利用涡日冕仪反射光实现低阶波前控制的实验室演示
Laboratory demonstration of low order wavefront control using light reflected off the vortex coronagraph
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中文总结 AI 辅助
该研究在实验室首次演示基于矢量涡日冕仪反射光的低阶波前控制倾斜环路，经测试可有效抑制漂移、维持高对比度，为高对比度日冕仪波前控制提供可行方案。
中文摘要 AI 辅助
2020年天文十年调查将系外行星成像确定为宜居世界天文台（HWO）的高度优先任务，该天文台必须以1×10⁻¹⁰的对比度成像和表征类地系外行星。矢量涡日冕仪（VVC）因具有小的内工作角和高透射率，是该任务的领先架构。利用VVC反射光进行波前传感与控制，为提高对残余波前误差的鲁棒性、最小化对比度劣变提供了潜在路径。本文在加州理工学院系外行星技术实验室的高对比度与光谱测试台（HCST）上，首次展示了基于VVC反射光运行的低阶波前传感与控制（LOWFS）倾斜环路的实验室演示。该演示得益于HCST对CATKit2的升级，CATKit2是一种面向服务的框架，我们在其中将相位检索、电场共轭（EFC）和LOWFS环路实现为并发例程。我们的相位检索将科学相机的波前误差从71.6 nm RMS降低至7.9 nm RMS，提升幅度超过9倍。在12小时的开环运行中，我们发现点扩散函数（PSF）漂移与光学平台温度密切相关（相关系数r>0.88）。闭合倾斜环路可将1 Hz以下的漂移抑制两个数量级以上，并将指向保持在<0.005 λ/D。与EFC并发运行时，闭合环路在1小时内维持暗区对比度约为5×10⁻⁸，而开环下约0.2–0.4 λ/D的漂移会使对比度劣化一个数量级以上。这些结果确立了VVC反射光传感作为高对比度日冕仪未来波前控制架构的可行基础。
英文摘要
The Astro2020 Decadal Survey identified exoplanet imaging as a high priority for the Habitable Worlds Observatory (HWO), which must image and characterize exo-Earths at contrasts of $1\times10^{-10}$. The vector vortex coronagraph (VVC) is a leading architecture for this task owing to its small inner working angle and high throughput. Using light reflected from the VVC for wavefront sensing and control provides a potential path to improving robustness to residual wavefront errors and minimizing contrast degradation. Here we present the first laboratory demonstration of a low order wavefront sensing and control (LOWFS) tip-tilt loop operating on light reflected from a VVC, carried out on the High Contrast and Spectroscopy Testbed (HCST) at Caltech's Exoplanet Technology Laboratory. The demonstration is enabled by HCST's upgrade to CATKit2, a service-oriented framework in which we implement phase retrieval, electric field conjugation (EFC), and the LOWFS loop as concurrent routines. Our phase retrieval reduces the science camera wavefront error from 71.6 to 7.9 nm RMS, a $>$9$\times$ improvement. Over a 12 hour open loop run, we find that PSF drift is strongly correlated with bench temperature ($r>0.88$). Closing the tip-tilt loop suppresses drift below 1 Hz by more than two orders of magnitude and holds pointing to $<0.005~λ/D$. Run concurrently with EFC, the closed loop maintains a dark hole contrast of $\sim$5$\times10^{-8}$ over one hour, whereas in open loop a drift of $\sim$0.2--0.4 $λ/D$ degrades contrast by more than an order of magnitude. These results establish reflected light sensing off a VVC as a viable foundation for future wavefront control architectures in high contrast coronagraphy.
