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We herein reported our strategy to assemble planar π-conjugated [B(OH)3] and [C2O4]2−/[HC2O4]−/[C4O4]2− functional groups to explore short-wavelength birefringent crystals. Three compounds, K2C2O4·B(OH)3, Cs4(HC2O4)2(C2O4)·[B(OH)3]2 and K(C4O4)0.5·B(OH)3, which all exhibit a layered structure favorable for generating large optical anisotropy, were synthesized and characterized. The strategy of assembling π-conjugated [B(OH)3] and C–O functional modules shows the potential to explore promising UV birefringent materials. [ABSTRACT FROM AUTHOR]

Nonlinear optical (NLO) crystals that can expand the spectral range of laser outputs have attracted significant attention for their optoelectronic applications. The research progress from the discovery of new single crystal structures to the realization of final device applications involves many key steps and is very time consuming and challenging. Consequently, exploring efficient design strategies to shorten the research period and accelerate the rational design of novel NLO materials has become imperative to address the pressing demand for advanced materials. The recent shift in paradigm toward exploring new NLO crystals involves significant progress from extensive "trial and error" methodologies to strategic approaches. This review proposes the concept of rational structure design for nonlinear optical crystals leveraging advantageous templates. It further discusses their optical characteristics, promising applications as second-order NLO materials, and the relationship between their structure and performance, and highlights urgent issues that need to be addressed in the field of NLO crystals in the future. The review aims to provide ideas and driving impetus to encourage researchers to achieve new breakthroughs in the next generation of NLO materials. [ABSTRACT FROM AUTHOR]

The combination of SnII or SbIII with π, non‐π‐conjugated units has produced birefringent crystals with birefringence ranging from 0.005 to 0.468@1064 nm. It is proven that introducing SnII or SbIII into crystals is a feasible strategy to enlarge the birefringence, which not only promotes the miniaturization of fabricated devices, but also effectively modulates polarized light. Herein, recently discovered SnII, SbIII‐based birefringent crystals with birefringence investigated are summarized, including their crystal structure and optical properties, especially birefringence. This review also presents the influence of SnII, SbIII with stereochemically active lone pair on the optical anisotropy. We hope that this work provides a clear perspective on the crystal chemistry of SnII, SbIII‐based optical functional crystals and promotes the development of new birefringent crystals with large optical anisotropy. [ABSTRACT FROM AUTHOR]

A long‐lasting challenge in ultraviolet (UV) nonlinear optical (NLO) materials design is to combine conflicting and harsh properties into one structure, including wide UV transparency, strong NLO efficiency, and moderate birefringence to realize phase‐matching at short wavelength. A fluorine‐directed material design strategy is adopted to accelerate the process of finding NLO materials with optimal performances. In this work, taking LiB3O5 (LBO) as a maternal structure, one O atom with two F atoms is substituted and LiNaB6O9F2 which possesses novel double interpenetrating 3[B6O9F2]∞ networks and fluorine‐directed optimal performances including enhanced birefringence and phase‐matching capacity is successfully obtained. The perfect balance among deep‐UV cutoff edge, large second‐harmonic generation (SHG) response (1.1 × KDP), and moderate birefringence (0.067 at 1064 nm) of LiNaB6O9F2 makes it a promising UV NLO crystal. [ABSTRACT FROM AUTHOR]

Deep-ultraviolet (DUV) nonlinear optical (NLO) crystals that can extend the output range of coherent light below 200 nm are pivotal materials for solid-state lasers. To date, KBe2BO3F2 (KBBF) is the only usable crystal that can generate DUV coherent light by direct second harmonic generation (SHG), but the layered growth habit and toxic ingredients limit its application. Herein, we report a new fluoroborophosphate, (NH4)3B11PO19F3 (ABPF), containing four different functional units: [BO3], [BO4], [BO3F] and [PO4]. ABPF exhibits a KBBF-like structure while eliminating the limitations of KBBF crystal. The unique [B5PO10F]∞ layers enhance ABPF's performance; for example, it has a large SHG response (1.2 × KDP) and a sufficient birefringence (0.088 at 1064 nm) that enables the shortest phase-matching wavelength to reach the DUV region. Meanwhile, the introduction of strong B-O-P covalent bonds decreases the layered growth habit. These findings will enrich the structural chemistry of fluoroborophosphate and contribute to the discovery of more excellent DUV NLO crystals. [ABSTRACT FROM AUTHOR]

Polarization modulation of deep‐UV light is of significance to current technologies, and to this end, the birefringent crystal has emerged as an invaluable material as it allows for effective light modulation. Herein, a double‐modification strategy driven by F and OH anions that makes double effects towards the critical property enhancement of deep‐UV birefringent crystals is proposed. This leads to a new hydroxyborate (NH4)4[B12O16F4(OH)4] with giant cluster as a deep‐UV birefringent crystal with large birefringence (Δnexp.=0.12@546.1 nm). This birefringence is a record among inorganic hydroxyborates with experimentally measured birefringence. Structural analysis shows that the near‐plane arrangement of [B12O16F4(OH)4] cluster is responsible for the large optical anisotropy. Theoretical calculations indicate that its π‐conjugated [BO3] and [BO2OH] units are the main source of this large optical anisotropy. [ABSTRACT FROM AUTHOR]

Discovery of new efficient nonlinear optical (NLO) materials with large second‐order nonlinearity for the short‐wave ultraviolet spectral region (λPM≤266 nm, PM=phase‐matching) is still very challenging. Herein, a new beryllium‐free borate CaZn2(BO3)2 with Sr2Be2B2O7 (SBBO) double‐layered like configuration was rationally designed, which not only preserves the structural merits but also eliminates the limitations of the SBBO crystal. CaZn2(BO3)2 shows a large PM second harmonic generation (SHG) reponse of 3.8×KDP, which is 38 times higher than that of its barium analogue. This enhancement mainly originates from the 1[Zn2O6]∞ polar chains with a large net dipole moment and [BO3] units with a high NLO active density. Our findings show the great significance of the [ZnO4] tetrahedra introduced strategy to design beryllium‐free SBBO‐type NLO crystals and also verify the feasibility of using simple non‐isomorphic substitution to induce giant second‐order nonlinearity enhancement. [ABSTRACT FROM AUTHOR]

Discovery of new efficient nonlinear optical (NLO) materials with large second‐order nonlinearity for the short‐wave ultraviolet spectral region (λPM≤266 nm, PM=phase‐matching) is still very challenging. Herein, a new beryllium‐free borate CaZn2(BO3)2 with Sr2Be2B2O7 (SBBO) double‐layered like configuration was rationally designed, which not only preserves the structural merits but also eliminates the limitations of the SBBO crystal. CaZn2(BO3)2 shows a large PM second harmonic generation (SHG) reponse of 3.8×KDP, which is 38 times higher than that of its barium analogue. This enhancement mainly originates from the 1[Zn2O6]∞ polar chains with a large net dipole moment and [BO3] units with a high NLO active density. Our findings show the great significance of the [ZnO4] tetrahedra introduced strategy to design beryllium‐free SBBO‐type NLO crystals and also verify the feasibility of using simple non‐isomorphic substitution to induce giant second‐order nonlinearity enhancement. [ABSTRACT FROM AUTHOR]

Exploring non π‐conjugated phosphate birefringent crystal with a large birefringence has been a great challenge. Herein, based on the unique two‐dimensional layered structure in KBe2BO3F2 (KBBF), two new compounds, Sn2PO4I and Sn2BO3I, were designed and synthesized successfully, maintaining the layer structural feature and enhancing the optical anisotropy of crystals. In particular, the birefringence of Sn2PO4I is larger than or equal to 0.664 @546 nm, which is largest among the reported borates and phosphates, even surpassing commercial birefringent crystals YVO4 and TiO2. This work indicates that a breakthrough in birefringence of inorganic compound was achieved. Also, it provides a guiding idea for exploring large birefringence materials in the future. [ABSTRACT FROM AUTHOR]

The chlorine barium nitrate Ba(NO3)Cl was synthesized, for the first time to the best of our knowledge, by using a mild hydrothermal method. Its structure was observed to feature an ABW-type topology (BaCl-ABW) framework, which can be considered as stacks of honeycomb-shaped sheets. Also, Ba(NO3)Cl crystals with dimensions of up to 2 × 1 × 0.5 mm3 were grown. Remarkably, Ba(NO3)Cl was found to exhibit a short UV cutoff edge (below 213 nm) and a markedly enhanced birefringence (Δn = 0.178 @ 1064 nm), about 19 times that of its parent phase BaCl2 (Δn = 0.009 @ 1064 nm). Theoretical calculations indicated that the birefringence enhancement mainly derived from the planar [NO3] triangles. [ABSTRACT FROM AUTHOR]

Maximizing the optical anisotropy in birefringent materials has emerged as an efficient route for modulating the polarization‐dependent light propagation. Currently, the generation of deep‐ultraviolet (deep‐UV) polarized light below 200 nm is essential but challenging due to the interdisciplinary significance and insufficiency of high‐performing birefringent crystals. Herein, by introducing multiple heteroanionic units, the first sodium difluorodihydroxytriborate‐boric acid Na[B3O3F2(OH)2]⋅[B(OH)3] has been characterized as a novel deep‐UV birefringent crystal. Two rare heteroanionic units, [B3O3F2(OH)2] and [B(OH)3], optimally align to induce large optical anisotropy and also the dangling bonds are eliminated with hydrogens, which results in an extremely large birefringence and band gap. The well‐ordered OH/F anions in [B3O3F2(OH)2] and [B(OH)3] were identified and confirmed by various approaches, and also the origin of large birefringence was theoretically discussed. These results confirm the feasibility of utilizing hydrogen involved heteroanionic units to design crystals with large birefringence, and also expand the alternative system of deep‐UV birefringent crystals with new hydroxyfluorooxoborates. [ABSTRACT FROM AUTHOR]

A new compound Cs2AlB5O10 was synthesized by a high temperature solution method in open air. It features a DUV cutoff edge below 190 nm and a moderate SHG response (0.8 × KDP at 1064 nm), indicating that it may have certain application prospects in the UV nonlinear optical region. [ABSTRACT FROM AUTHOR]

The main commercially used birefringent oxides α‐BaB2O4 and YVO4 have the birefringences of 0.12 and 0.22. We propose a targeted high‐throughput screening system to search birefringence‐active functional modules (FMs) and large birefringent materials. A series of π‐conjugated C−O units [C2O4]2−, [C2O6]2−, [C4O4]2−, and [C6O6]2− are discovered to be birefringence‐active FMs. Theoretical and experimental studies on the crystals with C−O units confirm the feasibility of strategy. Based on this, the C−O containing compounds ranging from deep‐ultraviolet to near‐infrared region with large birefringence from 0.1 to 1.35 are found, and most of them break through the birefringent limit of oxides. The (NH4)2C2O4⋅H2O crystal is grown and its experimental birefringence is 0.248 at 546 nm, which is identified as a promising UV birefringent crystal. The A‐site cations play significant roles in optical properties by influencing the density and arrangement of the C−O units. [ABSTRACT FROM AUTHOR]

We demonstrate a 355 nm ultraviolet nanosecond laser produced by the type I phase-matched frequency doubling in a K3B6O10Br (KBOB) nonlinear optical crystal. The use of 5022 μJ, 710 nm pump pulses at 10 Hz repetition rate produces 4.273 ns, 355 nm, 717 μJ pulses that corresponds to a frequency doubling conversion efficiency of 14.3%. The energy instability of the frequency-doubled pulse train measured is less than ±1% for maximum output pulse energy (∼717 μJ). Our experimental results show that KBOB is a promising nonlinear optical crystal for generating ultraviolet nanosecond laser pulses through frequency doubling. [ABSTRACT FROM AUTHOR]

The first triple‐layered borate with edge‐sharing BO4 tetrahedra, β‐CsB9O14 was obtained under vacuum‐sealed condition. It represents a new structure type and enriches the structural diversity of borates. Moreover, β‐CsB9O14 exhibits a short UV cutoff edge and a large birefringence, indicating that it could be regarded as a DUV birefringent crystal. [ABSTRACT FROM AUTHOR]

Abstract: KBe2BO3F2 (KBBF) is still the only practically usable crystal that can generate deep‐ultraviolet (DUV) coherent light by direct second harmonic generation (SHG). However, applications are hindered by layering, leading to difficulty in the growth of thick crystals and compromised mechanical integrity. Despite efforts, it is still a great challenge to discover new nonlinear optical (NLO) materials that overcome the layering while keeping the DUV SHG available. Now, two new DUV NLO beryllium borates have been successfully designed and synthesized, NH4Be2BO3F2 (ABBF) and γ‐Be2BO3F (γ‐BBF), which not only overcome the layering but also can be used as next‐generation DUV NLO materials with the shortest type I phase‐matching second‐harmonic wavelength down to 173.9 nm and 146 nm, respectively. Significantly, γ‐BBF is superior to KBBF in all metrics and would be the most outstanding DUV NLO crystal. [ABSTRACT FROM AUTHOR]

Metal borate halides refer to the metal borates containing additional halogen anions ( i.e. , F, Cl, Br or I). In recent years, motivated by the well-known high performance nonlinear optical (NLO) material, KBe 2 BO 3 F 2 (KBBF), metal borate halides have been arousing intensive interest. The combination of halogen anions with borate groups affords a large number of metal borate halides with anionic structures ranging from 0D clusters, 1D chains, 2D layers to 3D networks. In addition, the introduction of halogen anions into borates is proven to be an effective strategy to design new noncentrosymmetric (NCS) crystals, which is required for NLO materials. In this review, recently discovered metal borate halides are summarized, including their synthesis, crystal structure features, properties and second-order NLO performances. This review also presents the structure–properties relationship studies focusing on the positive influence of introducing halogen anions on the optical properties. We hope that this work will obtain a clear perspective on crystal chemistry of metal borate halides and facilitate the discovery of new second-order NLO materials for urgent demands in laser sciences. [ABSTRACT FROM AUTHOR]

A series of LiSr1−xPbxBO3 (x = 0.138, 0.285, 0.320, 0.379, 0.417, and 0.5) crystals have been obtained through a high-temperature solution reaction with spontaneous nucleation technique, and the crystal structures were solved from single-crystal X-ray diffraction data. Through a great deal of experiments, it was determined that the maximum value of x cannot be greater than 0.5 possibly because the Sr/Pb–O bond length and the equivalent isotropic displacement parameter of O(3) atoms continuously increased with the increased ratio of Pb2+ cations. It is found that when the Sr atoms were partially substituted with Pb atoms with optical anisotropies, the birefringence improved from 0.0494 at 1064 nm in LiSrBO3 to 0.0721 at 1064 nm in LiSr0.5Pb0.5BO3. Based on the first-principles and real-space atom-cutting method, the origin of birefringence was attributed to the Pb2+ cations and (BO3)3− groups in LiSr0.5Pb0.5BO3. The infrared spectrum properties and thermal behavior were also reported. [ABSTRACT FROM AUTHOR]

A noncentrosymmetric aluminum borate crystal, Al5BO9, was obtained via high-temperature solution method. Considering the structure diversities of Al5BO9, the single crystal structure was cautiously redetermined before the investigation. The fundamental building blocks of the structure are BO3 triangles, AlO4 tetrahedra, and AlO6 octahedra. Since Al5BO9 only consists of strong covalent B–O and Al–O bonds, it is worth investigating the structure–optical property relationship thoroughly, especially the linear and nonlinear optical properties. To gain further insight into the origin of the nonlinear optical response of Al5BO9, the electronic structure calculations, second harmonic generation (SHG)-weighted electron density, and dipole moment of polyhedra were analyzed in detail. All evidences deduced from calculated results indicate that the SHG contribution from the Al–O polyhedra is more pronounced than that of the BO3 group in Al5BO9, which is anticipated to open a window for the search and design of new inorganic materials. [ABSTRACT FROM AUTHOR]

The magnesium borate fluoride Mg5(BO3)3F was grown by spontaneous crystallization with molten flux based on the MgF2-LiF-Na2CO3-H3BO3 solvent. Structure solution from single-crystal X-ray diffraction shows that the title compound crystallizes in the orthorhombic space group Pnma (No. 62) with cell dimensions of a = 10.068(5) Å, b = 14.858(7) Å, c = 4.540(2) Å and Z = 4. Its structure features a three-dimensional (3D) Mg-O-F framework composed of MgO5F and MgO6 polyhedra and isolated BO3 groups. The detailed structure comparison referred to Mg5(BO3)3F, Mg3BO3F3 and β-Mg2BO3F was carried out. The infrared spectrum (IR) and the bond valence sum (BVS) calculations of Mg5(BO3)3F verify the validity of the structure. The calculated band structure and the density of states of Mg5(BO3)3F suggest that its indirect bandgap is 5.27 eV. The compound was additionally investigated by UV/Vis-NIR diffuse reflectance spectroscopy and thermal analysis. [ABSTRACT FROM AUTHOR]

For the first time, single crystals of KPbBP2O8 with sizes up to 18 × 13 × 6 mm have been grown from a stoichiometric mixture of its components by the top seed growth method. The crystal structure was determined from single-crystal X-ray data: tetragonal, space group I $\bar {4}$2 d, a = 7.1464(7) Å, c = 13.8917(16) Å, Z = 4. It exhibits an isolated [BP2O8]3- unit that is built from nearly ideal tetrahedral BO4 and PO4 groups, which are connected to each other alternatively by corner-sharing O atoms to make a 12-membered ring. Transmission spectroscopy illustrates that the UV cutoff edge is at approximately 235 nm. Furthermore, IR spectroscopy, thermal analysis, and second-harmonic generation (SHG) measurements were also performed on the reported material. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new lithium dilead pentaborate, LiPb2B5O10, has been synthesized. [•] LiPb2B5O10 is a congruent melting compound. [•] The band gap calculation of LiPb2B5O10 revealed an indirect gap with 3.433eV. [Copyright &y& Elsevier]

Abstract: Single crystals of Pb2Bi2AlB3O11 were grown from a PbO/Bi2O3/Al2O3/H3BO3/PbF2 flux. The single-crystal X-ray structural analysis showed that Pb2Bi2AlB3O11 crystallizes in the monoclinic space group C2/c (No. 15) with a =17.263(2)Å, b =8.7322(11)Å, c =6.8081(9)Å, α =90°, β =90.566(2)°, γ =90°, Z =4 and R 1 =0.0393, wR 2 =0.1013. Its structure may be described as three-dimensional frameworks formed of (100) [Pb6Bi6Al3O6]∞ layers stacked along a-axis. The layers are interconnected via BO3 groups. The IR spectrum further confirmed the presence of BO3 groups in the structure. The thermal analysis suggests that Pb2Bi2AlB3O11 is a congruently melting compound. [Copyright &y& Elsevier]

Single crystals of LisCuB4Olo have been synthesized, and its crystal structure has been determined. Li6CuB4O10 crystallizes in the non-centrosymmetric triclinic space group P1 (No. 1). The structure consists of isolated [CuB4O10]8- polyanions that are bridged by six LiO4 tetrahedra. Li6CuB4O10 is a congruently melting compound. It produces SHG intensity similar to that produced by KH2PO4 and is phase-matchable. [ABSTRACT FROM AUTHOR]

Abstract: Single crystals of Pb2CuB2O6 were grown from a PbO/CuO/B2O3 flux, and crystallize in a monoclinic cell of dimensions a =5.6311(6), b =8.7628(9), c =6.2025(6)Å, and β =115.7060(10)° with Z =2; the space group is P21/c (no. 14). The structure was determined from 662 unique reflections and refined to the final residuals R 1 =0.0217, R 2 =0.0586. The structure is characterized by the two-dimensional layer of interconnected rectangular planar CuO4 and triangular planar BO3 groups. The results of quantitative analysis ICP, DTA, vibrational spectroscopy, and magnetic investigations are also presented. [Copyright &y& Elsevier]

Abstract: Pb8B9O21F has been synthesized from the PbO–PbF2–B2O3 system for the first time. It crystallizes in the trigonal system, space group R-3c with unit-cell parameters a =9.740(3)Å, b =9.740(3)Å, c =38.167(15)Å, Z =6, and volume=3135.5(8)Å3. The structure of the compound is solved by the direct methods and to the best of our knowledge, Pb8B9O21F is the first structure reported so far with isolated boron–oxygen anionic [B9O21]15−compound. Functional groups present in the sample were identified by Fourier transform infrared spectrum. The Diffuse reflectance spectrum shows that the ultraviolet cutoff edge for the Pb8B9O21F crystal is about 276nm. [Copyright &y& Elsevier]

We demonstrate the output of femtosecond (fs) green and ultraviolet (UV) lasers through second-harmonic generation using type-I phase-matched K3B6O10Br (KBOB) nonlinear optical (NLO) crystals. The wavelengths of the fs green and UV lasers are 515 and 400 nm, respectively. The 1030-nm fs laser is used to pump the KBOB crystal to generate the green output. When the laser pump power reached 880 mW with a repetition rate of 1 kHz, an output power of 235 mW was obtained from the green laser with an optical conversion efficiency of 26.7%. When a pump power of 5.87 W was attained with repetition rate of 10 kHz, a green output power of 1.03 W was generated. The fs UV laser is pumped by an 800-nm fs laser, with 132-mW output power achieved when the pump power was 470 mW with an optical conversion efficiency of 28.1%. The experimental results indicate that the KBOB crystal is a promising NLO crystal for generating fs green and UV lasers because of its excellent NLO properties. [ABSTRACT FROM AUTHOR]

Single crystals of the title compounds are prepared by the spontaneous crystallization method from mixtures of NaOH, NaBr or NaCl, and H3BO3 in the molar ratio of 1:1:2 (Pt crucible, 300 °C for 12 h and 500 °C for 10 h). [ABSTRACT FROM AUTHOR]

Nonlinear optical (NLO) crystals are essential materials for generation of coherent UV light in solid state lasers. KBBF is the only material that can achieve coherent light below 200 nm by direct second harmonic generation (SHG). However, its strong layer habits and the high toxicity of the beryllium oxide powders required for synthesis limit its application. By substituting Be with Zn and connecting adjacent [Zn2BO3O2]∞ layers by B3O6 groups, a new UV nonlinear optical material, Cs3Zn6B9O21, was synthesized. It overcomes the processing limitations of KBBF and exhibits the largest SHG response in the KBBF family. [ABSTRACT FROM AUTHOR]

Discovery of new efficient nonlinear optical (NLO) materials with large second‐order nonlinearity for the short‐wave ultraviolet spectral region (λPM≤266 nm, PM=phase‐matching) is still very challenging. Herein, a new beryllium‐free borate CaZn2(BO3)2 with Sr2Be2B2O7 (SBBO) double‐layered like configuration was rationally designed, which not only preserves the structural merits but also eliminates the limitations of the SBBO crystal. CaZn2(BO3)2 shows a large PM second harmonic generation (SHG) reponse of 3.8×KDP, which is 38 times higher than that of its barium analogue. This enhancement mainly originates from the 1[Zn2O6]∞ polar chains with a large net dipole moment and [BO3] units with a high NLO active density. Our findings show the great significance of the [ZnO4] tetrahedra introduced strategy to design beryllium‐free SBBO‐type NLO crystals and also verify the feasibility of using simple non‐isomorphic substitution to induce giant second‐order nonlinearity enhancement. [ABSTRACT FROM AUTHOR]

Discovery of new efficient nonlinear optical (NLO) materials with large second‐order nonlinearity for the short‐wave ultraviolet spectral region (λPM≤266 nm, PM=phase‐matching) is still very challenging. Herein, a new beryllium‐free borate CaZn2(BO3)2 with Sr2Be2B2O7 (SBBO) double‐layered like configuration was rationally designed, which not only preserves the structural merits but also eliminates the limitations of the SBBO crystal. CaZn2(BO3)2 shows a large PM second harmonic generation (SHG) reponse of 3.8×KDP, which is 38 times higher than that of its barium analogue. This enhancement mainly originates from the 1[Zn2O6]∞ polar chains with a large net dipole moment and [BO3] units with a high NLO active density. Our findings show the great significance of the [ZnO4] tetrahedra introduced strategy to design beryllium‐free SBBO‐type NLO crystals and also verify the feasibility of using simple non‐isomorphic substitution to induce giant second‐order nonlinearity enhancement. [ABSTRACT FROM AUTHOR]

The chlorine barium nitrate Ba(NO3)Cl was synthesized, for the first time to the best of our knowledge, by using a mild hydrothermal method. Its structure was observed to feature an ABW-type topology (BaCl-ABW) framework, which can be considered as stacks of honeycomb-shaped sheets. Also, Ba(NO3)Cl crystals with dimensions of up to 2 × 1 × 0.5 mm3 were grown. Remarkably, Ba(NO3)Cl was found to exhibit a short UV cutoff edge (below 213 nm) and a markedly enhanced birefringence (Δn = 0.178 @ 1064 nm), about 19 times that of its parent phase BaCl2 (Δn = 0.009 @ 1064 nm). Theoretical calculations indicated that the birefringence enhancement mainly derived from the planar [NO3] triangles. [ABSTRACT FROM AUTHOR]

According to the relationship between structure and properties, it is difficult for UV/DUV nonlinear optical crystals constructed by single π-conjugated or tetrahedral units to achieve the balance of large bandgap, large SHG effect and moderate birefringence. Therefore, the combination of π-conjugated groups and tetrahedra is the effective way to construct UV/DUV nonlinear optical crystals. According to the structural characteristics, a series of NLO crystals with shortest PM wavelength shorter than 266 nm are summarized and investigated, which mainly involve their cutoff edge, SHG effect, birefringence, and shortest PM wavelength. [Display omitted] • The combination of π-conjugated [XY 3 ] and tetrahedral [XY 4 ] as NLO materials (λ pm <266 nm) are summarized. • The benefits of the combination of [XY 3 ] and [XY 4 ] are analyzed. • It is classified and described in detail from the perspective of structural chemistry. • Efficient strategies toward design of novel UV/DUV NLO materials are provided. As the critical devices in laser science and technology, nonlinear optical (NLO) crystals can expand the wavelength to the ultraviolet (UV), or deep-ultraviolet (DUV) region. Generally speaking, a functional UV/DUV NLO material should satisfy the following basic requirements: wide transmittance range; large NLO coefficient (d ij > 0.39 pm/V); moderate birefringence (Δ n : 0.05–0.10@1064 nm) to achieve the shortest phase-matching (PM) wavelength to the short UV (λ PM ≤ 266 nm) or even DUV region (λ PM ≤ 200 nm). Nevertheless, it is challenging to satisfy all of the aforementioned conditions with the single π-conjugated or tetrahedra groups. In this review, we will focus on UV or DUV NLO crystals by combining π-conjugated planar [XY 3 ] ([BO 3 ], [CO 3 ], [C(NH 2) 3 ]) with tetrahedral [XY 4 ] units ([BO 4 ], [PO 4 ], [SO 4 ], [BeO 4 /BeO 3 F], [AlO 4 /AlO 3 F], [ZnO 4 /ZnO 3 F/ZnO 3 Cl], [BO x F 4-x ], etc.), which can eliminate the dangling bonds of π-conjugated groups through tetrahedra and compensate for the birefringence and second-harmonic generation (SHG) through π-conjugated groups. According to this strategy, about 120 compounds were screened, including theoretically predicted, we summarized their structures, linear and nonlinear properties, and classified them into the following main categories according to the different π-conjugated groups in the structure: 1. Borate-based NLO crystals, 2. Carbonate-based NLO crystals, 3. Guanidinium-based NLO crystals. More importantly, by combining π-conjugated [XY 3 ] and tetrahedral [XY 4 ] genes, we anticipate that this review will provide useful implications for the thoughtful design and synthesis of novel NLO materials with the desired features. [ABSTRACT FROM AUTHOR]

The combination of Sn2+ cations with stereochemically active lone pair and the smaller electronegativity of Cl− and Br− anions generates two new birefringent crystal materials, Sn 9 O 4 Br 10 and Sn 9 O 4 ClBr 9. The first-principles calculations reveal that the two crystals possess a large birefringence, 0.273 and 0.258@1064 nm, respectively, deriving from the extremely intensive stereochemically active lone pair of highly distorted Sn–O/X (X = Cl, Br) polyhedra. And it is worth noting that the birefringence of Sn 9 O 4 Br 10 is the largest among the tin(II)-containing oxyhalides reported so far. This work provides an approach for the future exploration of new birefringent crystal materials. Two new birefringent crystal materials, Sn 9 O 4 Br 10 and Sn 9 O 4 ClBr 9 were systematically investigated. The first-principles calculations reveal that the two crystals possess a large birefringence, 0.273 and 0.258@1064 nm, respectively, deriving from the extremely intensive stereochemical activity lone pair of highly distorted Sn–O/X (X = Cl, Br) polyhedra. [Display omitted] [ABSTRACT FROM AUTHOR]

Chalcopyrite-type AgGaQ2 (Q = S, Se) and ZnGeP2 are the main commercial infrared nonlinear optical (IR NLO) crystals. Unfortunately, performance defects including low laser damage threshold (LDT), harmful two-photon absorption (TPA), or small birefringence limit their application. With this background, four new compressed chalcopyrite-like IR NLO materials Li2BaMIVQ4 (MIV = Ge, Sn; Q = S, Se) were successfully synthesized with the typical AgGaQ2 as templates. Remarkably, Li2BaGeS4 and Li2BaSnS4 not only maintain the good NLO responses (0.5 and 0.7 x AgGaS2) but also overcome low LDTs and TPA of commercial chalcopyrites, demonstrating that they satisfy critical demands as promising IR NLO candidates. All of them exhibit phasematching abilities. Furthermore, the discovery of chalcopyrite- like compounds also provides a feasible design strategy to explore new promising IR NLO materials. [ABSTRACT FROM AUTHOR]

Single crystals of the title compounds are prepared from the elements (graphite crucible, 500-700 °C, 90 h). [ABSTRACT FROM AUTHOR]

The new title compounds are prepared by solid state reactions of stoichiometric mixtures of MO3 (M: Mo, W), Rb2CO3, and Na2CO3 (673 K for 10 h and 843 K for 48 h). [ABSTRACT FROM AUTHOR]

Birefringence plays an important role on angle phase-matching or modulating the polarization of light. Aiming at the demands in large birefringence or new applied spectral region, a series of crystals have emerged that hold great great potential as optical functional crystals with large birefringence. We provide a review of the developments of emergent candidates with the experimentally measured birefringence larger than 0.1 in the field of optical crystals. The recent efforts and active advances in exploring potential optical functional crystals with large birefringence according to different optical transmittance regions are discussed. The relationship between the crystal structure and birefringence performance is analyzed. [Display omitted] • Potential optical functional crystals measured birefringence ≥ 0.1 are summarized. • The structure-property relationship and crystal growth are discussed. • Strategies for designing new potential optical functional crystals are proposed. Birefringence is one of key performance for optical functional crystals owing to their indispensable role in angle phase-matching or adjusting the polarization of light. In the past few decades, commercial birefringent crystals MgF 2 , α -BaB 2 O 4 , CaCO 3 , YVO 4 , TiO 2 , and LiNbO 3 with the moderate birefringence ranging from 0.01 to 0.2 have been widely used as polarization devices. Aimed at the demands in large birefringence or new applied spectral region, a series of crystals have appeared and possessed great potential as optical functional crystals with large birefringence. Herein, the authors review the developments of emergent candidates with the experimentally measured birefringence ≥ 0.1 in the field of optical materials. Recent efforts and active progress in exploring crystal with large birefringence according to different optical transmittance regions are discussed. The relationship between the crystal structures and birefringence was analyzed. It is hoped that this review will expound a clear perspective on structural chemistry of potential optical functional crystals with large birefringence and expedite the discovery of new birefringent crystals with expected properties to satisfy the urgent demands. [ABSTRACT FROM AUTHOR]

Single crystals of the new nonlinear optical compound of title are obtained from a stoichiometric melt of CsCO3, H3BO3, and SiO2 (Pt crucible, 750 °C, 10 h). [ABSTRACT FROM AUTHOR]

Abstract: Single crystals of BPO4 with sizes up to 15×10×12mm3 were grown by top-seeded solution growth method using Li2O–Li4P2O7 as fluxes. The components volatilized from the melt were characterized by the method of X-ray powder diffraction. The defects of grown crystals have also been investigated. The measured ultraviolet cutoff edge of BPO4 was about 130nm. Its density was 2.82g/cm3 determined using drainage method. [Copyright &y& Elsevier]

We demonstrate the 355 nm ultraviolet (UV) femtosecond (fs) laser through second harmonic generation using a type-I phase-matched nonlinear optical crystal of K 3 B 6 O 10 Br (KBOB). The effects of the length of nonlinear optical crystals and the focal length of lenses on the output power and conversion efficiency were investigated systematically. The maximum output power of 265 mW UV fs laser at 355 nm was obtained with a pump of 1.408 W fs laser at 710 nm with a repetition rate of 80 MHz. The corresponding optical conversion efficiency was 18.8%. The experimental results show that KBOB crystal is a promising crystal in generating high-power UV fs laser because of its excellent nonlinear optical properties. • The effects of the length of nonlinear optical crystals and the focal length of lenses on the output power and conversion efficiency were investigated systematically. • The maximum output power of 265 mW UV fs laser at 355 nm was obtained with a pump of 1.408 W fs laser at 710 nm with a repetition rate of 80 MHz. The corresponding optical conversion efficiency was 18.8%. The experimental results show that KBOB crystal is a promising crystal in generating high-power UV fs laser. • The Sellmeier equations and Fresnel loss in SHG of 355 nm fs laser were researched. [ABSTRACT FROM AUTHOR]

Colorless and transparent crystals of the new title compounds are prepared by melting mixtures of Sr(NO3)2, ZnO (CdO), PbO, and H3BO3 in a molar ratio of 1:4:12:4 (Pt crucible, 900 °C, 24 h). Both compounds crystallize in the rhombohedral space group R...c with Z = 6 (single crystal XRD). Their structures contain isolated [B18O36]18- anionic groups. The Sr:M ratio of 8:1 is discussed. [ABSTRACT FROM AUTHOR]

Small colorless crystals of the new polymorph β-Cd3B2O6 are prepared in a PbO-MoO3 flux using a mixture of CdO, H3BO3, PbO, and MoO3 in the molar ratio of 3.3:2:1:1 (Pt crucible, 700 °C). [ABSTRACT FROM AUTHOR]