Optical Waveguiding Properties of (Pb,La)TiO3/Al2O3 Planar Structures

Thin films of lead 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°C to 650°C. X-ray (–2) diffraction studies have shown that films are crystallized with a strong (111) orientation and the best crystalline structure is reported at 600°C. The optical properties were both demonstrated by spectrophotometry and prism coupling. PLT thin films with a transparency of 80% in the wavelength range 300–2000nm have exhibited a refractive index of 2.38 @ 632.8nm representing 97% of the bulk corresponding material. Investigation of optical propagation has been accomplished in a 10mm long planar optical waveguide using a butt-coupling configuration.