Development of an entrance window for cryogenic optical testing with a He-Ne laser interferometer

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K21883
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 16:Astronomy and related fields
• Research Institution: Nagoya University
• Principal Investigator: Kaneda Hidehiro 名古屋大学, 理学研究科, 教授 (30301724)
• Project Period (FY): 2019-06-28 – 2022-03-31
• Keywords: 低温光学系 / 光学窓 / 宇宙赤外線観測

Outline of Final Research Achievements

The measurement system consisting of a cryo-chamber and a He-Ne laser interferometer has been established for optical testing of aspherical mirrors at low temperatures. In particular, special entrance windows have been developed to prevent thermal radiation from outside the chamber as much as possible, which are installed at the entrance of the innermost low-temperature shroud of the cryo-chamber. More specifically, a band-pass optical filter tuned at the central wavelength of 633 nm (He-Ne) is fabricated on the substrate of selected fused silica with metal meshes. In parallel, the method of optical alignment with a CGH interferometer is studied for the aspherical mirror to be measured at low temperatures in the cryo-chamber with the special entrance windows.

Free Research Field

天文学

Academic Significance and Societal Importance of the Research Achievements

近年は、天文観測のみならず、さまざまな光学計測分野において、広視野・高解像度が求められており、光学系の複雑化が進んでいる。その一方で、性能を向上させるためには、熱的に安定な光学系の実現が強く求められる。とくに宇宙赤外線観測では、装置からの熱放射による赤外線フォトンノイズを軽減するために極低温に冷やす必要がある。多彩な低温光学計測を可能にするためには、熱をできるだけ遮断した環境下での低温チャンバーによるレーザー干渉計測の実現が必要不可欠であり、本研究ではその原理実証を行った。