Design of a compact polarization rotator for silicon-based slot waveguides

Abstract

A design scheme of compact polarization rotator (PR) for silicon-based slot waveguides is proposed, where the slot including the upper claddings is filled with liquid crystals (LCs). With this design, the transverse field components of eigenmodes supported by the slot waveguides have almost identical amplitudes due to the anisotropic features of the LCs, leading to a high modal hybridness, which plays a pivotal role in designing an efficient PR. As a consequence, the input TE (TM) mode can be converted efficiently to the TM (TE) mode at the output port within a short length. The numerical results show that a PR of 11.3m in length at the operating wavelength of 1.55m is achieved with the extinction ratio and insertion loss of 12.6 (11.5) dB and 0.22 (0.30) dB, for TE-to-TM (TM-to-TE) conversion, respectively. Moreover, field evolution along the propagation distance through the PR is also demonstrated.