Concentration effect of Nd3+ ion on the spectroscopic properties of Er3+/Nd3+ co-doped LiYF4 single crystal

• High quality LiYF4:Er3+/Nd3+ single crystals are prepared by a Bridgman method.
• Concentration effect of Nd3+ ion on the spectroscopic properties are discussed.
• The energy transfer efficiencies for the two ions are calculated via the lifetimes.
• Inokuti–Hirayama model is used to analyze the cross relaxation process.

High quality Er3+/Nd3+:LiYF4 single crystals were grown by a Bridgman method. Their spectroscopic properties were studied to understand the Nd3+ concentration effect upon excitation of an 800 nm laser diode. The intensest 2.7 μm emission was observed in the LiYF4 crystal codoped with 0.99 mol% Er3+ and 0.62 mol% Nd3+. Meanwhile, the emission intensity for the green up-conversion and 1.5 μm downconversion of Er3+ decreased with increasing of the Nd3+ concentration. The modified Inokuti–Hirayama model was used to analyze the decay curves of the 1.06 (Nd3+) and 1.5 (Er3+) μm emissions. The results indicated that the energy transfer process (Er3+:4I13/2 + Nd3+:4I9/2 → Er3+:4I15/2 + Nd3+:4I15/2) is mainly due to the electric dipole–dipole interaction. The energy transfer efficiencies between Nd3+ and Er3+ ions were calculated. All results suggested that the Er3+/Nd3+:LiYF4 single crystals may have potential applications in mid-infrared lasers.

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