New Metasurface Technology Controls Light for Secure Data Transmission

Compared to traditional optical technologies, metasurface technology offers more advanced, lighter, and precise light control using nanometer-sized artificial structures. Researchers at KAIST have developed a Janus metasurface capable of precisely managing asymmetric light transmission, addressing the limitations of existing metasurface technologies. The study was published in Advanced Materials.

The KAIST research team also proposed a new method to significantly enhance security by restricting the conditions under which information can be decoded using this technology. Led by Professor Jonghwa Shin from the Department of Materials Science and Engineering, the team developed a Janus metasurface capable of precisely regulating asymmetric light transmission.

Asymmetric properties, where the response changes depending on the direction, are crucial in various scientific and engineering fields. The Janus metasurface they created operates similarly to the dual-faced Roman god Janus, showing entirely different optical responses based on the direction of incoming light. This allows a single metasurface to perform different optical tasks depending on the direction of the light, such as functioning as a polarized camera in one direction and a magnifying lens in another.

In other words, depending on the direction of the light, this technology can run two distinct optical systems (such as a lens and a hologram).

This breakthrough addresses a long-standing limitation in metasurface technologies by allowing precise control over light's intensity, phase, and polarization based on its direction of incidence. Previous metasurfaces lacked this ability. The KAIST research team successfully implemented various vector holograms in both directions, demonstrating a fully functional asymmetric light transmission control system.

The team also developed a novel optical encryption method using this technology. They created an optical encryption system that significantly boosts security by enabling information to be decoded only under specific conditions. By employing the Janus metasurface, they produced vector holograms that generate different images depending on the direction and polarization of the incoming light.

This technology has the potential to serve as a next-generation security solution for applications such as secure data transmission and quantum communication. Additionally, the ultra-thin structure of the metasurface is expected to reduce the weight and volume of traditional optical devices, supporting the development of more compact and lightweight next-generation electronics.

This research has enabled the complete asymmetric transmission control of light’s intensity, phase, and polarization, which has been a long-standing challenge in optics. It has opened up the possibility of developing various applied optical devices. We plan to continue developing optical devices that can be applied to various fields, such as augmented reality (AR), holographic displays, and LiDAR systems for autonomous vehicles, utilizing the full potential of metasurface technology.

Jonghwa Shin, Professor, Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology

This research, with Hyeonhee Kim (a doctoral student in the Department of Materials Science and Engineering at KAIST) and Joonkyo Jung as co-first authors, was funded by the Nano Materials Technology Development Program and the Mid-Career Researcher Program of the National Research Foundation of Korea.

Journal Reference:

Kim, H., et al. (2024) Bidirectional Vectorial Holography Using Bi‐Layer Metasurfaces and Its Application to Optical Encryption. Advanced Materials. doi.org/10.1002/adma.202406717.