By high-dose MeV oxygen implantation into 6H-SiC bulk crystals at temperatures between 650 degrees C and 700 degrees C buried SiC-SiOx layers were produced. In the infrared and visible region these layers exhibit a refractive index which is significantly reduced with respect to the virgin SIC making them useable as cladding layers for SIC waveguides. For the first time waveguiding at lambda = 633 nm was demonstrated after annealing such an ion implanted SiC-SiO, layer system. (C) 1998 Elsevier Science B.V. All rights reserved.