The design, fabrication and characterisation of birefringent silicon oxynitride planar optical waveguides are described for applications at the wavelength of 1.54 mu m. Form birefringence is attained by interposing a thin silicon nitride film in the waveguide stack, and can be controlled by adjusting the nitride layer thickness. Dispersion characteristics of the oxynitride waveguides have been measured and compared with theory.
Aarnio, J., Heimala, P., Del Giudice, M., & Bruno, F. (1991). Birefringence control and dispersion characteristics of silicon oxynitride optical waveguides. Electronics Letters, 27(25), 2317 - 2318. https://doi.org/10.1049/el:19911435