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 the lower cladding, is reported. The waveguides were designed with a cross-section comparable in size to the mode-field-diameter of standard single-mode optical fiber, so reducing the fiber-waveguide coupling losses. Propagation losses of about 1.0 dB/cm, for lambda = 1. 3 mum, in the single mode regime, have been measured. Numerical evaluation of the theoretical attenuation and the transverse optical Weld profiles has been performed, both for lambda = 1.3 mum and lambda = 1.55 mum. The proposed technique is low-cost, fully compatible with standard very large scale integration (VLSI) processes.