Optical waveguiding properties of (Pb,La)TiO3/Al2O3 planar structures

Thin films of lend lanthanum titanate (Pb,La)TiO3 have been grown by radio-frequency magnetron sputtering on (0001) Al2O3 substrates. The structure, the microstructure and the optical properties of the films have been investigated as a function of the postdeposition annealing. Films deposited at low temperatures crystallize to a perovskite phase after the annealing treatment from 500 degrees C to 650 degrees C. X-ray (theta - 2 theta) diffraction studies have shown that films are crystallized with a strong (111) orientation and the best crystalline structure is reported at 600 degrees C. The optical properties were both demonstrated by spectrophotometry and prism coupling. PLT thin films with a transparency of 80% in the wavelength range 300-2000 nm have exhibited a refractive index of 2.38 @ 632.8 nm representing 97% of the bulk corresponding material. Investigation of optical propagation has been accomplished in a 10 mm long planar optical waveguide using a butt-coupling configuration.