Novel hybrid method for efficient 3-D fiber-to-chip coupling analysis

An efficient hybrid method has been developed to analyze, for the first time, the three-dimensional problem of fiber-to-chip coupling. The method employs the numerical finite difference beam propagation method to model the fields in the planar chip guide and the semi-analytical free space radiation mode method to model the fields in the fiber guide. The two methods are linked via an iterative algorithm. The results for the transmission, backreflection, and radiation losses are presented for the case of direct butt-coupling and coupling via an antireflection coating. Finally, the effect of the vertical misalignment is analyzed and results are compared with the ones obtained experimentally.