Abstract

A novel polarization beam splitter (PBS) with an extremely small footprint is proposed based on a multimode interference (MMI) coupler with a silicon hybrid plasmonic waveguide. The MMI section, covered with a metal strip partially, is designed to achieve mirror imaging for TE polarization. On the other hand, for TM polarization, there is almost no MMI effect since the higher-order TM modes are hardly excited due to the hybrid plasmonic effect. With this design, the whole PBS including the 1.1 μm long MMI section as well as the output section has a footprint as small as $\sim 1.8\mathrm{\mu m}\times 2.5\mathrm{\mu m}$. Besides, the fabrication process is simple since the waveguide dimension is relatively large (e.g., the input/output waveguides widths $w\ge 300\mathrm{nm}$ and the MMI width $w_{\mathrm{MMI}}=800\mathrm{nm}$). Numerical simulations show that the designed PBS has a broad band of $\sim 80\mathrm{nm}$ for an ER $>10\mathrm{dB}$ as well as a large fabrication tolerance to allow a silicon core width variation of $-30\mathrm{nm}<\mathrm{\Delta }w<50\mathrm{nm}$ and a metal strip width variation of $-200\mathrm{nm}<\mathrm{\Delta }{w}_m<0$.

© 2014 Optical Society of America