Highly efficient silicon mode converter and polarization rotator using a silicon-based hybrid plasmonic waveguide

We propose and numerically analyze a broadband, ultracompact hybrid plasmonic mode converter/polarization rotator. The proposed device converts the fundamental transverse magnetic mode (TM 0 ) to the first-order transverse electric mode (TE 1 ). The mode converter is designed using a tapered hybrid plasmonic waveguide in which metal parts are directly surrounding both the input Si waveguide and the tapered output waveguide without a thin low-index layer. After optimizing the proposed structure, a TM 0 -to-TE 1 mode converter with a modal conversion efficiency of 98.2% is achieved. A broad operating bandwidth of 100 nm is achieved with a compact footprint of only 0.8µm×12.5µm for the whole device. At a wavelength of 1550 nm, the insertion loss ranges from 0.91 dB to 1.19 dB using different metal materials, and the extinction ratio of the TE 1 and TM 0 modes is higher than 21 dB in the output Si waveguide.