Low loss all-silicon single mode optical waveguide with small cross-section

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 waveguides were designed with a cross-s ection comparable in size to the mode-field-diameter of standard single-mod e optical fiber, so reducing the fiber-waveguide coupling losses. Propagati on losses of about 1.0 dB/cm, for lambda = 1. 3 mum, in the single mode reg ime, have been measured. Numerical evaluation of the theoretical attenuatio n and the transverse optical Weld profiles has been performed, both for lam bda = 1.3 mum and lambda = 1.55 mum. The proposed technique is low-cost, fu lly compatible with standard very large scale integration (VLSI) processes.