Korea Atomic Energy Research Institute and Korea Advanced Institute of Science & Technology Co-Develop Technology That Increase Optical Modulation of All Light Energies

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Korea Atomic Energy Research Institute (KAERI, Director Ha Jae-joo) has developed a technology that increases optical modulation of all light energies including terahertz radiation by making graphene, which is a 2D matter, into a 3D matter. It seems that this technology will be used as a basic technology to develop optical modulation device for next-generation communication with high performance.

KAERI announced on the 15th that a research team led by Professor Baek In-hyeong of Quantum Optical Research Department’s Ultra-fast Radiation Laboratory and a research team led by Professor Lee Sang-min of KAIST Physics Department co-developed single-layer graphene as 3D device and co-developed optical modulation technology that can effectively control absorption and penetration of light.

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Graphene is 2D matter that forms a layer as carbon atoms are combined as a shape of honeycomb and it can absorb every wavelength of light as valence band and conduction band meet at a point. However it was difficult to use it as an optical modulation device as it absorbed only 2.3% of light from outside. Optical modulation device lets strong light to pass through while it absorbs weak light. If light is not absorbed enough, it affects adjacent devices and lowers their performance.

Although there had been researches that were trying to increase absorption rate by stacking graphenes into a 3D structure, they were not that effective. Instead conductivity dropped as these graphenes displayed a structure of crystalline. Movement of electrons was also limited due to distortion of a structure.

Research teams noticed the fact that crystalline structure disappears is layers of graphenes are made by gathering small pieces of graphenes and developed layers of graphenes with tens of thousands of 100-micrometer graphenes.

Schematic diagram of a structure of 3D graphene developed by research teams from KAERI and KAIST. This structure lets strong light to go through and absorbs weak light.

Schematic diagram of a structure of 3D graphene developed by research teams from KAERI and KAIST. This structure lets strong light to go through and absorbs weak light.

This 3D grapheme maximizes optical modulation performance. If 3D structure is made by 8 layers, performance of optical modulation increases by 70% compared to current 2D graphene structure.

This structure also displays excellent performance in terahertz radiation (light that has properties of both photon and electromagnetic wave) that has been seen as the ‘dream frequency band’. Until now there haven’t been many researches on optical modulation utilizing terahertz radiation.

Research teams were able to confirm that efficiency of optical modulation of terahertz radiation increases as there are more layers of graphenes. It showed excellent performance as photons and free electrons within graphenes interacted very rapidly.

Research teams are going to carry out further researches that will increase performance and level of use of optical modulation by adding other materials to 3D graphene. These technologies will be used to push forward commercialization of next-generation optical modulation device with high performance.

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"Although our researches had focused on graphenes, level of use of 3D graphenes is very high as they can be applied to other 2D materials." said Jung Young-wook who is the head of KAERI’s Ultra-Fast Radiation Laboratory. "We expect that 3D graphenes will create new industries as they are used as a basic technology for developing next-generation optical communication and semiconductor devices."

Staff Reporter Kim, Youngjoon | kyj85@etnews.com

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