A STUDY OF LIGHT-INDUCED ABSORPTION AND TWO-WAVE MIXING IN PHOTOREFRACTIVE CRYSTALS / Y QIU DONGXIAO

Abstract

Photorefractive materials are essential to the optical signal processing, which is considered a promising substitute to our nearly fully-developed semiconductor technology. Thus the understanding of the properties of photorefractive materials is very important to the applications and the material-tailoring. In this thesis, we did both theoretical and experimental studies. Theoretically, we consolidated and integrated several essential parts of the photo refractive effects into a consistent context and derived new expressions of the light-induced absorption for electron-conductivity crystals. Experimentally, first we focused on the study of the light-induced absorption of lightly Ce-doped photorefractive SBN:60 and SBN:75 under different intensities, temperatures, polarization, and wavelengths; second, we performed experiments on the two-wave mixing on these SBN crystals and one iron-eloped LiNbO3 crystal. Analysis of the experimental results reveals that the two-center model might be suitable for lightly Ce-doped SBN crystals. In addition, the results show that the mechanism of photorefractive effects in LiNbO3 is quite different from that in SBN, clue to the photovoltaic effect which is the main force of photorefractive effects in iron-eloped LiNbO3.