Mid-infrared (mid-IR) nonlinear optical (NLO) materials are extensively researched as a vital optoelectronic material family with widespread applications ranging from civil to military fields. Metal chalcogenides possess a wide range of IR transparency and vast structural diversity, making them ideal system for exploration of novel mid-IR NLO materials. Incorporating rare earth elements with 4 and 5 electrons, including Sc, Y, and La, into chalcogenide structures in mid-IR NLO materials has been actively studied in the recent years. In this review, we categorize all typical rare earth (RE = Sc, Y, La) chalcogenides in the inorganic crystal structure database based on their NLO functional groups. We then assess their energy band gaps, NLO coefficients, birefringence, IR cut-offs, and mechanical properties using available experimental data and first-principles results and investigate the correlation between structural features and mid-IR NLO performance. It is showed that the rare earth chalcogenides can possess suitable birefringence and NLO response for mid-IR NLO applications, while not compromising energy band gap, thus may have a well-balanced mid-IR NLO performance. The prospects of novel rare earth chalcogenides with favorable mid-IR NLO performance are also discussed.

中文翻译：

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f0稀土(RE=Sc、Y、La)硫属化物中红外非线性光学材料评价与展望

中红外（mid-IR）非线性光学（NLO）材料作为重要的光电材料家族得到了广泛的研究，广泛应用于从民用到军事领域。金属硫属化物具有广泛的红外透明度和巨大的结构多样性，使其成为探索新型中红外非线性光学材料的理想系统。近年来，将具有 4 个和 5 个电子的稀土元素（包括 Sc、Y 和 La）掺入中红外 NLO 材料的硫族化物结构中得到了积极的研究。在这篇综述中，我们根据 NLO 官能团对无机晶体结构数据库中所有典型稀土 (RE = Sc、Y、La) 硫属化物进行了分类。然后，我们使用现有的实验数据和第一原理结果评估它们的能带隙、非线性光学系数、双折射、红外截止和机械性能，并研究结构特征和中红外非线性光学性能之间的相关性。结果表明，稀土硫属化物可以具有适合中红外非线性光学应用的双折射和非线性光学响应，同时不影响能带隙，因此可能具有良好平衡的中红外非线性光学性能。还讨论了具有良好中红外非线性光学性能的新型稀土硫属化物的前景。