Asymmetric, periodically loaded waveguide for polarization rotation

摘要

Polarization rotation is achieved in an exemplary embodiment in an optical waveguide by augmenting the waveguide structure with a plurality of spaced-apart sections for loading the refractive index of the waveguide to cause a lateral asymmetry in the refractive index profile of the waveguide viewed in the plane transverse to the waveguide longitudinal axis. Each spaced-apart section induces non-zero coupling between the principal orthogonal polarization modes. Phase matched coupling between the principal orthogonal polarization modes is achieved by spacing the sections periodically by a distance LAMBDA equal to lambda / DELTA N where lambda is the propagation wavelength in the waveguide and DELTA N is the difference between the effective refractive indices for the principal orthogonal polarization modes. Realizations of the waveguide structure are shown using Group III-V semiconductor rib waveguide structures.