On the origin of the high Kerr coefficient measured in thallium–zinc–tellurite glasses

Measurements of Kerr electrooptical sensitivity of several zinc-thallium-tellurite glasses are presented, and composition dependence of Kerr sensitivity is compared with the dependence of the second harmonic generation efficiency collected for optically poled TeO2-TlO0.5-ZnO glasses. These data being analyzed jointly with Raman measurements data allowed us to conclude that the high electrooptical Kerr coefficient and nonlinearity of Tl2O-ZnO-TeO2 glasses, and their sharp increase with augmenting concentration of thallium oxide TlO0.5 above 15% should be attributed to the presence of Tl+ cations having very high non-linear polarizability most likely related to their electronic lone pairs.