A TE-TM mode splitter on lithium niobate using Ti, Ni, and MgO diffusions

A new TE-TM mode splitter with an asymmetric Y-junction structure fabricated by diffusing different materials into Y-cut lithium niobate is presented. Randomly polarized light launched into a titanium indiffused waveguide is split into TE and TM modes by two different single-polarization waveguides. The ordinary-polarized waveguide is made by nickel indiffusion and the extraordinary-polarized waveguide by magnesium-oxide induced lithium outdiffusion. The measured extinction ratios are greater than 20 dB for both TE and TM modes. The devices operate over a wide wavelength range and have a large fabrication tolerance.<<ETX>>