Fabrication of Lithium Niobate Light Guiding Films

In optical communications systems lithium niobate films could play an important role due to the large electrooptic, acousto-optic and non linear coefficients of this material. In this paper we discuss two methods for preparing such films and the resultant film properties. The methods used are out diffusion and R. F. sputtering. The basic element in integrated optics is the thin film optical waveguide. A light guiding layer is one which have an index of refraction higher than that of the surounding materials. On LiNbO3 this can be achieved by varying the Li/Nb ratios by out diffusion of Li from a monocrystal, or by appropriately controlling the sputtering conditions when depositing LixNbyO3 films onto a lower index substrate such as LiNbO3, glass, etc. ... This usually leads to polycrystalline films. In out-diffusion we have an index gradient waveguide extending into the bulk material with a large depth below the surface (~100–350 µm). Sputtered films have an abrupt index discontinuity with a lower thickness (1–10 µm). Both techniques will be discussed and compared.