Unidirectional large-scale waveguide grating with uniform radiation for optical phased array

Abstract

Two novel waveguide gratings for optical phased array transmitters are investigated. By offsetting the grating structures along the waveguide on the upper and lower surfaces of the silicon nitride (Si3N4) waveguide, the dual-level chain and dual-level fishbone structures can achieve 95% of unidirectional radiation with a single Si3N4 layer by design. With apodized perturbation along the gratings, both structures can achieve uniform radiation without compromising the unidirectional radiation performance. In experiment, both demonstrate ∼ 80-90% unidirectionality. With further analysis, it is found that the dual-level fishbone structure is more feasible and robust to process variations in uniform radiation.

High-performance millimeter-scale silicon grating emitters for beam steering applications

“…Unfortunately, through the simulated result, the unidirectionality of our device only exceeds 46.2%, which can be improved by dual-layer grating misalignment [21] . At the wavelength of 1550 nm, the far-field beam profile for our proposed grating with the approximate Gaussian near-field emission intensity is shown in Fig.…”

“…In addition, the downward radiant power of the grating always introduces destructive interference, which reduces the performance of the grating emitter. An effective approach of dual-layer grating misalignment has been proposed, consequently achieving more than 95% unidirectional radiation [21] .…”

High-Efficiency Grating Couplers for Pixel-Level Flat-Top Beam Generation

“…Light propagating from left to right within the waveguide will encounter shallowly or fully etched grooves which act as a phased array of scatterers and couple light out of the plane efficiently. As shown in Figure 1c, assuming that light is emitted from the center of the sidewall of the groove [54], the phase difference between light propagating from the fully etched grating and the shallowly etched grating can be decomposed into a vertical phase difference and a lateral phase difference. When the vertical and lateral phase differences accumulate π/2 phase shifts, respectively, constructive interference in the upward direction and destructive interference in the downward direction can be realized, and then unidirectional radiation can be achieved.…”

Focal plane array with small-scale grating antenna receiving array for LiDAR

“…Additionally, the blind spot issue significantly limits the range of LiDAR detection as well 16,17 . According to the guided mode theory, we can easily analyze that there is both upward (free space) and downward (substrate) energy radiation in the antenna.…”