采用193-nm DUV光刻的二维光栅耦合器实现高效偏振分集光纤-芯片耦合的实验验证
Experimental Demonstration of Efficient and Polarization-Diversity Fiber-Chip Coupling by 2D Grating Couplers with 193-nm DUV Lithography
AI总结：
本研究提出并实验验证了一种基于双层介质结构激发多极共振的高效二维光栅耦合器，采用193-nm DUV光刻制备，实现了低损耗、宽带宽、低偏振相关损耗的光纤-芯片垂直耦合，可推广至多集成光学平台。
摘要：
二维（2D）衍射光栅为平面光子芯片与光纤之间提供了一种偏振无关的耦合解决方案，具有放置灵活、制备简便、对准误差容限高等优势。在本研究中，我们首次提出并通过实验验证了一种高效2D光栅耦合器，该耦合器通过双层介质结构激发多极共振实现性能提升。我们提出的2D光栅耦合器采用了70-nm浅刻蚀孔阵列和160-nm厚的沉积多晶硅齿阵列结构。通过可从商业硅光子代工厂便捷获取的193-nm深紫外（DUV）光刻工艺，该结构可实现强光场限制和增强的辐射方向性。实验测得的峰值耦合效率为-2.54 dB，最小特征尺寸为180 nm。我们的设计3-dB带宽约为23.4 nm，且具备良好的光纤位置容限。得益于完全垂直耦合的优势，实验测得的偏振相关损耗在3-dB工作带宽内低于0.3 dB。我们提出的2D光栅结构和设计方法也可应用于其他集成光学平台，在降低特征尺寸要求的同时，实现光纤与光子芯片之间的高效偏振分集耦合。
英文摘要：
Two-dimensional (2D) diffraction gratings offer a polarization-independent coupling solution between the planar photonic chips and optical fibers, with advantages including placement flexibility, ease of fabrication, and tolerance to alignment errors. In this work, we first proposed and experimentally demonstrated a highly efficient 2D grating coupler enabled by exciting multipolar resonances through bi-level dielectric structures. A 70-nm shallow-etched hole array and a 160-nm-thick deposited polycrystalline silicon tooth array are employed in our proposed 2D grating coupler. Strong optical field confinement and enhanced radiation directionality can thus be attained through the use of 193-nm deep-ultraviolet (DUV) lithography, which is readily accessible from commercial silicon photonics foundries. The measured experimental peak coupling efficiency is -2.54 dB with a minimum feature size of 180 nm. Our design exhibits a 3-dB bandwidth of around 23.4 nm with good positioning tolerance for optical fibers. Due to the benefits of perfectly vertical coupling, the measured polarization-dependent loss in our experiments is below 0.3 dB within the 3-dB working bandwidth. Our proposed 2D grating structure and design method can also be applied to other integrated optics platforms, enabling an efficient and polarization-diversity coupling between optical fibers and photonic chips while reducing requirements on feature size.
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