Abstract
An efficient enhancement of 2.78 μm emission from the transition of Er3+: 4I11/2 → 4I13/2 by Tm3+ introduction in the Er/Tm: PbF2 crystal was grown by the Bridgman technique for the first time. The spectroscopic properties, energy transfer mechanism, and first-principles calculations of as-grown crystals were investigated in detail. The co-doped Tm3+ ion can offer an appropriate sensitization and deactivation effect for Er3+ ion at the same time in PbF2 crystal under the pump of conventional 800 nm laser diodes (LDs). With the introduction of Tm3+ ion into the Er3+: PbF2 crystal, the Er/Tm: PbF2 crystal exhibited an enhancing 2.78 μm mid-infrared (MIR) emission. Furthermore, the cyclic energy transfer mechanism that contains several energy transfer processes and cross-relaxation processes was proposed, which would well achieve the population inversion between the Er3+: 4I11/2 and Er3+: 4I13/2 levels. First-principles calculations were performed to find that good performance originates from the uniform distribution of Er3+ and Tm3+ ions in PbF2 crystal. This work will provide an avenue to design MIR laser materials with good performance.
Highlights
Over the past several decades, mid-infrared (MIR) solid-state lasers operating around2.7–3 μm have received extensive attention for numerous applications in medicine surgery, communications, remote sensing, pollution monitoring, and military countermeasures, etc. [1,2,3,4,5]
Theoretical calculations were performed to discover that the co-doping of the Tm3+ ion can make the Er3+ and Tm3+ ions more evenly distributed in PbF2 crystals, which can effectively break the local clusters of the Er3+ in Er: PbF2 crystal, ensuring efficient energy transfer between Er3+ and Tm3+ ions, and resulting in the enhancement of 2.78 μm MIR
The The results demonstrate suc3+ and Tm3+ ions in PbF crystal without phase transitions
Summary
Over the past several decades, mid-infrared (MIR) solid-state lasers operating around. We can focus attention on co-doping a suitable deactivation ion for Er3+ ion to suppress the self-terminating effect, such as Pr3+ , Ho3+ , Dy3+ , or Tm3+ ions [25,26,27,28] These deactivation ions can dramatically reduce the population of lower Er3+ : 4 I13/2 levels, thereby achieving efficient 2.7 μm midinfrared emission. (432 cm−1 ), LiYF4 (442 cm−1 ), LuLiF4 (400 cm−1 ) and BaY2 F8 (415 cm−1 ) crystals [32,33,34] Such low phonon energy is conducive to reducing the non-radiative transition probability and enhancing the spontaneous radiation transition probability between 4 I11/2 and 4 I13/2 levels of Er3+ ion [35]. Theoretical calculations were performed to discover that the co-doping of the Tm3+ ion can make the Er3+ and Tm3+ ions more evenly distributed in PbF2 crystals, which can effectively break the local clusters of the Er3+ in Er: PbF2 crystal, ensuring efficient energy transfer between Er3+ and Tm3+ ions, and resulting in the enhancement of 2.78 μm MIR fluorescence emission
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