A planar optical waveguide has a set of diffractive elements and confines propagating optical signals in at least one transverse spatial dimension. Each diffractive element set routes, between input and output ports, a corresponding diffracted portion of an input optical signal propagating in the planar...http://www.google.com/patents/US7359597?utm_source=gb-gplus-sharePatent US7359597 - Birefringence control in planar optical waveguides
