Thick SiO2 layer produced by anodisation

A method for oxidising porous silicon to obtain thick SiO2 as the cladding layer of silicon-based silica waveguides is presented. The experimental res ults of oxidation are given. The following conclusions are drawn: the oxida tion rate of porous silicon is several orders higher than that of bulk sili con, the appropriate temperature variation rate during oxidation combined w ith proper porosity can prevent SiO2 on silicon substrates from cracking. a nd a 25 mu M thick silicon dioxide layer has been obtained.