A Tri-Layer Si₃N₄-on-Si Optical Phased Array With High Angular Resolution.

We demonstrate a $1\times 256$ optical phased array based on the tri-layer Si3N4-on-Si platform. By optimizing the thickness and vertical position of the Si3N4 overlay, the grating antenna exhibits a ultra-low emission rate of 13.9 dB/cm at 1550 nm and a large bandwidth of 120 nm. Based on the optimized Si3N4 assisted grating antenna, the OPA realizes an ultra-sharp beam divergence of $0.154^{\circ }\times 0.0435$ , a two-dimensional beam steering range of $45.6^{\circ }\times 16.1$ , and a side lobe suppression ratio better than 10.8 dB. [ABSTRACT FROM AUTHOR]