Optical characterization of lithium niobate thin films

Optical waveguiding thin films of lithium niobate were RF sputtered onto single-crystal sapphire substrates. A polarized He-Ne laser light with a wavelength of 6328 Å was successfully fed into the optical waveguide by a rutile prism coupler. The guided modes excited by the prism coupler were observed and used to examine the optical properties of the waveguide. The effective thickness and the refractive index for transverse electric and transverse magnetic modes were calculated. The birefringence observed in the films and X-ray diffraction studies have confirmed the polycrystalline nature of the films. The attenuation of the light propagation in the waveguide was determined to be 1.2±0.1 dB/cm