutionizing telecommunications, computation, and sensing,” notes Bergman, who specializes in optical interconnection networks for advanced computing systems. “This is a very strong area at SEAS, and the arrival of Michal and Alex will greatly broaden our research impact—I’m really excited that their labs are practically next door to mine and our students can work together.”

One of their primary foci is on developing frequency combs, light sources that generate multiple colors—or frequencies—that are spaced to extraordinary precision and can be visualized like the teeth of a comb. Frequency combs can be used to measure light colors to very high precision over a broad frequency range, over an octave of spectrum, which enables a direct link from microwave to optical frequencies; their “teeth” are used to perform ultraprecision measurements in time or frequency in a similar fashion to atomic clocks. The combs can also be used in sensing devices that can, for instance, rapidly detect explosives or drugs from 30 meters away or be applied to high bandwidth communications that connect data centers and their thousands of servers at very high speeds.

“Measuring time is essential to almost everything in our lives,” says Gaeta, a pioneer of laser physics, the field that underlies nanophotonics. “We can use these combs to precisely measure frequency and thus measure time extraordinarily accurately. And if you can measure time accurately, you can measure distance with very high precision.”

Frequency combs are expected to generate all kinds of critical real-world applications, from vastly improved GPS positioning to predicting earthquakes and volcanoes, from sensing chemical agents to detecting oil and gas underground. Gaeta and Lipson have been able to control the dimensions of their devices, “controlling them exquisitely well—to a nanometer precision—so that these optical processes can occur really efficiently,” Gaeta adds. Bergman brings her expertise in large-scale optical network systems.

And it’s only the beginning.

“Only 15 years ago, the optical components we were making, whether they were clocks or sensors, were all really big,” says Bergman.

Lipson adds, “And now, with nanotechnology, we can fit the optics onto a chip.”

“It’s really cool that these innovations at the nanoscale enable you to do things for real life that were never possible before at the macroscopic scale,” Bergman concludes. “We’re very lucky to be working in such a transformative field at the right time—and now we can do it together.”