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 (TM0) to the first-order transverse electric mode (TE1). 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 TM0-to-TE1 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 0.8 mu m x 12.5 mu m 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 TE1 and TM0 modes is higher than 21 dB in the output Si waveguide. (c) 2023 Optica Publishing Group