Imagine if your daily commute suddenly switched from a crowded expressway to a high-speed train. This is the kind of advancement that scientists are chasing in developing ultrafast communication and computing technologies, as they aim to extend today’s gigahertz (GHz) electronics into the 1000-fold faster terahertz (THz) range.
One promising approach lies in spintronics, which transforms the magnetic spin of electrons into electrical currents to transmit information. This process, known as spin-to-charge conversion (SCC), happens almost instantaneously, with small and short-lived signals that many conventional methods fail to capture dynamically. Conversion efficiency also depends on the quality and structure of the materials used in spintronic devices, requiring precise fabrication methods. As such, measuring and achieving SCC at THz timescales has so far proven challenging.
On a mission to make THz devices a more practical reality is Lin Ke, former Principal Scientist at the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE). To explore new materials for accessing these ultrafast processes, Ke and the A*STAR team collaborated with the Singapore Institute of Technology; Nanyang Technological University, Singapore; National University of Singapore; and National Institute of Laser Enhanced Sciences in Egypt.
The researchers developed a tiny layered device with cobalt and strontium iridate (SIO), using scalable fabrication techniques that are compatible with current manufacturing practices. They then fired an extremely fast burst of light called a femtosecond (fs) laser pulse, generating spin currents. “When the fs laser hits the cobalt magnetic layer, it creates a very fast flow of spin-polarised electrons. This happens on ultrafast timescales, naturally matching THz frequencies,” explained Ke.
In the SIO layer, a phenomenon known as the inverse spin Hall effect then converts spin to charge currents and produces transient electrical signals. Because this current rapidly appears and disappears, the team’s device emits THz signals, effectively harnessing ultrafast spin dynamics. Beyond achieving THz SCC in these materials, the team also showed that the process can unfold at room temperature, bypassing the need for ultralow conditions that have typically limited the practical use of many advanced electronic effects in modern devices.
“Our work provides a practical pathway towards real THz spintronic devices that could eventually be integrated into future technologies,” Ke remarked. The researchers believe that fs laser-driven SCC could open doors to a range of next-generation technologies, from ultra high-speed wireless communication and more energy-efficient computing to THz imaging and sensing applications in the medical and manufacturing sectors.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE).
