High Efficiency Tapered Waveguide Antenna for End-fire Optical Phased Array Device

The optical signal injected into an end -fire optical phased array propagates along the waveguides inside the device and is emitted from the edge of the antenna. In general, reflection and scattering occur at the boundary, thereby reducing the emission efficiency of the optical signal. In this article, we propose a silicon nitride (Si 3 N 4 ) tapered waveguide antenna structure whose width is tapered toward the emitting edge, achieving high emission efficiency operating at the 1,550 nm wavelength. The Si 3 N 4 tapered waveguide antenna was numerically designed using the 3D finite-difference timedomain method. The optical signal emission efficiency increased from 78% to 96.3%, while reflectance decreased from 22% to 3.7% compared with the untapered waveguide antenna counterpart. This result will not only boost the optical signal intensity but also mitigate optical noise resulting from back reflection along the waveguide in the end -fire optical phased array device.