利用反射式光栅和分布布喇格反射镜的反射特性, 分别从光栅耦合器的侧面和底部对光进行高反射, 通过合理选取反射光栅和耦合光栅的间距使两组光栅的反射光实现相消干涉来减弱耦合光栅在实现垂直耦合时存在的负二阶反射, 从而设计出高效率垂直耦合的光栅耦合器.采用本征模展开方法, 模拟计算了垂直耦合光栅耦合器的耦合效率随不同结构参量而变化的相关特性, 在绝缘体硅平面波导和单模光纤之间对波长1 550 nm的光获得了最高89%的耦合效率.所得结果对实际垂直耦合光栅耦合器的制备具有一定参考价值.

A high-efficiency grating coupler is designed for vertical coupling between silicon-on-insulator waveguides and single-mode fibers. The reflection characteristics of reflector grating and distributed bragg reflector are employed to obtain a high reflection from the right side and bottom of the coupler. The reflected light is interfered destructively to reduce the negative second-order reflection by selecting a reasonable spacing between the reflector grating and the coupler grating when the coupler grating is in the vertical coupling. The coupler is optimized using eigenmode expansion-based simulations. The highest coupling efficiency of 89% at a wavelength 1 550 nm is achieved by simulation. The results provide some useful references for the fabrication of the actual vertical coupling grating coupler.