Abstract-Broadband operation of active terahertz quarter-wave plate achieved with vanadium-dioxide-based metasurface switchable by current injection

Applied Physics Letters

Toshihiro Nakanishi,  Yosuke Nakata, Yoshiro Urade, Kunio Okimura,

(a) Photomicrograph of the metasurface. (b) Whole structure of the device. (c) Current–voltage characteristics between electrodes. (d) Current–resistance characteristics between electrodes.

https://aip.scitation.org/doi/abs/10.1063/5.0019265

We demonstrate the broadband operation of a switchable terahertz quarter-wave plate achieved with an active metasurface employing vanadium dioxide. For this purpose, we utilize anisotropically deformed checkerboard structures, which present broadband characteristics compatible with deep modulation. Moreover, the metasurface is integrated with a current injection circuit to achieve state switching; this injection circuit can also be employed to monitor the electric state of vanadium dioxide. We estimate the Stokes parameters derived from the experimental transmission spectra of the fabricated metasurface and confirm the helicity switching of circularly polarized waves near a designed frequency of 0.66 THz. The relative bandwidth is evaluated to be 0.52, which is 4.2 times broader than that in a previous study.

The metasurface was fabricated with the help of the Kyoto University Nano Technology Hub, as part of the “Nanotechnology Platform Project” sponsored by the MEXT in Japan. The present research was supported by JSPS KAKENHI Grant Nos. 17K05075, 17K17777, and 20K05360 and the Shimadzu Science Foundation.

Abstract-Reconfigurable Terahertz Quarter-Wave Plate for Helicity Switching Based on Babinet Inversion of an Anisotropic Checkerboard Metasurface

Yosuke Nakata, Kai Fukawa, Toshihiro Nakanishi, Yoshiro Urade, Kunio Okimura, and Fumiaki Miyamaru

https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.044008

Dynamic helicity switching by utilizing metasurfaces is challenging because it requires deep modulation of polarization states. To realize such helicity switching, this paper proposes a dynamic metasurface functioning as a switchable quarter-wave plate, the fast axis of which can be dynamically rotated by ${90}^{\circ }$. The device is based on the critical transition of an anisotropic metallic checkerboard, which realizes the deep modulation and simultaneous design of the switchable states. After verifying the functionality of the ideally designed device in a simulation, we tune its structural parameters to realize practical experiments in the terahertz frequency range. By evaluating the fabricated sample with vanadium dioxide, the conductivity of which can be controlled by temperature, its dynamic helicity switching function is demonstrated.

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Abstract-Reconfigurable terahertz quarter-wave plate for helicity switching based on Babinet inversion of anisotropic checkerboard metasurface

Yosuke Nakata, Kai Fukawa, Toshihiro Nakanishi, Yoshiro Urade, Kunio Okimura, Fumiaki Miyamaru

https://arxiv.org/abs/1805.10034

Dynamic helicity switching by utilizing metasurfaces is challenging because it requires deep modulation of polarization states. To realize such helicity switching, this paper proposes a dynamic metasurface functioning as a switchable quarter-wave plate, the fast axis of which can be dynamically rotated by 90∘. The device is based on the critical transition of an anisotropic metallic checkerboard, which realizes the deep modulation and simultaneous design of the switchable states. After verifying the functionality of the ideally designed device in a simulation, we tune its structural parameters to realize practical experiments in the terahertz frequency range. By evaluating the fabricated sample with vanadium dioxide, the conductivity of which can be controlled by temperature, its dynamic helicity switching function is demonstrated.

Abstract-Broadband and energy-concentrating terahertz coherent perfect absorber based on a self-complementary metasurface

Yoshiro Urade, Yosuke Nakata, Toshihiro Nakanishi, and Masao Kitano

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-41-19-4472

We demonstrate that a self-complementary checkerboard-like metasurface works as a broadband coherent perfect absorber (CPA) when symmetrically illuminated by two counter-propagating incident waves. A theoretical analysis based on wave interference and the results of numerical simulations of the proposed metasurface are provided. In addition, we experimentally demonstrate the proposed CPA in the terahertz regime by using a time-domain spectroscopy technique. We observe that the metasurface can work as a CPA below its lowest diffraction frequency. The size of the absorptive areas of the proposed CPA can be much smaller than the incident wavelength. Unlike conventional CPAs, the presented one simultaneously achieves the broadband operation and energy concentration of electromagnetic waves at the deep-subwavelength scale.

© 2016 Optical Society of America

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Abstract-Dynamically Babinet-invertible metasurface: a capacitive-inductive reconfigurable filter for terahertz waves using vanadium-dioxide metal-insulator transition

Yoshiro Urade, Yosuke Nakata, Kunio Okimura, Toshihiro Nakanishi, Fumiaki Miyamaru, Mitsuo W. Takeda, Masao Kitano

(Submitted on 24 Feb 2016)

https://www.blogger.com/blogger.g?blogID=124073320791841682&pli=1#editor/target=post;postID=2197810776175091966

This paper proposes a reconfigurable planar metamaterial that can be switched between capacitive and inductive responses using local changes in the electrical conductivity of its constituent material. The proposed device is based on Babinet's principle and exploits the singular electromagnetic responses of metallic checkerboard structures, which are dependent on the local electrical conductivity. Utilizing the heating-induced metal-insulator transition of vanadium dioxide (VO2), the proposed metamaterial is designed to compensate for the effect of the substrate and is experimentally characterized in the terahertz regime. This reconfigurable metamaterial can be utilized as a switchable filter and as a switchable phase shifter for terahertz waves.

Abstract-Dynamically Babinet-invertible metasurface: a capacitive-inductive reconfigurable filter for terahertz waves using vanadium-dioxide metal-insulator transition

Yoshiro Urade, Yosuke Nakata, Kunio Okimura, Toshihiro Nakanishi, Fumiaki Miyamaru, Mitsuo W. Takeda, and Masao Kitano

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-5-4405

This paper proposes a reconfigurable planar metamaterial that can be switched between capacitive and inductive responses using local changes in the electrical conductivity of its constituent material. The proposed device is based on Babinet’s principle and exploits the singular electromagnetic responses of metallic checkerboard structures, which are dependent on the local electrical conductivity. Utilizing the heating-induced metal-insulator transition of vanadium dioxide (VO2), the proposed meta-material is designed to compensate for the effect of the substrate and is experimentally characterized in the terahertz regime. This reconfigurable metamaterial can be utilized as a switchable filter and as a switchable phase shifter for terahertz waves.

© 2016 Optical Society of America

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