Electro-optic potassium-tantalate-niobate films prepared by pulsed laser deposition from segmented pellets

Abstract

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 measurements. For applications in longitudinal electro-optic modulators, a transparent electrode is required between substrate and electro-optic layers. Suitable electrode materials, which at the same time permit epitaxial growth of KTN, were identified and prepared. The resulting layered samples were not only of good epitaxial and optical quality, but also exhibited the expected maximum of the longitudinal electro-optic effect at temperatures between the phase transitions from cubic to tetragonal and from tetragonal to orthorhombic. However, the maximum achievable electro-optic phase shift was found to be limited to roughly τ/100 for KTN films in the thickness range around 1 μm. Therefore, much thicker films are probably necessary for most practical applications, which requires significant improvements in the long-term stability and homogeneity of the deposition process.