Experimental characterization of Inverse-Designed Vertical Grating Couplers in the O-band

We perform wafer-level testing of perfectly vertical grating couplers in a c-Si 193nm DUV immersion lithography process. We designed single polarization grating couplers using the adjoint method and experimentally obtain an insertion loss of 1.91dB, a 18.9nm 1dB-bandwidth, and <−10dB in-waveguide reflection.