Title: 3D-Structured Polyethylene Windows for Low-Loss Transmission in Wideband Cryogenic Terahertz Systems Show Chinese title

Title: 用于宽频低温太赫兹系统低损耗传输的三维结构聚乙烯窗

Abstract: We present the design, fabrication, and characterisation of a broadband vacuum window and infrared filter based on ultra-high molecular weight polyethylene (UHMWPE) for millimeter wave receivers operating across ALMA Band 6 and 7 (211-373 GHz). The window incorporates pyramidal anti-reflection (AR) structures, machined directly into the polyethylene using CNC machining, which provide impedance matching over a broad frequency range. The structured UHMWPE method was implemented in two distinct components: a vacuum window and a cryogenic infrared filter. This surface structuring approach provides mechanical robustness, cryogenic compatibility, and low insertion loss. We characterize the transmission properties using Terahertz Time-Domain Spectroscopy (THz-TDS), which demonstrates reflection below $5\%$ across the full band. Complementary heterodyne measurements confirm improved receiver noise performance. These results establish 3D structured UHMWPE as a promising platform for broadband cryogenic optics in high-sensitivity THz instrumentation. Show Chinese abstract

Abstract: 我们介绍了基于超高分子量聚乙烯（UHMWPE）的宽频带真空窗和红外滤光器的设计、制造和表征，用于在ALMA波段6和7（211-373 GHz）工作的毫米波接收器。 该窗包含金字塔形抗反射（AR）结构，直接通过CNC加工在聚乙烯中加工而成，可在宽频率范围内提供阻抗匹配。 结构化的UHMWPE方法被应用于两个不同的组件：一个真空窗和一个低温红外滤光器。 这种表面结构方法提供了机械坚固性、低温兼容性和低插入损耗。 我们使用太赫兹时域光谱（THz-TDS）表征了传输特性，结果表明在整个频段内反射低于$5\%$。 互补的外差测量证实了接收器噪声性能的改善。 这些结果确立了三维结构化的UHMWPE作为高灵敏度太赫兹仪器中宽频带低温光学的有前景的平台。