Strong Second Harmonic Generation Response Research Articles

Designing a Strong Second-Harmonic Generation Polar Iodate by the Structure-Directing Properties of the “Tumbler-like” [Zn(IO3)(I2O5(OH))] Polyanions

Materials with second-harmonic generation (SHG) properties have attracted great attention in the field of photon technology. However, synthesis of materials with strong SHG responses and polar structure still faces enormous challenges. Herein, a new iodate K2Zn(IO3)3(I2O5(OH))(IO2(OH))(H2O) (KZIOH) was synthesized by coupling distorted ZnO6 octahedra with three diverse asymmetrical chromophores to assemble “tumbler-like” clusters, [Zn(IO3)(I2O5(OH))], which was the first noncentrosymmetric (NCS) and polar iodate containing isolated [IO3], [I2O5(OH)], and [IO2(OH)]. KZIOH exhibits the strongest SHG response (∼12 × KH2PO4 (KDP)@1064 nm) among the polyiodates with two or more types of isolate units and a short ultraviolet cutoff edge (262 nm). It also possesses a moderate birefringence (0.055@532 nm) and a wide band gap (4.0 eV), indicating KZIOH is a promising SHG material. Theoretical calculations and crystal structure analysis show that the asymmetric and top-heavy configurations of I–O groups around Zn-centered octahedral units with the aid of hydrogen bonding favor its polar structure and strong SHG response.

Nonlinear optical crystals KPb3(3-C5H4NCOO)2Br5 and KPb3(3-C5H4NCOO)2Cl3Br2 with new Pb-centered nitrogen-halide polyhedrons obtained by the halide anionic substitution

The rational synthesis of nonlinear optical (NLO) crystals with good performances remains a great challenge. Herein, the total/partial halide anionic substitution has been successfully expanded to discover two new NLO crystals, KPb3(3-C5H4NCOO)2Br5 and KPb3(3-C5H4NCOO)2Cl3Br2. Interestingly, KPb3(3-C5H4NCOO)2Br5 and KPb3(3-C5H4NCOO)2Cl3Br2 not only contain highly distorted [PbO2Br] and [PbO2Cl] trigonal pyramids, but also possess unique Pb-centered nitrogen-halide functional units, including [PbNBr4] square pyramid, as well as [PbNBr2Cl] four-coordinated polyhedron with mixed halogen anions. Remarkably, after the total halide anionic substitution, the net polarization of the Pb-centered nitrogen-halide functional units runs parallel to that of the π-conjugated nicotinate groups, resulting in the enhancement of macroscopic polarization. Therefore, KPb3(3-C5H4NCOO)2Br5 displays a strong phase-matching second-harmonic generation response of 2.9 × KDP. Furthermore, KPb3(3-C5H4NCOO)2Br5 has a high laser damage threshold of 149 MW/cm2, a wide transparent window of 0.39–5.5 µm, a suitable birefringence of 0.11 @ 1064 nm and good stability. Theoretical calculations have been performed to elucidate the origin of their optical properties.

Polarization-Independent Second Harmonic Generation in 2D Van Der Waals Kagome Nb3 SeI7 Crystals.

Second harmonic generation (SHG) of 2D crystals has been of great interest due to its advantages of phase-matching and easy integration into nanophotonic devices. However, the polarization-dependence character of the SHG signal makes it highly troublesome but necessary to match the laser polarization orientation relative to the crystal, thus achieving the maximum polarized SHG intensity. Here, it is demonstrated a polarization-independent SHG, for the first time, in the van der Waals Nb3 SeI7 crystals with a breathing Kagome lattice. The Nb3 triangular clusters and Janus-structure of each Nb3 SeI7 layer are confirmed by the STEM. Nb3 SeI7 flake shows a strong SHG response due to its noncentrosymmetric crystal structure. More interestingly, the SHG signals of Nb3 SeI7 are independent of the polarization of the excitation light owing to the in-plane isotropic arrangement of nonlinear active units. This work provides the first layered nonlinear optical crystal with the polarization-independent SHG effect, providing new possibilities for nonlinear optics.

Strong Nonlinear Optical Response and Transient Symmetry Switch in Type‐II Weyl Semimetal β‐WP2

AbstractThe topological Weyl semimetals (WSMs) with peculiar band structures exhibit novel nonlinear optical enhancement phenomena, even for light at optical wavelengths. While many intriguing nonlinear optical effects are constantly uncovered in type‐I WSMs, few experimental works focuse on basic nonlinear optical properties in type‐II WSMs. Here a static and time‐resolved second harmonic generation (SHG) is performed on the 3D type‐II WSM candidate β‐WP2. Although β‐WP2 exhibits extremely high conductivity and a high carrier density (≈1021 cm−3), the SHG is unscreened by conduction electrons, and a rather strong SHG response is observed, comparing with non‐topological polar metals. Additionally, the time‐resolved SHG experiment traces ultrafast symmetry switch and reveals that polar metal β‐WP2 tends to form an inversion symmetric metastable state after photo‐excitation. Intense femtosecond laser pulse can optically drive symmetry switch and tune nonlinear optical response on ultrafast timescales although the interlayer coupling of β‐WP2 is very strong. These findings are illuminating for the polar metal nonlinear optics and provide a new perspective for future ultrafast topological optoelectronic devices.

Two Chiral YbIII Enantiomeric Pairs with Distinct Enantiomerically Pure N-Donor Ligands Presenting Significant Differences in Photoluminescence, Circularly Polarized Luminescence, and Second-Harmonic Generation.

Using enantiomerically pure bidentate and tridentate N-donor ligands (1LR/1LS and 2LR/2LS) to replace two coordinated H2O molecules of Yb(tta)3(H2O)2, respectively, two eight- and nine-coordinated YbIII enantiomeric pairs, namely, Yb(tta)31LR/Yb(tta)31LS (Yb-R-1/Yb-S-1) and [Yb(tta)32LR]·CH3CN/[Yb(tta)32LS]·CH3CN (Yb-R-2/Yb-S-2), were isolated, in which Htta = 2-thenoyltrifluoroacetone, 1LR/1LS = (-)/(+)-4,5-pinene-2,2'-bipyridine, and 2LR/2LS = (-)/(+)-2,6-bis(4',5'-pinene-2'-pyridyl)pyridine. Interestingly, they not only present distinct degrees of chirality but also show large differences in near-infrared (NIR) photoluminescence (PL), circularly polarized luminescence (CPL), and second-harmonic generation (SHG). Eight-coordinated Yb-R-1 with an asymmetric bidentate 1LR ligand has a high NIR-PL quantum yield (1.26%) and a long decay lifetime (20 μs) at room temperature, being more than two times those (0.48%, 8 μs) of nine-coordinated Yb-R-2 with a C2-symmetric tridentate 2LR ligand. In addition, Yb-R-1 displays an efficient CPL with a luminescence dissymmetry factor glum = 0.077, being 4 × Yb-R-2 (0.018). In particular, Yb-R-1 presents a strong SHG response (0.8 × KDP), which is 8 × Yb-R-2 (0.1 × KDP). More remarkably, the precursor Yb(tta)3(H2O)2 exhibits a strong third-harmonic generation (THG) response (41 × α-SiO2), while the introduction of chiral N-donors results in the switching of THG to SHG. Our interesting findings provide new insights into both the functional regulation and switching in multifunctional lanthanide molecular materials.

Tuning of Second-Harmonic Generation in Zn-Based Metal–Organic Frameworks by Controlling the Structural Interpenetrations: A First-Principles Investigation

To explain the huge difference in the second harmonic generation (SHG) response of two novel interpenetrated metal–organic frameworks (MOFs) that consist of Zn2+ ions coordinated to the trans-2-(4-pyridyl)-4-vinylbenzoate (pvb) ligand, eightfold interpenetrated Zn(pvb)2 (M1) and sevenfold interpenetrated [Zn(pvb)2]·DMF (M2), first-principles calculations were performed to study the geometries, band structures, and various linear and second-order nonlinear optical properties of M1 and M2 and two other hypothetical Zn-MOFs. Our results indicate that the structural transformation from M2 to M1 by the loss of the DMF guest is energetically favorable, and the M1 compound with the most tightly packed structure has the largest dielectric constant. For MOFs with the same order of interpenetration, the presence of the DMF guest has a small effect on the optical anisotropy of the system. Due to the different coordination environments of two kinds of Zn atoms, eightfold interpenetrated M1 shows more significant optical anisotropy than M2, and correspondingly, the range of phase matchability of M1 (>863 nm) is wider than that of M2 (>1126 nm). This means that at an experimental wavelength of 950 nm, M1 has a favorable phase-matching feature and displays strong SHG response, while the phase-mismatched behavior of M2 with sevenfold interpenetration leads to a weak SHG signal. Therefore, the difference in the interpenetrated structure induced by the guest DMF solvent is the main reason for the giant deviation in SHG intensity between M1 and M2 compounds. The present work provides new insights into how the phase-matching ability can be tuned by switching of the degree of interpenetration to enhance SHG response of MOFs.

Toward Large Second-Harmonic Generation and Deep-UV Transparency in Strongly Electropositive Transition Metal Sulfates

The development of deep-ultraviolet (DUV)/solar-blind UV nonlinear optical (NLO) crystals simultaneously possessing wide UV transparency, strong second-harmonic generation (SHG) response, and suitable birefringence is a major challenge in advanced laser technology. We herein propose a "cation compensation" strategy for strong optical nonlinearity in inorganic solids that is exemplified by the introduction of strongly electropositive transition metals (TMs). Following this strategy, the first d0 TM UV-transparent NLO sulfates, MF2(SO4) (M = Zr (ZFSO), Hf (HFSO)), have been synthesized. Short UV cutoff edges of 206 nm and below 190 nm are observed for bulk ZFSO and HFSO crystals, respectively, together with the strongest powder SHG responses (3.2 × (ZFSO) and 2.5 × KDP (HFSO)) for solar-blind UV/DUV NLO sulfates, as well as suitable birefringence. This work provides a new and efficient approach to the development of urgently needed high-performance NLO materials for applications in the short-wavelength UV region.

New lead-iodide formates with a strong second-harmonic generation response and suitable birefringence obtained by the substitution strategy.

Nonlinear optical (NLO) crystals featuring a strong second-harmonic generation (SHG) response and suitable birefringence to achieve phase-matching are in urgent demand in industrial and commercial applications. Based on the substitution strategy, two new NLO lead-iodide formates, K2[PbI2(HCOO)2] and Rb2[PbI2(HCOO)2], have been successfully synthesized using a moderate mixed-solvothermal method. K2[PbI2(HCOO)2] and Rb2[PbI2(HCOO)2] exhibit strong phase-matching SHG responses of 8 and 6.8 × KDP, respectively, a suitable birefringence and transparent window covering most of the visible light and mid-IR region. Crystal structures and theoretical calculations unveil that the origins of the strong SHG response and suitable birefringence can be credibly attributed to the oriented arrangement of the highly distorted [PbI2O4] hexa-coordinated polyhedra, which are consistent in their local dipole moments, as well. This research provides a new strategy to explore high-performance NLO crystals.

Synthesis and characterization of a new rare earth borate nonlinear optical crystal K7PbLu2B15O30.

A new complex rare earth borate K7PbLu2B15O30 was prepared by the spontaneous crystallization method. K7PbLu2B15O30 is crystallized in the chiral trigonal space group R32 with cell parameters a = b = 13.0893(3) Å, c = 15.2379(6) Å, α = β = 90°, γ = 120°, and Z = 3. The basic structure of the crystal can be seen as composed of B5O10 groups and LuO6 polyhedra sharing oxygen atoms, while K+ and Pb2+ fill the space to balance the charge. The UV transmission cut-off edge of K7PbLu2B15O30 was less than 300 nm, and the powder SHG response was roughly 1.1 times that of KDP. Furthermore, a first-principles analysis was performed to see more about the relationship between the crystal structure and optical characteristics.

From H12C4N2CdI4 to H11C4N2CdI3: a highly polarizable CdNI3 tetrahedron induced a sharp enhancement of second harmonic generation response and birefringence.

In this study, we identify a novel class of second-order nonlinear optical (NLO) crystals, non-π-conjugated piperazine (H10C4N2, PIP) metal halides, represented by two centimeter-sized, noncentrosymmetric organic-inorganic metal halides (OIMHs), namely H12C4N2CdI4 (P212121) and H11C4N2CdI3 (Cc). H12C4N2CdI4 is the first to be prepared, and its structure contains a CdI4 tetrahedron, which led to a poor NLO performance, including a weak and non-phase-matchable second harmonic generation (SHG) response of 0.5 × KH2PO4 (KDP), a small birefringence of 0.047 @1064 nm and a narrow bandgap of 3.86 eV. Moreover, H12C4N2CdI4 is regarded as the model compound, and we further obtain H11C4N2CdI3via the replacement of CdI4 with a highly polarizable CdNI3 tetrahedron, which results in a sharp enhancement of SHG response and birefringence. H11C4N2CdI3 exhibits a promising NLO performance including 6 × KDP, 4.10 eV, Δn = 0.074 @1064 nm and phase matchability, indicating that it is the first OIMH to simultaneously exhibit strong SHG response (>5 × KDP) and a wide bandgap (>4.0 eV). Our work presents a novel direction for designing high-performance NLO crystals based on organic-inorganic halides and provides important insights into the role of the hybridized tetrahedron in enhancing the SHG response and birefringence.

Tetrahedron-based deep-ultraviolet nonlinear optical crystal with optimized KBe2BO3F2-like structure and disordered cations

The Li2NH4Rb(SO4)2 crystal exhibits a strong second-harmonic generation response of 2 × KH2PO4 and a large band gap of 7.56 eV.

Deep-ultraviolet nonlinear-optical crystal BaNa2[PO3(OH)]2 with large birefringence and strong second-harmonic-generation response

Deep-ultraviolet (DUV, λ ​< ​200 ​nm) nonlinear-optical (NLO) crystals play a pivotal role in modern laser science and technology. Metal phosphates have been considered as fascinating candidates for DUV NLO crystal material. However, how to generate both strong second-harmonic-generation (SHG) response and large birefringence for promising DUV NLO metal phosphates is a long-standing issue. Herein, a new DUV NLO metal phosphate, BaNa2[PO3(OH)]2, was successfully synthesized, which features a two-dimensional [NaPO3(OH)]∞ alveolate layer alternately connected by highly asymmetric [PO3(OH)] groups and NaO5 triangular bipyramids. BaNa2[PO3(OH)]2 can realize a good balance of DUV nonlinear properties covering short UV absorption edge less than 190 ​nm, strong SHG response with the magnitude of ∼1.2 ​× ​benchmark KH2PO4 (KDP), and the largest birefringence with the experimental value of 0.064@590 ​± ​3 ​nm in reported alkaline/alkaline-earth metal phosphates, producing the shortest phase-matching output down to the wavelength of 164 ​nm. These research results show that BaNa2[PO3(OH)]2 crystal is a potential DUV NLO crystal material.

A High-Performance Nonlinear Optical Crystal with a Building Block Containing Expanded π-Delocalization.

Common nonlinear optical (NLO) crystals consist of traditional functional building blocks with inherent optical limitation. Herein, inspired by traditional (B3 O6 )3- inorganic building block, we theoretically identified a new type of organic functional building blocks and then successfully synthesized the first cyamelurate NLO crystal, Ba(H2 C6 N7 O3 )2 ⋅ 8 H2 O. To our surprise, the constituent (H2 C6 N7 O3 )- building block is not in structurally optimal arrangement, but Ba(H2 C6 N7 O3 )2 ⋅ 8 H2 O exhibits excellent optical properties including wide band gap of 4.10 eV, very large birefringence of 0.24@550 nm, and exceptionally strong second-harmonic generation (SHG) response of about 12×KH2 PO4 . Both the SHG response and birefringence are much larger than those of commercial NLO crystal β-BaB2 O4 with optimally aligned (B3 O6 )3- building block. Theoretical calculations suggest that the expanded π-conjugation delocalization within (H2 C6 N7 O3 )- vs (B3 O6 )3- should be responsible to the enhanced performance. This work implies that there is still much room to develop new NLO crystals with excellent functional building blocks that may be longly neglected.

A High‐Performance Nonlinear Optical Crystal with a Building Block Containing Expanded π‐Delocalization

AbstractCommon nonlinear optical (NLO) crystals consist of traditional functional building blocks with inherent optical limitation. Herein, inspired by traditional (B3O6)3− inorganic building block, we theoretically identified a new type of organic functional building blocks and then successfully synthesized the first cyamelurate NLO crystal, Ba(H2C6N7O3)2 ⋅ 8 H2O. To our surprise, the constituent (H2C6N7O3)− building block is not in structurally optimal arrangement, but Ba(H2C6N7O3)2 ⋅ 8 H2O exhibits excellent optical properties including wide band gap of 4.10 eV, very large birefringence of 0.24@550 nm, and exceptionally strong second‐harmonic generation (SHG) response of about 12×KH2PO4. Both the SHG response and birefringence are much larger than those of commercial NLO crystal β‐BaB2O4 with optimally aligned (B3O6)3− building block. Theoretical calculations suggest that the expanded π‐conjugation delocalization within (H2C6N7O3)− vs (B3O6)3− should be responsible to the enhanced performance. This work implies that there is still much room to develop new NLO crystals with excellent functional building blocks that may be longly neglected.

Perfectly Encoding π‐Conjugated Anions in the RE5(C3N3O3)(OH)12 (RE=Y, Yb, Lu) Family with Strong Second Harmonic Generation Response and Balanced Birefringence

AbstractNonlinear optical (NLO) crystal, which simultaneously exhibits strong second‐harmonic‐generation (SHG) response and desired optical anisotropy, is a core optical material accessible to the modern optoelectronics. Accompanied by strong SHG effect in a NLO crystal, a contradictory problem of overlarge birefringence is ignored, leading to low frequency doubling efficiency and poor beam quality. Herein, a series of rare earth cyanurates RE5(C3N3O3)(OH)12 (RE=Y, Yb, Lu) were successfully characterized by 3D electron diffraction technique. Based on a “three birds with one stone” strategy, they enable the simultaneous fulfillment of strong SHG responses (2.5–4.2× KH2PO4), short UV cutoff (ca. 220 nm) and applicable birefringence (ca. 0.15 at 800 nm) by the introduction of rare earth coordination control of π‐conjugated (C3N3O3)3− anions. These findings provide high‐performance short‐wavelength NLO materials and highlight the exploration of cyanurates as a new research area.

Perfectly Encoding π-Conjugated Anions in the RE5 (C3 N3 O3 )(OH)12 (RE=Y, Yb, Lu) Family with Strong Second Harmonic Generation Response and Balanced Birefringence.

Nonlinear optical (NLO) crystal, which simultaneously exhibits strong second-harmonic-generation (SHG) response and desired optical anisotropy, is a core optical material accessible to the modern optoelectronics. Accompanied by strong SHG effect in a NLO crystal, a contradictory problem of overlarge birefringence is ignored, leading to low frequency doubling efficiency and poor beam quality. Herein, a series of rare earth cyanurates RE5 (C3 N3 O3 )(OH)12 (RE=Y, Yb, Lu) were successfully characterized by 3D electron diffraction technique. Based on a "three birds with one stone" strategy, they enable the simultaneous fulfillment of strong SHG responses (2.5-4.2× KH2 PO4 ), short UV cutoff (ca. 220 nm) and applicable birefringence (ca. 0.15 at 800 nm) by the introduction of rare earth coordination control of π-conjugated (C3 N3 O3 )3- anions. These findings provide high-performance short-wavelength NLO materials and highlight the exploration of cyanurates as a new research area.

AeMg6Ga6S16 (Ae = Ca, Sr, Ba): The First Double Alkaline‐Earth Metal Chalcogenides with Excellent Performances

AbstractInfrared nonlinear optical (IR NLO) crystals are of quite significance in the development of laser technology, yet rationally designing new IR NLO crystal that can satisfy all the property requirements is still a great challenge owing to the incompatibility between large second harmonic generation (SHG) response and wide band gap. Herein, taking AgGaS2 (AGS) as the template and using highly electropositive alkaline‐earth metal cations substituting Ag+ cations, the first examples of double alkaline‐earth (Ae) metal chalcogenide IR NLO crystals, AeMg6Ga6S16 (Ae = Ca, Sr, Ba), are successfully designed and synthesized. Structurally, they possess stable [Mg/GaS]∞ open frameworks, which can accommodate a wide range of cations from the small size of Ca2+ to large Ba2+ cations and all of the resulting compounds melt congruently. More importantly, these materials achieve the optimal balance among the critical performance parameters, including the strong SHG response (≈0.7–0.8 × AGS) and wide band gap (Eg = 3.50–3.54 eV). Theoretical calculations and structure analysis reveal that their superior NLO properties can be attributed to the synergistic contribution of the polarizable MgS6 and GaS4 groups.

Importance of Solvent-Bridged Structures of Fluorinated Diphenylalanines: Synthesis, Detailed NMR Analysis, and Rotational Profiles of Phe(2-F)-Phe(2-F), Phe(2-F)-Phe, and Phe-Phe(2-F).

The crystal structure of l-phenylalanyl l-phenylalanine (Phe-Phe, FF, a.k.a. diphenylalanine) is not merely noncentrosymmetric, but it is highly dipole parallel aligned. It is for this reason that FF is a nonlinear optical (NLO) material and exhibits strong second harmonic generation (SHG). Enhancement of the SHG response by ortho fluorination was demonstrated. Crystallization is nontrivial, and learning about the zwitterion structures in solution is important for the rational improvement of the crystallization process. Here, we present an NMR study of di-fluorinated FF (Phe(2-F)-Phe(2-F)) and mono-fluorinated FF isomers (Phe(2-F)-Phe and Phe-Phe(2-F)). The dipeptides were prepared by solid-phase synthesis and purified by high-performance liquid chromatography (HPLC). Their 1H and 13C NMR spectra were recorded in partially deuterated water (10% D2O), and two-dimensional (2D) NMR techniques were employed for signal assignments. The unambiguous assignments are reported of all chemical shifts for the aliphatic H and C atoms and of the C atoms of the carboxylate, the amide carbonyl, the CF carbons, and of every arene C atom in each phenyl ring. The dipeptides are trans amides and intramolecular hydrogen bonding between the ammonium group and the amide carbonyl restricts the H3N-CH-C(O) geometry. We explored the rotational profile of the diphenylalanines as a function of the τ = ∠(C-N-C-CO2) dihedral angle at the SMD(B3LYP/6-31G*) level without and with specific hydration and report the associated Karplus curves J(θ) vs θ = ∠(H-N-C-H). The rotational profiles show a maximum of three stationary structures, and relative conformer stabilities of the free diphenylalanines show that the conformation found in the crystal M1 is the least stable among the three, M3 > M2 ≫ M1. Specific water solvation makes all of the difference and adds a large competitive advantage to the water-bridged ion pair M1a. In fact, M1a becomes the most stable and dominant conformation for the parent diphenylalanine and mono1 F-FF and M1a becomes competitive with M3c for mono2 F-FF and di F-FF. Implications are discussed regarding the importance of the conformational preorganization of diphenylalanines in solution and the facility for their crystallization.

Isoreticular Design of KTiOPO4-Like Deep-Ultraviolet Transparent Materials Exhibiting Strong Second-Harmonic Generation.

Second-harmonic generation (SHG) is of great technological importance for applications in nonlinear optics, but it remains challenging to engineer large SHG responses in the short-wavelength ultraviolet (UV) region owing to competing microstructure requirements. Herein, we report the first examples of d0 transition-metal-based (TM-based) deep-UV-transparent nonlinear optical (NLO) crystals MOF4H2 (M = Zr (ZOF), Hf (HOF)), which exhibit unprecedented short UV absorption edges (below 190 nm). Evolving from the KTiOPO4 (KTP) structure by an isoreticular node substitution strategy, the three-dimensional frameworks of ZOF and HOF consist of corner-sharing [MO2F6] moieties that are new functional units in deep-UV NLO material design, conferring wide UV transparency and strong phase-matchable SHG response (2.2 × KH2PO4 (ZOF) and 1.8 × KH2PO4 (HOF) at 1064 nm). Such d0-TM-based [MO2F6] polyhedra preclude deleterious d-d electronic transitions, resulting in significantly blue-shifted UV absorption edges of ZOF and HOF (<190 nm). The d0-TM-based [MO2F6] polyhedra introduced in this work offer a new perspective in the construction of deep-UV transparent NLO materials, demonstrating the feasibility of an isoreticular design strategy in developing functional NLO materials.

BaSb(H2PO2)3Cl2: An excellent UV nonlinear optical hypophosphite exhibiting strong second-harmonic generation response

Non π-conjugated tetrahedral groups have emerged as potential basic modules for developing ultraviolet (UV) nonlinear optical materials. However, their intrinsic weak hyperpolarizability and small polarizability anisotropy severely restrict the performance of the designed material. Herein, the first antimony hypophosphite, BaSb(H2PO2)3Cl2, was successfully synthesized via rational design, which exhibits superior nonlinear optical properties including strong second harmonic generation response, appropriate birefringence and wide transmittance, indicating it is a potential UV nonlinear optical material. Remarkably, the title compound exhibits the largest nonlinear optical coefficient (5 × KDP) among all reported antimony-based oxyacid compounds. Detailed theoretical calculations confirmed that its excellent nonlinear optical properties are primarily derived from the ordered [Sb(H2PO2)3Cl2]2- anionic clusters composed of [H2PO2]- pseudo-tetrahedra and [SbO3Cl2]5- distorted polyhedra. This work would extend UV nonlinear optical material system to hypophosphites and lead the further inquiry of new structure-driven functional materials.