Vectorial simulation of passive TE/TM mode converter devices on InP

Accurate calculations of polarization rotation at abrupt waveguide interfaces are performed by a vectorial two-dimensional finite difference scheme. It is shown that the small orthogonal component of the vector field in rib waveguides can play an important role in mode polarization rotation. Polarization rotations in mode converters fabricated on InGaAsP/InP by periodically arranged tilted waveguides or periodic loading of the rib are explained by these calculations, and design rules for passive mode converter devices are given.