Improving polarizability is an important strategy for designing high-performance mid-infrared (mid-IR) nonlinear optical (NLO) materials. The substitution of equivalent or aliovalent atoms can manipulate the polarizability by adjusting the symmetry of the polyhedron. Herein, the Li⁺ and Cd²⁺ are introduced into the Cu₃PS₄ as the equivalent and aliovalent dopants for the Cu site. As a result, Li⁺ can significantly improve the bandgap (E_g) of Li_xCu_3−xPS₄ from 2.38 to 2.88 eV, leading to a higher laser-induced damage threshold (LIDT) of 4.9 times than AgGaS₂ (AGS) with a comparable second harmonic generation (SHG) response of AGS (26−45 µm). Interestingly, Cd²⁺ can improve the SHG response and enlarge the E_g simultaneously. As a result, Cd_0.4Cu_2.2PS₄ has a large SHG response of 10 × AGS at 2050 nm (26−45 µm) and a LIDT of 2.6 × AGS. Theoretical calculations reveal that lattice vacancies induced by Cd²⁺ significantly boost polarizability compared to Li_xCu_3−xPS₄ with no vacancy, leading to a strong NLO response.

中文翻译：

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类金刚石 Cu3PS4 的空位引起的异常二次谐波产生响应


提高偏振率是设计高性能中红外（mid-IR）非线性光学（NLO）材料的重要策略。当量或异价原子的取代可以通过调节多面体的对称性来控制极化率。这里，Li ⁺ 和Cd ²⁺ 被引入到Cu ₃ PS ₄ 中作为Cu位点的等价和异价掺杂剂。因此，Li ⁺ 可以显着提高Li _x Cu _{3− x} 从 2.38 eV 到 2.88 eV，导致比 AgGaS ₂ (AGS) 更高的激光诱导损伤阈值 (LIDT) 4.9 倍，并具有可比的二次谐波产生 (SHG) ) AGS (26−45 µm) 的响应。有趣的是，Cd ²⁺ 可以提高SHG响应，同时放大E _g 。因此，Cd _0.4 Cu _2.2 PS ₄ 在 2050 nm (26−45 µm) 处具有 10 × AGS 的大 SHG 响应和 LIDT 2.6×AGS。理论计算表明，与Li _x Cu _{3− x} PS ₄