Subwavelength Structure Enabled Ultra-Long Waveguide Grating Antenna

Because of the high index contrast, current silicon photonics based optical phased arrays cannot achieve small beam divergence and large field-of-view simultaneously without increasing fabrication complexity. To resolve the dilemma, we propose an ultra-long waveguide grating antenna formed by placing subwavelength segments within the evanescent field of a conventional strip waveguide. Bound state in the continuum effect is leveraged to suppress the sidewall emission. As a proof of concept, we theoretically demonstrated a millimeter-long through-etched waveguide grating antenna with a divergence angle of 0.081 degrees and a feature size compatible with current silicon photonics foundries. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement