this is a fabrication process for y - branch nickel / zinc - indiffused polarization splitters on lithium niobate . the fabrication technology needs only two nickel / zinc indiffusions ; one at a high temperature and the other at a lower temperature . nickel / zinc - indiffused waveguides can support single - ordinary , single - extraordinary , and random polarization waves depending on the fabrication process parameters . high extinction ratios can be achieved due to the inherent single - polarization of the waveguides . the splitting ratios of the te and tm modes are sufficiently high for practical applications .