Highly Efficient Ultra-Broad Beam Silicon Nanophotonic Antenna for Two-Dimensional Optical Phased Arrays

we demonstrate a novel design of an ultracompact silicon grating antenna for off-chip light emission, with an unprecedented performance combining a wide far-field beam width of 52° and 62°, a very compact footprint of $3.1 \mu \mathrm{m}\times 1.7 \mu \mathrm{m}$, and a high diffraction efficiency of 82% after incorporating a bottom reflector for improved directionality. This is achieved by a single-etch grating structure and a Bragg reflector designed on a 300-nm-thick SOI platform.