Abstract-Terahertz transmission resonances in complementary multilayered metamaterial with deep subwavelength interlayer spacing

Muhan Choi1, Byungsoo Kang2,3, Yoonsik Yi3, Seung Hoon Lee2, Inbo Kim1, Jae-Hyung Han1, Minwoo Yi4, Jaewook Ahn4 and Choon-Gi Choi3,a)
http://scitation.aip.org/content/aip/journal/apl/108/20/10.1063/1.4950863
1 School of Electronics Engineering, Kyungpook National University, Daegu 41566, South Korea
2 Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
3 Creative Research Center for Graphene Electronics, Electronics and Telecommunications Research Institute (ETRI), Daejeon 34129, South Korea
4 Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
a) Electronic mail: cgchoi@etri.re.kr.
Appl. Phys. Lett. 108, 201103 (2016); http://dx.doi.org/10.1063/1.4950863

We introduce a flexible multilayered THz metamaterial designed by using the Babinet's principle with the functionality of narrow band-pass filter. The metamaterial gives us systematic way to design frequency selective surfaces working on intended frequencies and bandwidths. It shows highly enhanced transmission of 80% for the normal incident THz waves due to the strong coupling of the two layers of metamaterial complementary to each other.

Semi- OT Abstract-Graphene–ferroelectric metadevices for nonvolatile memory and reconfigurable logic-gate operations

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  Woo Young Kim,
• Hyeon-Don Kim,
• Teun-Teun Kim,
• Hyun-Sung Park,
• Kanghee Lee,
• Hyun Joo Choi,
• Seung Hoon Lee,
• Jaehyeon Son,
• Namkyoo Park
• & Bumki Min
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  • http://www.nature.com/ncomms/2016/160127/ncomms10429/abs/ncomms10429.html

Memory metamaterials are artificial media that sustain transformed electromagnetic properties without persistent external stimuli. Previous memory metamaterials were realized with phase-change materials, such as vanadium dioxide or chalcogenide glasses, which exhibit memory behaviour with respect to electrically/optically induced thermal stimuli. However, they require a thermally isolated environment for longer retention or strong optical pump for phase-change. Here we demonstrate electrically programmable nonvolatile memory metadevices realised by the hybridization of graphene, a ferroelectric and meta-atoms/meta-molecules, and extend the concept further to establish reconfigurable logic-gate metadevices. For a memory metadevice having a single electrical input, amplitude, phase and even the polarization multi-states were clearly distinguishable with a retention time of over 10 years at room temperature. Furthermore, logic-gate functionalities were demonstrated with reconfigurable logic-gate metadevices having two electrical inputs, with each connected to separate ferroelectric layers that act as the multi-level controller for the doping level of the sandwiched graphene layer.

Switching terahertz waves with gate-controlled active graphene metamaterials

http://graphenetimes.com/2012/09/switching-terahertz-waves-with-gate-controlled-active-graphene-metamaterials/

Authors: Seung Hoon Lee, Muhan Choi, Teun-Teun Kim, Seungwoo Lee, Ming Liu, Xiaobo Yin, Hong Kyw Choi, Seung S. Lee, Choon-Gi Choi, Sung-Yool Choi, Xiang Zhang & Bumki Min

The extraordinary electronic properties of graphene provided the main thrusts for the rapid advance of graphene electronics. In photonics, the gate-controllable electronic properties of graphene provide a route to efficiently manipulate the interaction of photons with graphene, which has recently sparked keen interest in graphene plasmonics. However, the electro-optic tuning capability of unpatterned graphene alone is still not strong enough for practical optoelectronic applications owing to its non-resonant Drude-like behaviour. Here, we demonstrate that substantial gate-induced persistent switching and linear modulation of terahertz waves can be achieved in a two-dimensional metamaterial, into which an atomically thin, gated two-dimensional graphene layer is integrated. The gate-controllable light–matter interaction in the graphene layer can be greatly enhanced by the strong resonances of the metamaterial. Although the thickness of the embedded single-layer graphene is more than six orders of magnitude smaller than the wavelength (<λ/1,000,000), the one-atom-thick layer, in conjunction with the metamaterial, can modulate both the amplitude of the transmitted wave by up to 47% and its phase by 32.2° at room temperature. More interestingly, the gate-controlled active graphene metamaterials show hysteretic behaviour in the transmission of terahertz waves, which is indicative of persistent photonic memory effects.

Nature Materials. doi:10.1038/nmat3433

Abstract-Metamaterials: Reversibly Stretchable and Tunable Terahertz Metamaterials with Wrinkled Layouts

Seungwoo Lee,  Seongnam Kim,  Teun-Teun Kim,  Yushin Kim,  Muhan Choi,  Seung Hoon Lee,  Ju-Young Kim,  Bumki Min 

http://onlinelibrary.wiley.com/doi/10.1002/adma.201290159/abstract

When metamaterials are arranged in a stretchable platform, their practical applications (e.g., reconfigurable optoelectronic devices and biological sensors) can be greatly extended. B. Min and co-workers take inspiration from the wrinkled structures of various bio-organisms to develop a generic strategy for reversibly stretchable metamaterials. The structural integrities of the wrinkled THz metamaterials described, remain intact after repeated stretching/relaxing, and the wrinkled metamaterial makes a mechanically reversible transition between artificial homogeneous and inhomogeneous broadenings

Abstract-Reversibly Stretchable and Tunable Terahertz Metamaterials with Wrinkled Layouts

http://onlinelibrary.wiley.com/doi/10.1002/adma.201200419/abstract
The use of wrinkling provides a generic route to stretchable metamaterials, with unprecedented terahertz tunability. The wrinkled metamaterial can be stretched reversibly up to 52.5%; the structural integrity can be maintained during at least 100 stretching/relaxing cycles. Importantly, the wrinkling of meta-atoms offers a deterministic way to achieve controlled broadening of electrical resonance.