Plasmonic-Assisted TE-Pass Polarizer for Silicon-Based Slot Waveguides

Compact and low-loss TM-pass polarizer based on a hybrid plasmonic waveguide with a semiround arch Si core

A compact and low loss TM-pass polarizer based on a hybrid plasmonic waveguide (HPW) has been demonstrated. By introducing the hollow HPW with a semiround arch (SRA) Si core, the unwanted TE mode can be effectively cut off and the TM mode can pass through by hybrid plasmonic mode with excellent transmission characteristics. The hollow structure realizes lower index with n=1 due to the air region, and the SRA construction effectively suppresses the energy loss of the TM mode caused by the corner effect. Thus, TM modes pass through with negligible loss and exhibit the characteristic of strong mode limitation. By optimizing the width of metal, the width of the HPW, and the length of the tapered mode converter, an optimum performance with a high polarization extinction ratio of 67.87 dB and a low insert loss of 0.029 dB at the work wavelength=1550nm is achieved. Detailed analysis also proves that the proposed polarizer has a compact size of only 7 µm and a great fabrication tolerance. This work offers a simple and effective scheme of polarization control on-chip.

Broadband TE-pass slot waveguide polarizer using an asymmetrical directional coupler

A compact TE-pass polarizer for silicon-based slot waveguides is numerically proposed based on a directional coupler where an asymmetrical slot waveguide (ASW) and hybrid plasmonic waveguide (HPW) are involved. The input section is linearly tapered to an ASW to markedly enlarge the modal birefringence. Beneficially, only the TM mode can be coupled into the adjacent HPW and attenuated while the injected TE mode just passes through the slot waveguide without coupling by properly choosing the dimensions. As a consequence, an efficient TE-pass polarizer can be implemented. From the simulation results, the proposed polarizer has an extinction ratio (ER) of 45 dB and insertion loss (IL) of 0.44 dB at 1.55 μm, and its bandwidth exceeds 130 nm with the ER>30  dB and IL<1  dB. In addition, fabrication tolerances to the key structural parameters are analyzed and field evolution along the propagation distance is also demonstrated.