In this paper, an improved design for a short and low-loss polarization rotator is proposed, consisting of a single-section asymmetrical waveguide butt-coupled between two standard rib waveguides. At a wavelength of 1.55 m, nearly 100% polarization conversion ratio is obtained, with a relatively short (320 m) device length and an extremely low 0.5 dB total insertion loss. The simulation results are obtained using the full vectorial finite-element-based beam propagation, the junction analysis, and the modal solution approaches.
B. M. A. Rahman, S. S. A. Obayya, N. Somasiri, M. Rajarajan, K. T. V. Grattan, and H. A. El-Mikathi, "Design and Characterization of Compact Single-Section Passive Polarization Rotator," J. Lightwave Technol. 19, 512- (2001)