Researchers have broken through the challenges posed by current metasurface technologies and have successfully created a Janus metasurface that can expertly manage asymmetric light transmission.
Metasurface technology represents a cutting-edge approach in optics, offering advantages such as being thinner, lighter, and having the ability to accurately manipulate light via tiny artificial structures compared to traditional technologies. Researchers from KAIST have advanced this field by developing a Janus metasurface that can adeptly control asymmetric light transmission. This innovation also introduces a novel approach to enhance security by ensuring that information can only be decoded under specific circumstances.
On October 15, KAIST, under the leadership of President Kwang Hyung Lee, revealed that a team led by Professor Jonghwa Shin from the Department of Materials Science and Engineering successfully created a Janus metasurface that precisely controls the direction-dependent nature of light transmission.
The unique asymmetric properties, which respond differently based on the incoming light’s direction, are vital across several scientific and engineering domains. The Janus metasurface developed by the team can function as an optical system that performs distinct roles in both directions.
Similar to the Roman deity Janus, known for having two faces, this metasurface reacts quite differently depending on the light’s direction. It operates two separate optical systems within one device (for instance, functioning as a magnifying lens from one angle while doubling as a polarized camera from another). Essentially, this technology allows for the simultaneous operation of two optical systems, such as a lens in one direction and a holographic image in the other.
This groundbreaking work addresses a key issue that previous metasurface technologies struggled with. Traditional approaches were limited in their ability to selectively manage light’s three primary characteristics: intensity, phase, and polarization, depending on the direction of the incoming light.
The research group proposed an innovative mathematical and physical approach to this problem, successfully implementing different vector holograms for both directions. This success demonstrates a complete system for controlling asymmetric light transmission.
Moreover, the team has introduced a new optical encryption method based on this metasurface technology. Utilizing the Janus metasurface, they created vector holograms that produce varying images according to the light’s direction and polarization state, thereby establishing an optical encryption system that significantly boosts security by restricting decoding capabilities to specific conditions.
This technology is anticipated to be a next-generation security solution, with applications spanning fields like quantum communication and secure data transfer.
In addition, the ultra-slim design of the metasurface is set to greatly reduce the dimensions and weight of conventional optical devices, aiding in the miniaturization of future devices.
Professor Jonghwa Shin from the Department of Materials Science and Engineering at KAIST expressed, “This research has achieved complete control over asymmetric light transmission in terms of intensity, phase, and polarization, which has been a significant challenge in the field of optics. It opens the door to the development of various applied optical devices.” He further mentioned, “We aim to continue our work in developing optical devices applicable to various sectors including augmented reality (AR), holographic displays, and LiDAR technology for self-driving cars, maximizing the potential of metasurface technology.”
This research involved contributions from Hyeonhee Kim and Joonkyo Jung, both co-first authors and doctoral students in the Department of Materials Science and Engineering at KAIST. It has been published online in the prestigious journal Advanced Materials and is set to appear in the October 31 issue. (Title of the paper: “Bidirectional Vectorial Holography Using Bi-Layer Metasurfaces and Its Application to Optical Encryption”)
The study received funding from the Nano Materials Technology Development Program and the Mid-Career Researcher Program of the National Research Foundation of Korea.
