2023 Fiscal Year Research-status Report
Quick 2D birefringence measurement and compensation
| Project/Area Number |
23K19053
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| Research Institution | National Astronomical Observatory of Japan |
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Principal Investigator |
Eisenmann Marc 国立天文台, 重力波プロジェクト, 特任研究員 (80984541)
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| Project Period (FY) |
2023-08-31 – 2025-03-31
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| Keywords | birefringence / kagra / gravitational wave / liquid crystal |
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| Outline of Annual Research Achievements |
We developed characterization and simulations for electro-variable polarization retarder. Using a pair of identical liquid crystal, we were able to generate arbitrary polarization states covering most of the Poincare sphere at about 40Hz. This was then use to successfully compensate for the birefringence of a 23kg sapphire substrate in 1D. We also developed a birefringence measurement apparatus based on this technique that allows us to reconstruct the Jones matrix of optical elements in both transmission and reflection.
Finally, we also used a pair of LCD monitor as liquid crystal array to generate 2D polarization. After designing the mounting apparatus and performing the required calibration, we are now able to generate 2D polarization over large beam.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
We developed an automated calibration and characterization of a liquid crystal cell. We were able to generate polarization states as predicted from our simulations. This was then used to successfully compensate for the birefringence of a 23kg sapphire by a factor 100 000. This result has been accepted for publication.
We also developed a new way to measure birefringence of sample in transmission and reflection based on this technique. It is an initially unplanned benefit of our experimental apparatus. We were also able to succesfully control in 2D birefringence, albeit with low efficiency. This was however useful to test this technique and developed the required software and hardware.
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| Strategy for Future Research Activity |
The plan for next fiscal year is to develop 2D the birefringence readout. The strategy is to use similar components as used in the polarization actuation part. We also plan to improve the efficiency of the 2D polarization actuation.
We will also finalize the newly developed birefringence measurement technique. It will also allow us to study new components as well as possibly studying the Jones matrix of components that are not yet described by this formalism.
We expect these results to lead to publications.
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| Causes of Carryover |
We wanted to confirm our understanding of liquid crystals before proceeding for the next steps of the experiment. This careful checks allow us to refine our requirements for the next steps of this project.
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