Scientists accidentally create a tiny “rainbow chip” that could supercharge the internet

"As we sent more and more power through the chip, we noticed that it was creating what we call a frequency comb," says Andres Gil-Molina, a former postdoctoral researcher in Lipson's lab.

A frequency comb is a unique kind of light made up of many distinct colors (or frequencies) that appear side by side in an organized sequence, much like the bands of a rainbow. Each color shines brightly while the spaces between them remain dark. On a spectrogram, these bright frequencies form evenly spaced spikes that look like the teeth of a comb. This pattern allows dozens of data channels to operate at once since each color of light can carry information without interfering with the others.

Ordinarily, generating a powerful frequency comb requires bulky, expensive lasers and amplifiers. In a new study published in Nature Photonics, Lipson, the Eugene Higgins Professor of Electrical Engineering and professor of Applied Physics, and her colleagues demonstrate how to achieve the same effect using a single microchip.

"Data centers have created tremendous demand for powerful and efficient sources of light that contain many wavelengths," says Gil-Molina, who is now a principal engineer at Xscape Photonics. "The technology we've developed takes a very powerful laser and turns it into dozens of clean, high-power channels on a chip. That means you can replace racks of individual lasers with one compact device, cutting cost, saving space, and opening the door to much faster, more energy-efficient systems."

"This research marks another milestone in our mission to advance silicon photonics," Lipson said. "As this technology becomes increasingly central to critical infrastructure and our daily lives, this type of progress is essential to ensuring that data centers are as efficient as possible."

Cleaning up messy light

The team's breakthrough began with a simple question: how powerful a laser could they integrate onto a chip?

They decided to work with a multimode laser diode -- a type of laser commonly used in medicine and industrial cutting tools. While these lasers can produce enormous amounts of light, their beams are typically chaotic or "messy," making them unsuitable for precision applications.

Incorporating such a laser into a silicon photonics chip, where light travels through microscopic pathways only a few microns or even hundreds of nanometers wide, required intricate engineering.

"We used something called a locking mechanism to purify this powerful but very noisy source of light," Gil-Molina says. The method relies on silicon photonics to reshape and clean up the laser's output, producing a much cleaner, more stable beam, a property scientists call high coherence.

Once the light is purified, the chip's nonlinear optical properties take over, splitting that single powerful beam into dozens of evenly spaced colors, a defining feature of a frequency comb. The result is a compact, high-efficiency light source that combines the raw power of an industrial laser with the precision and stability needed for advanced communications and sensing.

Why it matters now

The timing for this breakthrough is no accident. With the explosive growth of artificial intelligence, the infrastructure inside data centers is straining to move information fast enough, for example, between processors and memory. State-of-the-art data centers are already using fiber optic links to transport data, but most of these still rely on single-wavelength lasers.

Frequency combs change that. Instead of one beam carrying one data stream, dozens of beams can run in parallel through the same fiber. That's the principle behind wavelength-division multiplexing (WDM), the technology that turned the internet into a global high-speed network in the late 1990s.

By making high-power, multi-wavelength combs small enough to fit directly on a chip, Lipson's team has made it possible to bring this capability into the most compact, cost-sensitive parts of modern computing systems. Beyond data centers, the same chips could enable portable spectrometers, ultra-precise optical clocks, compact quantum devices, and even advanced LiDAR systems.

"This is about bringing lab-grade light sources into real-world devices," says Gil-Molina. "If you can make them powerful, efficient, and small enough, you can put them almost anywhere."