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Polar materials play a crucial role in numerous essential fields; however, efficiently synthesizing them remains a significant challenge. In this study, a viable approach is proposed to enhance the probability of discovering polar materials by developing new functional basic units (FBUs) with strong polarity and high configurational entropy. To validate this approach, a site‐modification strategy is applied to the high configurational entropy flexible (C3H2O4)2− FBU, resulting in the development of four new polar‐enhancing FBUs: (C3(CH3)2O4)2−, (C3F2O4)2−, (C3H(OH)O4)2−, and (C3HFO4)2−. Moreover, 11 new compounds through temperature‐driven conformational changes in FBUs are successfully synthesized. Among these, the proportion of polar structures reaches an impressive 54%. Remarkably, all of these novel polar compounds exhibit outstanding nonlinear optical (NLO) properties. The [Li2C3(CH3)2O4]2·3H2O demonstrates the rare coexistence of a moderate birefringence (0.071@514 nm), short UV cutoff edge (210 nm), and the strongest second harmonic generation (SHG) effect (6.5 × KDP) among ionic‐organic fourth harmonic generation crystals. Preliminary laser experiments have also proven its potential practical value as a fourth harmonic generation crystal. This research not only discovers a variety of exceptional UV NLO crystals but also provides a feasible method to increase the likelihood of finding polar materials. [ABSTRACT FROM AUTHOR]

Polar molecular crystals, with their densely stacked polar nonlinear optical (NLO) active units, are favored for their large second harmonic generation (SHG) responses and birefringence. However, their potential for practical applications as Infrared (IR) NLO materials has historically been underappreciated due to the weak inter‐molecular interaction forces that may compromise their physicochemical properties. In this study, we propose molecular crystals with polar molecular cages as a treasure‐house for the development of superior IR NLO materials and a representative system, binary chalcogenide molecular crystals, composed of [P4Sn] (n=3–9) polar molecular cages, is introduced. These crystals may not only achieve wide band gap, large SHG response, and birefringence in a single structure, but also exhibit favorable physicochemical properties. We subsequently obtained a polar molecular crystal, α‐P4S5, which demonstrated exceptional IR optical properties, including a strong SHG response (1.1×AGS), wide band gap (3.02 eV), large birefringence (0.134@2050 nm), and a broad transmission range (0.41–14.7 μm). Moreover, it showed excellent water resistance and hardness. These findings highlight the potential of polar molecular crystals as a promising platform for the development of high‐performance IR NLO materials. [ABSTRACT FROM AUTHOR]

Acquiring high‐performance ultraviolet (UV) nonlinear optical (NLO) materials that simultaneously exhibit a strong second harmonic generation (SHG) coefficients, as short as possible SHG phase‐matching (PM) wavelength and non‐hygroscopic properties has consistently posed a significant challenge. Herein, through multicomponent modification of KBe2BO3F2 (KBBF), an excellent UV NLO crystal, Mg(C3O4H2)(H2O)2, was successfully synthesized in malonic system. This material possesses a unique 2D NLO‐favorable electroneutral [Mg(C3O4H2)3(H2O)2]∞ layer, resulting in the rare coexistence of a strong SHG response of 3×KDP (@1064 nm) and short PM wavelength of 200 nm. More importantly, it exhibits exceptional water resistance, which is rare among ionic organic NLO crystals. Theoretical calculations revealed that its excellent water‐resistant may be originated from its small available cavity volumes, which is similar to the famous LiB3O5 (LBO). Therefore, excellent NLO properties and stability against air and moisture indicate it should be a promising UV NLO crystal. [ABSTRACT FROM AUTHOR]

Ionic organic crystals containing organic planar π‐conjugated units has become one of the hot spots as nonlinear optical (NLO) materials. However, although this type of ionic organic NLO crystals commonly have remarkable second harmonic generation (SHG) responses, they also suffer from overlarge birefringences and relatively small band gaps that be hardly beyond 6.2 eV. Herein, a flexible π‐conjugated [C3H(CH3)O4]2− unit was theoretically revealed, showing great potential for designing NLO crystals with balanced optical properties. Accordingly, through the reasonable NLO‐favourable layered design, a new ionic organic material, NH4[LiC3H(CH3)O4], was successfully obtained. As expected, it achieves not only a large SHG effect (4×KDP), but also a suitable birefringence (0.06@546 nm) and an ultrawide band gap (>6.5 eV). This study provides a new flexible π‐conjugated NLO‐active unit, contributing to design more ionic organic NLO materials with excellent balanced optical properties. [ABSTRACT FROM AUTHOR]

We herein report two asymmetric germanate crystals, KNbGe3O9 and K3Nb3Ge2O13, with different structures and optical properties derived from divergent polymerized forms of GeO4 and NbO6 groups. Remarkably, K3Nb3Ge2O13 achieved a rare combination of the strongest second harmonic generation (SHG) response of 17.5×KDP @ 1064 nm and the largest birefringence of 0.196 @ 546 nm in germanates. It features unique [Nb3O12]∞ tubular chains constructed by circular Nb3O15 tripolymers. Theoretical calculations reveal that the d‐p interactions in the Nb3O15 group are responsible for outstanding optical properties. This work emphasizes the significance of the polymerizable functional units in obtaining high‐performance nonlinear optical (NLO) crystals. [ABSTRACT FROM AUTHOR]

Because mid‐ and far‐infrared (IR) nonlinear optical (NLO) materials play an important role in military and civil fields, plenty of excellent IR NLO materials have been discovered in recent decades, such as chalcogenides with T2 supertetrahedra. Pnictides with T2 supertetrahedra instead of MQ4 (M = IIB, IIIA, IVA metals; Q = P, As) tetrahedra, may favor high second‐harmonic generation (SHG) efficiency due to their large hyperpolarizability, but they have been rarely reported. Therefore, in this study, two pnictides with T2 supertetrahedra, BaSi7P10 and SrSi7P10, are synthesized and studied. With three‐dimensional (3D) framework structures assembled from 1D zigzag chains of [Si7P16] dual‐T2 supertetrahedra, both BaSi7P10 and SrSi7P10 exhibit strong phase‐matching (PM) SHG responses (3.2‐ and 3.0‐times that of AgGaS2), large birefringences (0.077 and 0.112), and wide infrared transparency. In addition, theoretical calculation also reveals that the two‐coordinated P atom can enhance the SHG effects. This study provides a new strategy for exploring new IR NLO materials. [ABSTRACT FROM AUTHOR]

For the first time, the polar covalent tetrahedron [SO2(NH2)2] is revealed as a new deep‐ultraviolet (DUV) nonlinear optical (NLO)‐active unit according to theoretical calculations. Furthermore, sulfamide consisting of polar [SO2(NH2)2] units was confirmed as an excellent candidate as a DUV NLO crystal. Sulfamide provides the optimal balance between composition, structure, and properties, in addition to a very short absorption of 160 nm. It achieves multiple optical performance records for non‐π‐conjugated DUV NLO materials, including the strongest second harmonic generation (SHG) efficiency (about 4 times that of KDP), the largest birefringence (obv.: 0.07@589.3 nm) and the shortest SHG wavelength predicted as 188 nm. [ABSTRACT FROM AUTHOR]

Infrared (IR) nonlinear optical (NLO) crystals are of great significance in modern laser technology, and metal chalcogenides are receiving increasing interest as promising IR NLO candidates. To explore new IR NLO materials with enhanced properties, two quaternary chalcogenides with multiple chromophores, KCu 4 AsS 4 and RbCu 4 AsS 4 , were synthesized using the solvothermal method. KCu 4 AsS 4 and RbCu 4 AsS 4 feature 2D [Cu 6 As 2 S 6 ] ∞ anionic layers with multiple chromophores, and exhibit strong phase-matched second-harmonic generation (SHG) responses (1.8–2.0 × AgGaS 2), wide band gaps, suitable birefringence (0.083 and 0.074 @ 2050 nm) and wide infrared transparency. The theoretical calculation results suggest that the strong SHG responses are ascribed to the 2D [Cu 6 As 2 S 6 ] ∞ anionic layers. Two quaternary chalcogenides with multiple chromophores, KCu 4 AsS 4 and RbCu 4 AsS 4 , exhibit excellent nonlinear optical properties. [Display omitted] [ABSTRACT FROM AUTHOR]