A trilayer waveguide grating antenna with offset etching grooves for high directionality and large effective length

Abstract In this study, a trilayer waveguide grating antenna with offset etching grooves is proposed, the trilayer waveguide composed of a diffractive layer (Si 3 N 4 ) - waveguide layer (Si) - diffractive layer (Si 3 N 4 ) buried in SiO 2 cladding. The inserted Si 3 N 4 diffraction layers effectively reduce the refractive index contrast between the traditional Si waveguide layer and SiO 2 cladding, which diminishes the disturbance coefficient of the conventional antenna, resulting in a large effective length. In addition, the offset etching grooves located on the diffraction layers break the vertical symmetry of the antenna, which enhances the directionality markedly. Simulation results demonstrate a directionality exceeding 87% and a beam steering range of 6.9° along the θ axis in a range of wavelength from 1500 nm to 1600 nm. Specifically, at a wavelength of 1550 nm, the peak directivity of the antenna exceeds 96% while the maximum effective length exceeds 4.4 mm.