Astronomical spectropolarimeters require high accuracy polarizers with large aperture and stringent uniformity requirements. In solar applications, wire grid polarizers are often used as performance is maintained under high heat loads and temperatures over 200°C. DKIST is the NSF’s new 4-m aperture solar telescope designed to deliver accurate spectropolarimetric solar data across a wide wavelength range, covering a large field of view simultaneously using multiple facility instruments. Polarizers at 120 mm diameter are used to calibrate DKIST instruments but vary spatially in transmission, extinction ratio, and orientation of maximum extinction. We combine new spatial and spectral metrology for polarizers and retarders to simulate the accuracy losses with field angle and wavelength caused simultaneously by spatial variation of several optical parameters including beam decenter from misalignments. We also present testing of a new crystal sapphire substrate polarizer designed and fabricated to improve DKIST long wavelength calibrations. We assess spatial thickness variation of sapphire and fused silica wafer substrates using spectral interference fringes.

中文翻译：

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DKIST 的偏振建模和预测，第 8 部分：校准偏振器空间变化影响

天文分光偏振计需要具有大孔径和严格均匀性要求的高精度偏振器。在太阳能应用中，线栅偏振器通常用于在高热负荷和超过 200°C 的温度下保持性能。DKIST 是 NSF 的新型 4 米孔径太阳望远镜，设计用于在宽波长范围内提供准确的分光偏振太阳数据，使用多种设施仪器同时覆盖大视野。直径为 120 毫米的偏振器用于校准 DKIST 仪器，但在透射率、消光比和最大消光方向上存在空间变化。我们为偏振器和延迟器结合了新的空间和光谱计量学，以模拟由多个光学参数（包括未对准导致的光束偏心）的空间变化同时引起的场角和波长的精度损失。我们还展示了对设计和制造以改进 DKIST 长波长校准的新型水晶蓝宝石衬底偏振器的测试。我们使用光谱干涉条纹评估蓝宝石和熔融石英晶片基板的空间厚度变化。