Extremely small polarization beam splitter based on a multimode interference coupler with a silicon hybrid plasmonic waveguide

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 mu m long MMI section as well as the output section has a footprint as small as similar to 1.8x x mu m x 2.5 mu m. Besides, the fabrication process is simple since the waveguide dimension is relatively large (e. g., the input/output waveguides widths w >= 300 nm and the MMI width w(MMI) = 800 nm). Numerical simulations show that the designed PBS has a broad band of similar to 80 nm for an ER > 10 dB as well as a large fabrication tolerance to allow a silicon core width variation of -30 nm < Delta w < 50 nm and a metal strip width variation of -200 nm < Delta w(m) < 0. (C) 2014 Optical Society of America