Ryohei Hokari

National Institute of Advanced Industrial Science and Technology

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Kazuma Kurihara

National Institute of Advanced Industrial Science and Technology

Kazuhiro Hane

Tohoku University

Naoki Takada

National Institute of Advanced Industrial Science and Technology

Hiroshi Hiroshima

National Institute of Advanced Industrial Science and Technology

Sohei Matsumoto

National Institute of Advanced Industrial Science and Technology

Yoshiaki Kanamori

The University of Tokyo

Junichi MATSUMOTO

National Institute of Advanced Industrial Science and Technology

Genki Kuwano

University of Tsukuba

Koji Miyake

National Institute of Advanced Industrial Science and Technology

Sho Yakabe

Sumitomo Electric Industries (Japan)

Cooperative Institutions

National Institute of Advanced Industrial Science and Technology

The University of Tokyo

University of Tsukuba

Tokyo Institute of Technology

Tokyo University of Science

Tohoku University

National Institute for Materials Science

Osaka University

Japan Science and Technology Agency

Kyoto University

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Numerical Simulation of Motion of Droplet on Fine-textured Solid Surface Using Diffuse-interface Model

The Proceedings of Ibaraki District Conference (2016)

Naoki Takada Kazuma Kurihara Ryohei Hokari Sohei Matsumoto

The applicability of a numerical method is preliminarily examined to determine its suitability for simulations of microscopic immiscible liquid-liquid motion on solid walls with textured surfaces, which is used for evaluating flexible large-area fluidic devices and a novel screen printing process. In the method, a conservation-modified Allen-Cahn equation is adopted for calculations of diffuse-interface advection and formation based on a phase-field model, and a lattice-Boltzmann method is employed as numerical scheme for solving the two-phase fluid-dynamics equations. The simulations demonstrate the ability of the method to successfully capture the shape and motion of a droplet, not only in a liquid flow inside a rectangular micro channel with linearly grooved wall, but also on wettable parallel-wall structured surface under capillary force.

Lattice Boltzmann methods

10.1299/jsmeibaraki.2016.24.101

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Numerical study on resonant wavelength control of split ring resonators with inductance variable structures in the optical wavelength region

Transactions of the Materials Research Society of Japan (2013)

Ryohei Hokari Yoshiaki Kanamori Kazuhiro Hane

We investigate resonant wavelength control of optical metamaterials consisting of split ring resonators (SRRs) with inductance variable structures in the optical wavelength region toward the realization of tunable optical metamaterial devices.The metamaterials consist of SRRs, cut wires, and connecting bars.There are air gaps between the SRRs and the cut wires.The cut wires supported by the connecting bars are located over the SRRs with constant gap distance.The resonant wavelength can be controlled by inductance changes in coil structures of the metamaterial, because the inductance depends on positions of the cut wires.On the other hand, capacitance in the metamaterial is not affected by the position of the cut wires.Numerical simulations using rigorous coupled-wave analysis show that the resonant wavelengths shifts between 1025 nm and 805 nm and varies approximately linearly according to the position of the cut wire.At the resonant wavelength, the transmittance decreases to about 10% and quality factors of around 4.5 are obtained.At non-resonant wavelength, on the other hand, the transmittances of around 70% are obtained.Therefore, the metamaterial functions as band-stop filter, in which the center wavelength can be controlled by the positions of the cut wires over the SRRs.

10.14723/tmrsj.38.615

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Citations (1)

103 Fabrication of Silicon Microlenses by Xenon Difluoride Gas Etching and Hydrogen Annealing

The Proceedings of Conference of Tohoku Branch (2014)

Kazuhiro Sugawara Yosuke Abe Ryohei Hokari Masaki Yoshida T. Sasaki

Xenon difluoride

10.1299/jsmeth.2014.49.7

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3D Printed Broadband Sub-terahertz Absorber for Absolute Power Sensors in Free Space

Journal of Infrared Millimeter and Terahertz Waves (2024)

Genki Kuwano Kazuma Kurihara Ryohei Hokari Yuya Tojima Moto Kinoshita

Free space

Absolute power

10.1007/s10762-024-00996-9

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Comparison of electromagnetically induced transparency between silver, gold, and aluminum metamaterials at visible wavelengths

Optics Express (2014)

Ryohei Hokari Yoshiaki Kanamori Kazuhiro Hane

Electromagnetically induced transparency (EIT)-like effects in silver, gold, and aluminum metamaterials consisting of dipole resonators and quadrupole resonators were demonstrated at visible wavelengths. Optical characteristics of the metamaterials could be controlled by the gap distance between the two resonators. EIT-like effects were observed at wavelengths between 603 and 789 nm, 654 and 834 nm, and 462 and 693 nm for the silver, gold, and aluminum EIT metamaterials, respectively. At wavelengths longer than around 650 nm, the silver metamaterials had better EIT-like features. At wavelengths shorter than around 650 nm, on the other hand, the aluminum metamaterials showed promising EIT-like results.

Electromagnetically Induced Transparency

Split-ring resonator

Photonic metamaterial

10.1364/oe.22.003526

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Citations (49)

Precise shape nano-replication for an antireflective imaging lens using a mould with a thermal insulation layer

Microelectronic Engineering (2019)

Kazuma Kurihara Ryohei Hokari Nobuyuki Ootsu Motoyuki Narita Koji Miyake

Anti-reflective coating

Replication

10.1016/j.mee.2019.111106

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Fabrication of planar metamaterials with sharp and strong electromagnetically induced transparency-like characteristics at wavelengths around 820 nm

Journal of the Optical Society of America B (2014)

Ryohei Hokari Yoshiaki Kanamori Kazuhiro Hane

Fabrication of plasmonic metamaterials having electromagnetically induced transparency (EIT)-like characteristics with sharp and strong spectral responses is a challenging task for device applications at near-infrared wavelengths. EIT-like effects in silver metamaterials consisting of dipole resonators and quadrupole resonators were experimentally demonstrated, and their characteristics were evaluated. Optical characteristics of the metamaterials could be controlled by the gap distance between the two resonators. At wavelengths around 820 nm, EIT-like effects with transmittance between 72% and 28% were observed for the metamaterials with gap distances between 13 and 69 nm. At a gap of 13 nm, a maximum modulation depth of 2.29 was achieved.

Electromagnetically Induced Transparency

Photonic metamaterial

Split-ring resonator

10.1364/josab.31.001000

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Citations (34)

Printed optical metamaterials composed of embedded silver nanoparticles for flexible applications

Optics Express (2018)

Ryohei Hokari Kazuma Kurihara Naoki Takada Hiroshi Hiroshima

For development of next-generation light control, a simple manufacturing technology to produce flexible metamaterials is a key component. Here, we report development of a printing method involving combination of a thermal nanoimprint method and a squeegeeing method, and demonstrate printed optical metamaterials made of commercially available ink consisting of silver nanoparticles. Optical evaluations of printed dipole resonators indicate dipole resonances corresponding to the structure lengths; these resonances are observed at wavelengths of 765-1346 nm. In particular, we report the important finding that, in metamaterials strongly affected by their constituent materials, a metamaterial structure made of the ink exhibits optical properties comparable to those produced by a vacuum deposition process.

Photonic metamaterial

Split-ring resonator

10.1364/oe.26.010326

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Citations (14)

242 Numerical Simulation of Droplet Motion on Micro-textured Solid Surface Using Phase-field Model

Keisan Rikigaku Koenkai koen ronbunshu/Keisan Rikigaku Kouenkai kouen rombunshuu (2015)

Naoki Takada Junichi MATSUMOTO Sohei Matsumoto Kazuma Kurihara Ryohei Hokari

本報では,MEMSデバイス・表面機能部材・微細製造プロセスの他,砂岩等地質環境等で見られる,凹凸構造を持つ固体表面上の微小液滴・気泡挙動の予測のため,フェーズフィールドモデルに基づく数値流体力学シミュレーション法の適用結果を示す.

Solid surface

Motion simulation

10.1299/jsmecmd.2015.28._242-1_