Hybrid chips allow bidirectional conversion between Terra Hearts and optical signals for ultra-high speed communication

Researchers at EPFL and Harvard University have designed a chip that can convert between the light ranges of the same device as the TerraHearts electromagnetic pulse. Their integrated design allows for the development of devices for ultra-high speed communication, range, spectroscopy, and computing.

Terahertz radiation describes a band of waves on the electromagnetic spectrum that is higher than electron waves (used in communication technologies such as Wi-Fi), but lower than infrared (used in lasers and optical fibers). Their short wavelengths mean that Terahertz (THZ) signals can transmit large quantities of data very quickly, but connecting THZ radiation to existing optical and microwave technologies is extremely difficult.

In 2023, researchers at the Hybrid Photonics Institute took a step closer to filling this gap when they created an extremely thin photonic chip made from niobet lithium. Now, the team is reporting a new design that not only generates THZ waves, but also detects incoming waves by converting them into optical signals.

This bidirectional conversion on a single miniaturized platform is an essential step in bridging the THZ and optical domains, allowing the development of compact, power-efficient devices for communication, sensing, spectroscopy and computing. This study is published in Nature Communications.

“In addition to demonstrating the initial detection of THZ pulses on a niobate lithium photonic circuit chip, it also enhances the THZ electric field by over 100 times and increases the bandwidth by five times (increasing from 680 GHz to 3.5 THz).”

From Terahertz Radar to 6G Communication

PhD student and first author Yazan Lampert explain that the team’s innovative design focuses on embedding micron-sized structures into lithium-niobate photonic chips called transmission systems. These lines act like chip-scale radio cables to guide THZ waves along the chip. By placing a second structure nearby to guide the light (light) waves, scientists have minimized energy losses and enhanced the interaction and transformation between the two.

“A miniaturized circuit design can be used to control both optical and THZ pulses on the same platform. This approach combines photonic and THZ circuits on a single device with unprecedented bandwidth,” says Lampert.

For example, broadband THZ signals generated by hybrid devices can be used to develop Terahatz-based radars. This radar allows you to estimate the distance (range) of objects within a millimeter using very short THZ pulses. Thanks to its compact, energy efficient design, the chip is also compatible with existing photonic technologies such as lasers, optical modulators and detectors. The team is already working to fully miniaturize chip designs, allowing for seamless integration into next-generation communication and range systems, such as those used in self-driving vehicles.

“Thin-film lithium Niobate has proven to be a powerful platform for integrated optics, unexposed THZ domain,” said Amirhassan Shams-Ansari, a co-author of the work and now a leading laser engineer at DRS Daylight Solutions (formerly a post-doctor researcher at Harvard University).

“We expect the design guidelines we propose to be important in future Terahertz applications, such as high-speed 6G communication,” Benea-Chelmus said.