Integrated optical cross strip polarizer concept

Passing across an abrupt junction from a thick vertically bimodal waveguide to a thinner single mode segment, guided light can undergo complete destru ctive interference, provided that the geometry and the phases of the modes in the initial segment are properly adjusted. We propose to employ this eff ect to realize a simple polarizer configuration, using a strip that is etch ed from a planar waveguide. A beam of light is made to pass the strip perpe ndicularly. The light enters from the single mode waveguide outside the str ip into the strip segment, which is configured to support two modes. At the end of the strip, apart from reflections, the amount of power that is guid ed in the following lower segment depends on the local phases of the two mo des. These phases are different for TE and TM light, hence we may expect a polarization dependent power transfer, resulting in polarizer performance f or a properly selected geometry. The paper describes in detail the modeling of the device in terms of rigorous mode expansion. Design guidelines and t olerance requirements for geometric and material parameters are discussed. For typical Si3N4/SiO2 materials, our calculations predict a peak performan ce of 34 dB polarization discrimination and 0.3 dB insertion loss for a dev ice with a total length of about 12 mum that selects TE polarization at a w avelength of 1.3 mum.