Mid-far infrared nonlinear optical (NLO) materials are gaining both scientific and technological interest in wide applications. The practical properties of one crystal are determined by its constituent atoms, electrons, lattices and their coupled interaction. Herein, by applying a hierarchical molecular design strategy, we synthesized a promising NLO material Ag₂HgI₄ by a simple solution method, which shows the strongest second harmonic generation (SHG) response in inorganic halides (4×AgGaS₂ (AGS)) and wide transparency range. The deep insights on nonlinearity enhancement and broadening transmittance were elaborated by theoretical calculations, which are attributed to reduced phonon frequency and increased nonbonding electronic states on top valence band. This physical mechanism is applicable in all NLO optical materials generally, opening a novel and exciting avenue for explorations of new NLO candidates with high performance.

中远红外非线性光学（NLO）材料在广泛的应用中正在获得科学和技术兴趣。一种晶体的实际性能取决于其组成原子，电子，晶格及其耦合的相互作用。在这里，我们通过应用分级分子设计策略，通过简单的求解方法合成了有前途的NLO材料Ag ₂ HgI ₄，该方法显示了无机卤化物（4×AgGaS ₂）中最强的二次谐波生成（SHG）响应。（AGS））和广泛的透明度范围。通过理论计算阐述了对非线性增强和增宽透射率的深刻见解，这归因于声子频率的降低和最高价带上非键电子态的增加。这种物理机制通常适用于所有NLO光学材料，从而为探索具有高性能的新NLO候选者开辟了一条新颖而令人兴奋的途径。