Na2Hg3M2S8 (M = Si, Ge, and Sn): New Infrared Nonlinear Optical Materials with Strong Second Harmonic Generation Effects and High Laser-Damage Thresholds

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• 作者：Kui Wu ; Zhihua Yang ; Shilie Pan
• 刊名：Chemistry of Materials
• 出版年：2016
• 出版时间：April 26, 2016
• 年：2016
• 卷：28
• 期：8
• 页码：2795-2801
• 全文大小：445K
• 年卷期：0
• ISSN：1520-5002

文摘

A new family of noncentrosymmetric isostructural compounds, Na₂Hg₃M₂S₈ (M = Si, Ge, and Sn), was successfully synthesized. They crystallize in the tetragonal space group P4̅c2 with Z = 2. Their major structures are composed of infinite cross-connected _∞(HgS₃)_n chains and isolated [MS₄] ligands and show the interesting tunnel features. Interestingly, compared with the structures of A₂Hg₃M₂S₈ (A = alkali metal, Na–Cs), it can be found that the structural symmetries show a gradually rising tendency from Cs to Na analogues as a result of cation size effect, which rarely exists in quaternary alkali metal chalcogenides. Property measurements show that title compounds exhibit strong second harmonic generation (SHG) effects with a phase-matching behavior at 2.09 μm, wide transparency range in the infrared (IR) region, and large laser-damage thresholds (LDTs). Remarkably, Na₂Hg₃Si₂S₈ and Na₂Hg₃Ge₂S₈ achieve the suitable balance between large SHG effects (1.3 and 2.2 × benchmark AgGaS₂) and high LDTs (4.5 and 3 × AgGaS₂), respectively, and can be expected to be potential nonlinear optical (NLO) candidates in the IR region. Moreover, band structures and NLO properties of title compounds are also theoretically studied, and the calculated NLO coefficients are consistent with the experimental observations.