为了研究光纤与宽波导光栅的有效耦合,基于高斯光束与波导光栅的光耦合理论,以30 μm 宽波导光栅为研究对象,利用矩阵光学和高斯光束理论分析和设计了一种扩束光纤,并通过分析其耦合损耗,建立了扩束光纤与波导光栅耦合模型。优化所设计扩束光纤的结构参数后,得到束腰半径为10.8 μm 的输出光束。最后分析了扩束光纤的结构容差,并讨论了所设计扩束光纤的输出光束、单模光纤的输出光束以及束腰半径为16 μm 的自由空间高斯光束各自在光栅表面的位置变化对光栅耦合效率的影响。可知扩束光纤输出的光束与单模光纤输出的光束相比具有较大的位置容差,与束腰半径为16 μm 的自由空间高斯光束相比,光耦合效率基本相同。

In order to study the effective coupling between optical fiber and wide waveguide grating (≥30 microns), an expand core fiber is designed for a given wide waveguide grating of 30 microns based on the theory of coupling Gaussian beam into waveguide grating, by using the method of matrix optics technologies and Gaussian beam theories. After the coupling loss is analyzed, the model of coupling expand core fiber with waveguide grating is built. By optimizing the structure of the fiber, 10.8 microns waist radius of output beam is obtained theoretically. At last the structure tolerance of the expand core fiber is studied. And then the optical coupling efficiency imposed by the position of Gaussian beam on the grating is discussed by comparing the Gaussian beam output from expand core fiber, single mode fiber and free space Gaussian beam with waist radius of 16 microns. The results are that the position tolerance of the expand core fiber is more than that of single mode fiber and almost the same as that of Gaussian beam with waist radius of 16 microns.