US scientists shrink terahertz lab onto a chip, bring faster wireless tech closer

Between microwaves and infrared light lies a region of the electromagnetic spectrum that researchers have spent decades trying to harness. Known as the terahertz band, it could enable faster data transmission and new imaging technologies, but building practical systems has proven notoriously difficult. Despite decades of research, terahertz systems have remained largely confined to laboratories because the equipment needed to generate, manipulate, and detect these signals is often bulky, expensive, and difficult to scale. Now, researchers at the University of California, Los Angeles (UCLA) have demonstrated a practical route toward overcoming this obstacle by integrating many of these functions onto a single semiconductor chip. “By demonstrating that many of these functions can be integrated onto a single chip using proven industry-standard fabrication platforms, our study opens the door to practical, scalable terahertz technologies for real-world applications,” Mona Jarrahi, one of the study authors and a professor of engineering at the University of California, said. Rethinking a long-standing assumption Many previous attempts to build integrated terahertz systems depended on specialized materials or fabrication methods that were difficult to combine with standard photonic chip manufacturing. The UCLA-led team chose a different strategy. Instead of designing entirely new materials, the researchers focused on quantum wells—extremely thin semiconductor layers already widely used in photonic integrated circuits. For years, many researchers believed quantum wells would struggle to support efficient terahertz operation because electrons could become trapped inside the structures for too long. The UCLA team found otherwise. Their measurements showed that electrons escape the quantum wells in less than a trillionth of a second, fast enough to support terahertz-frequency operation. This finding helped establish quantum wells as a viable foundation for integrated terahertz devices. The researchers used quantum-well PIN photodiodes made from gallium arsenide and aluminum gallium arsenide (GaAs/AlGaAs). They demonstrated that these structures could both generate and detect terahertz signals through a process known as gain-enhanced interband photomixing. Using light to create and detect terahertz waves The principle behind the system is relatively straightforward. Two laser beams with slightly different frequencies are directed into the quantum well device. When the light waves overlap, they create an electrical oscillation equal to the difference between the two laser frequencies. If that frequency falls within the terahertz range, the device produces a terahertz signal. The same structure can also work in reverse, detecting incoming terahertz waves with high sensitivity. “In a prototype fabricated on a GaAs/AlGaAs QW PIC substrate, we demonstrate frequency-tunable terahertz generation and detection across the 100–500 GHz range, achieving both higher terahertz generation efficiency and improved terahertz detection sensitivity,” the study authors note. The researchers further enhanced performance by integrating a semiconductor optical amplifier on the same chip. This boosted terahertz generation efficiency by roughly an order of magnitude while reducing the optical power required for operation. The work forms the basis of what the team calls the Monolithically Integrated Terahertz Optoelectronics (MITO) platform, which is designed to support sources, detectors, amplifiers, modulators and other photonic components on a shared semiconductor substrate using fabrication methods already compatible with commercial photonic foundries. More importantly, the prototype still relies on external lasers, but the platform was designed with future integration in mind. The researchers envision eventually incorporating tunable lasers and additional photonic components directly onto the chip, creating more complete terahertz systems in a compact format. A step toward practical terahertz technology If the platform proves scalable, it could have an impact similar to the one integrated circuits had on conventional electronics, replacing large laboratory assemblies with compact, manufacturable chips. Such systems could support future wireless communication technologies operating beyond today’s networks, while also enabling portable imaging devices, chemical sensing systems, industrial inspection tools, and advanced remote-sensing platforms. The work stands apart from many earlier terahertz integration efforts because it combines efficient signal generation and sensitive detection on a platform that remains compatible with established photonic manufacturing processes. This compatibility could make large-scale production more realistic than approaches requiring specialized fabrication techniques. However, the technology is still at the prototype stage, and significant engineering work remains before fully integrated terahertz communication or imaging systems become commercially available. The next steps include incorporating additional on-chip components, improving performance, and expanding the platform into larger arrays of terahertz sources and detectors. The study is published in the journal Nature Communications. Recommended ArticlesGet the latest in engineering, tech, space & science - delivered daily to your inbox.Rupendra Brahambhatt is an experienced writer, researcher, journalist, and filmmaker. With a B.Sc (Hons.) in Science and PGJMC in Mass Communications, he has been actively working with some of the most innovative brands, news agencies, digital magazines, documentary filmmakers, and nonprofits from different parts of the globe. As an author, he works with a vision to bring forward the right information and encourage a constructive mindset among the masses.