We report on the development of a novel laser crystal with broadband emission properties at ∼2 µm – a Tm³⁺,Li⁺-codoped calcium tantalum gallium garnet (Tm:CLTGG). The crystal is grown by the Czochralski method. Its structure (cubic, sp. gr. $Ia\bar{3}d$, a = 12.5158(0) Å) is refined by the Rietveld method. Tm:CLTGG exhibits a relatively high thermal conductivity of 4.33 Wm^-1K^-1. Raman spectroscopy confirms a weak concentration of vacancies due to the charge compensation provided by Li⁺ codoping. The transition probabilities of Tm³⁺ ions are determined using the modified Judd-Ofelt theory yielding the intensity parameters Ω₂ = 5.185, Ω₄ = 0.650, Ω₆ = 1.068 [10⁻²⁰ cm²] and α = 0.171 [10⁻⁴ cm]. The crystal-field splitting of the Tm³⁺ multiplets is revealed at 10 K. The first diode-pumped Tm:CLTGG laser generates 1.08 W at ∼2 µm with a slope efficiency of 23.8%. The Tm³⁺ ions in CLTGG exhibit significant inhomogeneous spectral broadening due to the structure disorder (a random distribution of Ta⁵⁺ and Ga³⁺ cations over octahedral and tetrahedral lattice sites) leading to smooth and broad gain profiles (bandwidth: 130 nm) extending well above 2 µm and rendering Tm:CLTGG suitable for femtosecond pulse generation.

中文翻译：

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Tm3+ 掺杂的钙锂钽镓石榴石 (Tm:CLTGG)：新型激光晶体

我们报告了一种新型激光晶体的开发，该晶体具有~2 µm 的宽带发射特性——一种 Tm ³⁺ ,Li ⁺共掺杂的钙钽镓石榴石 (Tm:CLTGG)。晶体通过直拉法生长。它的结构（立方体，sp. gr. $Ia\bar{3}d$ , a = 12.5158(0) Å）通过 Rietveld 方法进行了改进。Tm:CLTGG 表现出4.33 Wm ^-1 K ^-1的相对高的热导率。由于 Li ⁺共掺杂提供的电荷补偿，拉曼光谱证实了弱浓度的空位。Tm ³⁺离子的跃迁概率使用修正的 Judd-Ofelt 理论确定，产生强度参数 Ω₂ = 5.185，Ω ₄ = 0.650，Ω ₆ = 1.068 [10 ^-20 cm ² ] 和α = 0.171 [10 ^-4 cm]。Tm ³⁺多重峰的晶体场分裂在 10 K 处显示。第一个二极管泵浦的 Tm:CLTGG 激光器在约 2 µm 处产生 1.08 W 的功率，斜率为 23.8%。由于结构无序（Ta ⁵⁺和Ga ³⁺的随机分布），CLTGG 中的Tm ³⁺离子表现出明显的不均匀光谱展宽。 八面体和四面体晶格位置上的阳离子）导致平滑和宽广的增益曲线（带宽：130 nm）延伸远高于 2 µm，并使 Tm:CLTGG 适用于飞秒脉冲生成。