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 (Si3N4) - waveguide layer (Si) - diffractive layer (Si3N4) buried in SiO2 cladding. The inserted Si3N4 diffraction layers effectively reduce the refractive index contrast between the traditional Si waveguide layer and SiO2 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.