Vertical directional coupling based grating emissionengineering for optical phased arrays

In this Letter, a novel, to the best of our knowledge, verticaldirectional coupling waveguide grating (VDCWG) archi-tecture is proposed to inerease the length of waveguidegrating antennas for large aperture on-chip optical phasedarrays (OPAs). In this new architecture, the grating emissionstrength is engineered by the vertical directional coupler,which provides additional degrees of design freedom. The-oretical analysis and numerical simulation show that the VDCWG can adjust the grating strength in the range ofmore than two orders of magnitude, corresponding to aneffective grating length more than a centimeter. For proof-of-concept, a VDCWG antenna with a length of 1.5 mm isexperimentally demonstrated, The grating strength is meas-ured to be 0.17mm^-1, and the far-field divergence angle is 0.061°. A 16-channel OPA is also developed based on theproposed VDCWG, which proves the potential of the newarchitecture for large aperture OPAs. 

DOI: 10.1364/0L.524198