Optical characterization of lithium niobate thin film waveguides sputtered on sapphire substrates

Thin films of lithium niobate on various oriented sapphire substrates were fabricated by the rf sputtering method. Polarized He-Ne laser light with a wavelength of 6328 A was successfully coupled into the optical waveguides by a rutile prism coupler. A description of the prism coupler used for this research is given. The guided modes excited by the prism coupler were observed and used to examine the optical properties of the waveguide. The refractive indices and thicknesses of various samples were calculated and tabulated. The birefringence observed in the films and x-ray diffraction studies have confirmed the polycrystalline nature of the films. The attenuation of the light propagating in various (zeroth- to second-order) waveguide modes was determined to be in the range of 1.1 to 1.3 $\pm$ 0.1 dB/cm