Electronic and thermal contributions to the non-linear refractive index of Nd 3+ ion-doped fluoride glasses

Abstract

In some rare-earth ion-doped solids there is a non-linear refractive index n 2 due to the polarizability difference, Δα, between excited and ground states, the so-called population lens effect. In addition to that, part of the absorbed energy is converted into heat, generating the so-called thermal lens effect. The time-resolved Z-scan technique may, in some cases, discriminate electronic (population lens) and thermal non-linearities. In this study, n 2 measurements of Nd 3+ doped fluoride glasses are taken. The polarizability difference, Δα, and absorption cross-section difference, Δσ, between excited ( 4F 3/2) and ground ( 4I 9/2) states of Nd 3+ are presented. We studied different kinds of fluoride glasses (fluorozirconate, fluorindate and fluoroaluminate) and the Δα's obtained vary between 1 and 3×10 −26 cm 3.