A polarization-insensitive $2\times 2$ thermo-optic Mach–Zehnder switch (MZS) on silicon is proposed and demonstrated experimentally by utilizing silicon-on-insulator (SOI) nanophotonic waveguides with a 340-nm-thick silicon core layer. The present MZS consists of two $2\times 2$ 3 dB multimode interference (MMI) couplers, which are designed to be polarization-insensitive by choosing the core width optimally. Meanwhile, the MZS arms are designed with square SOI nanophotonic waveguides with a cross section of $340\mathrm{nm}\times 340\mathrm{nm}$ in order to achieve polarization-insensitive phase shift. The fabricated silicon MZS has an excess loss of $1\sim 4\mathrm{dB}$ and an extinction ratio of $>20\mathrm{dB}$ in the C-band ($1530\sim 1565\mathrm{nm}$) for both TM and TE polarizations.

中文翻译：

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偏振不敏感的2×2热光Mach–Zehnder开关在硅上

偏振不敏感 $\mathrm{2个}\times \mathrm{2个}$提出并通过利用绝缘体上硅（SOI）纳米光子波导和340 nm厚的硅芯层，对硅上的热光马赫曾德尔开关（MZS）进行了实验演示。目前的MZS包括两个$\mathrm{2个}\times \mathrm{2个}$3 dB多模干扰（MMI）耦合器，通过最佳选择磁芯宽度，设计成对偏振不敏感的。同时，MZS臂设计有方形SOI纳米光子波导，其横截面为$340\mathrm{纳米}\times 340\mathrm{纳米}$为了实现对极化不敏感的相移。所制造的硅MZS具有过量的损耗$\mathrm{1个}〜4\mathrm{D\; b}$ 消光比为 $>20\mathrm{D\; b}$ 在C波段（$1530〜1565\mathrm{纳米}$）对于TM和TE极化。