Frequency Comb (Photonics, Optics)

[Astronuc]

A frequency comb is a special type of light that contains many colors lined up next to each other in an orderly pattern, kind of like a rainbow. Dozens of colors—or frequencies of light—shine brightly, while the gaps between them remain dark.

When you look at a frequency comb on a spectrogram, these bright frequencies appear as spikes, or teeth on a comb. This offers the tremendous opportunity of sending dozens of streams of data simultaneously. Because the different colors of light don't interfere with each other, each tooth acts as its own channel.

https://phys.org/news/2025-10-powerful-precise-multi-lasers-chip.html

All one needs is the right materials, junctions and optics.

A few years ago, researchers in Michal Lipson's lab noticed something remarkable. They were working on a project to improve LiDAR, a technology that uses lightwaves to measure distance. The lab was designing high-power chips that could produce brighter beams of light.

"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.

The breakthrough started with a simple question: What's the most powerful laser we can put on a chip?

The team chose a type called a multimode laser diode, which is used widely in applications like medical devices and laser cutting tools. These lasers can produce enormous amounts of light, but the beam is "messy," which makes it hard to use for precise applications.

Integrating such a laser into a silicon photonics chip, where the light pathways are just a few microns—even hundreds of nanometers—wide, required careful engineering.

Andres Gil-Molina et al, High-power electrically pumped microcombs, Nature Photonics (2025). DOI: 10.1038/s41566-025-01769-z

 

[jedishrfu]

While not a frequency comb, a YouTube video explained how Disney lost a critical optical splitter that enabled them to create some amazing effects (examples include Mary Poppins, where the characters dance in front of fanciful scenery with no blur) that current technology cannot achieve.

The individuals in the video managed to reconstruct the lost technology, which Disney used, featuring sodium lamps that emitted a specific frequency of light.



Essentially, it's related to a single-tooth comb.

 

[tech99]

How would the individual lines in the comb be modulated with different data streams? As you may know, the technique is used for digital TV and mobile phones. By splitting a high speed data stream into many parallel ones, the system becomes much more robust and insensitive to echo distortion.

tive to

 

[sophiecentaur]

How would the individual lines in the comb be modulated with different data streams? As you may know, the technique is used for digital TV and mobile phones. By splitting a high speed data stream into many parallel ones, the system becomes much more robust and insensitive to echo distortion.

tive to

I imagine a monochromatic source is modulated by a number of sub-carriers, each with its own data stream. It wouldn't be hard to make the subcarrier frequencies harmonically related to produce a comb. That could make demodulation easier, too.