Influence of Nd³⁺ concentration on mid-infrared emission in PbF₂ crystal co-doped with Ho³⁺ and Nd³⁺ ions

A promising series of HoyNdxPb(1-x-y)F2 (x = 0, 0.01, 0.02, 0.03, 0.04; y = 0.02) crystals was grown by the Bridgman method. The influence of the Nd3+ ions concentration on mid-infrared (-2.0, -2.9 and -3.9 mu m) fluorescence emissions of Ho3+ ions in the PbF2 crystal excited by 808 nm laser diode was investigated in this work. The energy transfer mechanism between Nd3+ ions and Ho3+ ions under different concentrations of the Nd3+ ions was systematically analyzed. The results show that the Nd3+ ions have good sensitization and deactivation effect on the Ho3+ ions to stimulate the mid-infrared fluorescence emissions. The experimental analysis proves that the sensitization efficiency of the Nd3+ ions is relatively stable at around 93.45% with varying Nd3+-doping concentrations. Concentration dependence studies indicate that the concentration of the Nd3+ ions has significant influence on mid-infrared emissions. When the doping concentration of the Nd3+ ions is up to 2.0 at%, the intensity of -2.0, -2.9 and -3.9 mu m emissions all reach the maximum. The output characteristics of a 3.9 mu m laser are simulated, and it is found that with the increase of the Nd3+-doping concentration, the peak power, pulse width, and peak energy all meet the trend of first increasing and then decreasing, and Ho0.02Nd0.02Pb0.96F2 crystal displays the best performance. All the results show that the Nd3+/Ho3+ co-doped PbF2 crystals might act as a useful optical medium for mid-infrared laser applications. (c) 2023 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.