Experimental demonstration of silicon nitride waveguide gratings with excellent effciency and divergence angle

Abstract Silicon nitride (Si 3 N 4 ) photonic platform has recently attracted increasing attention for Si 3 N 4 photonic integrated circuits (PIC). A diffraction grating with the only etched top-layer in tri-layer Si 3 N 4 optical waveguides is proposed, which shows a simple fabrication process, high upward diffraction effciency and lower far-field divergence angle. The measured results of the diffraction grating at a wavelength of 905nm show the average upward diffraction effciency of 90.5% and average far-field divergence angle of 0.154°, which shows a good agreement with the design results with the upward diffraction effciency of 91.6% and far-field divergence angle of 0.105°.