Nonlinear refraction and absorption through phase transition in a Nd:SBN laser crystal

Abstract

Time-resolved Z-scan measurements were performed in a Nd 3+ -doped Sr 0.61 Ba 0.39 Nb 2 O 6 laser crystal through ferroelectric phase transition. Both the differences in electronic polarizability ͑⌬␣ p ͒ and cross section ͑⌬͒ of the neodymium ions have been found to be strongly modified in the surroundings of the transition temperature. This observed unusual behavior is concluded to be caused by the remarkable influence that the structural changes associated to the ferro-to-paraelectric phase transition has on the 4f → 5d transition probabilities. The maximum polarizability change value ⌬␣ p = 1.2ϫ 10 −25 cm 3 obtained at room temperature is the largest ever measured for a Nd 3+ -doped transparent material.

Energy transfer upconversion determination by thermal-lens and Z-scan techniques in Nd^3+-doped laser materials

“…This sensitivity enhancement is a consequence of heat diffusion that makes the refractive-index profile ⌬n͑r͒ wider than the excitation intensity profile. On the other hand, in the PL effect there is no diffusion mechanism, so the PL signal decreases when the probe beam waist increases [21]. From the definition of the m = ͑w p / w e ͒ 2 TL parameter [14], it was shown that, for m 1, the PL signal decreases as m −1 [11].…”

Thermo-optical and spectroscopic properties of Nd:YAG fine grain ceramics: towards a better performance than the Nd:YAG laser crystals

“…In principle, both thermal and population (electronic) lenses contribute to the observed transient signal [31,[42][43][44], but their relative magnitudes can be controlled by choosing the appropriate excitation beam diameters and detection time [31]. The electronic response time is approximately constant, around 250 μs for Nd:cYAG with a low Nd concentration, and it reduces when increasing the ion content.…”