A compact polarization converter for silicon-based slot waveguides using a hybrid plasmonic effect

A compact polarization converter for silicon-based slot waveguides is proposed, in which a metal strip of silver (Ag) with a right-angled cross section located at the upper-right corner of the slot waveguide is embedded in its upper claddings. Owing to the characteristics of the introduced asymmetric hybrid plasmonic waveguide, the modal hybridness is highly enhanced and the optimal optical axis rotation angle, 45 degrees, is realized by optimizing the location and size of the Ag, resulting in high polarization conversion efficiency (PCE). Numerical results show that a polarization converter of 15.2 mu m in length, operating at a wavelength of 1.55 mu m for TM-to-TE conversion, is achieved, where the PCE and insertion loss are 96.9% and 0.7 dB, respectively, and bandwidth with PCE >92% is similar to 67 nm (from 1524 to 1591 nm), covering the entire C-band. Moreover, fabrication tolerances to the structural parameters and field evolution along the propagation distance are investigated.