超小型・高速相変化光スイッチ
1.研究背景
近年のインターネットトラフィック量の増加により、光ネットワークノードに高性能な光スイッチが求められている。そこで我々はSi細線導波路と相変化材料(PCM)を用いた光スイッチを提案している。相変化材料は相変化に伴う屈折率変化が大きくメモリ性を有するので、小型で低消費電力な光スイッチが実現可能である。
2.研究目標
Siフォトニクス技術とGeSbTe等の相変化材料を組み合わせた新規の光スイッチを実現する。具体的には、スイッチング時間が100 ns以下、全長が20 μm以下、かつ、自己保持機能を有する光スイッチ構成法を確立する。
3.研究項目
(a)光ゲートスイッチ
Fig. 1. Structure of the optical gate switch.
・光ゲートスイッチ構造を図１に示す。相変化材料の吸収係数の変化により光の出力をON/OFFする。マルチモード干渉(MMI)導波路中央部に直径僅か1 μmの相変化材料(Ge2Sb2Te5)薄膜が蒸着されている。MMI導波路は、相変化材料搭載箇所に光が集中する構造となっている。また、素子のSEM写真を図２に示す。
・光ゲートスイッチ上面から光パルスを入射し、消光比9.2 dBで2000回のスイッチングを達成した。スイッチング時間は立ち上がり130 ns、立ち下がり400 nsであった。これらの結果を図３、４に示す。
Fig. 2. SEM image of the fabricated switch.
Fig. 3. Measured output power by number of laser irradiation cycles.
(a) 950 to 1000 irradiation cycles. (b) 1950 to 2000 irradiation cycles.
Fig. 4. Dynamic responses with (a)OFF/ON and (b)ON/OFF operation.
(b)MZI型光スイッチ
Fig. 5. Structure of the MZI-type optical switch.
マッハツェンダー干渉(MZI)型光スイッチの構造と光学顕微鏡写真を図５と図６に示す。相変化材料の相変化により伝搬光の位相をシフトさせ、出力波長を切り替えることが出来る。
Fig. 6. Microscopic image of the fabricated switch.
(c)方向性結合器型光スイッチ
Fig. 7. Structure of the directional coupler-type optical switch.
方向性結合器型光スイッチの構造を図７に示す。相変化材料の相変化により、光信号の出力ポートを切り替えることが出来る。図８に示すように、FDTDシミュレーションによってスイッチング動作を確認した。
Fig. 8. Simulation results of directional coupler-type optical switch.
(d)低損失相変化材料
光吸収の低減により光スイッチの性能が向上するので、既存の相変化材料(GeTe)に窒素を添加することで、相変化材料による光吸収の低減を検討している。
(4)本研究に関する研究発表リスト
| (a)．論文 | |
|---|---|
| [1] | Takumi Moriyama, Daiki Tanaka, Paridhi Jain, Hitoshi Kawashima, Masashi Kuwahara, Xiaomin Wang, and Hiroyuki Tsuda, “Ultra-compact, self-holding asymmetric Mach-Zehnder interferometer switch using Ge2Sb2Te5 phase-change material,” IEICE Electron. Express, Vol. 11, No. 15, pp. 20140538 (2014). |
| [2] | Daiki Tanaka, Yuya Shoji, Masashi Kuwahara, Xiaomin Wang, Kenji Kintaka, Hitoshi Kawashima, Tatsuya Toyosaki, Yuichiro Ikuma, and Hiroyuki Tsuda, “Ultra-small, self-holding, optical gate switch using Ge2Sb2Te5 with a multi-mode Si waveguide,” Optics Express Vol. 20, Iss. 9, pp. 10283–10294 (2012). |
| [3] | D. Tanaka, Y. Ikuma, Y. Shoji, M. Kuwahara, X. Wang, K. Kintaka, H. Kawashima, T. Toyosaki and H. Tsuda, “Demonstration of 1000-times switching of a phase-change optical gate with Si wire waveguides,” Electron. Lett., Vol. 47, No. 4, pp. 268-269(2011). |
| [4] | Y. Ikuma, Y. Shoji, M. Kuwahara, X. Wang, K. Kintaka, H. Kawashima, D. Tanaka, and H. Tsuda, “Reversible optical gate switching in a Si wire waveguide integrated with a Ge2Sb2Te5 thin film,” Electron. Lett., Vol. 46, No. 21, pp. 1460-1462(2010). |
| [5] | Y. Ikuma, Y. Shoji, M. Kuwahara, X. Wang, K. Kintaka, H. Kawashima, D. Tanaka, and H. Tsuda, “Small-sized optical gate switch using Ge2Sb2Te5 phase-change material integrated with a silicon waveguide,” Electron. Lett., Vol. 46, No. 5, pp. 368-369(2010). |
| [6] | Y. Ikuma, T. Saiki, and H. Tsuda, “Proposal of a small self-holding 2×2 optical switch using phase-change material,” IEICE Electronics Express Vol. 5, No. 12 pp.442-445(2008). |
| (b)．国際会議発表 | |
|---|---|
| [1] | Yasuro Shimazaki, Masashi Kuwahara, Xiaomin Wang, Takumi Moriyama, and Hiroyuki Tsuda, “High-performance Mach-Zehnder Interferometer Type Optical Switch Using N-doped GeTe Thin Films,” European / Phase Change and Ovonics Symposium 2014 (E/PCOS2014), Marseille, France, Sep. 7-9, (2014). |
| [2] | Takumi Moriyama, Hitoshi Kawashima, Masashi Kuwahara, Xiaomin Wang, Hideaki Asakura, and Hiroyuki Tsuda, “Small-sized Mach-Zehnder Interferometer Optical Switch Using Thin Film Ge2Sb2Te5 Phase-change Material,” OFC2014, Tu3E.4, San Francisco, U. S. A., Mar 9-13, (2014). |
| [3] | Yasuro Shimazaki, Masashi Kuwahara, Xiaomin Wang, Hiroyuki Tsuda, “Mach-Zehnder Interferometer Optical Switch Using Low-loss N-doped GeTe Thin Film,” The Symposium on Phase Change Optical Information Storage 2013, P08, Akiu, Japan, Nov. 28-29, (2013). |
| [4] | Hiroyuki Tsuda, Takumi Moriyama, Paridhi Jain, Daiki Tanaka, Masashi Kuwahara, Xiaomin Wang, and Hitoshi Kawashima, “Compact optical switch using phase-change material for transparent photonic network,” The Symposium on Phase Change Optical Information Storage 2013, S22, Akiu, Japan, Nov. 28-29, (2013). |
| [5] | Takumi Moriyama, Daiki Tanaka, Paridhi Jain, and Hiroyuki Tsuda, "Low Crosstalk Design of an Optical Matrix Switch Using Phase-Change Material", Integrated Photonics Research, Silicon and Nano Photonics (IPR2013), IT4A.4, Rio Grande, Puerto Rico, July. 16, (2013). |
| [6] | Hiroyuki Tsuda, Daiki Tanaka, Masashi Kuwahara, Xiaomin Wang, and Hitoshi Kawashima, “Self-holding optical switch using phase-change material for energy efficient photonic network,” The 24th Symposium on Phase Change Oriented Science (PCOS 2012), A13, Hamamatsu, Japan, Nov. 30, (2012). |
| [7] | P. Jain, D. Tanaka, H. Tsuda, M. Kuwahara, X. Wang, and H. Kawashima, “Mach Zehnder Interferometer Optical Switch Using Phase-Change Material,” The 24th Symposium on Phase Change Oriented Science (PCOS 2012), P6, Hamamatsu, Japan, Nov. 29, (2012). |
| [8] | (Invited) Hiroyuki Tsuda, “Optical Switches for Future Photonic Network System Using Phase-Change Material and Si Waveguides,” International Symposium on Optical Memory 2012 (ISOM2012), Mo-E-01, Tokyo, Japan, Sep. 30-Oct. 4, (2012). |
| [9] | Paridhi Jain, Daiki Tanaka, and Hiroyuki Tsuda, “Mach Zehnder Interferometer Optical Switch Using Phase-Change Material,” Photonics in Switching 2012, Th-S4-P09, Ajaccio, France, Sep. 11-14, (2012). |
| [10] | Daiki Tanaka, Yuichiro Ikuma, Hiroyuki Tsuda, Masashi Kuwahara, Hitoshi Kawashima, and Xiaomin Wang, “Ultracompact 2×2 Directional Coupling Optical Switch with Si Waveguides and Phase-Change Material,” Photonics in Switching 2012, We-S22-O03, Ajaccio, France, Sep. 11-14, (2012). |
| [11] | (Invited) H. Tsuda, “Self-holding optical switch using phase-change material,” The 6th International Joint Workshop on OCDMA and OPS 2011, Tu.6, Dec.12-13, Okinawa, Japan (2011). |
| [12] | T. Toyosaki, D. Tanaka，Y. Ikuma，Y. Shoji，M. Kuwahara，X. Wang，K. Kintaka， H. Kawashima, and H. Tsuda, “Repetitive Switching of Optical Gate Switch Using Phase-Change Material and Si Waveguide,” The Symposium on Phase Change Optical Information Storage (PCOS) 2011, Session 3 - No. 5, Atami, Japan, Nov. 18 (2011). |
| [13] | (Invited) H. Tsuda, D. Tanaka, T. Toyosaki, Y. Ikuma, Y. Shoji, M. Kuwahara, X. Wang, K. Kintaka, H. Kawashima, “Small-sized self-holding optical switch using phase-change material,” 13th International Conference on Transparent Optical Networks (ICTON) 2011, Mo.B5.3, June 27- July 1, Stockholm, Sweden (2011). |
| [14] | D. Tanaka, Y. Ikuma, Y. Shoji, M. Kuwahara, X. Wang, K. Kintaka, H. Kawashima, T. Toyosaki, and H. Tsuda, “Reversible Switching of an Optical Gate Based on Si Rib Waveguides with a Ge2Sb2Te5 Thin Film,” 1st International Symposium on Access Spaces (IEEE-ISAS 2011), GS3-B-2, Yokohama, Japan, Jun. 18 (2011). |
| [15] | Y. Ikuma, T. Saiki, H. Tsuda, H. Kawashima, and K. Kintaka, “Feasibility investigation on 2x2 Optical Switch Using Silicon Waveguide and Phase-Change Material,” 1st International Symposium on Access Spaces (IEEE-ISAS 2011), GS3-B-1, Yokohama, Japan, Jun. 18 (2011). |
| [16] | T. Toyosaki, D. Tanaka, Y. Shoji, M. Kuwahara, X. Wang, K. Kintaka, H. Kawashima, Y. Ikuma and H. Tsuda, “Phase change characteristics of Ge2Sb2Te5 thin film for a self-holding optical gate switch,” Photonics West 2011, OPTO, Silicon Photonics IV, 7943-03, Jan. 23-26, San Jose, U. S. A. (2011). |
| [17] | H. Tsuda, "Ultra-Compact Optical Switch Using Phase-Change Material," Asia Communications and Photonics Conference and Exhibition 2010, SE-3, Dec. 8-12, Shanghai, China (2010). |
| [18] | Daiki Tanaka, Yuichiro Ikuma, Yuya Shoji, Masashi Kuwahara, Xiaomin Wang, Kenji Kintaka, Hitoshi Kawashima, Tatsuya Toyosaki and Hiroyuki Tsuda, "Optical Gate Switch Using Phase-Change Material and Si Wire Waveguide," The Symposium on Phase Change Optical Information Storage (PCOS 2010), 21, Nov. 25-26, Atami, Japan (2010). |
| [19] | Takashi Hira, Yuki Hongo, Kazuyuki Tajima, Takashi Honma, Nariaki Kitamura and Toshiharu Saiki, "Amorphization and crystallization of GeSbTe thin films induced by a nanoscale femtosecond light source," The Symposium on Phase Change Optical Information Storage (PCOS 2010), 9, Nov. 25-26, Atami, Japan (2010). |
| [20] | Xiaomin Wang, Masashi Kuwahara, Makoto Fujimaki, Hitoshi Kawashima, Hiroyuki Tsuda, Yoshimichi Ohki, "Fabrication of a grating with phase change material and its static optical switching performance," 36th International Conference on Micro & Nano Engineering, P-NANO-120, Genoa, Italy, (2010). |
| [21] | Y. Ikuma, Y. Shoji, M. Kuwahara, X. Wang, K. Kintaka, H. Kawashima, D. Tanaka, and H. Tsuda, "Reversible Switching of an Optical Gate Using Phase-Change Material and Si waveguide," Integrated Photonics Research, Silicon and Nano Photonics (IPR 2010), IWA6, July 25-28, Monterey, U. S. A. (2010). |
| [22] | H. Tsuda, "Photonic functional devices for future communication systems," 12th International Conference on Transparent Optical Networks (ICTON) 2010, Mo.D2.1, June 27- July 1, Munich, Germany (2010). |
| [23] | (Invited) H. Tsuda, “Self-holding optical switches using phase-change material for future photonic network nodes,” 20th Phase Change Optical Information Storage (PCOS 2008), 10, Dec. 4-5, Shuzenji, Japan (2008). |
| [24] | (Invited) H. Tsuda, “Proposal of an optical switch using phase-change material for future photonic network nodes,” PCOS2007 (The 19th Symposium on Phase Change Optical Information Strage), Proceedings, pp. 39-42, November 29-30, Atami, Japan (2007). |
| [25] | Y. Osada and H. Tsuda, “Self-holding Optical Switch Using Phase-change Material,” CPT2007 (10th International Symposium on Contemporary Photonics Technology), LM-17, January 10-12, Tokyo, (2007). |
