Researchers from EPFL and Harvard University have developed a single chip capable of converting electromagnetic pulses between terahertz and optical frequencies. This integrated approach could pave the way for advanced technologies in ultrafast telecommunications, spectroscopy, ranging, and computing.
Terahertz radiation refers to a range of electromagnetic waves with frequencies higher than microwaves—used in technologies like Wi-Fi—but lower than infrared light, which powers lasers and fiber optics. Thanks to their short wavelengths, THz signals can carry vast amounts of data at high speeds. However, integrating THz radiation with current optical and microwave systems has proven to be a major challenge.
Breakthrough Chip Design Enables Both Generation and Detection of Terahertz Waves
In 2023, scientists from the Laboratory of Hybrid Photonics made progress by developing an ultra-thin lithium niobate photonic chip that, when paired with a laser, could generate tunable THz waves. Now, the team has introduced a new chip design that not only creates THz waves but also detects them, converting incoming THz signals into optical ones.
This two-way conversion on a compact, integrated platform marks a key advance in uniting the THz and optical fields, opening the door to efficient, miniaturized technologies for high-speed communication, sensing, spectroscopy, and computing. The findings were published in Nature Communications.
“We not only achieved the first detection of THz pulses on a lithium niobate photonic circuit chip, but also generated THz electric fields more than 100 times stronger and expanded the bandwidth fivefold—from 680 GHz to 3.5 THz,” says Cristina Benea-Chelmus, who leads the Laboratory of Hybrid Photonics.
From Terahertz Radar to Next-Generation 6G Communication Systems
Ph.D. student and lead author Yazan Lampert explains that the team’s breakthrough centers on incorporating microscopic structures known as transmission lines into their lithium niobate photonic chip. These structures function like miniature radio cables, guiding THz waves along the chip. A second nearby structure channels optical signals, enabling efficient interaction and conversion between THz and optical waves with minimal energy loss.
“Our compact circuit design allows us to manipulate both optical and THz pulses on the same chip. This integration of photonic and THz circuits delivers record-breaking bandwidth on a single device,” Lampert says.
Engineers could harness the broadband THz signals generated by the hybrid chip for terahertz radar, using ultrashort pulses to measure object distances with millimeter accuracy. Its compact, low-power design also makes it compatible with current photonic components like lasers, modulators, and detectors. The researchers are now working to fully miniaturize the chip to support future communication and ranging technologies, including those used in autonomous vehicles.
Thin-Film Lithium Niobate Expands Into Promising Terahertz Frontier, Says Co-Author
Amirhassan Shams-Ansari, co-first author of the study and now Principal Laser Engineer at DRS Daylight Solutions (formerly a postdoctoral researcher at Harvard University), notes, “Thin-film lithium niobate has emerged as a powerful platform for integrated photonics, paving the way for a new generation of devices and applications. It’s exciting to witness this technology expanding into the promising but largely untapped terahertz domain.”
Cristina Benea-Chelmus adds, “We expect the design principles we introduce to play a vital role in future terahertz technologies, particularly in next-generation 6G networks, where sensing and ranging will be integral to communication infrastructure.”
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