Researchers have placed photon filters and modulators on standard chips for the first time

Researchers at the University of Sydney combined photon filters and modulators on a single chip, enabling them to accurately detect signals on the broadband RF spectrum. This work brings photonic chips closer to one day, potentially replacing larger and more complex electronic RF chips in fiber optic networks.

The Sydney team utilized stimulated Brillouin scattering technology, which involves converting electric fields in certain insulators into pressure waves. In 2011, researchers reported that Brillouin scattering has the potential for high-resolution filtering and developed new manufacturing techniques that combine sulfur based Brillouin waveguides on silicon chips. In 2023, they managed to combine photon filters and modulators on the same type of chip. The team reported in a paper published in Nature Communications on November 20th that this combination resulted in a spectral resolution of 37 megahertz for the experimental chip, with a wider bandwidth than previous chips.

"The integration of the modulator with this active waveguide is a key breakthrough here," said David Marpaung, a nanophotonics researcher at the University of Twente in the Netherlands. Marpaung collaborated with the Sydney team ten years ago and now leads his own research team, which is adopting different methods to seek broadband, high-resolution photon radio sensitivity in tiny packages. Marpaung said that when someone achieves spectral resolution below 10 MHz in the 100 GHz frequency band, they will be able to replace bulky electronic RF chips on the market. Another advantage of this chip is that it can convert RF signals into optical signals for direct transmission through fiber optic networks. The winner of this competition will be able to enter the huge market of telecommunications providers and defense manufacturers, who need radio receivers that can reliably navigate complex RF environments.

"Sulfide compounds have a very strong Brillouin effect; this is good, but there is still a question of whether this is scalable... It is still considered a laboratory material.", Marpaung said that the Sydney research team must find a new method to install chalcogenide waveguides in 5-squaremm packages into standard manufactured silicon chips, which is not an easy task. In 2017, the team came up with how to combine chalcogenides onto silicon input/output rings, but it was not until this year that anyone managed this combination using standard chips.

Other research groups are studying different materials that may provide similar performance. For example, lithium niobate has better modulator characteristics than silicon, and Marpaung's ongoing peer review work indicates that lithium niobate can provide similar high-resolution filtering through Brillouin scattering. Another group led by Peter Laki of Yale University demonstrated last year that pure silicon waveguides and chip combinations can achieve filtering at 2.7 MHz in the 6 GHz frequency band. This work does not integrate modulators, but it suggests a potentially simpler manufacturing path involving fewer materials.

That is to say, the Sydney team's method may require better acoustic performance than silicon. Researchers have known that the Brillouin effect has a history of over 100 years, but in recent decades it has aroused people's interest. In the past, researchers used it to store information in light pulses before retransmitting it, which was a technique to avoid converting light into electrical energy and returning it again.

Of course, the dream of integrating photonic chips has many moving parts. Researchers in Sydney wrote that modulators manufactured by others are rapidly improving, which will also benefit their technology. Other advancements in related technologies may benefit other teams dedicated to integrating photonic chips. "If you solve integration, performance, and practicality issues, you will gain market recognition," said Marpaung.

Source: Laser Net