An excellent lead oxyiodide with a strong second-harmonic generation response and a large birefringence induced by the oriented arrangement of highly distorted [PbO4I2] polyhedra†
*ab
Xin-Tao
Wu
a
Abstract
Nonlinear optical (NLO) crystals are an important component in modern lasers. Nevertheless, it is a great challenge to rationally synthesize NLO crystals with strong second-harmonic generation (SHG) responses and large birefringence. Herein, a cationic substitution strategy has been successfully developed to transform SHG-inert centrosymmetric Cs2I2[Pb(OOCCH2COO)] into SHG-active K2I[PbI(OOCCH2COO)] with a NCS polar structure. K2I[PbI(OOCCH2COO)] features highly distorted [PbO4I2] polyhedra that are aligned in an oriented arrangement, resulting in the effective superposition of their microscopic second-order nonlinear susceptibilities. Remarkably, K2I[PbI(OOCCH2COO)] not only exhibits the strongest phase-matching SHG response of 6.3 × KDP to date among malonates, but also possesses a large birefringence (Δnobv. = 0.218@546 nm) and good thermal stability. As elucidated through theoretical calculations its strong SHG response and large birefringence mainly originate from the highly distorted [PbO4I2] polyhedron. This paper presents a new approach for the development of NLO crystals with prominent performance.
![Graphical abstract: An excellent lead oxyiodide with a strong second-harmonic generation response and a large birefringence induced by the oriented arrangement of highly distorted [PbO4I2] polyhedra](/en/Image/Get?imageInfo.ImageType=GA&imageInfo.ImageIdentifier.ManuscriptID=D2QI01143C&imageInfo.ImageIdentifier.Year=2022)
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