Radiation-Enhanced Crosstalk Suppression for Silicon Waveguide Grating Antenna by Harnessing Bound States in the Continuum

Waveguide grating antenna arrays offer an integrated-photonic route to optical beam emission and steering for applications such as free-space optical communication, light detection and ranging (LiDAR), and holographic projection display, but crosstalk between adjacent antennas limits their integration density. In radiative waveguide gratings, crosstalk is not governed solely by evanescent-field coupling; grating-assisted coupling mediated by radiation field can provide an additional contribution. Here, a bound-state-in-the-continuum (BIC)-based approach is proposed and experimentally demonstrated to suppress this contribution. Using quasi-BIC (qBIC)-enabled diffraction engineering, sideward radiation from the grating is selectively suppressed through destructive interference, thereby eliminating the radiation-mediated coupling channels. Compared with non-BIC fishbone grating exhibiting strong sideward radiation, qBIC grating reduces interantenna crosstalk to a level comparable to that of strip waveguide with the same width. As a system-level illustration, qBIC-optimized waveguide gratings are used as the emitting antennas in an optical phased array. The proposed approach highlights qBIC-enabled radiation-channel engineering as a promising route to mitigating crosstalk constraints in the high-density integration of waveguide grating antennas.