【公開日：2025.06.10】【最終更新日：2025.05.01】

課題データ / Project Data

課題番号 / Project Issue Number

24IT0022

利用課題名 / Title

メタマテリアルを用いた機能素子開発

利用した実施機関 / Support Institute

東京科学大学 / Science Tokyo

機関外・機関内の利用 / External or Internal Use

内部利用（ARIM事業参画者）/Internal Use (by ARIM members)

技術領域 / Technology Area

【横断技術領域 / Cross-Technology Area】（主 / Main）加工・デバイスプロセス/Nanofabrication（副 / Sub）-

【重要技術領域 / Important Technology Area】（主 / Main）量子・電子制御により革新的な機能を発現するマテリアル/Materials using quantum and electronic control to perform innovative functions（副 / Sub）-

キーワード / Keywords

電子線リソグラフィ/ EB lithography,リソグラフィ/ Lithography,フォトニクス/ Photonics,光リソグラフィ/ Photolithgraphy

利用者と利用形態 / User and Support Type

利用者名（課題申請者）/ User Name (Project Applicant)

雨宮 智宏

所属名 / Affiliation

東京科学大学　工学院電気電子系

共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes

ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes

利用形態 / Support Type

（主 / Main）機器利用/Equipment Utilization（副 / Sub）-

利用した主な設備 / Equipment Used in This Project

IT-014：ダイヤモンド用ICPリアクテブイオンエッチング装置
IT-015：SiO2プラズマCVD 装置
IT-038：電子ビーム露光装置

報告書データ / Report

概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)

Using IT-014, IT-015, IT-038, we experimentally demonstrated that the nonlinear optical coefficient of the original Si can be enhanced by incorporating a metamaterial structure into an existing silicon waveguide. The two-photon absorption coefficient enhanced by the metamaterial structure was 424 cm/GW, which is 1.2 × 103 times higher than that of Si. Using this metamaterial waveguide-based nonlinear optical activation function, we achieved a high inference accuracy of 98.36% in the handwritten character recognition task, comparable to that obtained with the ReLU function as the activation function. Therefore, our approach can contribute to the realization of more power-efficient and compact all-optical neural networks.

実験 / Experimental

Using IT-014, IT-015, IT-038, we experimentally demonstrated that the nonlinear optical coefficient of the original Si can be enhanced by incorporating a metamaterial structure into an existing silicon waveguide. Figure 1(a) shows the experimental setup. The optical nonlinear characteristics of the metamaterial optical waveguide were determined by injecting ultrashort pulses into the submicron-sized waveguide and measuring the output as a function of the input power. The light source produced a 44-ps pulse with a wavelength of 1.59 um and a repetition rate of 25 MHz. The input power, controlled by a variable attenuator, passed through a polarizer and a beam splitter and was coupled with the waveguide in free space using an objective lens with a numerical aperture (NA) of 0.25 and a focal length of 12 mm. The polarizer was adjusted to excite the TE mode in the waveguide. Light was introduced into the waveguide via free-space coupling to prevent the adverse effect of the nonlinearity induced in the fiber on the transmission spectrum of the waveguide. The output from the chip was collected using a tapered lensed fiber and measured using an optical spectrum analyzer (OSA) and a power monitor. We used the broadband amplified spontaneous emission (ASE) source to measure the spectrum of the metamaterial waveguide. To achieve low coupling loss with the optical fiber, a beam spot size converter comprising a 100-mm-long tapered core was used at both ends. The total length of the waveguide, including the spot size converter, was 5 mm.

結果と考察 / Results and Discussion

Figure 1(b) shows the input–output characteristics of the Si waveguide measured in the experiment, and Fig. 1(c) shows those of the metamaterial waveguide. The horizontal and vertical axes represent the input and output powers, respectively. We compared the original Si waveguide shown in Fig. 1(b) with the metamaterial waveguides having different resonant frequencies. The results showed that the metamaterial waveguide with SRRs (w=150), where the center wavelength of the incident light matched the resonant wavelength, exhibited the lowest threshold power of approximately 3.2 mW. Here, we define the threshold power as the optical power required to achieve a 50% change in transmission power relative to the transmission when the input is zero. In other words, the nonlinearity of the Si waveguide can be enhanced by matching the resonant wavelength of the SRR with that of the incident light.

図・表・数式 / Figures, Tables and Equations

Fig. 1 (a) Experimental setup. Experimental results for the (b) silicon and (c) metamaterial waveguides with different SRR sizes.

その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)

成果発表・成果利用 / Publication and Patents

論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)

1. Yoshihiro Honda, Optical activation function using a metamaterial waveguide for an all-optical neural network, Optics Letters, 49, 5811(2024).
   DOI: doi.org/10.1364/OL.540234
   

口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.

1. 雨宮 智宏. メタマテリアルを用いた光学迷彩技術, 第49回 光学シンポジウム, Jun. 2024.
2. 雨宮 智宏. メタマテリアルを内包した有機薄膜フィルム, 公益社団法人 新化学技術推進協会（JACI）ナノフォトニクスエレクトロニクス交流会主催講演会, Mar. 2025.

特許 / Patents

特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件