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利用不同占空比的亚波长结构剪裁光栅槽的等效折射率来改变光栅的衍射特性实现衍射输出光束与单模光纤之间的模式匹配,通过优化埋氧化层厚度和集成底部金反射镜,可以改善光栅耦合器弱的方向性,从而设计出用于SOI波导与光纤之间高效率耦合的光栅耦合器。采用本征模展开方法,模拟了光栅耦合器随剪裁的光栅槽等效折射率变化的相关特性,在SOI波导和单模光纤之间对波长为1550nm的光获得了最高93.1%的耦合效率,3dB带宽为82nm。
The sub-wavelength structure with different duty cycle is used to cut the equivalent refractive index of the grating groove to change the diffraction characteristic of the grating to realize the pattern matching between the diffraction output light beam and the single mode fiber. By optimizing the thickness of the buried oxide layer and integrating the gold reflecting mirror at the bottom, The weak directivity of the grating coupler can be improved, thereby designing a grating coupler for efficient coupling between the SOI waveguide and the optical fiber. The eigenmode expansion method is used to simulate the correlation characteristics of the grating coupler with the change of the equivalent refractive index of the grooved grating. The coupling efficiency between the SOI waveguide and the single mode fiber is up to 93.1% for the light with the wavelength of 1550 nm, 3dB bandwidth is 82nm.