Stress-induced birefringence in the lenses of Wide-Area Linear Optical Polarimeter-South
Creators
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Anche, Ramya M.1
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Maharana, Siddharth1
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Ramaprakash, Anamparambu N.1
- Khodade, Pravin1
- Modi, Deepa1
- Rajarshi, Chaitanya1
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Kypriotakis, John A.2
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Blinov, Dmitry2
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Eriksen, Hans K.3
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Ghosh, Tuhin4
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Panopoulou, Georgia V.5
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Pelgrims, Vincent2
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Skalidis, Raphael2
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Pearson, Timothy J.5
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Gjerløw, Eirik3
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Mandarakas, Nikolaos2
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Pavlidou, Vasiliki2
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Potter, Stephen .6
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Readhead, Anthony C. S.5
- Tassis, Konstantinos2
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Basyrov, Artem3
- Papadaki, Katerina2
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Svalheim, Trygve Leithe3
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Wehus, Ingunn .3
- 1. Inter-Univ. Ctr. for Astronomy and Astrophysics (India)
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2.
FORTH Institute of Chemical Engineering Sciences
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3.
University of Oslo
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4.
National Institute of Science Education and Research
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5.
California Institute of Technology
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6.
South African Radio Astronomy Observatory
Contributors
Editors:
Abstract
Two unique wide-field and high-accuracy polarimeters named WALOP (Wide-Area Linear Optical Polarimeter)- North and WALOP-South are currently under development at the Inter-University Center for Astronomy and Astrophysics (IUCAA), India, to create a large area optical polarization map of the sky for the upcoming PASIPHAE sky survey. These instruments are designed to achieve a linear polarimetric measurement accuracy of 0.1% across a field of view (FoV) of 30×30 arcminutes. The WALOP-South instrument will be installed first on a 1 m telescope at the Sutherland Observatory, where the temperatures during the night can vary between 10 to -5°C. These temperature variations and the instrument's pointing to various non-zenithal positions in the sky can introduce stress birefringence in the lenses, leading to time-varying instrumental polarization. This work estimates stress-induced birefringence due to thermal, and gravity stresses on WALOP-South lenses. Using the optomechanical model of the WALOP-South, we carried out Finite Element Analysis (FEA) simulations in SolidWorks software to estimate the stresses for various scenarios of temperature, telescope pointing airmass, and lens mount material (aluminum and titanium). Further, we use the stress tensor analysis to estimate the principal stresses and their directions and consequent birefringence and retardance introduced in the lenses. The stressinduced birefringence will change the optical path length for orthogonal polarization states of the beam passing through the lenses and introduce phase retardation. Overall, with the lens mount design of the instrument, we find that the retardation and consequent instrumental polarization will be within the instrumental accuracy requirements. Additionally, the stress birefringence is found to be higher for aluminum compared to titanium mounts. We further incorporated this retardance in the instrument Mueller matrix estimation to understand its effects on the polarization measurements.
Copyright and License
© 2022 Society of Photo-Optical Instrumentation Engineers (SPIE).
Acknowledgement
The PASIPHAE program is supported by grants from the European Research Council (ERC) under grant
agreement No 771282 and No 772253, from the National Science Foundation, under grant number AST-1611547 and the National Research Foundation of South Africa under the National Equipment Programme. This project
is also funded by an infrastructure development grant from the Stavros Niarchos Foundation and from the Infosys
Foundation.
Additional details
Funding
- European Research Council
- 771282
- European Research Council
- 772253
- National Science Foundation
- AST-1611547
- National Research Foundation
- Stavros Niarchos Foundation