In an example, a photonic system includes a Si PIC with a Si substrate, a SiO2 box formed on the Si substrate, a first layer, and a second layer. The first layer is formed above the SiO2 box and includes a SiN waveguide with a coupler portion at a first end and a tapered end opposite the first end. The second layer is formed above the SiO2 box and vertically displaced above or below the first layer. The second layer includes a Si waveguide with a tapered end aligned in two orthogonal directions with the coupler portion of the SiN waveguide such that the tapered end of the Si waveguide overlaps in the two orthogonal directions and is parallel to the coupler portion of the SiN waveguide. The tapered end of the SiN waveguide is configured to be adiabatically coupled to a coupler portion of an interposer waveguide.