A Compact TE-Pass Polarizer for Silicon-Based Slot Waveguides

A compact TE-pass polarizer for silicon-based slot waveguides is proposed by utilizing a strip waveguide right above the slot waveguide and two identical metal strips symmetrically located on its outer sides. With the unique modal features of the slot waveguide and optimal designs for the vertical structure, only the input TE mode can directly output, while the input TM mode will be coupled to the upper waveguides, and thus, an efficient TE-pass polarizer can be realized. Moreover, the added metal strips can help to enhance the device performance significantly using their hybrid plasmonic effects. Results show that a polarizer of 3.2 μm in coupling length is achieved with the extinction ratio (ER) of 19.61 dB, insertion loss of 0.39 dB, and reflection losses of -24.15 dB (TM mode) and -34.41 dB (TE mode) at 1.55 μm, respectively. The optical bandwidth is ~110 nm for an ER >18 dB. In addition, fabrication tolerances and field evolution are presented.