Lees Harrison, Gao Weijie, Withayachumnankul Withawat
Opt Lett. 2021 Nov 1;46(21):5469-5472. doi: 10.1364/OL.436039.
All-silicon effective-medium-clad waveguides are a promising candidate for an integrated terahertz platform with high efficiency and broad bandwidth. Waveguide crossings are essential circuit components, allowing for wave routing over shorter paths to increase circuit density. However, the simple intersection of two orthogonal effective-medium-clad waveguides results in terahertz wave scattering, leading to relatively high cross talk. In this work, a low-loss, 40% fractional bandwidth crossing utilizing Maxwell-Garnet effective-medium theory and wavefront planarization techniques is proposed. This monolithic structure is fabricated on a single high-resistivity float-zone silicon wafer using a deep reactive ion etching process with a modest 4.4 mm diameter (4.03) structure footprint. Experimentally verified results show low insertion loss, less than 1 dB, and average cross talk level of -39 for both 11 and 11 operating modes, over 220-330 GHz with a 40% fractional bandwidth. This waveguide crossing can be foreseen as a useful routing component for terahertz all-silicon integrated circuits. The proposed techniques are applicable to other dielectric waveguide platforms at infrared and optical frequencies.
全硅有效介质包层波导是构建高效、宽带宽集成太赫兹平台的一个有潜力的选择。波导交叉是关键的电路组件，能使波在较短路径上进行路由，从而提高电路密度。然而，两个正交的有效介质包层波导简单相交会导致太赫兹波散射，进而产生相对较高的串扰。在这项工作中，利用麦克斯韦 - 加尼特有效介质理论和波前平面化技术，提出了一种低损耗、分数带宽为40%的交叉结构。这种单片结构是在单个高电阻率浮区硅片上通过深反应离子蚀刻工艺制造的，其结构占地面积适中，直径为4.4毫米（4.03）。实验验证结果表明，在220 - 330吉赫兹、分数带宽为40%的情况下，对于11和11两种工作模式，插入损耗均低于1分贝，平均串扰水平为 -39分贝。这种波导交叉有望成为太赫兹全硅集成电路中一个有用的路由组件。所提出的技术适用于红外和光频的其他介质波导平台。
