A tapered waveguide improves insertion loss occurring at the slab/waveguide interface of an optical array waveguide grating (AWG). The tapered waveguide has two segments. The first segment decreases from a first thickness, nearest the slab of the AWG to a second thickness moving away from the slab. The second segment has a substantially constant or uniform thickness equal to the second thickness of the first segment. The second segment may also have a swallowtail shape comprising a forked end having two sidewalls tapered back towards the first segment. Light that would otherwise be lost at the slab/waveguide interface is instead captured by the tapered waveguide which laterally channels the light back into the waveguides thus mitigating insertion loss.