ELECTROOPTIC POTASSIUM-TANTALATE-NIOBATE FILMS PREPARED BY PULSED-LASER DEPOSITION FROM SEGMENTED PELLETS

Thin films of potassium tantalate niobate (KTN) were prepared by means of pulsed excimer-laser deposition and investigated with a number of analytical techniques, including electrical and electro-optical measur ements. For applications in longitudinal electro-optic modulators, a t ransparent electrode is required between substrate and electro-optic l ayers. Suitable electrode materials, which at the same time permit epi taxial growth of KTN, were identified and prepared. The resulting laye red samples were not only of good epitaxial and optical quality, but a lso exhibited the expected maximum of the longitudinal electro-optic e ffect at temperatures between the phase transitions from cubic to tetr agonal and from tetragonal to orthorhombic. However, the maximum achie vable electro-optic phase shift was found to be limited to roughly pi/ 100 for KTN films in the thickness range around 1 mum. Therefore, much thicker films are probably necessary for most practical applications, which requires significant improvements in the long-term stability an d homogeneity of the deposition process.