Two-wave mixing in Fe doped KNSBN

Abstract

Photorefractive materials such as LiNbOa3, BaTiOa3, KNbO3, Sr1- x Ba x Nb2O6 (SBN), Ba2- x Sr x K1- y Na y Nb5O15 (KNSBN), and Bi12SiO20 (BSO) are attractive candidates for optical data processing applications. The real time holographic gratings formed by the photorefractive effect produce energy coupling between the two writing beams (two-wave mixing). This energy transfer from one optical to another has potential applications in image amplification and correlation convolution operations. In this work, investigation of two-wave mixing (beam coupling) has been performed for the first time in Fe-doped (K x Na1- x )0.4(Sr y Ba1- y )0.8Nb2O6 (KNSBN) crystals. These crystals have photorefractive sensitivity and time response comparable with those of BaTiO3, KNbO3, and SBN. Large size crystals of relatively good optical quality have been grow. The composition of the crystal used is (K0.5Na0.5)0.4 (Sr0.61Ba0.39)0.8Nb2O6 with 0.05-wt. % Fe doping. The crystal dimension is 10 × 6.7 × 3.5 mm with the c-axis normal to the 10 × 3.5-mm face. Beam coupling and object beam amplification have been investigated as a function of light intensity, light wavelength, object beam to reference beam ratio, and the ange between the two beams. Beam coupling at 488-nm wavelength is observed to be stronger than that at 514.5 nm. The object beam gain is observed to be less dependent on the total beams' intensity and on the ratio between the object and reference beams.