TY - GEN
T1 - Calibration of the instrumental polarization effects of SCExAO-CHARIS' spectropolarimetric mode∗
AU - van Holstein, Rob G.
AU - Bos, Steven P.
AU - Ruigrok, Jasper
AU - Lozi, Julien
AU - Guyon, Olivier
AU - Norris, Barnaby
AU - Snik, Frans
AU - Chilcote, Jeffrey
AU - Currie, Thayne
AU - Groff, Tyler D.
AU - Hart, Joost't
AU - Jovanovic, Nemanja
AU - Kasdin, Jeremy
AU - Kudo, Tomoyuki
AU - Martinache, Frantz
AU - Mazin, Ben
AU - Sahoo, Ananya
AU - Tamura, Motohide
AU - Vievard, Sébastien
AU - Walter, Alex
AU - Zhang, Jin
N1 - Funding Information:
R.G. van Holstein thanks ESO for the studentship at ESO Santiago during which part of this project was performed. The research of S.P. Bos and F. Snik leading to these results has received funding from the European Research Council under ERC Starting Grant agreement 678194 (FALCONER). The development of SCExAO was supported by the Japan Society for the Promotion of Science (Grant-in-Aid for Research #23340051, #26220704, #23103002, #19H00703 & #19H00695), the Astrobiology Center of the National Institutes of Natural Sciences, Japan, the Mt Cuba Foundation and the director's contingency fund at Subaru Telescope. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are very fortunate to have the opportunity to conduct observations from this mountain.
Funding Information:
R.G. van Holstein thanks ESO for the studentship at ESO Santiago during which part of this project was performed. The research of S.P. Bos and F. Snik leading to these results has received funding from the European Research Council under ERC Starting Grant agreement 678194 (FALCONER). The development of SCExAO was supported by the Japan Society for the Promotion of Science (Grant-in-Aid for Research #23340051, #26220704, #23103002, #19H00703 & #19H00695), the Astrobiology Center of the National Institutes of Natural Sciences, Japan, the Mt Cuba Foundation and the director’s contingency fund at Subaru Telescope. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are very fortunate to have the opportunity to conduct observations from this mountain.
Publisher Copyright:
© 2020 SPIE
PY - 2020
Y1 - 2020
N2 - SCExAO at the Subaru telescope is a visible and near-infrared high-contrast imaging instrument employing extreme adaptive optics and coronagraphy. The instrument feeds the near-infrared light (JHK) to the integral field spectrograph CHARIS. Recently, a Wollaston prism was added to CHARIS' optical path, giving CHARIS a spectropolarimetric capability that is unique among high-contrast imaging instruments. We present a detailed Mueller matrix model describing the instrumental polarization effects of the complete optical path, thus the telescope and instrument. The 22 wavelength bins of CHARIS provide a unique opportunity to investigate in detail the wavelength dependence of the instrumental polarization effects. From measurements with the internal light source, we find that the image derotator (K-mirror) produces strong wavelength-dependent crosstalk, in the worst case converting ∼95% of the incident linear polarization to circularly polarized light that cannot be measured. Theoretical calculations show that the magnitude of the instrumental polarization of the telescope varies with wavelength between approximately 0.5% and 0.7%, and that its angle is exactly equal to the altitude angle of the telescope. We plan to more accurately determine the instrumental polarization of the telescope with observations of a polarization standard star, and fit more comprehensive physical models to all experimental data. In addition, we plan to integrate the complete Mueller matrix model into the existing CHARIS post-processing pipeline, with the aim to achieve a polarimetric accuracy of <0.1% in the degree of linear polarization. Our calibrations of CHARIS' spectropolarimetric mode will enable unique quantitative polarimetric studies of circumstellar disks and planetary and brown dwarf companions.
AB - SCExAO at the Subaru telescope is a visible and near-infrared high-contrast imaging instrument employing extreme adaptive optics and coronagraphy. The instrument feeds the near-infrared light (JHK) to the integral field spectrograph CHARIS. Recently, a Wollaston prism was added to CHARIS' optical path, giving CHARIS a spectropolarimetric capability that is unique among high-contrast imaging instruments. We present a detailed Mueller matrix model describing the instrumental polarization effects of the complete optical path, thus the telescope and instrument. The 22 wavelength bins of CHARIS provide a unique opportunity to investigate in detail the wavelength dependence of the instrumental polarization effects. From measurements with the internal light source, we find that the image derotator (K-mirror) produces strong wavelength-dependent crosstalk, in the worst case converting ∼95% of the incident linear polarization to circularly polarized light that cannot be measured. Theoretical calculations show that the magnitude of the instrumental polarization of the telescope varies with wavelength between approximately 0.5% and 0.7%, and that its angle is exactly equal to the altitude angle of the telescope. We plan to more accurately determine the instrumental polarization of the telescope with observations of a polarization standard star, and fit more comprehensive physical models to all experimental data. In addition, we plan to integrate the complete Mueller matrix model into the existing CHARIS post-processing pipeline, with the aim to achieve a polarimetric accuracy of <0.1% in the degree of linear polarization. Our calibrations of CHARIS' spectropolarimetric mode will enable unique quantitative polarimetric studies of circumstellar disks and planetary and brown dwarf companions.
KW - Crosstalk
KW - High-contrast imaging
KW - Instrumental polarization
KW - Mueller matrix model
KW - Near-infrared
KW - Polarimetric accuracy
KW - SCExAO-CHARIS
KW - Spectropolarimetry
UR - http://www.scopus.com/inward/record.url?scp=85107459889&partnerID=8YFLogxK
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U2 - 10.1117/12.2576188
DO - 10.1117/12.2576188
M3 - Conference contribution
AN - SCOPUS:85107459889
T3 - Proceedings of SPIE - The International Society for Optical Engineering
BT - Ground-Based and Airborne Instrumentation for Astronomy VIII
A2 - Evans, Christopher J.
A2 - Bryant, Julia J.
A2 - Motohara, Kentaro
PB - SPIE
T2 - Ground-Based and Airborne Instrumentation for Astronomy VIII 2020
Y2 - 14 December 2020 through 22 December 2020
ER -