Apparatus for photoelectrochemical polishing of silicon wafers

An apparatus for the photoelectrochemical polishing of a silicon wafer comprising (a) a photoelectrolytic cell with said silicon wafer, when present, adapted to be an electrode, (b) a waveguide which provides evanescent radiation of predetermined wavelength(s) in close proximity to the surface of said silicon wafer electrode, and (c) means for containing an electrolyte in the space between said silicon wafer surface and said waveguide, said electrolyte having an absorption coefficient for said predetermined wavelength(s) such that said evanescent radiation is reduced to at most 10% of its initial intensity over a path length of 2 microns.