A Compact Silicon-Based TE-Pass Polarizer Using Three-Guide Directional Couplers

A compact TE-pass polarizer for silicon wires (SWs) based on a symmetrical three-guide directional coupler (DC) is proposed, where two identical hybrid plasmonic waveguides (HPWs), including bends are symmetrically located at both sides of the central SW. By properly choosing the structural parameters, the phase-matching condition is only satisfied for TM mode. Therefore, the input TE-mode can directly pass through while the injected TM-mode will be evenly coupled to the adjacent HPWs and attenuated via the HPWs. Consequently, an efficient TE-pass polarizer is realized. With the symmetrical three-guide DC configuration, device length is significantly reduced, and more importantly, an ultralow insertion loss (IL) can be obtained. From the results, the proposed polarizer has an extinction ratio (ER) of 40.8 dB and an IL of 0.09 dB at 1.55 μm, and its bandwidth is ~160 nm for an ER > 30 dB. In addition, fabrication tolerances to the key structural parameters are analyzed and field evolution through the polarizer is also presented.