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

Thin films of lithium niobate have been grown in-situ by radiofrequency mag netron sputter ing on (0001) sapphire substrates. The epitaxial quality has been studied as a function of deposition parameters. The films prepared un der optimized conditions, exhibited a high degree of c-axis oriented crysta lline structure as shown by x-ray diffraction in the theta-2 theta and phi- scans configurations. Stoichiometry has been obtained at the substrate temp erature of 490 degrees C and gas (Ar/O-2) pressure of 30mTorr. The optimum conditions for growing epitaxial LiNbO3 layers are reported in this work. M irorlike thin films with a small surface roughness of 30 Angstrom have been qualified optically using the prism coupling technique. Both ordinary and extraordinary refractive indices have been determined (n(0)=2.348 and n(e)= 2.208 respectively) at 632.8nm from the transverse electric and transverse magnetic mode excitations. The optical-propagation loss is evaluated to be around 2dB.cm(-1) for a 150nm thick planar waveguide.