A planar core and a cladding disposed on opposite sides of thereof. In the best mode, the rotator includes a very low Numerical Aperture (NA) planar waveguide. The cladding is birefringent and the refractive index and birefringence thereof are optimized to provide equal mode propagation velocities for both TE and TM modes for at least one transverse mode. The refractive index and birefringence of the cladding are optimized to provide equal mode propagation velocities for both TE and TM modes for a wide range of transverse modes.