Large effective length and high efficiency by embedding L-shaped radiating blocks in subwavelength grating slot waveguide

Abstract

Abstract Integrated optical antennas featuring large effective lengths and high radiation efficiency (RE) are essential to chip-scale light detection and ranging technology. However, there are challenges in simultaneously achieving both large effective length and high RE in silicon photonics platforms with high refractive index contrast. For traditional silicon waveguide grating antennas based on silicon photonics, the RE is relatively low and the antenna effective lengths are constrained to several hundred micrometers because of the high refractive index contrast. In this article, an embedded grating waveguide antenna which is L-shaped radiating blocks embedded in the slot gap of a silicon subwavelength grating slot waveguide is proposed and investigated numerically. Simulation results indicate the antenna’s effective length is above 4.25 mm, and the far-field divergence angle is near 0.0197°. Using L-shaped radiation blocks can break the diffraction’s perpendicular symmetry and increase the antenna’s RE to near 0.75 at 1550 nm compared to traditional design. Meanwhile, the antenna’s field-of-view reaches around 17.5° × 48.15° (θ× ϕ) to satisfy the needs of conventional optical phased arrays.