Second Harmonic Generation Coefficients Research Articles

Wide‐Bandgap RBa3(B3O6)3 (R = Nd, Sm, Tb, Dy, and Er) Single Crystals for Ultraviolet Nonlinear Optics

AbstractDiscovery of new materials with enhanced optical properties in the visible and UV‐C range can impact applications in lasers, nonlinear optics, and quantum optics. Here, the optical floating zone growth of a family of rare earth borates, RBa3(B3O6)3 (R = Nd, Sm, Tb, Dy, and Er), with promising linear and nonlinear optical (NLO) properties is reported. Although previously identified to be centrosymmetric, the X‐ray analysis combined with optical second harmonic generation (SHG) assigns the noncentrosymmetric P space group to these crystals. Characterization of linear optical properties reveals a direct bandgap of ≈5.61–5.72 eV and strong photoluminescence in both the visible and mid‐IR regions. Anisotropic linear and nonlinear optical characterization reveals both Type‐I and Type‐II SHG phase matchability, with the highest effective phase‐matched SHG coefficient of 1.2 pm V−1 at 800‐nm fundamental wavelength (for DyBa3(B3O6)3), comparable to β‐BaB2O4 (phase‐matched d22 ≈ 1.9 pm V−1). Laser‐induced surface damage threshold for these environmentally stable crystals is 650–900 GW cm−2, which is four to five times higher than that of β‐BaB2O4, thus providing an opportunity to pump with significantly higher power to generate about six to seven times stronger SHG light. Since the SHG arises from disorder on the Ba‐site, significantly larger SHG coefficients may be realized by “poling” the crystals to align the Ba displacements. These properties motivate further development of this crystal family for laser and wide bandgap NLO applications.

K2HgGe3Se8: A Quaternary Hg-Based Selenide with Nonlinear Optical Properties.

A new quaternary Hg-based selenide K2HgGe3Se8 was successfully synthesized and characterized as an engaging infrared (IR) nonlinear optical (NLO) material, which crystallizes in the P21 space group of the noncentrosymmetric monoclinic crystal system. The crystal structure of K2HgGe3Se8 is characterized by the stacking of countless layers with K+ cations filling the interlayers. The UV-vis-NIR diffuse reflectance spectrum shows that K2HgGe3Se8 possesses an indirect band gap of 2.13 eV. The second harmonic generation (SHG) response of K2HgGe3Se8 is approximately 1.1 times that of AgGaS2 (AGS) within the particle size of 20-50 μm along with a nonphase-matching (NPM) behavior at 2090 nm, as indicated by the SHG test. K2HgGe3Se8 also has a large powder laser-induced damage threshold (∼ 2.3 × AGS). As revealed by theoretical calculations, the optical properties of K2HgGe3Se8 are predominantly determined by [HgSe4] and [GeSe4] tetrahedra, and K2HgGe3Se8 possesses a calculated optical band gap of 1.44 eV together with a maximum SHG coefficient d22 of -7.70 pm V-1.

Remarkable Second Harmonic Generation Response in (C5H6NO)+(CH3SO3)−: Unraveling the Role of Hydrogen Bond in Thermal Driven Nonlinear Optical Switch

AbstractHeat‐activated second harmonic generation (SHG) switching materials are gaining interest for their ability to switch between SHG on and off states, offering potential in optoelectronic applications. The novel nonlinear optical (NLO) switch, (C5H6NO)+(CH3SO3)− (4‐hydroxypyridinium methylsulfonate, 4HPMS), is a near‐room‐temperature thermal driven material with a strong SHG response (3.3 × KDP), making it one of the most potent heat‐stimulated NLO switches. It offers excellent contrast of 13 and a high laser‐induced damage threshold (2.5 × KDP), with reversibility > 5 cycles. At 73 °C, 4HPMS transitions from the noncentrosymmetric Pna21 room temperature phase (RTP) to the centrosymmetric P21/c phase, caused by the rotation of the (C5H6NO)+ and (CH3SO3)− due to partially thermal breaking of intermolecular hydrogen bonds. The reverse phase change exhibits a large 50 °C thermal hysteresis. Density functional theory (DFT) calculations show that (C5H6NO)+ primarily dictates both the SHG coefficient (dij) and birefringence (▵n(Zeiss) = 0.216 vs ▵n(cal.) = 0.202 at 546 nm; Δn(Immersion) = 0.210 vs ▵n(cal.) = 0.198 at 589.3 nm), while the band gap (Eg) is influenced synergistically by (C5H6NO)+ and (CH3SO3)−. Additionally, 4HPMS‐RTP also exhibits mechanochromism upon grinding as well as an aggregation‐enhanced emission in a mixture of acetone and water.

Enhanced UV Nonlinear Optical Properties in Layered Germanous Phosphites through Functional Group Sequential Construction

AbstractThis study pioneers a novel strategy for synthesizing solar‐blind ultraviolet (UV) nonlinear optical (NLO) crystals through functional groups sequential construction, effectively addressing the inherent trade‐offs among broad transmittance, enhanced second‐harmonic generation (SHG), and optimal birefringence. We have developed two innovative van der Waals layered germanous phosphites: GeHPO3, the first Ge(II)‐based oxide NLO crystal which exhibits a black phosphorus‐like structure, and K(GeHPO3)2Br, distinguished by its exceptional birefringence and graphene‐like structure. Significantly, GeHPO3 exhibits a remarkable array of NLO properties, including the highest SHG coefficient recorded among all NLO crystals for phase‐matching and generating 266 nm coherent light via quadruple frequency conversion. It delivers a potent SHG intensity, surpassing KH2PO4 (KDP) by 10.3 times at 1064 nm and β‐BaB2O4 by 1.3 times at 532 nm, complemented by a distinct UV absorption edge at 211 nm and moderate birefringence of 0.062 at 546 nm. Comprehensive theoretical analysis links these exceptional characteristics to the unique NLO‐active GeO34− units and the distinctive, highly ordered layered structures. Our findings deliver essential experimental insights into the development of Ge(II)‐based optoelectronic materials and present a strategic blueprint for engineering structure‐driven functional materials with customized properties.

Enhanced UV Nonlinear Optical Properties in Layered Germanous Phosphites through Functional Group Sequential Construction.

This study pioneers a novel strategy for synthesizing solar-blind ultraviolet (UV) nonlinear optical (NLO) crystals through functional groups sequential construction, effectively addressing the inherent trade-offs among broad transmittance, enhanced second-harmonic generation (SHG), and optimal birefringence. We have developed two innovative van der Waals layered germanous phosphites: GeHPO3, the first Ge(II)-based oxide NLO crystal which exhibits a black phosphorus-like structure, and K(GeHPO3)2Br, distinguished by its exceptional birefringence and graphene-like structure. Significantly, GeHPO3 exhibits a remarkable array of NLO properties, including the highest SHG coefficient recorded among all NLO crystals for phase-matching and generating 266 nm coherent light via quadruple frequency conversion. It delivers a potent SHG intensity, surpassing KH2PO4 (KDP) by 10.3 times at 1064 nm and β-BaB2O4 by 1.3 times at 532 nm, complemented by a distinct UV absorption edge at 211 nm and moderate birefringence of 0.062 at 546 nm. Comprehensive theoretical analysis links these exceptional characteristics to the unique NLO-active GeO3 4- units and the distinctive, highly ordered layered structures. Our findings deliver essential experimental insights into the development of Ge(II)-based optoelectronic materials and present a strategic blueprint for engineering structure-driven functional materials with customized properties.

La3Ga5M0.5Sn0.5O14, (M = Ge, Si): Design and Synthesis of Two Langasite Nonlinear Optical Materials with Large Second Harmonic Generation and Birefringence Induced by Distorted (Sn/M)O6 Octahedra.

Nonlinear optical (NLO) coherent light sources are widely applied in many areas of science and technology. As the core medium, the NLO material is required to have a wide transparent range, a large NLO response, and a high laser damaged threshold (LDT). It is common knowledge that langasite (La3Ga5SiO14, LGS) crystal has an underdeveloped second-harmonic generation (SHG) coefficient and a small birefringence, which seriously restrict its application in the NLO field, despite that it has a broad transmittance spectrum and a moderate LDT. Herein, we have successfully obtained novel langasite NLO crystals LGSS (La3Ga5Si0.5Sn0.5O14) and LGGS (La3Ga5Ge0.5Sn0.5O14), with short UV absorption edges of 209 and 212 nm, respectively. Incorporating heavy ions Sn4+ into the structure, a distorted BO6 octahedron was adjusted by the radius difference between Sn4+ and Si4+/Ge4+, which caused the strong SHG responses in LGSS (∼10.77 × KDP) and LGGS (∼9.23 × KDP) and increased birefringences of 0.034 and 0.025, respectively. Besides, they also had large energy band gaps (4.95 eV for LGSS, and 4.93 eV for LGGS), which allowed high LDTs with LGSS of 1.3 GW/cm2 and LGGS of 813 MW/cm2. This work demonstrates a new strategy to enhance SHG responses and birefringence for existing NLO materials and enriches langasite family crystals.

Remarkable Second Harmonic Generation Response in (C5H6NO)+(CH3SO3)-: Unraveling the Role of Hydrogen Bond in Thermal Driven Nonlinear Optical Switch.

Heat-activated second harmonic generation (SHG) switching materials are gaining interest for their ability to switch between SHG on and off states, offering potential in optoelectronic applications. The novel nonlinear optical (NLO) switch, (C5H6NO)+(CH3SO3)- (4-hydroxypyridinium methylsulfonate, 4HPMS), is a near-room-temperature thermal driven material with a strong SHG response (3.3 × KDP), making it one of the most potent heat-stimulated NLO switches. It offers excellent contrast of 13 and a high laser-induced damage threshold (2.5 × KDP), with reversibility > 5 cycles. At 73 °C, 4HPMS transitions from the noncentrosymmetric Pna21 room temperature phase (RTP) to the centrosymmetric P21/c phase, caused by the rotation of the (C5H6NO)+ and (CH3SO3)- due to partially thermal breaking of intermolecular hydrogen bonds. The reverse phase change exhibits a large 50 °C thermal hysteresis. Density functional theory (DFT) calculations show that (C5H6NO)+ primarily dictates both the SHG coefficient (dij) and birefringence (▵n(Zeiss) = 0.216 vs ▵n(cal.) = 0.202 at 546 nm; Δn(Immersion) = 0.210 vs ▵n(cal.) = 0.198 at 589.3 nm), while the band gap (Eg) is influenced synergistically by (C5H6NO)+ and (CH3SO3)-. Additionally, 4HPMS-RTP also exhibits mechanochromism upon grinding as well as an aggregation-enhanced emission in a mixture of acetone and water.

Optical second harmonic generation of tunable spherical quantum dots under Inversely Quadratic Hellmann Plus Inversely Quadratic Potential

Herein, we employ the effective mass approximation and the iterative method to investigate the Second harmonic generation (SHG) coefficient of a spherical quantum dot (QD) system with Inversely Quadratic Hellmann Plus Inversely Quadratic Potential (IQHIQP), considering the regulation of the quantum size, confinement potential depth and external environment. The numerical simulation results show that the SHG coefficient is highly reliant on the tunable factor, which can affect the energy level interval and dipole moment elements. Interestingly, the effect of temperature on the SHG coefficient in terms of peak location and size is consistent with the quantum dot radius but opposite to the hydrostatic pressure. Therefore, it is necessary to pay more attention to the influence of internal and external parameters on nonlinear optical effects, and apply the theory to practical experiments and the manufacture of optoelectronic devices.

Nonlinear Optical Second Harmonic Generation Characteristics in Cylindrical GaAs/Ga1–ηAlηAs Quantum Dots

This article theoretically examines the effect of various variables on the second harmonic generation (SHG) coefficients of cylindrical GaAs/Ga1–ηAlηAs quantum dots. The iterative approach and the compact‐density matrix method have been utilized to determine the expression of the SHG coefficient. The outcomes demonstrate that the variation of the SHG coefficient is closely related to structural parameters, external conditions, and incident photon energy.

The electronic structures and optical properties induced by spin-orbit-coupling in LiPbPO4 compound

Phosphate materials are excellent candidates for nonlinear optical materials, thus necessitating a comprehensive and in-depth study of them. Here, inspired by the interesting phenomenon induced by the spin-orbit coupling (SOC) effect, we extend it to LiPbPO4 compounds using a first-principles approach to probe the influence of SOC on the electronic structure and optical properties of post-transition metal compounds. The results show that only the bottom of the conduction band shows an energy level splitting with the inclusion of SOC, which is analyzed to come from the SOC in the Pb 6p state since the SOC in the O 2p state is very weak. The splitting of the conduction band triggers the decrease of the band gap and the change of the optical properties. The performance analysis shows that both the refractive index and the second harmonic generation (SHG) coefficient are enhanced with the inclusion of SOC, however, the change in the birefringence is insignificant, and it is further found that the enhanced SHG coefficient values are closer to the experimental values. In conclusion, our study reveals the impact of SOC effect on the electronic structure and optical properties of LiPbPO4 compounds, contributing to a deeper understanding of the nonlinear optical in post-transition metal compounds.

Second harmonic generation in Harmonic-Gaussian asymmetric double quantum well: effect of magnetic and intense laser fields

We have theoretically analyzed the effects of externally applied fields (magnetic and intense laser) as well as various structural parameters such as well width, barrier width, barrier height, and structural asymmetry on the second harmonic generation (SHG) coefficients of GaAs/Al0.3Ga0.7As Harmonic-Gaussian asymmetric double quantum wells (QW). The time-independent Schrödinger equation was solved using the diagonalization method and effective mass approximation to obtain the energy eigenvalues and eigenfunctions of the structure. An expression derived within the compact density matrix approach has been used to evaluate the second harmonic generation (SHG) coefficient. Our numerical results indicate that increasing the magnitude of the magnetic (intense laser) field causes the peak positions of SHG to shift towards higher energy regions/blue (lower energy regions/red). On the other hand, as the structural parameters A1 and A2 ( k and z0 ) increase, the peak positions of the SHG coefficients exhibit a shift towards higher energy regions/blue (lower energy regions/red). We expect that the results of our study will contribute to the development of new optoelectronic devices based on the Harmonic-Gaussian asymmetric double quantum well structure.

The first Hg-based oxychalcogenide Sr2HgGe2OS6: Achieving balanced IR nonlinear optical properties through synergistic cation and anion substitution

Recently, newly emerging Hg-based chalcogenides with fascinating non-centrosymmetric (NCS) structures and superior optical properties have received wide attention as candidates for infrared nonlinear optics (IR-NLO). However, simultaneously optimizing three key performance indicators in these materials, namely the second-harmonic generation coefficient (deff), optical energy gap (Eg), and birefringence (Δn), remains a major challenge due to their often-competing structural requirements. Herein, the first Hg-based oxychalcogenide, Sr2HgGe2OS6, was rationally obtained using a synergistic strategy of cation and anion design based on the well-known melilite-type oxide Sr2ZnGe2O7. By substituting Hg2+ for Zn2+ cations and S2− for O2− anions, Sr2HgGe2OS6 features new 2D Cairo pentagonal tiling layers of [HgGe2OS6]4–, separated by charge-balanced Sr2+ cations. Notably, it exhibits well-balanced IR-NLO properties with a substantial deff (1.2 × AgGaS2@2050 nm), wide Eg (3.25 eV) resulting in a favorable laser-induced damage threshold (15.6 × AgGaS2@1064 nm), broad transparent window (up to 14.3 μm), and sufficient calculated Δn (0.147@2050 nm) for phase-matching ability across a wide range. Moreover, detailed theoretical analyses suggest that the simultaneous presence of excellent linear and NLO properties in Sr2HgGe2OS6 can be attributed to the cooperative effect of heteroligand [Ge2OS6] and tetrahedral [HgS4] asymmetric functional motifs. This study offers valuable insights into the development of NCS materials through logical chemical substitution strategies, and the intriguing optical properties of this new oxychalcogenide holds promise for applications in the IR-NLO field.

Electro-optic effects of lithium borate crystals studied by first-principles method

In respect to the electro-optic (EO) effect, LiB3O5 (LBO) and Li2B4O7 (LB4) contain the same elements but represent two extremes in the family of nonlinear optical (NLO) borate crystals: one with large second harmonic generation (SHG) coefficients but very small reported EO coefficients, the latter has extremely small SHG coefficients yet EO coefficients were found even larger than the practical EO modulator crystal β-BaB2O4 (BBO). The puzzle was unraveled through first-principles studies of the two crystals and it is found that the vibrational and electronic contributions to the EO effect were canceled in LBO and the major contributions are from piezoelectric induced effect for LB4 with electronic contributions negligible. In addition to the EO and NLO coefficients, dielectric, elastic, piezoelectric and elasto-optic constants are all obtained simultaneously. More importantly, fully determining the elastic, elasto-optic constants, all 4th rank tensors, can be adopted to calibrate the experimental uncertainties and help to design practical surface acoustic wave (SAW) or acoustic optic modulator (AOM) devices.

Nonlinear Optical Mechanism of β‐BaB2O4 Revealed by Experimental Electron Density

AbstractNonlinear optical (NLO) materials are of immense scientific and technological importance. However, debate has long prevailed theoretically regarding the structural origin of the second harmonic generation (SHG) effect. In this work, the experimental electron density (ED) of controversial β‐BaB2O4 (BBO) is studied by high‐resolution X‐ray diffraction, indicating that the [B3O6]3− motif dominates two large non‐zero SHG tensors (d222 and d311) while Ba atoms contribute mostly to the smallest one (d333), and the atomic SHG contributions of terminal O atoms in [B3O6]3− motifs are much larger than those of B and bridged O atoms, clarifying the disputes on its NLO response mechanism. Besides, the contraction of inner electron shells (5s25p6) of the Ba atom and partial covalent behavior of the Ba─O interaction are first observed experimentally. Furthermore, the SHG coefficients of BBO derived from experimental ED are in excellent agreement with those from bulk crystals, providing a high‐efficient and low‐cost method of screening high‐performance NLO materials with just an easy‐to‐obtain tiny crystal.

High harmonic generations in GaAs/AlGaAs superlattice: Effect of electric and magnetic field

In this study, we have examined the nonlinear optical rectification (NOR), the second harmonic generation (SHG), and the third harmonic generation (THG) coefficients of the AlxGa1-xAs/GaAs superlattice with a periodically increased barrier width under magnetic field (B) and electric field (F). All calculations are completed using the finite element method under the effective mass approximation. The electric field's polarity (±) changes the probability density of wavefunctions. For B = 0, F = −5 kV/cm (particularly for the difference between energy levels (Efi)) is a critical value. Whereas the Efi value decreases between −40 <F < −5 kV/cm, then it increases in the range of −5<F < 40 kV/cm. This change causes a red or blue shift in the optical spectrum. We also see that F = 40 kV/cm causes a change in the transition energies of the structure more than F = −40 kV/cm. The confinement of electrons under applied magnetic fields occurs in the center of the superlattice. The NOR, SHG, and THG coefficients can be adjusted over a wide energy range and size of the resonance peak with changes in the F and B values. It is believed that with the combined effect of the electric and magnetic fields, the electro-optical properties of the superlattices can be tuned for the desirable property of semiconductor optical device applications.

MgSiP2: An Infrared Nonlinear Optical Crystal with a Large Non‐Resonant Phase‐Matchable Second Harmonic Coefficient and High Laser Damage Threshold

AbstractSuperior infrared nonlinear optical (NLO) crystals are in urgent demand in the development of lasers and optical technologies for communications and computing. The critical challenge is to find a crystal with large non‐resonant phase‐matchable NLO coefficients and high laser damage threshold (LDTs) simultaneously, which however scale inversely. This work reports such a material, MgSiP2, that exhibits a large second harmonic generation (SHG) coefficient of d14≈d36 = 89 ± 5 pm V−1 at 1550 nm fundamental wavelength, surpassing the commercial NLO crystals AgGaS2, AgGaSe2, and ZnGeP2. First principles theory reveals the polarizability and geometric arrangement of the [SiP4] tetrahedral units as the origin of this large nonlinear response. Remarkably, it also exhibits a high LDT value of 684 GW cm−2, which is six times larger than ZnGeP2 and three times larger than CdSiP2. It has a wide transparency window of 0.53–10.35 µm, allowing broadband tunability. Further, it is Type I and Type II phase‐matchable with large effective SHG coefficients of deff,I ≈80.2 pm V−1 and deff,II ≈73.4 pm V−1. The outstanding properties of MgSiP2 make it a highly attractive candidate for optical frequency conversion in the infrared.

Effects of applied external fields on the nonlinear optical second harmonic generation in a GaAs/Ga0.7Al0.3As quantum dots

This work has studied some nonlinear optical properties of Al0.3Ga0.7As/GaAs quantum dot system with tangent-square potential (TSP), with special emphasis on the role of second harmonic generation (SHG) coefficient under hydrostatic pressure and temperature. Due to the strain of external application conditions, the changes of the energy level and wave function of the neutron band in the system structure provide valuable insights into the optical properties of the quantum dot structure. In this paper, we report the effects of structural parameters, temperature and hydrostatic pressure on the SHG coefficient. According to the results obtained in the work, it can be reported that the nonlinear optical properties of the quantum dot system can be improved by adjusting the hydrostatic pressure and temperature. At the same time, the interaction of various parameters has produced some interesting observations, which are relevant in relevant research fields.

The second, third harmonic generations and nonlinear optical rectification of the Mathieu quantum dot with the external electric, magnetic and laser field

In this study, the nonlinear optical properties of the InxGa1−xAs/GaAs Mathieu quantum dot (MQD) are investigated for the first time, focusing on the nonlinear optical rectification (NOR), second harmonic generation (SHG), and third harmonic generation (THG). The effects of external fields such as the electric field, magnetic field, and laser radiation field on the nonlinear optical properties of MQD are examined, along with structural parameters such as quantum dot depth and width determined by the indium concentration. The motivation of the study is to explain the NOR, SHG, and THG characteristics of MQD in response to changes in external fields and structural factors. To investigate the effects of the laser field, the time-dependent part of the laser field is transferred to the potential energy term of the wave equation using the Kramers–Henneberger (KH) and dipole approximations, creating a laser-dressed potential. Then, the effective potential wave equation is solved using the tridiagonal matrix method. The effects of external fields and structural parameters of MQD on the NOR, SHG, and THG coefficients are discussed in detail. The optimality of the structure for device design and applications considering MQD is revealed, and alternative parameter analysis is conducted for this optimality.

Recent advances in IR nonlinear optical chalcogenides with well-balanced comprehensive performance

Infrared nonlinear optical (IR-NLO) crystals have attracted many attentions due to the frequency-conversion capability to generate coherent tunable IR laser output for military and civil applications. Chalcogenides as a most popular branch of IR-NLO materials are the competitive candidates owing to their large second-harmonic generation (SHG) coefficient (deff) and broad transmission regions. Currently, how to obtain the non-centrosymmetric (NCS) structure and realize the coexistence of wide energy gap (Eg ≥ 3.0 eV), sufficient deff (≥ 1.0 × AgGaS2), and beneficial phase-matching (PM) feature are the two major challenges faced in this field. The former can be effectively solved through the combination of local asymmetric units and chemical substitution strategy, while for the latter, there is no systematic survey and lack of universally applicable methodology. In this review, 40 IR-NLO chalcogendides are selected based on the aforementioned two challenges and divided into 7 types according to the different chemical components. The composition-structure-performance relationships and the theoretical origin of their IR-NLO properties are summarized systematically. At length, some useful information and development prospects were briefly discussed, which may offer new ideas and promote the discovery of IR-NLO materials with the ideal comprehensive performance.

Zn2BS3Br: An Infrared Nonlinear Optical Material with Significant Dual-Property Enhancements Designed through a Template Grafting Strategy

Developing high-performance infrared nonlinear optical (IR-NLO) materials with high second-harmonic generation (SHG) coefficients (dij) and wide band gaps (Eg) has been a serious challenge owing to the intrinsic negative correlativity between the two key properties. Herein, taking π-delocalized BS3 as core functional motifs (FMs), a template grafting strategy that facilitates dual-property enhancement is proposed and novel thioborates of Zn2BS3Br with target IR-NLO performances are predicted by the first-principles evolutionary algorithm. They not only possess wide band gaps of 3.63–4.05 eV, increasing by 1.0 eV over the benchmark AgGaS2 (AGS, 2.62 eV); moreover, benefiting from the parallel alignments of FMs, five phases exhibit high SHG effects (dij > 1.0 × AGS), particularly I (2.0 × AGS & 3.68 eV) and II (2.2 × AGS & 3.77 eV), in which significant enhancements in dij and Eg can be achieved concurrently, surpassing almost all of the accessible IR-NLO materials. Remarkably, the sufficiently wide band gaps and large birefringence of I and II lead to very short phase-matching wavelengths (λPM = 443.9/370.1 nm), enabling them a dual-waveband application potential, which is rarely found in IR-NLO chalcogenides. In addition, the isomorphic selenides show record high SHG coefficients of 3.8 × AGS in the wide-band-gap range of Eg > 3.0 eV. Therefore, the Zn2BS3Br-family crystals would be promising IR-NLO materials. Profound mechanism explorations conclusively demonstrate the effectiveness of our design strategy.