Optical waveguides in porous silicon pre-patterned by localised nitrogen implantation.

FIPOS technology forms islands of silicon isolated from a silicon substrate by (oxidised) porous silicon. The larger refractive index of the silicon i slands suggests their use as optical waveguides. Sets of these silicon isla nds have been fabricated and the anticipated waveguiding has been observed at wavelengths of 1.15 and 1.3 mu m in the silicon islands. However, the do minant waveguiding in these FIPOS structures is observed in the porous sili con between the silicon islands, close to the sample surface. A simple dyna mic model of the anodisation process has been developed to explain the orig in of this unexpected waveguiding. (C) 1999 Elsevier Science B.V. All right s reserved.