Bridging oxygen atoms in trigonal prism units driven strong second-harmonic-generation efficiency in SrGeOTe.

Herein, a novel IR NLO oxytelluride SrGeOTe was successfully designed and synthesized through a "partial O-to-Te substitution" strategy. Compared with the parent oxide, SrGeOTe not only successfully achieves a phase-matchability transition (from NPM to PM), but also greatly improves the linear and NLO performances, including a wide band gap (2.26 eV), strong SHG response (1.

Synthesis, Crystal Structure, and Characterizations of Two Tantalum Phosphates ATaPO (A=K, Na).

Two new compounds KTaPO and NaTaPO were obtained by spontaneous crystallization with KHPO and KHPO or NaHPO and NaHPO as fluxes, respectively. KTaPO belongs to the 2/ space group of the monoclinic system, with cell parameters of = 9.8912(7) Å, = 7.

Second-Harmonic-Generation Effect and Giant Optical Birefringence in the Weyl Material CaAgAs.

Nonlinear-optical (NLO) materials suitable for the "8-14 μm" atmospheric transparent window are in urgent need. Arsenide is one of the most promising material systems for such an application. However, the second-harmonic-generation (SHG) effect of arsenide is difficult to characterize using the conventional powder SHG technique with a 2 μm fundamental laser.

Proton-Rich POM-Type KMoO(HPO)(PO)Cl with Ion-Exchange Capabilities.

A proton-rich POM-type molybdenum phosphate KMoO(HPO)(PO)Cl was successfully obtained. It crystallizes in a noncentrosymmetric tetragonal space group of -4 (No. 81) with the unit cell parameters of = 9.

Synthesis, Structure Determination, and Characterizations of a Polar Salt-Inclusion Scandium Germanate, RbLiScGeOF.

A noncentrosymmetric salt-inclusion germanate, RbLiScGeOF, was grown through spontaneous crystallization from a LiF-RbF flux. It crystallizes in the polar space group 31 with cell parameters of = 10.7587(3) Å, = 21.

CdSiAs, a Nonchalcopyrite Arsenide with a Strong Nonlinear-Optical Response.

A new arsenide, CdSiAs, has been successfully synthesized and characterized. It is the first arsenide that adopts a nonchalcopyrite structure and possesses a strong nonlinear-optical (NLO) response. In the structure, the CdAs trigonal planar unit, a kind of π-conjugated planar NLO-active group, was identified for the first time.

Investigation into Structural Variation from 3D to 1D and Strong Second Harmonic Generation of the AHgPS (A = Na, K, Rb, Cs) Family.

The continuous exploration of multinary chalcogenide semiconductors has provided a variety of new functional materials. In this paper, four new quaternary chalcogenides AHgPS (A = Na, K, Rb, Cs) have been prepared by solid-state syntheses. These findings complement the lack of research on this quaternary system.

Ca(TeO)(MO) (M = Mo, W): Mid-Infrared Nonlinear Optical Tellurates with Ultrawide Transparency Ranges and Superhigh Laser-Induced Damage Thresholds.

Intense interests in mid-infrared (MIR) nonlinear optical (NLO) crystals have erupted in recent years due to the development of optoelectronic applications ranging from remote monitoring to molecular spectroscopy. Here, two polar crystals Ca(TeO)(MO) (M = Mo, W) were grown from TeO-MO flux by high-temperature solution methods. Ca(TeO)(MoO) and Ca(TeO)(WO) are isostructural, which feature novel structures consisting of asymmetric MO tetrahedra and TeO trigonal pyramids.

Novel van der Waals Deep-UV Nonlinear Optical Materials.

Van der Waals (vdW) deep-UV (DUV) nonlinear optical (NLO) crystal is an important material system recently developed. Herein, we review its concept and original intention, and then summarized the discovery process of related materials, including the role of A-site cations and the resulting two-/one-dimensional vdW DUV NLO systems. Finally, we evaluate the practical DUV NLO performance and prospected the opportunities and challenges.

Highly Distorted [HgS] Motif-Driven Structural Symmetry Degradation and Strengthened Second-Harmonic Generation Response in the Defect Diamond-Like Chalcogenide HgPS.

Chalcogenides with diamond-like (DL) structures are a treasury of infrared nonlinear optical (NLO) materials. Here, a ternary Hg-based chalcogenide with a defect DL structure, HgPS, is synthesized by solid-state reaction. Driven by the highly distorted [HgS] tetrahedra, this compound displays an interesting structural symmetry degradation from tetragonal to orthorhombic compared with its analogue ZnPS.

NaBi(IO): An Alkali-Metal Bismuth Iodate with Intriguing One-Dimensional [BiIO] Chains and Pressure-Induced Structural Transition.

An alkali-metal bismuth iodate, NaBi(IO), was successfully obtained by the hydrothermal method for the first time and contains intriguing one-dimensional [BiIO] chains. High-pressure Raman spectra were carried out to investigate the structural transition of NaBi(IO). Electronic states and anisotropic optical responses were also investigated by theoretical calculations.

BaZnBe(BO)F: a novel zinc-beryllium borate with SBBO-type structure overcoming the polymorphism problem.

A novel zinc-beryllium borate BaZnBe2(BO3)2F2 was grown by a high-temperature flux method for the first time. It crystallizes in P3[combining macron] with the cell parameters of a = b = 4.5998, c = 7.

Tunable deep ultraviolet laser based near ambient pressure photoemission electron microscope for surface imaging in the millibar regime.

A newly developed instrument comprising a near ambient pressure (NAP) photoemission electron microscope (PEEM) and a tunable deep ultraviolet (DUV) laser source is described. This NAP-PEEM instrument enables dynamic imaging of solid surfaces in gases at pressures up to 1 mbar. A diode laser (976 nm) can illuminate a sample from the backside for in situ heating in gases up to 1200 K in minutes.

EuHgGeSe and EuHgSnS: Two Quaternary Eu-Based Infrared Nonlinear Optical Materials with Strong Second-Harmonic-Generation Responses.

Metal chalcogenides play a critical role in the infrared (IR) nonlinear optical (NLO) field. However, Eu-based chalcogenide-type IR NLO materials are still scarce up to now. In this paper, two new quaternary Eu-based chalcogenides, EuHgGeSe and EuHgSnS, containing the "NLO active groups" [HgQ] (Q = S, Se) and [GeSe]/[SnS] were synthesized through traditional high-temperature solid-state reactions.

Two Mixed-Anion Units of [GeOSe] and [GeOS] Originating from Partial Isovalent Anion Substitution and Inducing Moderate Second Harmonic Generation Response and Large Birefringence.

Highly polarizable mixed-anion structural building units (SBUs) have been demonstrated as promising candidates for high-performing optical crystals. In this work, two new mixed-anion SBUs of [GeOSe] and [GeOS] are first designed through partial isovalent substitution of chalcogen atoms by O atoms in the classical [GeQ] (Q = S, Se) tetrahedra. On the basis of these SBUs, two new quaternary oxychalcogenides, SrGeOSe and SrGeOS, are successfully synthesized.

New quaternary chalcogenide BaHgAsS originating from the combination of linear [HgS] and tetrahedral [AsS] modules.

A new quaternary chalcogenide Ba4HgAs2S10 has been successfully synthesized with the aid of a KI flux. The compound crystallizes in the space group C2/c (no. 9) of the monoclinic system [a = 22.

Selenite bromide nonlinear optical materials PbGaF(SeO)Br and PbNbO(SeO)Br: synthesis and characterization.

Two new isomorphic selenite bromides, namely Pb2GaF2(SeO3)2Br (1) and Pb2NbO2(SeO3)2Br (2), were synthesized by mild hydrothermal reactions. These two compounds crystallize in the noncentrosymmertric space group P21 and feature 3D structures consisting of 1D (Pb2Br)3+ cationic chains and 2D [Ga2F4(SeO3)4]6-/[Nb2O4(SeO3)4]6- anonic chains. As measured, 1 and 2 are phase-matchable and exhibit excellent second harmonic generation (SHG) responses of 4.

Nonlinear-Optical Crystal RbYBO with Condensed BO Blocks That Exhibits an Intriguing Structural Arrangement and a Short Ultraviolet Absorption Edge.

Nonlinear-optical (NLO) crystals, which can regulate the laser wavelength through a cascading second-harmonic-generation technique, have been widely utilized in the field of optoelectronics. In this work, we grew the NLO borate crystal RbYBO (RYBO) using the spontaneous crystallization method. RYBO crystallizes in a chiral trigonal space group of 32 with a new type of structural arrangement built from Y-O short chains and BO groups.

Molten Salt Synthesis of an Open-Frame Aluminum Phosphate BaAlPO with a Rare-Pyramidal AlO Group.

A new open-frame aluminophosphate, BaAlPO, was synthesized by a high-temperature flux method. BaAlPO features discrete [AlPO] chains with rare square-pyramidal AlO groups adopted. Especially, this pyramidal AlO group acts as an ideal "plane builder" or "vacancy inducer" to construct open-frame structures compared with an ordinary trigonal-bipyramidal AlO group.

Gadolinium-Rich Borate Gd(BO)(BO)O Exhibiting a Magnetocaloric Effect.

A gadolinium-rich borate Gd(BO)(BO)O was successfully grown by the high-temperature solution method using the RbO-BO flux. The crystal crystallizes in centrosymmetric space group 2/ with lattice constants = 18.4300(2) Å, = 3.

SrGaOS: A Nonlinear Optical Oxysulfide with Melilite-Derived Structure and Wide Band Gap.

SrGaOS, which is a novel nonlinear optical oxysulfide, was discovered via solid-state reaction. The compound crystallizes in noncentrosymmetric space group 222 (No. 18) of the orthorhombic system.

Functional Chalcogenide NaHgSnSe and KMnGeSe Exhibiting Flexible Chain Structure and Intriguing Birefringence Tunability.

The two functional chalcogenides KMnGeSe and NaHgSnSe, featuring a straight-chain structure, have been successfully prepared and fully characterized. KMnGeSe shows paramagnetic behavior. The birefringence of NaHgSnSe is as large as 0.

"Old dog, new tricks": the lone pair effect inducing divergent optical responses in lead cyanurates containing π-bonds.

The stereochemically active lone pair (SCALP) effect of Pb2+ plays a vital role in enhancing the nonlinear optical response and engineering the band gap of lead-based materials with intriguing properties. Herein, we combined SCALP Pb2+ cations and π-conjugated (HC3N3O3)2- anions into one structure to investigate the tunable optical properties. Two lead cyanurates, namely, Pb3(HC3N3O3)2(OH)2 (I) and its partly cadmium-substituted analog Pb2Cd(HC3N3O3)2(OH)2 (II) were grown by the mild hydrothermal method.

Rb Li TiOGe O : A Titanyl Nonlinear Optical Material with the Widest Transparency Range.

Practical mid-infrared (MIR) coherent light beams generated by frequency conversion in nonlinear optical (NLO) crystals are indispensable in time-resolved infrared vibrational spectroscopy, remote light detection and ranging, and free-space communications. Herein, a new titanyl germanate Rb Li TiOGe O (RLTG) MIR NLO crystal was obtained by heavier element substitution. It features a complicated structure network composed of compressed TiO square pyramids and distorted GeO tetrahedra, separated by Rb and Li cations.