December 03, 2014

Professor Bumki Min from the Department of Mechanical Engineering at KAIST has developed a technology that can manipulate a polarized light in broadband operation with the use of a metamaterial.

It is expected that this technology will lead to the development of broadband optical devices that can be applied to broadband communication and display.

When an object or its structure is analyzed by using a polarized light such as a laser, the results are generally affected by the polarized state of the light. Therefore, in an optics laboratory, the light is polarized by various methods.

In such cases, researchers employ wave plates or photoactive materials. However, the performance of these devices depend vastly on wavelength, and so they are not suitable to be used as a polarizer, especially in broadband.

There were many attempts to make artificial materials that are very photoactive by using metamaterials which have a strong resonance. Nonetheless, because the materials had an unavoidable dispersion in the resonance frequency, they were not adequate for broadband operation.

Professor Min’s research team arranged and connected helical metamaterials that are smaller than the wavelength of light. They verified theoretically and experimentally that polarized light can be constantly rotated regardless of the wavelength by super-thin materials that have thickness less than one-tenth of the wavelength of the light. The experiment which confirmed the theory was conducted in the microwave band.

Broadband polarized rotational 3D metamaterials were found to rotate the polarized microwave within the range of 0.1 GHz to 40 GHz by 45 degrees regardless of its frequency. This nondispersive property is quite unnatural because it is difficult to find a material that does not change in a wide band.

In addition, the research team materialized the broadband nondispersive polarized rotational property by designing the metamaterial in a way that it has chirality, which determines the number of rotations proportional to the wavelength.

Professor Min said, “As the technology is able to manipulate ultrathin polarization of light in broadband, it will lead to the creation of ultra-shallow broadband optical devices.”

Sponsored by the Ministry of Science, ICT and Future Planning of the Republic of Korea and the National Research Foundation of Korea, this research was led by a PhD candidate, Hyun-Sung Park, under the guidance of Professor Min. The research findings were published online in the November 17th issue of Nature Communications.