Single-lobe steering of blue light with an active optical phased array

Integrated optical phased arrays for visible light have applications in displays, underwater communication, and biophotonics. However, the λ/2 emitter pitch required for single lobe emission is challenging to realize given the feature size limitations of conventional silicon photonics fabrication. Here, we use a free-propagation region slab, which acts as a spatial filter, to achieve single lobe steering at λ = 488 nm. We demonstrate an optical phased array consisting of a thermo-optically-tuned end-fire waveguide array coupled to a slab grating emitter and show a single-lobe beam-steering range of 52.8º with an average sidelobe level of -11.6 dB. In this proof-of-concept device, the number of resolvable spots is limited to 15 by the end-fire array size, and simulations are presented to investigate the scaling of this device architecture.