An optical integrated circuit (IC) structure includes: a substrate including a fiber slot formed in an upper surface of the substrate and extending from an edge of the substrate, and an undercut formed in the upper surface and extending from the fiber slot; a semiconductor layer disposed on the substrate; a dielectric structure disposed on the semiconductor layer; an interconnect structure disposed in the dielectric structure; a plurality of vents that extend through a coupling region of the dielectric structure and expose the undercut; a fiber cavity that extends through the coupling region of dielectric structure and exposes the fiber slot; and a barrier ring disposed in the dielectric structure, the barrier ring surrounding the interconnect structure and routed around the perimeter of the coupling region.