A research group from Professor Bumki Min’s lab in the KAIST Department of Mechanical Engineering has succeeded in controlling broadband light polarization in the microwave region using 3D metamaterials. The technology is expected to lead to the development of a wide array of broadband optical systems and applications.

In optical experiments, the polarization of light can greatly affect the results. Since much of the light used in such experiments are also heavily polarized, e.g. lasers, it is common practice to manipulate the polarization using optically active materials and waveplates. However, such materials are naturally dispersive, and its use is severely limited to polarization-control of broadband light. Recent research has aimed to aid the problem using highly resonant materials to synthesize modules of strong optical activity, but the dispersive physics of resonance has made it impossible for broadband use.

The Professor Min’s research team, led by Ph.D. degree student Hyun Sung Park, has shown theoretically (and has validated experimentally in the microwave region from 0.1GHz to 40GHz) that broadband control is available when a specific construction of metamaterials is used. The team created a meshed network of helical metamaterials in fourfold rotational symmetry along the direction of light using a metallic, helical structure. The material consistently rotated the polarization light of wavelengths reaching up to ten times the material width by 45 degrees. This was done by designing a structure in which chirality, and hence polarization rotation, of the material linearly varied with wavelength. Such non-dispersive materials are rare in nature, and the success of the experiment is a showcase of artificial metamaterial engineering.

Professor Min claimed, “The research opened the possibility of ultra-thin broadband optical modules by showing how to effectively control light polarization in broadband using very thin constructions.”

The research was funded by the Central Researcher Subsidy Programme (unofficial Romanization, UR) and the Extreme Control of Wave Energy Programme (UR) promoted by the Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation of Korea (NRF). The article was published online by Nature Communications past November 17.

Copyright © The KAIST Herald Unauthorized reproduction, redistribution prohibited