Dimpled scalar vortex coronagraph laboratory demonstration for the Habitable Worlds Observatory

Achieving the Habitable Worlds Observatory (HWO) goal of $10^{-10}$ contrast across a $\ge$20\% bandwidth requires coronagraph focal plane masks with both broadband high contrast performance and high planet throughput. Scalar vortex coronagraphs (SVCs) offer a promising alternative to polarization-sensitive vector vortex designs but face chromatic limitations. This work presents the latest laboratory demonstrations of second-generation scalar vortex prototypes that incorporate radial phase dimples to improve broadband starlight suppression. We compare these new “dimpled” sawtooth masks to previous-generation scalar designs through phase metrology, microscope inspection, and high-contrast imaging experiments on the In-Air Coronagraph Testbed. Using electric field conjugation, we achieve near testbed-limited contrasts across both narrow (2\%) and broadband (10\%) spectral ranges. We also show that the dimpled vortex lab and predicted bench-limited contrast performances for 2\%, 10\% and 18\% bandwidths agree within a factor of two, marking a significant step toward polarization-independent coronagraphs capable of meeting HWO performance requirements.

要达成宜居世界天文台（Habitable Worlds Observatory, HWO）所要求的、在带宽不低于20%的波段内实现$10^{-10}$量级对比度的目标，需要采用兼具宽带高对比度性能与高行星透射率的日冕仪焦平面掩模。标量涡旋日冕仪（Scalar Vortex Coronagraphs, SVCs）为偏振敏感型矢量涡旋设计提供了极具前景的替代方案，但存在色差局限。本研究展示了第二代标量涡旋原型的最新实验室验证结果，该原型引入径向相位凹陷结构以提升宽带星光抑制能力。我们通过相位测量、显微镜检测，以及在大气内日冕仪测试台（In-Air Coronagraph Testbed）上开展的高对比度成像实验，将这款新型"带凹陷"的锯齿掩模与前代标量设计进行了对比。借助电场共轭（electric field conjugation）技术，我们在窄带（2%带宽）与宽带（10%带宽）光谱范围内均实现了接近测试台极限的对比度水平。我们还证实，针对2%、10%与18%带宽的带凹陷涡旋掩模，其实验室测试结果与台架极限对比度预测值的偏差不超过一倍，这为研发能够满足HWO性能要求的偏振无关日冕仪迈出了重要一步。