Vertical integration...yes in the physical sense as well. Technically speaking the optical interposer addresses both vertical and lateral implementation. 

1. A photonic integrated circuit (PIC) grown by epitaxy on a substrate, the PIC comprising:

at least one active element formed over a first portion of the substrate, wherein the substrate and the at least one active element are formed using a III-V compound semiconductor material;

a III-V compound semiconductor waveguide formed over a second portion of the substrate, wherein the III-V compound semiconductor waveguide is formed from a III-V compound semiconductor structure, and wherein the III-V compound semiconductor structure is formed by etching the substrate; and

a dielectric waveguide, formed over a third etched portion of the substrate, such that the dielectric waveguide is in optical contact with the at least one active element by way of the III-V compound semiconductor waveguide, and abuts the III-V compound semiconductor waveguide.

8. The PIC of claim 1, wherein the PIC comprises an alloy of at least one of InGaAsP, AlGaAs, and InGaAlAs.