Development of ultra-low loss glass and the process for fiberization

2023 Fiscal Year Final Research Report

• Project/Area Number: 21H01835
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 30020:Optical engineering and photon science-related
• Research Institution: Tohoku University (2023); Hokkaido University (2021-2022)
• Principal Investigator: ONO MADOKA 東北大学, 工学研究科, 教授 (20865224)
• Co-Investigator(Kenkyū-buntansha): 小原 真司 国立研究開発法人物質・材料研究機構, マテリアル基盤研究センター, グループリーダー (90360833) ; 藤岡 正弥 北海道大学, 電子科学研究所, 助教 (40637740)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 量子暗号通信 / 光ファイバ / シリカガラス / レイリー散乱 / 超低損失

Outline of Final Research Achievements

The optical loss due to Rayleigh scattering in silica glass is significantly suppressed by hot-compression at the melting temperature. However, the pressure range of prior study had been only up to 0.2 GPa. In this study, the pressure range was extended to 0.98 GPa, and various physical properties such as density, refractive index, high-energy X-ray scattering, thermal conductivity, and expansion coefficient were successfully measured in addition to Rayleigh scattering. As a result, it was found that the density and refractive index monotonically increase with increasing pressure in the high-pressure frozen silica glass, but the structural fluctuation and Rayleigh scattering become minimum values around 0.8 GPa. We expected that the thermal conductivity would increase with homogenization and densification, but in fact it decreased. We also observed some unusual phenomena such as a shift of the minimum value of the thermal expansion coefficient to higher temperatures.

Free Research Field

光物性物理学

Academic Significance and Societal Importance of the Research Achievements

人工知能とセンシングによるスマート社会が大きく発展している.端末やデータセンタ間を往来する通信容量は急増し,エキサバイトを優に超えている.また,安全な通信を保証する量子暗号は原理的に増幅できないため,長距離通信に適用するためには超透明通信媒体が必須となる.本研究で目的とし,明らかにした超透明シリカガラスの広範囲の圧力依存性は,これらの課題を解決する超透明シリカガラスコアファイバを実現するための材料開発の工程で欠かすことのできない社会的な意義の大きいものである.ガラスの光散乱損失が0.8 GPa付近で極小になり,この時の原子構造が明確化されたことでファイバ化で目指すべき構造が明らかとなった.