High-efficiency thin-film lithium niobate apodized grating coupler utilizing negative diffraction angle

作者：Rujun Liao, Xiaofen Wang, Cuiwei Xue, Xueling Quan, Liping Xu, Liucheng Fu, Min Liu, Minni Qu, Yunliang Shen, Liying Wu, Xiulan Cheng · 发表于：Optics Express · 年份：2024 · DOI：10.1364/oe.542031 · 被引用次数：6 · 研究领域：Photorefractive and Nonlinear Optics、Photonic and Optical Devices、Advanced Fiber Laser Technologies

Lithium niobate on insulators (LNOI), which is an integrated optoelectronic material platform with essential prospects, has an excellent electro-optical coefficient and a low loss window covering from visible to mid-infrared. However, both the lower refractive index of lithium niobate (LN) and the immaturity of processing techniques cause difficulties in achieving high coupling efficiency in grating couplers. Therefore, an apodized LNOI grating coupler utilizing a negative diffraction angle is proposed. The simulated and experimental coupling efficiencies are -2.1 dB and -2.8 dB at 1550 nm wavelength, respectively, which is the highest efficiency reported for LNOI grating couplers that do not incorporate additional materials or complex fabrication processes. The grating coupler also has high process and test tolerances, making it possible to realize it on different process platforms.