A three-layer eight-octant phase mask towards broadband high-contrast observations
A three-layer eight-octant phase mask towards broadband high-contrast observations
复制标题
用于宽带高对比度观测的三层八分圆相位掩模
DOI：
10.1117/12.2231946
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
M. Tamura
中科院分区：
文献类型：
--
作者：
N. Murakami;J. Nishikawa;N. Akaiwa;Y. Komuro;N. Baba;M. Tamura
设计并制作了一种用于系外行星宽带日冕观测的消色差八八分相掩膜（8OPM）。所制备的8OPM由基于光子晶体的三层八八分半波片组成。通过Jones演算，表明三层8OPM在宽波长范围内比以前的单层设计具有更高的对比度。我们利用自制的三层8OPM进行了日冕仪的初步实验室实验。作为一颗模型星，我们使用几个可见激光光源来表征其日冕性能。因此，我们获得了比单层8OPM的理论对比度更高的对比度。然而，所获得的对比度低于理论值的三层。目前，我们怀疑8OPM半波片的制造误差限制了对比度的实现。
We designed and fabricated an achromatic eight-octant phase mask (8OPM) for broadband coronagraphic observations of exoplanets. The fabricated 8OPM is composed of three-layer eight-octant half-wave plates based on photonic crystals. By using Jones calculus, it is shown that the three-layer 8OPM achieves much higher contrast over broad wavelength range than that of the previous single-layer design. We carry out preliminary laboratory experiments of the coronagraph using the fabricated three-layer 8OPM. As a model star, we use several visible laser light sources for characterizing the coronagraphic performance. As a result, we obtain higher contrasts than theoretical ones of the single-layer 8OPM. However, the achieved contrasts are lower than the theoretical values of the three-layer one. At present we suspect that manufacturing errors of the half-wave plates in the 8OPM limit the achieved contrasts.