Characterization of birefringence inhomogeneity of KAGRA sapphire mirrors from transmitted wavefront error measurements
Cooling down test masses to cryogenic temperatures is a way to reduce the thermal noise of gravitational wave detectors. Crystalline materials are considered the most promising materials for fabricating cryogenic test masses and their coatings because of their excellent thermal and optical properties at low temperatures. However, birefringence owing to local impurities and inhomogeneities in the crystal can degrade the performance of the detector. The birefringence measurement or mapping over a two-dimensional area is thus important. This study describes a method for fast birefringence measurements of a large sample by simply combining a series of transmission wavefront error measurements using linearly polarized light with Fizeau interferometers. Using this method, the birefringence inhomogeneity information of KAGRA's two input test masses with a diameter of 22 cm was fully reconstructed. The birefringence information was then used to calculate the transverse beam shapes of the light fields in orthogonal polarization directions when passing through the substrate. It was possible to find a calculated beam shape consistent with in situ measurements using the KAGRA interferometer. This technique is crucial for birefringence characterization of test masses in future detectors, where even larger sizes are used.
Authors
- Yuta Michimura (ORCID: https://orcid.org/0000-0002-2218-4002)
- M. Eisenmann
- M. Leonardi (ORCID: https://orcid.org/0000-0002-7641-0060)
- Y. Aso (ORCID: https://orcid.org/0000-0002-1902-6695)
- G. Billingsley (ORCID: https://orcid.org/0000-0002-4141-2744)
- K. Kokeyama (ORCID: https://orcid.org/0000-0002-2896-1992)
- H. Wang (ORCID: https://orcid.org/0000-0002-6589-2738)
- Eiichi Hirose (ORCID: https://orcid.org/0000-0002-2925-232X)
- Masahide Tamaki
- T. Ushiba (ORCID: https://orcid.org/0000-0002-5059-4033)
Institutions
- California Institute of Technology (US)
- University of Trento (IT)
- CohBar (United States) (US)
- Japan Science and Technology Agency (JP)
- National Astronomical Observatory of Japan (JP)
- Institute for Cosmic Ray Research (JP)
- inhbar, Inc. (Japan)
- The University of Tokyo (JP)
- Cardiff University (GB)
Publication Details
- Journal
- Physical review. D/Physical review. D.
- Published
- 2024-10-18
- DOI
- https://doi.org/10.1103/physrevd.110.082007
- Citations
- 4
- Primary Topic
- Adaptive optics and wavefront sensing
- Type
- article
- Field-Weighted Citation Impact
- 1.35
Funders
- Alabama Space Grant Consortium
- National Research Foundation
- Ministry of Education, Culture, Sports, Science and Technology
- Academia Sinica
- Korea Institute of Science and Technology Information
- Korea Astronomy and Space Science Institute
- National Research Foundation of Korea
- National Astronomical Observatory of Japan
- High Energy Accelerator Research Organization
- Ministry of Science and ICT, South Korea
- National Science and Technology Council
- Japan Society for the Promotion of Science
- Japan Science and Technology Agency
- Institute for Cosmic Ray Research, University of Tokyo
- Great Southern Development Commission, Government of Western Australia
- Precursory Research for Embryonic Science and Technology