A photonic-plasmonic mode converter using mode-coupling-based polarization rotation for metal-inserted silicon platform

We present a photonic-plasmonic mode converter using modecoupling-based polarization rotation for connecting a silicon wire and hybrid plasmonic waveguides on a metal-inserted silicon platform. By using the polarization rotator based on defect-introduced silicon wire waveguide, the proposed mode converter can convert the photonic TE mode into the hybrid plasmonic TM mode. At the beginning, to identify a cross-sectional structure for polarization conversion, we investigate the hybrid parameters that determine the degree of mode rotation using the two-dimensional vector finite element method. Next, using the three-dimensional vector finite element method, we investigate the conversion characteristics of the whole device including input and output ports. Numerical results show that the extinction ratio of 46 dB and the insertion loss of 0.36 dB are achieved. The tolerance of the defect is also numerically evaluated. Our proposed mode converter can reduce insertion losses compared to conventional mode converters based on a taper-introduced butt joint structure.