Focusing grating couplers for the excitation of the fundamental transverse-magnetic (TM) mode in integrated silicon photonic waveguides are designed and characterized under the boundary conditions of a photonic BiCMOS foundry. Two types of waveguide geometries are considered – a nanowire and a rib waveguide. Wafer-scale experimental results for nanowire TM grating couplers are in excellent agreement with numerical investigations and demonstrate a robust behavior on the wafer. The mean coupling loss and the 3σ interval are -3.9 ± 0.3 dB. The on wafer variation is three times lower than for the fundamental transverse-electric (TE) polarization. Similarly, the coupling in rib waveguides is examined as well. The results indicate that the rib waveguides require a modified geometry when designed for TM. In general, the nanowire waveguide type is more suitable for TM coupling, showing a stable and repeatable performance.

中文翻译：

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光子BiCMOS技术中横向磁TM ₀₀模式集成聚焦光栅耦合器的设计和性能分析

在光子BiCMOS铸造厂的边界条件下，设计并表征了聚焦光栅耦合器，用于激发集成硅光子波导中的基本横向磁（TM）模式。考虑了两种类型的波导几何形状–纳米线和肋形波导。纳米线TM光栅耦合器的晶圆级实验结果与数值研究非常吻合，证明了在晶圆上的稳健性能。平均耦合损耗和3σ间隔为-3.9±0.3 dB。晶圆上的变化比基本横向电（TE）极化低三倍。类似地，还检查了肋形波导中的耦合。结果表明，当为TM设计时，肋形波导需要修改的几何形状。一般来说，