Research and development on compact, low-power, fin Si/LiNbO3 high-speed optical modulator

2023 Fiscal Year Final Research Report

• Project/Area Number: 18K04294
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 21060:Electron device and electronic equipment-related
• Research Institution: Tohoku Institute of Technology (2023); Gifu National College of Technology (2018-2022)
• Principal Investigator: Tomita Isao 東北工業大学, 工学部, 教授 (40611637)
• Project Period (FY): 2018-04-01 – 2024-03-31
• Keywords: 強誘電体 / 半導体 / スロット導波路 / 電気光学効果 / 光変調器

Outline of Final Research Achievements

A hybrid optical modulator using a Si slot waveguide was studied, which can be produced from well-established semiconductor manufacture. LiNbO3 or BaTiO3 was bonded to patterned Si structures, including a doped Si slot waveguide, which also works as electrodes. Static modulator performance, including optical confinement rate, electric-field distribution, and EO modulation rate, was analyzed. Despite performance differences depending on electrode structures, the performance surpassed the one with LiNbO3 without slot waveguides. A high electric field at the doped slot electrodes reduced the modulator size while keeping the static performance. Output limitations at high frequency modulation were overcome with the help of a stronger EO material BaTiO3. Appropriate control of the insulating-film thickness at the inner surface of the slot gap prevented high field-induced dielectric breakdown while maintaining dynamic modulation performance.

Free Research Field

光工学

Academic Significance and Societal Importance of the Research Achievements

10 Gbpsを超える電気信号印加に対して波長チャーピングを生じない優れた出力特性のLiNbO3変調器は、信頼性が高く、広く普及している。しかし、変調器小型化では、LiNbO3の加工が容易でなく、半導体微細加工と比較すると、エッチングレート、精度、軽原子拡散やコストの課題があった。そこで、SOI基板上のSiをスロット導波路に加工後、不純物ドーピングで電極化、無加工のLiNbO3またはBaTiO3を接合した小型スロット導波路型変調器を研究し、良好な静的・動的特性を得たことは、当該変調器の光通信システムへの導入で、システム・コンパクト化と省電力化に貢献すると考える。