Far-infrared absorbers exhibiting wideband performance are in great demand in numerous applications, including imaging, detection, and wireless communications. Here, a nonresonant far-infrared absorber with ultra-wideband operation is proposed. This absorber is in the form of inverted pyramidal cavities etched into moderately doped silicon. By means of a wet-etching technique, the crystallinity of silicon restricts the formation of the cavities to a particular shape in an angle that favors impedance matching between lossy silicon and free space. Far-infrared waves incident on this absorber experience multiple reflections on the slanted lossy silicon side walls, being dissipated towards the cavity bottom. The simulation and measurement results confirm that an absorption beyond 90% can be sustained from 1.25 to 5.00 THz. Furthermore, the experiment results suggest that the absorber can operate up to at least 21.00 THz with a specular reflection less than 10% and negligible transmission.

中文翻译：

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基于各向异性刻蚀的掺杂硅的超宽带远红外吸收器。

在包括成像，检测和无线通信在内的许多应用中，对具有宽带性能的远红外吸收器的需求量很大。在此，提出了一种具有超宽带操作的非共振远红外吸收器。该吸收剂为蚀刻成中等掺杂硅的倒金字塔形腔体的形式。借助于湿蚀刻技术，硅的结晶度以有利于有损硅与自由空间之间的阻抗匹配的角度将空腔的形成限制为特定形状。入射到该吸收器上的远红外波在倾斜的有损耗硅侧壁上经历多次反射，并向腔体底部消散。仿真和测量结果证实，从1.25到5.00 THz的吸收率可以保持超过90％。此外，