End-fire silicon optical phased array with half-wavelength spacing

We demonstrate an optical phased array with emitting elements spaced at half the operational wavelength. The device is a one-dimensional array fabricated on an integrated silicon platform for operation at a wavelength of 1.55 μm. Light is emitted end-fire from the chip edge where the waveguides are terminated. The innovative design and high confinement afforded by the silicon waveguides enables λ/2 spacing (775-nm pitch) at the output thereby eliminating grating lobes and maximizing the power in the main lobe. Steering is achieved by inducing a phase shift between the waveguide feeds via integrated thermo-optic heaters. The device forms a beam with a full-width half-maximum angular width of 17°, and we demonstrate beam steering over a 64° range limited only by the element factor.