Disclosed are apparatus and methods for optical coupling in optical communications. In one embodiment, an apparatus for optical coupling is disclosed. The apparatus includes: a planar layer; an array of scattering elements arranged in the planar layer at a plurality of intersections of a first set of concentric elliptical curves crossing with a second set of concentric elliptical curves rotated proximately 90 degrees to form a two-dimensional (2D) grating; a first taper structure formed in the planar layer connecting a first convex side of the 2D grating to a first waveguide; and a second taper structure formed in the planar layer connecting a second convex side of the 2D grating to a second waveguide. Each scattering element is a pillar into the planar layer. The pillar has a top surface whose shape is a concave polygon having at least 6 corners.