Development of silicon optical device for sensitivity improvement of the next generation CMB space mission

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K14506
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 15020:Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
• Research Institution: The University of Tokyo (2021-2022); Japan Aerospace EXploration Agency (2020)
• Principal Investigator: Hasebe Takashi 東京大学, カブリ数物連携宇宙研究機構, 特任研究員 (30794169)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 宇宙物理学 / 宇宙マイクロ波背景放射 / フォトリソグラフィ / ドライエッチング / 反射防止

Outline of Final Research Achievements

In order to increase the sensitivity of the next-generation CMB polarization observation satellite, we developed an antireflection fabrication technique that is necessary for broadband and high-frequency silicon optical devices used in the telescope. Anisotropic dry etching was used to fabricate a three-step micro-periodic structure on the surface of a 35 mm square silicon chip; each side of two chips was processed, and the unprocessed surfaces were bonded by surface activation using ion beam irradiation. Low-temperature transmittance measurements showed that an average transmittance of 98 % was achieved from 200 to 450 GHz. The measured transmittance agreed well with the results of electromagnetic field simulation.
This technology is expected to be a breakthrough for broadening the bandwidth and increasing the frequency of submillimeter-wave observation optical devices.

Free Research Field

宇宙物理学

Academic Significance and Societal Importance of the Research Achievements

本成果によって、CMB偏光観測に用いる光学素子の光学性能は格段に向上する。その結果、インフレーションモデルのより詳細な検証が可能となる。
また、本成果によって実証された反射防止加工技術はCMB観測だけでなくあらゆるサブミリ波用光学デバイスに応用可能である。平面への加工だけでなく曲面への加工が可能であることも部分的に実証済みであるため、多様な分野への応用が期待される。