A domestic research team has developed a technology that can control light at a speed thousands of times faster than existing technologies.
Dr. Shin Hee-jun of the Pohang Accelerator Laboratory and Professor Noh Jun-seok of Pohang University of Science and Technology (POSTECH) announced on the 7th that they successfully developed the world's fastest terahertz (THz) band optical modulation technology. The results of this research were published in Advanced Science.
Optical modulation technology is a method of transmitting information by controlling the intensity, frequency, and phase of light. Terahertz waves, one of the various light bands, are attracting attention as next-generation communication technology due to their wider bandwidth compared to existing radio waves. However, current technologies have limitations in practically modulating terahertz waves quickly.
To address this, the research team utilized metamaterials. Metamaterials are artificial substances with special structures that do not exist in nature and can alter the properties of light and radio waves. Attempts to use metamaterials have existed, but they only utilized the fixed characteristics of metamaterials, making rapid modulation difficult.
In this research, a method was applied to actively change the metamaterials by adjusting external conditions. The research team fabricated metamaterials on a silicon substrate and analyzed reactions by irradiating them with strong light. Silicon is a widely used semiconductor material; however, previous methods had slow modulation speeds, making it challenging to control terahertz waves. The team enabled control at a much faster rate than conventional semiconductor methods by using the 'photonic excitation' phenomenon to activate electrons by directing light onto the silicon substrate.
As a result, they successfully modulated at a speed of 1.3 picoseconds (one trillionth of a second), which is thousands of times faster than existing technologies. Furthermore, at specific frequencies, the modulation depth, or the extent to which light is controlled, exceeded 500%, demonstrating the ability to modulate terahertz waves with greater precision.
These results are expected to be applied in various fields including ultra-high-speed data transmission, next-generation image processing systems, and precision medical diagnostics. Dr. Shin Hee-jun noted, "This research is a significant milestone in overcoming the temporal limitations of optical modulation speeds in the terahertz frequency range," and added, "It will greatly contribute to the development of high-performance communication systems in the terahertz band, optical-based information processing, and optical sensing platforms."
References
Advanced Science (2025), DOI: https://doi.org/10.1002/advs.202413719