We present a detailed analysis of a coupler based on the Luneburg lens to couple a silica waveguide to a photonic crystal (PhC) waveguide. The dependence of coupling efficiency on the lens’s truncation, cut position of the PhC structure, coupler tip width, and misalignment are investigated with a two-dimensional finite element method. We implement the lens with a concentric ring-based multilayer structure. We also present a method to replace layers with very narrow widths by layers of predetermined minimum widths in the structure of the lens. The coupling loss of the designed 2.7-µm-long coupler, connecting a 2.79-µm-wide silica waveguide to a PhC structure with a rod-type square lattice, is lower than 0.49 dB in the C-band. The average coupling loss in the entire S, C, L, and U bands of optical communications is 0.70 dB.

中文翻译：

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通过多层Luneburg透镜将二氧化硅波导耦合到光子晶体波导

我们介绍基于Luneburg透镜的耦合器的详细分析，以将二氧化硅波导耦合到光子晶体（PhC）波导。用二维有限元方法研究了耦合效率对透镜截断，PhC结构的切割位置，耦合器尖端宽度和未对准的影响。我们使用基于同心环的多层结构来实现该镜头。我们还提出了一种在透镜结构中用预定最小宽度的层替换宽度非常窄的层的方法。设计的2.7 µm长的耦合器将宽2.79 µm的二氧化硅波导连接到具有杆型方格的PhC结构上，其耦合损耗在C波段低于0.49 dB。光通信的整个S，C，L和U频带中的平均耦合损耗为0.70 dB。