Characterization of a focusing waveguide grating coupler using a Bloch-wave analysis-based local linear grating model and near-field scanning optical microscope

For an efficient characterization of a focusing waveguide grating coupler (FWGC), we proposed a 2-dimensional Bloch-wave analysis-based local linear grating model. We also measured the coupler's focusing characteristics with a near-field scanning optical microscope (NSOM). The proposed model was successfully applied to analyzing two kinds of FWGC's, whose focusing characteristics were compared with those obtained by using the NSOM. From the comparison, we confirmed that the proposed model could be used as an approximate analysis tool.