An optical device comprises a substrate layer having an upper surface, and a waveguide layer over the upper surface of the substrate layer. The waveguide layer comprises an input waveguide defined by a first waveguide portion having a first refractive index; an input slab defined by the first waveguide portion, the input slab adjoined with the input waveguide; and a microlens array defined by a second waveguide portion having a second refractive index that is different from the first refractive index. The microlens array is in optical communication with the input waveguide through the input slab. The microlens array is configured to receive a diverging planar light beam from the input slab along a direction of propagation. The microlens array is configured to control a far-field emission of the light beam such that an emission profile of the light beam exhibits a substantially uniform intensity.