Foreign Team Builds More Stable, Efficient Comb Lasers

Recently, laser technology startup illumtra teamed up with the German Research Center for Electron Synchrotron (DESY) in Hamburg to successfully collaborate on the development of a comb laser that is more stable and efficient in design.
The highlight of this development is their demonstration of a microresonator with programmable synthesized reflections that provides customized injection feedback for driving the laser. This technology offers significant advantages over conventional self-injection locks and can be produced using standard lithography techniques.
The comb lasers are capable of emitting light sources in a wide range of colors with frequency spacings ranging from 100 GHz to 1 THz. The application of this technology is of great value for data transmission in the fields of optical communications and artificial intelligence.
The advantage of comb lasers is the purity of the colors they emit. In applications such as optical communications, there is a need for a laser that can emit multiple pure colors of light, and comb lasers meet this need.
To improve the purity of comb lasers, self-injection locking has become a standard method in the industry. This method utilizes a ring resonator to filter out noise, causes light to be reflected back from random defects within the ring through Rayleigh backscattering, and is injected back into the laser for locking.
"The problem with relying on random defects is that they can be color-dependent and the intensity is not strong and stable enough," said John Jost, one of the paper's authors and co-founder of Enlightenment, "There are some limitations, especially when we want to put more light back into the laser, as this is critical to achieve effective injection locking."
The key breakthrough in this research was the design of a special mode that allows for directional backscattering of light within the ring resonator. This mode is optimized specifically for a particular color, ensuring that more light is efficiently sent back to the laser for injection locking.
Illumtra's comb lasers have integrated light source capabilities that make them particularly suitable for optical I/O solutions and distributed computing and memory architectures.
To validate its effectiveness, the authors performed a variety of tests using customized nano-ring resonators with different structures. They docked a semiconductor laser diode to a photonic chip with an integrated ring resonator. The technique was validated in the C-band, but could theoretically be equally effective in all telecom bands. The actual resonator is built on an integrated photonic chip using silicon cladding technology and embedded with a silicon nitride photonic crystal ring resonator.
Jost said, "The photonic integrated circuits used in this work were fabricated on industrial-grade production lines, so the technology is ready for large-scale production." He further noted, "This ability to precisely control light scattering opens up a whole new range of possibilities for more advanced designs, which will allow us to customize the comb laser spectrum to meet real-world needs, enabling unprecedented flexibility."
The laser can be used in perfect combination with a wide range of photonic integrated circuits, such as for building fast optical I/O units or optical field-programmable gate arrays. The technology will have a significant impact on data-intensive applications, such as in the field of generative artificial intelligence, and will also provide a strong impetus for the development of new computing and memory architectures.