An optical bus of an integrated circuit comprises: a polymer waveguide, a micromirror, and an optical coupler. The polymer waveguide is disposed in a via formed through at least one die layer of the integrated circuit comprising an active circuit. The micromirror is disposed adjacent to the via and optically coupled to the polymer waveguide. The optical coupler is connected to the polymer waveguide to couple the active circuit to the optical bus. A stacked integrated circuit is described comprising such an optical bus. A method of fabricating a rear 45° micromirror on a silicon substrate that can be used in the optical bus is also described. Furthermore, alignment/lock mechanisms for use in a stacked integrated circuit comprising first and second silicon substrates are described.