研究：三次元光回路

これまで半導体集積回路は、素子の微細化により飛躍的な集積度の向上を続けて来ましたが、微細化が進むにつれて、グローバル配線におけるRC遅延、発熱などの問題が深刻になってきています。その解決手段として、本研究室では従来用いられている銅配線を光配線に代替する技術を開発しております。光配線では、遅延や発熱の問題を解決できる上に、波長多重による大容量通信が可能となります。またシリコンを用いた光回路は、①CMOS技術を一部転用できる、②大量生産性に優れている、③高密度集積性に優れている、というメリットがあり、世界中で盛んに研究されています。本グループではその中でも以下の研究を行っております。

Ⅰ. LSI上光回路の多層化

LSIチップ上にシリコンの光回路を集積するには、LSIロジック層に熱ダメージを与えないよう、すべてのプロセスを400°C以下で行う必要があります。そこで300°Cという比較的低温で成膜が可能なアモルファスシリコン(a-Si)を用いることでLSI上光回路を実現する研究を行っています。また、a-Siとクラッド材料を積層することで光回路を3次元的に構成することができ、配線の高密度化が可能となります。本研究グループでは、2層目導波路・3.8dB/cm、3層目導波路・3.7dB/cmの低い伝搬損失を得て多層回路の実現可能性を実証したうえ、高効率層間信号伝送用デバイスとして、図1に示すような回折格子と金属ミラーを用いた構造設計を報告しています。

Ⅱ. EOポリマーを用いた光変調器

図2に示すのは電気光学（Electro-Optic: EO）ポリマーを用いたシリコン光変調器の模式図です。一般的なシリコン変調器には変調効率や応答速度に課題がありました。しかし本研究室で提案する構造では、導波路ギャップ部分に伝搬光および電界を集中させることができるスロット型導波路を用いることに加え、印加する電界に対する屈折率変化が大きいEOポリマーを埋め込むことで変調効率の向上が見込め、小型化および低消費電力化が可能となります。またEOポリマーは電子分極により屈折率変化を起こすため応答速度が速く、100Gbpsを超える変調速度が期待できます。

Ⅲ. LSI上WDM通信のための温度無依存WDMシステムの実現

この研究は、LSI上集積での課題の一つである、温度変化に耐性を有する光集積回路の実現を目的としています。局所的に100度以上にもなるLSIロジック層からの拡散熱は、光特有である波長多重伝送において波長シフトを引き起こし、信号処理を不安定化させます。そこで、本研究グループでは図3のようなスロット導波路構造とクラッド材料の組み合わせにより温度無依存となる導波路デバイスを実現してまいりました(図4)。今後は温度無依存WDMシステム化に向け、波長フィルタ構造設計や波長トリミング技術の検討を進めています。

List of reports

Journal Papers

(1) K. Inoue, D. Plumwongrot, N. Nishiyama, S. Sakamoto, H. Enomoto, S. Tamura, T. Maruyama, and S. Arai, “Loss Reduction of Si Wire Waveguide Fabricated by Edge-Enhancement Writing for Electron Beam Lithography and Reactive Ion Etching Using Double Layered Resist Mask with C60,” Jpn. J. Appl. Phys., vol. 48, no. 3, pp. 030208-1-3, Mar. 2009.
(2) Y. Atsumi, K. Inoue, N. Nishiyama, and S. Arai, “Athermal Wavelength Characteristics of Si Slot Ring Resonator Embedded with Benzocyclobutene for Optoelectronic Integrated Circuits,” Jpn. J. Appl . Phys., vol. 49, pp. 050206-1-3, May. 2010.
(3) J. Kang, Y. Atsumi, M. Oda, T. Amemiya, N. Nishiyama, S. Arai, “Low-loss Amorphous Silicon Multilayer Waveguides Vertically Stacked on Silicon-on-Insulator Substrate,” Jpn. J. Appl. Phys., Vol. 50, No. 12, pp. 120208-1-3, Nov. 2011.
(4) Y. Atsumi, M. Oda, J. Kang, N. Nishiyama, and S. Arai, “Athermal Wavelength Filters toward Optical Interconnection to LSIs,” IEICE Trans. Electron., vol. E95-C, no. 2, pp. 229-236, Feb. 2012.
(5) J. Kang, Y. Atsumi, M. Oda, T. Amemiya, N. Nishiyama, S. Arai, “Layer-to-Layer Grating Coupler Based on Hydrogenated Amorphous Silicon for Three-Dimensional Optical Circuits,” Jpn. J. Appl. Phys., Vol. 51, No. 12, pp. 120203, Nov. 2012.
(6) Y. Atsumi, D-X. Xu, A. Delage, J. H. Schmid, M. Vachon, P. Cheben, S. Janz, N. Nobuhiko, and S. Arai, “Simultaneous Retrieval of Fluidic Refractive Index and Surface Adsorbed Molecular Film Thickness using Silicon Wire Waveguide Biosensors,” Opt. Express, Vol. 20, No. 24, pp. 26969?26977, Nov. 2012.
(7) J. Kang, Y. Atsumi, Y. Hayashi, J. Suzuki, Y. Kuno, T. Amemiya, N. Nishiyama, and S. Arai, “Amorphous-Silicon Inter-Layer Grating Couplers with Metal Mirrors toward 3D Interconnection,” J. Sel. Top. Quantum Electron., Vol. 20, No. 4, p 8202308, Jan. 2014.
(8) J. Kang, Y. Atsumi, Y. Hayashi, J. Suzuki, Y. Kuno, T. Amemiya, N. Nishiyama, and S. Arai, “50 Gbps data transmission thorugh amorphous silicon interlayer grating couplers with metal mirrors,” Appl. Phys. Express, Vol. 7, No. 3, p 32202, Feb. 2014.
(9) Y. Atsumi, J. Kang, Y. Hayashi, J. Suzuki, N. Nishiyama, and S. Arai, “Analysis of higher-order mode suppressed transmission in low-loss silicon multimode waveguide on silicon-on-insulator substrates,” Jpn. J. Appl. Phys., Vol. 53, No. 7, p. 078002, Jun. 2014.

International Conferences

(1) Y. Atsumi, N. Nishiyama, H. Enomoto, K. Inoue, and S. Arai, “Athermal Wavelength Property of Si-Slot Ring Resonator Embedded with Benzocyclobutene.” The 6th IEEE International Conference on Group IV Photonics (GFP). San Francisco (California), ThB3, Sep. 2009
(2) J. Kang, K. Inoue, Y. Atsumi, N. Nishiyama, and S. Arai, “Loss Measurement of Multiple Layer a-Si Waveguides toward 3D Si-Optical Circuits,” 2010 Int. Conf. on Solid State Devices and Materials (SSDM 2010), Tokyo (Japan), D-8-2, Sep. 2010.
(3) Y. Atsumi, J. Kang, Y. Maeda, M. Oda, N. Nishiyama, and S. Arai, “Low-Loss Si-Slot Waveguides and Ring Resonator Embedded with Benzocyclobutene,” The 23rd Annual Meeting of the IEEE Photonics Society (PHO 2010), Denver, Colorado (USA), TuP-3, Nov. 2010
(4) Y. Atsumi, M. Oda, J. Kang, N. Nishiyama, and S. Arai, “Wide-gap Athermal Si-Slot Mach-Zhender Interferometer Embedded with Benzocyclobutene.” The 8th IEEE International Conference on Group IV Photonics (GFP). London (U.K.), FC7, Sep. 2011
(5) J. Kang, Y. Nishikawa, Y. Atsumi, M. Oda, T. Amemiya, N. Nishiyama, and S. Arai, “Amorphous Silicon Grating-Type Layer-to-Layer Couplers for Intra-Chip Connection,” 2012 IEEE Optical Interconnects Conference (OIC-2012), TuD3, May. 2012.
(6) Y. Atsumi, D-X. Xu, A. Delage, J. Schmid, M. Vachon, P. Cheben, S. Janz, N. Nishiyama, and S. Arai, “Differentiation between Changes in Liquid Refractive Index and Surface Adsorbed Molecular Thickness using SOI Wire Waveguide Ring Resonator Biosensor Arrays,” OSA Integrated Photonics Research (IPR-2012), Colorado, USA, ITu3B, June 2012.
(7) Y. Atsumi, T. Sifer, J. Kang, Y. Hayashi, N. Nishiyama, and S. Arai, “Ultraviolet-induced Wavelength Trimming of BCB-buried Athermal Si Slot Wavelength Filters,” The 10th Conf. on Lasers and Electro-Optics Pacific Rim (CLEO-PR 2013), WM2-3, Kyoto, Japan, July 2013.
(8) J. Kang, N. Nishiyama, Y. Atsumi, T. Amemiya, and S. Arai, “Multi-stacked Silicon Wire Waveguides and Couplers toward 3D Optical Interconnects,” SPIE Photonics West 2013 (OPTO2013), San Jose, USA, 8630-7, Feb. 2013.
(9) J. Kang, Y. Atsumi, T. Sifer, Y. Hayashi, T. Amemiya, N. Nishiyama, and S. Arai, “Inter-Layer Grating Coupler with Metal Mirrors for 3D Optical Interconnects,” The 10th Conf. on Lasers and Electro-Optics Pacific Rim (CLEO-PR 2013), WM1-5, Kyoto, Japan, July 2013.
(10) Y. Atsumi, N. Taksatorn, Y. Miyamoto, N. Nishiyama, and S. Arai, “Minituarization of Exposure Area for Electron Beam Lithography using Proximity Effect Correction toward Si Optical Circuits,” The 26th Conf. on Microprocesses and Nanotechnology (MNC 2013), 6C-3-4, Sapporo, Japan, Nov. 2013.
(11) Y. Kuno, J. Kang, Y. Hayashi, J. Suzuki, T. Amemiya, N. Nobuhiko, and S. Arai, “High Efficiency Apodized Grating Couplers with Metal Mirrors between a-Si:H Multilayer Waveguides toward 3D Optical Interconnection,” Int. Conf. Solid State Devices and Materials (SSDM 2014), B-2-2, Tokyo, Japan, Sep. 2014.

Domestic Conferences

(1) K. Inoue, D. Plumwongrot, N. Nishiyama, S. Sakamoto, H. Enomoto, S. Tamura, T. Maruyama, S. Arai:「C60含有と非含有EBレジストZEPの重ね塗りによるSi導波路ドライエッチング形状の向上」. The 55th Spring Meeting, 2008, The Japan Society of Applied Physics and Related Societies, 29p-ZG-15, Chiba, Mar. 2008. Tokyo, Mar. 2001.
(2) Y. Atsumi, N. Nishiyama, H. Enomoto, K. Inoue, and S. Arai:「BCB埋め込みSiスロット導波路による波長フィルタの温度無依存化の検討」, The 56th Spring Meeting, 2009, The Japan Society of Applied Physics and Related Societies, 1a-B-12, Digest III, Ibaraki, Japan, Mar/Apr. 2009.
(3) Y. Atsumi，K. Inoue，N. Nishiyama，and S. Arai: 「BCB埋め込みSiスロット導波路構造を用いた温度無依存波長フィルタ」The 2009 IEICE Society Conf., C-3-7, Niigata, Japan, Sept. 2009.
(4) K. Inoue，Y. Atsumi，N. Nishiyama，S. Tamura，and S. Arai:「SOI基板上多層a-Si細線導波路の伝搬特性の評価」The 57th Spring Meeting, The Japan Society of Applied Physics and Related Societies, 17p-P3-7, Kanagawa, Japan, Mar. 2010.
(5) Y. Atsumi，K. Inoue，N. Nishiyama，and S. Arai:「BCB埋め込みSiスロット導波路の光伝搬損失の評価」The 57th Spring Meeting, The Japan Society of Applied Physics and Related Societies, 17p-P3-10, Kanagawa, Japan, Mar. 2010.
(6) Y. Atsumi, J. Kang, Y. Maeda, M. Oda, N. Nishiyama, and S.Arai:「BCB埋め込みスロットリング共振器の低損失化」 The 71st Autumn Meeting, The Japan Society of Applied Physics, 14p-G-16, Nagasaki, Japan, Sep. 2010.
(7) Y. Atsumi, M. Oda, J. Kang, N. Nishiyama, and S.Arai:「幅広ギャップ構造を有するBCB 埋め込み温度無依存SiスロットMZI」The 58th Spring Meeting, The Japan Society of Applied Physics and Related Societies, 24a-KB-8, Kanagawa, Japan, Mar. 2011.
(8) J. Kang, Y. Atsumi, N. Nishiyama, and S.Arai:「多層化されたアモルファスシリコン細線導波路の低損失伝搬特性」 The 58th Spring Meeting, The Japan Society of Applied Physics and Related Societies, 24a-KB-9, Kanagawa, Japan, Mar. 2011.
(9) Y. Atsumi, M. Oda, J. Kang, N. Nishiyama, and S.Arai:「幅広ギャップ構造を有する温度無依存BCB埋め込みSiスロット型リング共振器」The 72nd Autumn Meeting, The Japan Society of Applied Physics and Related Societies, 2a-ZN-9, Yamagata, Japan, Sept. 2011
(10) M. Oda, Y. Atsumi, J. Kang, T. Koguchi, T. Amemiya, N. Nishiyama, and S. Arai:「BCB 埋め込み温度無依存Si スロットMZI 型波長フィルタ信号伝送特性の温度依存性」, The 2011 IEICE Society Conf., C-3-49, Hokkaido, Japan, Sept. 2011
(11) J. Kang, Y. Nishikawa, Y. Atsumi, M. Oda, T. Amemiya, N. Nishiyama, and S. Arai:「多層アモルファスシリコン細線導波路間の信号伝送用グレーティングカプラ」, The 2012 IEICE General Conf., C-3-38, Tokyo, Japan, Mar. 2012.
(12) M. Oda, Y. Atsumi, T. Sifer, J. Kang, T. Amemiya, N. Nishiyama, S. Arai:「温度無依存BCB 埋め込みSi スロットリング共振器を用いたドロップフィルタ」, The 2012 IEICE General Conf., C-3-39, Tokyo, Japan, Mar. 2012
(13) Y. Atsumi, J. Kang, Y. Nishikawa, M. Oda, T. Amemiya, N.Nishiyama, and S. Arai:「ブロッホ波干渉型低損失連結クロス導波路の作製評価」The 59th Spring Meeting, The Japan Society of Applied Physics and Related Societies, 18a-GP4-22, Tokyo, Japan, Mar. 2011.
(14) J. Kang, Y. Atsumi, T. Sifer, T. Amemiya, N. Nishiyama, and S. Arai:「金属ミラー付き多層アモルファスシリコン細線導波路間のグレーティングカプラ」The 2012 IEICE Society Conf., C-3-59, Toyama, Japan, Sept. 2011.
(15) T. Sifer, Y. Atsumi, J. Kang, N. Nishiyama, and S. Arai, 「紫外線照射を用いた温度無依存シリコンスロットリング共振器の波長トリミング」The 73rd Autumn Meeting, The Japan Society of Applied Physics and Related Societies, 12p-C5-17, Ehime, Japan, Sept. 2011.
(16) M. Oda, Y. Atsumi, J. Kang, T. Koguchi, T. Amemiya, N. Nishiyama, and S Arai, “Signal Transmission Characteristics through an Athermal Mach-Zhender Interferometer by Si-Slot Waveguide Embedded with Benzocyclobuten”, The 2011 IEICE Society Conference, C-3-49, Sapporo, Sep. 2011.
(17) M. Oda, Y. Atsumi, T. Sifer, J. Kang, T. Amemiya, N. Nishiyama, and S Arai, “Wavelength Drop Filter by Athermal Si-Slot Ring Resonator Embedded with Benzocyclobutene”, The 2012 IEICE General Conference, C-3-39, Okayama, Mar. 2012.
(18) J. Kang, Y. Nishikawa, Y. Atsumi, M. Oda, T. Amemiya, N. Nishiyama, and S. Arai, “Grating Couplers between Multilayer Amorphous Silicon Waveguides,” The 2012 IEICE General Conference, C-3-38, Okayama, Mar. 2012.
(19) Y. Atsumi, J. Kang, Y. Nishikawa, M. Oda, T. Amemiya, N. Nishiyama, and S. Arai, “Fabrication of Low-loss Si Waveguide-crossing Arrays with Bloch Waves Interference” The 59th Spring Meeting, 2012; The Japan Society of Applied Physics and Related Societies, 18a-GP4-22, Tokyo, Mar. 2012.
(20) J. Kang, Y. Atsumi, T. Sifer, T. Amemiya, N. Nishiyama, and S. Arai, “Metal Mirror Reinforced Grating Couplers between Multilayer Amorphous Silicon Waveguides,” The 2012 IEICE Society Conference, C-3-59, Toyama, Sep. 2012.
(21) T. Sifer, Y. Atsumi, M. Oda, J. Kang, N. Nishiyama, and S. Arai, “UV exposure wavelength trimming of an athermal Si slot ring resonator”, The 73th Fall Meeting, 2012; The Japan Society of Applied Physics and Related Societies, 12p-C5-17, Ehime, Sep. 2012.
(22) J. Kang, Y. Atsumi, T. Sifer, Y. Hayashi, T. Amemiya, N. Nishiyama, and S. Arai, “Metal Mirror Reinforced Grating Couplers between Multilayer Amorphous Silicon Waveguides”, The 2013 IEICE General Conference, C-3-41, Gifu, Mar. 2013.
(23) Y. Atsumi, J. Kang, Y. Hayashi, J. Suzuki, N. Nishiyama, and S. Arai, “Evaluation of Humidity Protection for Athremal Si-Slot Wavelength Filters Embedded with Polymer”, The 2013 IEICE Society Conference, C-3-11, Fukuoka, Sep. 2013.
(24) J. Kang, Y. Atsumi, Y. Hayashi, J. Suzuki, Y. Kuno, T. Amemiya, N. Nishiyama, and S. Arai, “Grating Couplers between Multilayer Amorphous Silicon Waveguides with Metal Mirrors”, The 2013 IEICE Society Conference, C-3-14, Tokushima, Sep. 2013.
(25) Y. Kuno, J. Kang, Y. Atsumi, Y. Hayashi, J. Suzuki, T. Amemiya, N. Nishiyama, and S. Arai, “Apodized Grating Couplers between Si Multilayer Waveguides with Metal Mirrors,” The 2014 IEICE General Conference, C-3-12, Niigata, Mar. 2014.
(26) Y. Kuno, J. Kang, Y. Hayashi, J. Suzuki, T. Amemiya, N. Nishiyama, and S. Arai, “Apodized Grating Couplers with Circular Through-holes between Multilayer Waveguides with Metal Mirrors,” The 75th Fall Meeting, 2014; The Japan Society of Applied Physics and Related Societies, 18a-A18-5, Sapporo, Sep. 2014.
(27) J. Kang, Y. Kuno, Y. Hayashi, J. Suzuki, T. Amemiya, N. Nishiyama, and S. Arai, “Numerical Analysis of Apodized Grating Coupler Loaded with Metal Mirror for Optical Fiber Connection,” The 2014 IEICE Society Conference, C-3-49, Fukuoka, Sep. 2014.
(28) Y. Kuno, J. Kang, Y. Atsumi, Y. Hayashi, J. Suzuki, T. Amemiya, N. Nishiyama, and S. Arai, “Apodized Grating Couplers between Si Multilayer Waveguides with Metal Mirrors,” The 2014 IEICE Society Conference, C-3-50, Tokushima, Sep. 2014.
(29) K. Itoh, Y. Kuno, J. Kang, Y. Hayashi, J. Suzuki, T. Amemiya, N. Nishiyama, and S. Arai, “Coupling structures between crystal/amorphous Si waveguides for in-plane integration,” The 2015 IEICE Society Conference, C-3-58, Shiga, Mar. 2015.