Silicon-on-silicon rib waveguides with a high-confining ion-implanted lower cladding

The realization of single-mode rib waveguides in standard epitaxial silicon layer on lightly doped silicon substrate, using ion implantation to form t he lower cladding, is reported. The implanted buffer layer enhances the ver tical confinement and improves the propagation characteristics. Respect to similar standard all-silicon waveguides a propagation loss reduction of abo ut 7 dB/cm, in the single-mode regime, has been measured. A numerical analy sis has been performed to evaluate the theoretical attenuation and the tran sverse optical field profiles, As a result of the presence of the ion impla nted buffer layer, an increase of the fundamental mode confinement factor f rom 0.3 to 0.85 has been calculated. This results in a great enhancement of the coupling efficiency with standard single-mode optical fibers, Moreover , the proposed technique is low cost, fully compatible with standard VLSI p rocesses, and allows a great flexibility in the integration of guided-wave devices and electronic circuits. Finally, the very high thermal conductivit y characterizing these waveguides makes them attractive host-structures for electrically and thermally controlled active optical devices.