Frank Felix, Verstuyft Mattias, Teigell Beneitez Nuria, Missinne Jeroen, Roelkens Gunther, van Thourhout Dries, Lendl Bernhard
Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9, 1060 Wien, Austria.
Photonics Research Group, Ghent University-imec, Technologiepark-Zwijnaarde 126, 9052 Gent, Belgium.
ACS Appl Opt Mater. 2024 Aug 20;2(9):1926-1932. doi: 10.1021/acsaom.4c00280. eCollection 2024 Sep 27.
Alignment tolerant coupling interfaces are an important feat for mid-IR waveguides when moving closer to real-world sensing applications, as they allow for an easy and fast replacement of waveguides. In this work, we demonstrate the alignment tolerant behavior of a germanium-on-silicon trenched waveguide platform with monolithically integrated microlenses using backside coupling of an expanded beam for evanescent field sensing between 6.5 and 7.5 μm. The chip with a propagation loss of approximately 5 dB/cm was mounted and aligned, using active alignment, in a sample holder that could be moved in all three dimensions to induce misalignments with a precision of the manual actuator of 1.3 μm. Using this setup, the in-plane 1 dB alignment tolerances were measured to be ±16 μm, while the 1 dB alignment tolerances in the longitudinal direction were found to be larger than ±150 μm. Without the addition of the microlenses, we expect an in-plane 1 dB alignment tolerance of ±3 μm based on simulations. Additionally, it could be demonstrated that the integration of the microlenses significantly improves the stability of the broadband grating couplers in regard to misalignment-induced intensity changes in the obtained transmission spectra.
对于中红外波导而言，当更接近实际传感应用时，对准容忍耦合接口是一项重要成果，因为它们允许轻松快速地更换波导。在这项工作中，我们展示了一种硅基锗沟槽波导平台的对准容忍行为，该平台具有单片集成微透镜，通过扩展光束的背面耦合用于6.5至7.5μm之间的倏逝场传感。将传播损耗约为5dB/cm的芯片使用主动对准安装并对准在一个样品架中，该样品架可以在三个维度上移动，以产生精度为1.3μm的手动致动器的失准。使用该设置，测得面内1dB对准容差为±16μm，而纵向1dB对准容差大于±150μm。根据模拟，在不添加微透镜的情况下，我们预计面内1dB对准容差为±3μm。此外，可以证明，微透镜的集成在由失准引起的所得传输光谱强度变化方面显著提高了宽带光栅耦合器的稳定性。
