Enlightra and DESY Hamburg developed an improved and scalable comb laser

Laser technology startup Enlightra collaborates with DESY Hamburg to develop and design more stable and efficient comb lasers. This work demonstrates a microresonator with programmable synthetic reflection, providing tailored injection feedback for driving lasers. This technology has significantly improved compared to traditional self injection locking technology and can be produced using standard lithography.

A comb laser is a multi color light source with an equidistant range of 100 GHz to 1 THz. This technology has high value for the data required for artificial intelligence applications in optical communication.

One of the key aspects of the practicality of comb lasers is their color purity. Although lasers appear to have very pure colors, in most cases, the beam is composed of many very similar colors with different tones. In applications such as optical communication, it is hoped that a laser can emit many very pure different colors. This is where comb lasers come in handy.

Self injection locking has always been a standard method to improve the purity of comb lasers. This method uses a ring resonator to filter out noise. Through Rayleigh backscattering, light is reflected back from random defects within the ring and sent back to the laser for injection locking.

"The problem with relying on random defects is that they can rely on color, and they are not very strong," said John Jost, co-founder of Englightra and one of the authors of the paper. "There are some limitations, and you would like to send more light back to the laser, as this is very helpful for injection locking."

One of the main advances in this study is the design of how light scatters inward and backward in a ring resonator. They achieved this goal by designing the inner surface of the ring, which only strongly scatters a specific color. Jost told Photonics Media that when light moves around the ring, it feels the pattern and can send more light than usual for injection locking. The author conducted various tests using different customized nanostructured ring resonators. They use semiconductor laser tubes to dock and couple to photonic chips with ring resonators. This technology has been demonstrated in the C-band, but it is equally effective in all telecommunications frequency bands. The actual resonator is embedded in the integrated photonic chip, with a silicon nitride photonic crystal ring resonator embedded in the silicon dioxide cladding.

"The photonic integrated circuits used in this work were manufactured in industrial foundries, so the technology is ready to scale up," Jost said. "The ability to design light scattering has opened a whole new door to more advanced designs, allowing us to customize comb shaped laser spectra to our needs in an unprecedented way."

Laser can be combined with various photonic integrated circuits. For example, it can support fast optical I/O units or optical field programmable gate arrays. This technology will benefit data intensive applications such as generative artificial intelligence, as well as new types of decomposed computers and memory architectures.

According to Jost, he and his team have more ideas than they may have tried.
The study was published in Nature Photonics.

Source: Laser Net