Anisotropic self-diffraction in Mg-doped LiNbO3

Abstract

The characteristics of anisotropic self‐diffraction were studied for undoped LiNbO₃ crystals and LiNbO₃:Mg at doping levels of a few mole percent. From the absolute magnitude and the time dependence of the signal, it was possible to determine the induced refractive‐index change and the conductivity of the charges involved in the photorefractive effect for each sample. For these excitation conditions, only charge migration perpendicular to the c axis contributes to laser‐induced grating, and thus the conductivity is associated with charge diffusion. The results show that the total refractive‐index change causing the self‐diffraction is only slightly smaller for the Mg‐doped samples than for undoped LiNbO₃ while the conductivity is 1 order of magnitude greater for the Mg‐doped samples.