Chirped and apodized grating couplers were designed, fabricated and characterized in lithium niobate thin film for fiber-to-chip coupling. The maximum coupling efficiency of -1.8 dB and -6.9 dB for TE mode at a wavelength of 1550 nm was simulated and measured, respectively. The discrepancies were mainly attributed to the different fabrication errors of local periods and groove widths, which hampered the mode matching condition heavily. In addition, when a metal bottom reflector was added, the simulated and measured coupling efficiency were improved to -0.8 dB and -5.5 dB, respectively.

中文翻译：

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铌酸锂薄膜上的啁啾和切趾光栅耦合器

在用于光纤到芯片耦合的铌酸锂薄膜中设计、制造和表征啁啾和切趾光栅耦合器。分别模拟和测量了波长为 1550 nm 的 TE 模式的最大耦合效率为 -1.8 dB 和 -6.9 dB。差异主要归因于局部周期和凹槽宽度的不同制造误差，这严重阻碍了模式匹配条件。此外，当添加金属底部反射器时，模拟和测量的耦合效率分别提高到 -0.8 dB 和 -5.5 dB。