Design and characterization of an out-of-plane polymer waveguide grating coupler

A polymer waveguide grating coupler to vertically couple light between planar waveguide and fiber is proposed and designed. In order to estimate the coupling performance of the proposed coupler with curved and chirped grating, the diffraction characteristics of the waveguide grating with a uniform period as an in/out out-of-plane coupler are investigated. The coupling efficiency and coupling length exhibiting the diffraction characteristics of a uniform waveguide grating with various structure parameters are calculated based on Bloch-wave analysis. With the optimized structure parameters showing the high coupling performance, the overall coupling efficiency of the polymer waveguide grating coupler is obtained by introducing 2D Bloch-wave analysis-based local linear grating model. The calculated overall coupling efficiency of the coupler is determined to be approximately 30%.