LAUSR

A novel polarization mode converter bridging a conventional embedded silicon strip waveguide and a metal-capped hybrid plasmonic waveguide is proposed. Innovative design principles based on gradient ascent of the TM polarization fraction in conjunction with the modal index contour for practical initial designs are developed and numerically verified. The mode conversion efficiency (MCE), insertion loss (IL), and the polarization conversion efficiency (PCE) at $\lambda _{0}=1550$ nm are 87.58%, 0.5899 dB, and 99.84%, respectively. The respective 1-dB optical bandwidths for the MCE and IL are about 133 and 140 nm, while the PCE is > 98% over a 102-nm spectral range. The low-index silica spacer is found to impose the most stringent fabrication requirement.