Defrance Fabien, Jung-Kubiak Cecile, Sayers Jack, Connors Jake, deYoung Clare, Hollister Matthew I, Yoshida Hiroshige, Chattopadhyay Goutam, Golwala Sunil R, Radford Simon J E
Appl Opt. 2018 Jun 20;57(18):5196-5209. doi: 10.1364/AO.57.005196.
Although high-resistivity, low-loss silicon is an excellent material for terahertz transmission optics, its high refractive index necessitates an antireflection treatment. We fabricated a wide-bandwidth, two-layer antireflection treatment by cutting subwavelength structures into the silicon surface using multi-depth deep reactive-ion etching (DRIE). A wafer with this treatment on both sides has <-20 dB (<1%) reflectance over 187-317 GHz at a 15° angle of incidence in TE polarization. We also demonstrated that bonding wafers introduce no reflection features above the -20 dB level (also in TE at 15°), reproducing previous work. Together these developments immediately enable construction of wide-bandwidth silicon vacuum windows and represent two important steps toward gradient-index silicon optics with integral broadband antireflection treatment.
尽管高电阻率、低损耗的硅是太赫兹传输光学的优良材料，但其高折射率需要进行抗反射处理。我们通过使用多深度深反应离子刻蚀（DRIE）在硅表面刻蚀亚波长结构，制备了一种宽带双层抗反射处理。在15°入射角的TE偏振下，两面都经过这种处理的晶圆在187 - 317GHz范围内的反射率小于-20dB（<1%）。我们还证明，键合晶圆不会引入高于-20dB水平的反射特征（同样在15°的TE模式下），这重现了之前的工作。这些进展共同使得立即构建宽带硅真空窗口成为可能，并代表了朝着具有整体宽带抗反射处理的梯度折射率硅光学迈出的两个重要步骤。
