Optical losses in sol-gel derived lead lanthanum titanate waveguides

A series of solgel derived lead lanthanum titanate films were prepared on Corning 7059 glass substrates. Waveguiding properties of these films were studied as a function of La content and film thickness. 0.5M precursor solutions based on lead acetate, La nitrate and Ti Zr alkoxides were refluxed for 1 hour and later spincoated at various speeds on the substrates under clean room condition. Films were fired to 400C for 1 hr to burn off the organics and to consolidate the coatings. They were then fired at temperatures ranging from 500C to 600C. XRD was used to determine the phase assembly present in these films; the presence of La seemed to aid in the formation of the perovskite phase. Transmission spectra were gathered using a UV-Vis spectrometer; and the spectra were then used to calculate the refractive indices based on the envelope method. The waveguiding properties and optical attenuation were studied via prism coupling using a rutile prism. The optical losses in these films decrease with La content and also in thicker single-coated films. On the other hand, thicker films achieved by multiple coating appeared to exhibit higher losses. Crystalline PLZT 28/0/100 yielded loss of < 2 dB/cm, the lowest among reported literature values for any sol-gel or sputtered PLZT films.