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Thioborates are considered new potential mid-infrared nonlinear optical (NLO) crystals with wide band gaps and large second-harmonic generation (SHG) coefficients. Despite the fact that many rare-earth thioborates are structurally non-centrosymmetric, their SHG properties have only been studied very recently and their mid-infrared (Mid-IR) nonlinear optical properties have not yet been studied. In this work, we provide a new synthetic route for LaBS3 (LBS) by solid state reactions of La2S3, B and S with Li2S as flux, and we further study its thermal and optical properties, and theoretically explore the origin of its IR nonlinear optical properties by DFT calculations. Remarkably, LBS possesses balanced properties required for a good Mid-IR NLO crystal, a large SHG effect (1.2 × AgGaS2@2.05 μm – the largest among all known ortho-thioborates), a high laser induced-damage threshold (14 times of AgGaS2), a wide band gap (3.18 eV), a wide infrared transmission range (0.35–25 μm) and high thermal stability. Theoretical calculations suggest that its large SHG effect originates from the synergy effects of the π-conjugated [BS3]3− anions (41.82%) and the [LaS9]15− groups (58.18%). [ABSTRACT FROM AUTHOR]

The first NLO-active metal iodate-phosphates, namely, Cd2(IO3)(PO4) and Cd1.62Mg0.38(IO3)(PO4) (1 and 2), with three types of NLO groups, have been reported. 1 and 2 are isostructural and the structure of 1 features a 3D network formed by the Cd4(IO3)8/4(PO4)6/3 groups. 1 and 2 with strong SHG signals of 4 × and 3.5 × KH2PO4 are promising SHG materials in the visible region. [ABSTRACT FROM AUTHOR]

Three nonlinear optical materials Cd4REO(BO3)3 (RE = Sm, Eu, Tb) have been synthesized through high-temperature solid-state reactions. In their crystal structures, Cd(1)O8 and Cd(2)O6 polyhedra are interconnected via sharing edges and corners into a 3D anion framework with two types of tunnels based on 4- and 7-membered rings; the BO3 groups are grafted into the above-mentioned types, creating new tunnels based on Cd4B3 seven-membered rings, which are filled by RE3+ cations. Powder SHG measurements revealed that the Cd4REO(BO3)3 (RE = Sm, Eu, Tb) samples display SHG signals that are approximately 1.2, 5.6 and 1.5 times that of the KDP sample. In addition, Cd4EuO(BO3)3 and Cd4TbO(BO3)3 emit red and green light, respectively. The lifetime of the Eu(5D0) state for λex,em = 464, 610 nm in Cd4EuO(BO3)3 is measured to be about 1.43 ms whereas the lifetime of the Tb(5D4) state for λex,em = 376, 543 nm in Cd4TbO(BO3)3 is measured to be about 1.01 ms. [ABSTRACT FROM AUTHOR]

The introduction of coordination polyhedra containing stereo-chemically active lone pairs into the chalcogenide structures is beneficial for realizing centric-to-acentric structural transformation and further enhancing the second-harmonic generation (SHG) efficiency (dij) and the birefringence (Δn) for IR nonlinear optical (NLO) applications; however, this has been rarely reported. Herein, non-centrosymmetric (NCS) arsenates M2As2Q5 (M = Ba, Pb; Q = S, Se) have been screened out by combined experiments and theoretical calculations as a new source of IR NLO materials. Interestingly, they feature unique zero-dimensional structures containing diverse types of discrete As-based coordination polyhedra with M2+ cations located among them, which is discovered for the first time in the IR-NLO chalcogenides. More significantly, they all exhibit multiple key NLO parameters for practical applications in the IR region, including wide phase-matching ranges (>950–1370 nm), remarkable dij (1.0–2.7 × AgGaS2) and large laser-induced damage thresholds (LIDTs = 6.8–12.4 × AgGaS2). Theoretical studies demonstrate that the discrete As-based coordination polyhedra play a critical role in the linear optical and NLO responses of the title compounds. We believe that this work can not only enrich the diversity of NLO-active groups, but also provide a new choice for material design in NCS chalcogenides. [ABSTRACT FROM AUTHOR]

A novel mixed-anion NLO crystal, namely, Bi4O(I3O10)(IO3)3(SeO4), containing a brand-new "pinwheel-like" I3O105− polyiodate anion group was constructed from the trimeric condensation of IO43− monomers. Bi4O(I3O10)(IO3)3(SeO4) exhibits a complex 3D topological structure and gives a moderate second harmonic generation (SHG) signal about 1.1 times that of KH2PO4 (KDP). [ABSTRACT FROM AUTHOR]

It is highly desirable but challenging to design and synthesize novel non-centrosymmetric (NCS) metal–organic frameworks (MOFs) with excellent nonlinear optical (NLO) properties. And the origin of their NLO responses remains vague. Herein, a novel 1D Zn-based MOF with unique zigzag helical chains, [Zn(bct)(H2O)2] (MOF-FJ1), has been prepared from achiral precursors. It crystallizes in an NCS space group P212121 (no. 19) and is found to be a remarkable NLO material with a strong second-harmonic-generation (SHG) response (3.5 × commercial KH2PO4 (KDP)) and high laser-induced damage threshold (1.6 × commercial KDP). Moreover, theoretical calculations based on the length-gauge formalism are discussed to unveil a deepened cognition of the structure–property relationship, providing theoretical insight into the origin of the NLO response. [ABSTRACT FROM AUTHOR]

New middle and far-infrared (MFIR) nonlinear optical (NLO) chalcogenides have been receiving increasing attention for their great importance in military and civil fields. In addition, the current challenge in the efforts for identifying a promising MFIR NLO material lies in achieving simultaneously large second-harmonic generation (SHG) intensity and high laser-induced damage threshold (LIDT) in the same material. In this study, two quaternary non-centrosymmetric (NCS) sulfides, BaAg2GeS4 (1) and BaAg2SnS4 (2), were synthesized from a high-temperature solid-state reaction using BaCl2 flux in evacuated closed silica tubes. Although 1 and 2 show identical stoichiometry, they crystallize in different NCS space groups, tetragonal I4̅2m (no. 121) and orthorhombic I222 (no. 23), respectively, based on the results of crystal structure solution. In their structures, highly distorted AgS4 tetrahedra interconnect together via corner-sharing to form two-dimensional (2D) layers, which are further bridged with isolated GeS4 or SnS4 units to produce a three-dimensional (3D) framework structure with Ba cations lying in the tunnels. Remarkably, they not only possess phase-matchable (PM) abilities but also exhibit a good balance between strong SHG responses (1.7× and 0.4× AgGaS2) and high LIDTs (3.2× and 1.5× AgGaS2). Moreover, theoretical calculations based on density functional theory (DFT) methods have aided the understanding of energy bands, electronic structures, and linear and NLO properties. [ABSTRACT FROM AUTHOR]

Two new ternary rare earth chalcogenides, Dy3GaS6 (1) and Y3GaS6 (2), are reported here. They both crystallize in the orthorhombic space group Cmc21 (no. 36). Both are synthesized in pure phase and show phase-matchable second harmonic generation (SHG) of about 0.2 and 0.5 times, respectively for 1 and 2, as strong as that of KTiOPO4 (KTP) based on the powder SHG measurement at the wavelength of 1910 nm. They possess high powder laser induced damage thresholds (LIDTs), respectively, about 14 and 18 times that of AgGaS2 (AGS) based on the powder LIDT measurements under 1064 nm laser irradiation. They both exhibit wide transparency in the IR region (2.5–25 μm). It is believed that the title compounds are new candidates for nonlinear optical (NLO) materials in the IR region. To gain further insights into the NLO and LIDT properties of 1 and 2, the calculations of second-order NLO susceptibility and lattice energy density (LED) were also performed to explain their SHG efficiencies and high LIDTs. [ABSTRACT FROM AUTHOR]

New middle and far-infrared (MFIR) nonlinear optical (NLO) chalcogenides have been receiving increasing attention for their great importance in military and civil fields. In addition, the current challenge in the efforts for identifying a promising MFIR NLO material lies in achieving simultaneously large second-harmonic generation (SHG) intensity and high laser-induced damage threshold (LIDT) in the same material. In this study, two quaternary non-centrosymmetric (NCS) sulfides, BaAg2GeS4 (1) and BaAg2SnS4 (2), were synthesized from a high-temperature solid-state reaction using BaCl2 flux in evacuated closed silica tubes. Although 1 and 2 show identical stoichiometry, they crystallize in different NCS space groups, tetragonal I4̅2m (no. 121) and orthorhombic I222 (no. 23), respectively, based on the results of crystal structure solution. In their structures, highly distorted AgS4 tetrahedra interconnect together via corner-sharing to form two-dimensional (2D) layers, which are further bridged with isolated GeS4 or SnS4 units to produce a three-dimensional (3D) framework structure with Ba cations lying in the tunnels. Remarkably, they not only possess phase-matchable (PM) abilities but also exhibit a good balance between strong SHG responses (1.7× and 0.4× AgGaS2) and high LIDTs (3.2× and 1.5× AgGaS2). Moreover, theoretical calculations based on density functional theory (DFT) methods have aided the understanding of energy bands, electronic structures, and linear and NLO properties. [ABSTRACT FROM AUTHOR]

The first NLO-active metal iodate-phosphates, namely, Cd 2 (IO 3 )(PO 4 ) and Cd 1.62 Mg 0.38 (IO 3 )(PO 4 ) (1 and 2), with three types of NLO groups, have been reported. 1 and 2 are isostructural and the structure of 1 features a 3D network formed by the Cd 4 (IO 3 ) 8/4 (PO 4 ) 6/3 groups. 1 and 2 with strong SHG signals of 4 × and 3.5 × KH 2 PO 4 are promising SHG materials in the visible region.

A novel salt-inclusion fluoroiodate [GaF(H 2 O)][IO 3 F] derived from CsIO 2 F 2 was ingeniously obtained through anisotropic polycation substitution. Because the catenulate [GaF(H 2 O)] 2+ framework serves as a template for the favorable assembly of the polar [IO 3 F] 2- groups and contributes to the nonlinear coefficient, [GaF(H 2 O)][IO 3 F] exhibits a greatly improved second-harmonic generation (SHG) effect of 10 times that of KH 2 PO 4 (KDP) and a considerable band gap of 4.34 eV compared to the parent compound CsIO 2 F 2 (3 × KDP, 4.5 eV). Particularly, to the best of our knowledge, [GaF(H 2 O)][IO 3 F] has the largest laser-induced damage threshold (LDT) of 140 × AgGgS 2 of the reported iodates. All these results signify that [GaF(H 2 O)][IO 3 F] is a promising nonlinear optical (NLO) crystal. This work also proposes that anisotropic polycation substitution is an effective approach to optimize the SHG effect and develop excellent NLO materials., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

A novel mixed-anion NLO crystal, namely, Bi4O(I3O10)(IO3)3(SeO4), containing a brand-new "pinwheel-like" I3O105- polyiodate anion group was constructed from the trimeric condensation of IO43- monomers. Bi4O(I3O10)(IO3)3(SeO4) exhibits a complex 3D topological structure and gives a moderate second harmonic generation (SHG) signal about 1.1 times that of KH2PO4 (KDP).

New middle and far-infrared (MFIR) nonlinear optical (NLO) chalcogenides have been receiving increasing attention for their great importance in military and civil fields. In addition, the current challenge in the efforts for identifying a promising MFIR NLO material lies in achieving simultaneously large second-harmonic generation (SHG) intensity and high laser-induced damage threshold (LIDT) in the same material. In this study, two quaternary non-centrosymmetric (NCS) sulfides, BaAg 2 GeS 4 (1) and BaAg 2 SnS 4 (2), were synthesized from a high-temperature solid-state reaction using BaCl 2 flux in evacuated closed silica tubes. Although 1 and 2 show identical stoichiometry, they crystallize in different NCS space groups, tetragonal I4[combining macron]2m (no. 121) and orthorhombic I222 (no. 23), respectively, based on the results of crystal structure solution. In their structures, highly distorted AgS 4 tetrahedra interconnect together via corner-sharing to form two-dimensional (2D) layers, which are further bridged with isolated GeS 4 or SnS 4 units to produce a three-dimensional (3D) framework structure with Ba cations lying in the tunnels. Remarkably, they not only possess phase-matchable (PM) abilities but also exhibit a good balance between strong SHG responses (1.7× and 0.4× AgGaS 2 ) and high LIDTs (3.2× and 1.5× AgGaS 2 ). Moreover, theoretical calculations based on density functional theory (DFT) methods have aided the understanding of energy bands, electronic structures, and linear and NLO properties.