TY - GEN
T1 - Full characterization of the instrumental polarization effects of the spectropolarimetric mode of SCExAO/CHARIS
AU - Hart, Joost G.J.
AU - Van Holstein, Rob G.
AU - Bos, Steven P.
AU - Ruigrok, Jasper
AU - Snik, Frans
AU - Lozi, Julien
AU - Guyon, Olivier
AU - Kudo, Tomoyuki
AU - Zhang, Jin
AU - Jovanovic, Nemanja
AU - Norris, Barnaby
AU - Martinod, Marc Antoine
AU - Groff, Tyler D.
AU - Chilcote, Jeffrey
AU - Currie, Thayne
AU - Tamura, Motohide
AU - Vievard, Sébastien
AU - Sahoo, Ananya
AU - Deo, Vincent
AU - Ahn, Kyohoon
AU - Martinache, Frantz
AU - Kasdin, Jeremy
N1 - Funding Information:
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. 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.
Publisher Copyright:
© 2021 SPIE.
PY - 2021
Y1 - 2021
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 integralfield spectrograph CHARIS. The spectropolarimetric capability of CHARIS is enabled by a Wollaston prism and is unique among high-contrast imagers. We present a detailed Mueller matrix model describing the instrumental polarization effects of the complete optical path, thus the telescope and instrument. From measurements with the internal light source, we find that the image derotator (K-mirror) produces strongly wavelength-dependent crosstalk, in the worst case converting â1/495% of the incident linear polarization to circularly polarized light that cannot be measured. Observations of an unpolarized star show that the magnitude of the instrumental polarization of the telescope varies with wavelength between 0.5% and 1%, and that its angle is exactly equal to the altitude angle of the telescope. Using physical models of the fold mirror of the telescope, the half-wave plate, and the derotator, we simultaneously fit the instrumental polarization effects in the 22 wavelength bins. Over the full wavelength range, our model currently reaches a total polarimetric accuracy between 0.08% and 0.24% in the degree of linear polarization. We propose additional calibration measurements to improve the polarimetric accuracy to <0.1% and plan to integrate the complete Mueller matrix model into the existing CHARIS post-processing pipeline. 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 integralfield spectrograph CHARIS. The spectropolarimetric capability of CHARIS is enabled by a Wollaston prism and is unique among high-contrast imagers. We present a detailed Mueller matrix model describing the instrumental polarization effects of the complete optical path, thus the telescope and instrument. From measurements with the internal light source, we find that the image derotator (K-mirror) produces strongly wavelength-dependent crosstalk, in the worst case converting â1/495% of the incident linear polarization to circularly polarized light that cannot be measured. Observations of an unpolarized star show that the magnitude of the instrumental polarization of the telescope varies with wavelength between 0.5% and 1%, and that its angle is exactly equal to the altitude angle of the telescope. Using physical models of the fold mirror of the telescope, the half-wave plate, and the derotator, we simultaneously fit the instrumental polarization effects in the 22 wavelength bins. Over the full wavelength range, our model currently reaches a total polarimetric accuracy between 0.08% and 0.24% in the degree of linear polarization. We propose additional calibration measurements to improve the polarimetric accuracy to <0.1% and plan to integrate the complete Mueller matrix model into the existing CHARIS post-processing pipeline. Our calibrations of CHARIS' spectropolarimetric mode will enable unique quantitative polarimetric studies of circumstellar disks and planetary and brown dwarf companions.
KW - Based on data collected at Subaru Telescope
KW - which is operated by the National Astronomical Observatory of Japan.
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U2 - 10.1117/12.2602859
DO - 10.1117/12.2602859
M3 - Conference contribution
AN - SCOPUS:85116036820
T3 - Proceedings of SPIE - The International Society for Optical Engineering
BT - Polarization Science and Remote Sensing X
A2 - Kupinski, Meredith K.
A2 - Shaw, Joseph A.
A2 - Snik, Frans
PB - SPIE
T2 - Polarization Science and Remote Sensing X 2021
Y2 - 1 August 2021 through 5 August 2021
ER -