Hybrid three-arm coupler with long range surface plasmon polariton and dielectric waveguides

The characteristics of hybrid three-arm coupler, which consists of the middle long range surface plasmon polariton waveguide and two outside conventional dielectric waveguides, are analyzed numerically with finite element method. Since the middle arm can only transfer the TM mode from one dielectric arm to the other one, this structure is promising for realizing integrated polarization splitter. Compared with the two-arm hybrid coupler, the loss of three-arm hybrid coupler based device can be reduced. Furthermore, different from conventional three-arm dielectric coupler, the authors find that the three-arm hybrid coupler with asymmetric structure can reach a much higher extinction ratio.