Growth and optical waveguiding properties of RF sputtered lithium niobate thin films on sapphire substrates

摘要

Thin films of lithium niobate have been grown in-situ by radiofrequency magnetron sputtering on (0001) sapphiresubstrates. The epitaxial quality has been studied as a function ofdeposition parameters. The films prepared under optimizedconditions, exhibited a high degree of c-axis oriented crystallinestructure as shown by x-ray diffraction in the 0-20 and φ-scansconfigurations. Stoichiometry has been obtained at the substratetemperature of 4900C and gas (Ar/O2) pressure of 30m Torr. Theoptimum conditions for growing epitaxial LiNbO3 layers arereported in this work. Mirorlike thin films with a small surfaceroughness of 30A have been qualified optically using the prismcoupling technique. Both ordinary and extraordinary refractiveindices have been determined (n0=2.348 and ne=2.208respectively) at 632.8nm from the transverse electric andtransverse magnetic mode excitations. The optical propagationloss is evaluated to be around 2dB.cm-1 for a 150nm thick planar waveguide.