大口径氧化铝基Laser烧蚀减反射膜毫米波低通滤波器
A Large Diameter Millimeter-Wave Low-Pass Filter Made of Alumina with Laser Ablated Anti-Reflection Coating
摘要：
我们制作了一个302毫米直径的低通滤波器，由氧化铝制成，具有抗反射涂层（ARC）与激光烧蚀的亚波长结构（SWS）。该滤波器已被集成到与绿岸望远镜耦合的MUSTANG2仪器中并与之一起工作。滤波器在75和105 GHz之间的MUSTANG2工作频带中的平均透射率为98%。ARC引起的反射损失为1%。s偏振态和p偏振态之间的透射率差异小于1%。在1%的精度内，我们观察到这些结果没有变化时，在六个独立的过滤器空间位置测量传输。氧化铝过滤器取代了先前的MUSTANG 2 Teflon过滤器。滤波器散热到其标称40 K级时所获取的数据显示性能与预期一致：300 mK级上滤波器引起的光功率负载以及探测器上的带内光负载降低了约50%。用激光烧蚀氧化铝盘两侧的SWS所需时间不到4天。这是第一份使用手术工具部署带有SWS ARC的氧化铝过滤器的报告，也是第一次使用激光消融大面积制造SWS。
英文摘要：
We fabricated a 302 mm diameter low-pass filter made of alumina that has an anti-reflection coating (ARC) made with laser-ablated sub-wavelength structures (SWS). The filter has been integrated into and is operating with the MUSTANG2 instrument, which is coupled to the Green Bank Telescope. The average transmittance of the filter in the MUSTANG2 operating band between 75 and 105 GHz is 98%. Reflective loss due to the ARC is 1%. The difference in transmission between the s- and p-polarization states is less than 1%. To within 1% accuracy we observe no variance in these results when transmission is measured in six independent filter spatial locations. The alumina filter replaced a prior MUSTANG2 Teflon filter. Data taken with the filter heat sunk to its nominal 40 K stage show performance consistent with expectations: a reduction of about 50% in filters-induced optical power load on the 300 mK stage, and in in-band optical loading on the detectors. It has taken less than 4 days to laser-ablate the SWS on both sides of the alumina disk. This is the first report of an alumina filter with SWS ARC deployed with an operating instrument, and the first demonstration of a large area fabrication of SWS with laser ablation.
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