An apparatus includes an optical rib waveguide on a substrate, the optical rib waveguide further includes: a slab layer of silicon, a shallow rib of silicon in height that tapers laterally along a taper region, a deep rib of silicon that meets the shallow rib along the taper region of the shallow rib, and wherein the deep rib and the shallow rib have a same width, and wherein the shallow rib has a greater height than the deep rib, a core of silicon that tapers laterally in a range of 50-90% and extends on top of the deep rib and the shallow rib, and a cladding layer of silicon oxide that covers the slab, core, deep rib, and shallow rib.