Two-dimensional grating coupler with a low polarization dependent loss of 025 dB covering the C-band

We design and demonstrate a two-dimensional grating coupler (2D GC) with a low polarization dependent loss (PDL) based on the silicon-on-insulator (SOI) platform. Using a grating cell consisting of five cylinders and carefully optimizing the distances between the cylinders, a maximum PDL of 0.25 dB covering the C-band is realized, which is 1.25 dB better than a conventional 2D GC with a single cylinder etching pattern fabricated on the same SOI wafer.