Full characterization of the instrumental polarization effects of the spectropolarimetric mode of SCExAO/CHARIS
Full characterization of the instrumental polarization effects of the spectropolarimetric mode of SCExAO/CHARIS
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SCExAO/CHARIS 分光偏振模式的仪器偏振效应的全面表征
DOI：
10.1117/12.2602859
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
et al.
中科院分区：
文献类型：
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作者：
't Hart Joost;van Holstein Rob G.;Bos Steven;Ruigrok Jasper;Snik Frans;Lozi Julien;Guyon Olivier;Kudo Tomoyuki;et al.
斯巴鲁望远镜的SCExAO是一种可见光和近红外高对比度成像仪器，采用极端自适应光学和日冕照相术。该仪器将近红外光（JHK）馈送到积分场光谱仪CHARIS。CHARIS的分光偏振能力由Wollaston棱镜实现，在高对比度成像仪中是独一无二的。我们提出了一个详细的Mueller矩阵模型，描述了完整的光路，从而望远镜和仪器的仪器偏振效应。从内部光源的测量，我们发现，图像反旋器（K-镜）产生强烈的波长依赖性串扰，在最坏的情况下，转换的95%的入射线偏振光的圆偏振光，无法测量。对非偏振星星的观测表明，望远镜仪器偏振的大小随波长的变化在0.5%到1%之间，其角度正好等于望远镜的高度角。利用望远镜的折叠镜、半波片和消旋器的物理模型，我们同时拟合了22个波长箱中的仪器偏振效应。在整个波长范围内，我们的模型目前达到了0.08%和0.24%之间的线性偏振度的总偏振精度。我们提出了额外的校准测量，以提高极化精度<0.1%，并计划将完整的Mueller矩阵模型集成到现有的CHARIS后处理管道中。我们的校准CHARIS的光谱偏振模式将使独特的定量偏振研究的拱星盘和行星和褐矮星的同伴。
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 ∼95% 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.