ATE-TM MODE SPLITTER ON LITHIUM-NIOBATE USING TI, NI, AND MGO DIFFUSIONS

A new TE-TM mode splitter with an asymmetric Y-junction structure fabr icated by diffusing different materials into y-cut lithium niobate is presented. Randomly polarized light launched into a titanium indiffuse d waveguide is split into TE and TM modes by two different single-pola rization waveguides. The ordinary-polarized waveguide is made by nicke l indiffusion and the extraordinary-polarized waveguide by magnesium-o xide 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.