Analysis of a Y-branch polarization splitter using the full-vectorial beam-propagation method

The polarization splitter with a Y-branch waveguide is investigated using the full-vectorial beam-propagation method. The splitter consists of a polymer waveguide and a birefringence polyimide that is buried under one branch. Calculation shows that the crosstalk reduces as the branch angle is decreased. For a branch angle of θ=1/400 rad, the splitter yields a crosstalk of less than -25 dB. It is also shown that polarization coupling occurs in the transition region of the Y-branch waveguide.