Abstract-Electrically Controllable Molecularization of Terahertz Meta‐Atoms

Hyunseung Jung,   Jaemok Koo,   Eunah Heo,   Boeun Cho,   Chihun In,   Wonwoo Lee,   Hyunwoo Jo,  Jeong Ho Cho,   Hyunyong Choi,   Moon Sung Kang,  Hojin Lee,

https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.201802760

Active control of metamaterial properties is critical for advanced terahertz (THz) applications. However, the tunability of THz properties, such as the resonance frequency and phase of the wave, remains challenging. Here, a new device design is provided for extensively tuning the resonance properties of THz metamaterials. Unlike previous approaches, the design is intended to control the electrical interconnections between the metallic unit structures of metamaterials. This strategy is referred to as the molecularization of the meta‐atoms and is accomplished by placing graphene bridges between the metallic unit structures whose conductivity is modulated by an electrolyte gating. Because of the scalable nature of the molecularization, the resonance frequency of the terahertz metamaterials can be tuned as a function of the number of meta‐atoms constituting a unit metamolecule. At the same time, the voltage‐controlled molecularization allows delicate control over the phase shift of the transmitted THz, without changing the high transmission of the materials significantly.

Abstract-Invited Article: Terahertz microfluidic chips sensitivity-enhanced with a few arrays of meta-atoms

Kazunori Serita, Eiki Matsuda, Kosuke Okada, Hironaru Murakami, Iwao Kawayama, Masayoshi Tonouchi,

http://aip.scitation.org/doi/abs/10.1063/1.5007681

We present a nonlinear optical crystal (NLOC)-based terahertz (THz) microfluidic chip with a few arrays of split ring resonators (SRRs) for ultra-trace and quantitative measurements of liquid solutions. The proposed chip operates on the basis of near-field coupling between the SRRs and a local emission of point like THz source that is generated in the process of optical rectification in NLOCs on a sub-wavelength scale. The liquid solutions flowing inside the microchannel modify the resonance frequency and peak attenuation in the THz transmission spectra. In contrast to conventional bio-sensing with far/near-field THz waves, our technique can be expected to compactify the chip design as well as realize high sensitive near-field measurement of liquid solutions without any high-power optical/THz source, near-field probes, and prisms. Using this chip, we have succeeded in observing the 31.8 fmol of ion concentration in actual amount of 318 pl water solutions from the shift of the resonance frequency. The technique opens the door to microanalysis of biological samples with THz waves and accelerates development of THz lab-on-chip devices.

Abstract-Direct Measurements of Terahertz Meta-atoms with Near-Field Emission of Terahertz Waves

• Kazunori Serita, 
• Juraj Darmo, 
• Iwao Kawayama, 
• Hironaru Murakami, 
• Masayoshi Tonouchi
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https://link.springer.com/article/10.1007/s10762-017-0417-7

We present the direct measurements of terahertz meta-atoms, an elementary unit of metamaterials, by using locally generated terahertz waves in the near-field region. In contrast to a conventional far-field terahertz spectroscopy or imaging, our technique features the localized emission of coherent terahertz pulses on a sub-wavelength scale, which has a potential for visualizing details of dynamics of each meta-atom. The obtained data show the near-field coupling among the meta-atoms and the impact of the electric field distribution from the excited meta-atom to neighbor meta-atoms. The observable LC resonance response is enhanced with an increase of numbers of meta-atoms. Furthermore, our approach also has a potential for visualizing the individual mode of meta-atom at different terahertz irradiation spots. These data can help us to understand the important role of the meta-atom in metamaterials and develop the novel terahertz components and devices such as active terahertz metamaterial and compact, high-sensitive bio-sensor devices.