<title>Nonlinear optical characteristics of sol-gel-derived highly oriented ferroelectric strontium barium niobate thin films</title>

Abstract

Highly c-axis oriented SBN films with various compositions were obtained on MgO(100) substrates using sol-gel process. Although the sol-gel process has been developed for ferroelectric thin films, it is known as being hard to fabricate highly oriented films. Thus, the preferential orientation of the films was enhanced by two methods: (1) poling the film by a high dc electric field (greater than E<SUB>c</SUB>) and (2) growing the film on an SBN-seeded MgO substrate. The mechanisms of these methods were discussed. For their optical applications, second-harmonic generation (SHG) effect of SBN films was studied. Fundamental beam of Nd:YAG laser with 1064 nm was used as a pump beam. From Maker fringe measurements with a quartz reference, second- order nonlinear optical (NLO) coefficients d of the films were obtained. The second-order NLO coefficients of the films could be enhanced to considerable extent by applying the electric poling and using a self-seeds layer. These phenomena indicate that the SHG effect is sensitive to crystallographic structure as well as ferroelectric polarization. Mathematical equation was derived to correlate this microstructure to the SHG effect of SBN films.