High Second Harmonic Generation Research Articles

Ferroelectric nematic fluids as spontaneous polarization field for enhanced orientational-dependent second-harmonic generation

ABSTRACT Second-order nonlinear optical effects have piqued researchers’ interest in fundamental physics and practical perspectives. The ferroelectric nematic liquid crystals (NF LCs) have recently drawn attention to LC nonlinear optical applications due to their relatively high second-harmonic generation output. Further improving the nonlinear optical properties to get closer to the performance of inorganic nonlinear optical materials is challenging. Here, we take a blending strategy to enhance the nonlinear optical response of a prototype NF LC, DIO. We mixed an organic nonlinear optical crystalline material, 3,5,5-trimethyl (cyclohex-2-enylidene) malononitrile (TCM), with DIO and investigated the effects of TCM doping at various concentrations. We quantitatively determined the second-harmonic generation and spontaneous polarization as functions of temperature and concentration. We found that, compared with the pure DIO, the second-harmonic generation performance increased by about 130% at maximum, 93% in maximum for the nonlinear optical coefficient, and 10% in maximum for spontaneous polarization.

Extraordinary Enhancement of Nonlinear Optical Interaction in NbOBr2 Microcavities.

2D materials are burgeoning as promising candidates for investigating nonlinear optical effects due to high nonlinear susceptibilities, broadband optical response, and tunable nonlinearity. However, most 2D materials suffer from poor nonlinear conversion efficiencies, resulting from reduced light-matter interactions and lack of phase matching at atomic thicknesses. Herein, a new 2D nonlinear material, niobium oxide dibromide (NbOBr2) is reported, featuring strong and anisotropic optical nonlinearities with scalable nonlinear intensity. Furthermore, Fabry-Pérot (F-P) microcavities are constructed by coupling NbOBr2 with air holes in silicon. Remarkable enhancement factors of ≈630 times in second harmonic generation (SHG) and 210 times in third harmonic generation (THG) are achieved on cavity at the resonance wavelength of 1500nm. Notably, the cavity enhancement effect exhibits strong anisotropic feature tunable with pump wavelength, owing to the robust optical birefringence of NbOBr2. The ratio of the enhancement factor along the b- and c-axis of NbOBr2 reaches 2.43 and 5.27 for SHG and THG at 1500nm pump, respectively, which leads to an extraordinarily high SHG anisotropic ratio of 17.82 and a 10° rotation of THG polarization. The research presents a feasible and practical strategy for developing high-efficiency and low-power-pumped on-chip nonlinear optical devices with tunable anisotropy.

Supramolecular Metal Halide Complexes for High-Temperature Nonlinear Optical Switches.

Nonlinear optical (NLO) switching materials, which exhibit reversible intensity modulation in response to thermal stimuli, have found extensive applications across diverse fields including sensing, photoelectronics, and photonic applications. While significant progress has been made in solid-state NLO switching materials, these materials typically showcase their highest NLO performance near room temperature. However, this performance drastically deteriorates upon heating, primarily due to the phase transition undergone by the materials from noncentrosymmetric to centrosymmetric phase. Here, we introduce a new class of NLO switching materials, solid-state supramolecular compounds 18-Crown-6 ether@Cu2Cl4·4H2O (1·4H2O), exhibiting reversible and stable NLO switching when subjected to near-infrared (NIR) photoexcitation and/or thermal stimuli. The reversible crystal structure in response to external stimuli is attributed to the presence of a weakly coordinated bridging water molecule facilitated by hydrogen bonding/chelation interactions between the metal halide and crown-ether supramolecules. We observed an exceptionally high second-harmonic generation (SHG) signal under continuous photoexcitation, even at temperatures exceeding 110 °C. In addition, the bridging water molecules within the complex can be released and recaptured in a fully reversible manner, all without requiring excessive energy input. This feature allows for precise control of SHG signal activation and deactivation through structural transformations, resulting in a high-contrast off/on ratio, reaching values in the million-fold range.

Second-harmonic generation in 2D moiré superlattices composed of bilayer transition metal dichalcogenides.

Moiré superlattices (MSLs) in twisted two-dimensional van der Waals materials feature twist-angle-dependent crystal symmetry and strong optical nonlinearities. By adjusting the twist angle in bilayer van der Waals materials, the second-harmonic generation (SHG) can be controlled. Here, we focus on exploring the electronic and SHG properties of MSLs in 2D bilayer transition metal dichalcogenides (TMDs) with different twist angles through first-principles calculations. We constructed MSL structures of five TMD materials, including three single-phase materials (MoS2, WS2, and MoSe2) and two heterojunctions (MoS2/MoSe2 and MoS2/WS2) with twist angles of 9.4°, 13.2°, 21.8°, 32.2°, and 42.1° without lattice mismatch. Our findings demonstrate a consistent variation in the SHG susceptibility among different TMD MSLs as a response to twist-angle changes. The underlying reason for the twist-angle dependence of SHG is that the twist angle regulates the interlayer coupling strength, affecting the optical band gap of MSLs and subsequently tuning the SHG susceptibility. Through a comparison of the static SHG susceptibility values, we identified the twist angle of 9.4° as the configuration that yields the highest SHG susceptibility (e.g. 358.5 pm V-1 for the 9.4° MoSe2 MSL). This value is even twice that of the monolayer (173.3 pm V-1 for monolayer MoSe2) and AA'-stacked bilayer structures (139.8 pm V-1 for AA' MoSe2). This high SHG susceptibility is attributed to the strong interlayer coupling in the 9.4° MSL, which enhances the valence band energy (contributed by the antibonding orbitals of chalcogen-pz and transition metal-dz2) and consequently leads to a small optical band gap, thus improving the optical transitions. The findings of this study provide a straightforward way to improve the SHG performance of bilayer TMDs and also throw light on the sensitive relationship between the twist angle, band structure and SHG properties of TMD MSLs.

Investigating the Photovoltaic Performance in ABO3 Structures via the Nonlinear Bond Model for an Arbitrary Incoming Light Polarization.

ABO3 structures commonly known as perovskite are of high importance in advanced material science due to their interesting optical properties. Applications range from tunable band gaps, high absorption coefficients, and versatile electronic properties, making them ideal for solar cells to light-emitting diodes and even photodetectors. In this work, we present, for the first time, a nonlinear phenomenological bond model analysis of second harmonic generation (SHG) in tetragonal ABO3 with arbitrary input light polarization. We study the material symmetry and explore the strength of the nonlinear generalized third-rank tensorial elements, which can be exploited to produce a high SHG response if the incoming light polarization is correctly selected. We found that the calculated SHG intensity profile aligns well with existing experimental data. Additionally, as the incoming light polarization varies, we observed a smooth shift in the SHG intensity peak along with changes in the number of peaks. These observations confirm the results from existing rotational anisotropy SHG experiments. In addition, we show how spatial dispersion can contribute to the total SHG intensity. Our work highlights the possibility of studying relatively complex structures, such as ABO3, with minimal fitting parameters due to the power of the effective bond vector structure, enabling the introduction of an effective SHG hyperpolarizability rather than a full evaluation of the irreducible SHG tensor by group theoretical analysis. Such a simplification may well lead to a better understanding of the nonlinear properties in these classes of material and, in turn, can improve our understanding of the photovoltaic performance in ABO3 structures.

Bright Second Harmonic Emission from Photonic Crystal Vertical Cavity

AbstractThis study presents photonic vertical cavities consisting of nonlinear materials embedded in photonic crystals (PhCs) for resonantly enhancing second harmonic generation (SHG). Previous attempts at SHG in such structures have been limited to efficiencies of 10−7 to 10−5, but a high SHG efficiency of 0.28% by constructing a vertical cavity with a lithium niobate membrane placed between two PhCs is demonstrated, which exhibits high‐quality resonances. The results open up new possibilities for compact laser frequency converters that can have a revolutionary impact on the fields of nonlinear optics and photonics.

High-Efficiency Second-Harmonic Generation Using Quasi-Bound State in LiNbO3 Metasurface

We numerically demonstrated a high-efficiency second-harmonic generation (SHG) using quasi-bound state in the continuum (quasi–BIC) in thin film LiNbO3 (TFLN) metasurface. The TFLN possessed exceptionally high second-order nonlinear coefficients, contributing to the enhanced SHG performance. An eccentric cylinder unit cell was presented to achieve high Q–factor resonances associated with the asymmetric parameter introduced. Simulations showed that the high efficiency of the second-harmonic conversion was obtained by using the high Q–factor of the asymmetric dielectric cylinder metasurface, and it achieved a high SHG efficiency of 6.5% at pump intensities as low as 1 MW/cm2 at a normal incident. Furthermore, the simulation results indicated that breaking the symmetry through oblique incidence was more effective in achieving a higher Q–factor compared to altering the structural parameters. Specifically, under 1° oblique incidences, the conversion efficiency could reach 1.2% at an incident power of 1 kW/cm². We have proposed a method to achieve a high conversion efficiency of second-harmonic generation in low-refractive-index materials. Our work not only offers theoretical support but also provides valuable insights for the advancement of efficient nonlinear frequency doubling technology, optical communication, and sensing applications.

Inherent law of SHG and phase-matching in 0D NLO materials: Permutation tetra-coordinated groups

Nonlinear optical (NLO) crystals, especially the mid-infrared nonlinear crystals play important roles in laser guidance and measurement. Among them, the tetra-coordinated structures have strong polarization ability. In this work, calculations for three zero-dimension (0D) tetra-coordinated structures (Na4Ca2SiP4, Cs2HgI2Cl2, Rb10Zn4Sn4S17) were analyzed by using density functional theory (DFT) simulations. Their crystal structure parameters, band structures, and optical properties are analyzed and compared. Meanwhile, the polarizability (electric dipole moment, dipole polarizability, first dipole hyper-polarizability) of these tetra-coordinated groups were analyzed separately. The results showed that the 0D isolated tetrahedron structure with strong consistent permutation may have excellent second harmonic generation (SHG) effect. It was worth mentioning that Na4Ca2SiP4 was predicted to have a large nonlinear effect and phase-matching ability. This enriches the theory of A/M (A = alkali or alkaline-earth metal cations except for Li; M = tetra-coordinated cations). In addition, the relationship between the Egap and electronegativity of the IA-IIA-M-Pn (IA = alkali metal; IIA = alkaline-earth metal; M = tetra-coordinated cations; Pn = P, As) structure was also investigated. This finding may shed light on the future construction of mid-infrared NLO materials with a wide Egap and high SHG effect.

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.

Plasmonic Nonlinear Energy Transfer Enhanced Second Harmonic Generation Nanoscopy.

Nonlinear optical response is a fingerprint of various physicochemical properties of materials related to symmetry, including crystallography, interfacial configuration, and carrier dynamics. However, the intrinsically weak nonlinear optical susceptibility and the diffraction limit of far-field optics restrict probing deep-subwavelength-scale nonlinear optics with measurable signal-to-noise ratio. Here, we propose an alternative approach toward efficient second harmonic generation (SHG) nanoscopy for SHG-active sample (zinc oxide nanowire; ZnO NW) using an SHG-active plasmonic nanotip. Our full-wave simulation suggests that the experimentally observed high near-field SHG contrast is possible when the nonlinear response of ZnO NW is enhanced and/or that of the tip is suppressed. This result suggests possible evidence of quantum mechanical nonlinear energy transfer between the tip and the sample, modifying the nonlinear optical susceptibility. Further, this process probes the nanoscale corrosion of ZnO NW, demonstrating potential use in studying various physicochemical phenomena in nanoscale resolution.

Magnetic Fano resonance enhanced second-harmonic generation in chiral hybrid bismuth halides

Magnetic Fano resonance provides a potential opportunity to control both linearity and nonlinearity of light for their low radiation loss and near-field enhancement. Previous investigations have demonstrated its significant enhancement of nonlinearity in a plasmonic structure and the 2D materials coupled to it. In this work, the enhancement of second harmonic generation (SHG) of hybrid bismuth halides at the important communication wavelength of 1550 nm with a magnetic Fano dip is theoretically studied. To this end, a hybrid system composed of two asymmetric silver square split rings (SSRs) and this chiral perovskite film is designed. The simulation results show that magnetic Fano-like resonance is induced at the destructive interface of two magnetic modes in the SSR dimer, which can be inherited to hybrid bismuth halides, thereby leading to the increase of four orders of magnitude in its SH near-field enhancement factor. With a peak intensity of 0.16 GW cm−2, the composite structure features a high SHG conversion efficiency of up to 1.6 × 10−3 at the Fano resonance position. By rotating the polarization angle of fundamental optical excitation, the emitted SHG signal is switched on–off. Our research provides a valuable thought for enhancing the nonlinear optical process of the perovskite films by coupling the magnetic modes.

Anisotropy-enhanced second-harmonic generation from graphene-wrapped nanoparticles

Due to the various applications of second-harmonic generation (SHG), achieving high SHG conversion efficiency is highly appreciated. In this paper, we achieve high SHG conversion efficiency from graphene-wrapped radial anisotropic nanoparticles by combining the strong second-order nonlinear effects of graphene and the field-enhancing effects of anisotropic materials. We find that the nonlinear conversion efficiency of radial anisotropic nanoparticles can be several orders of magnitude higher than that of isotropic counterpart. This is because the radial anisotropic provides the additional enhancement of field intensity near the boundary, and the graphene that provides SHG nonlinear effect is located at the particle boundary where the fundamental frequency field is significantly enhanced. Meanwhile, the highly tunable characteristic of graphene offers additional flexibility for manipulating the SHG spectrum in actual applications. Our results provide a promising method for improving the nonlinear conversion efficiency of photonic devices and the sensitivity of the nonlinear sensor.

D6versus d10, Which Is Better for Second Harmonic Generation Susceptibility? A Case Study of K2TGe3Ch8 (T = Fe, Cd; Ch = S, Se)

Two acentric chalcogenide compounds, K2CdGe3S8 and K2CdGe3Se8, were synthesized via conventional high-temperature solid-state reactions. The crystal structures of K2CdGe3S8 and K2CdGe3Se8 were accurately determined by single-crystal X-ray diffraction and crystallize in the K2FeGe3S8 structure type. K2CdGe3S8 is isostructural to K2FeGe3S8 with superior nonlinear optical properties. For the second harmonic generation (SHG) response, K2CdGe3S8 is 18× K2FeGe3S8 for samples of particle size of 38-55 μm. The superior nonlinear optical properties of K2CdGe3S8 over K2FeGe3S8 are mainly contributed by the chemical characteristics of Cd compared with Fe, which are elucidated by nonlinear optical property measurements, electronic structure calculations, and density functional theory calculations. The [CdS4] tetrahedra within K2CdGe3S8 exhibit a higher degree of distortion and larger volume compared to the [FeS4] tetrahedra in K2FeGe3S8. This study possesses a good platform to investigate how d-block elements contribute to the SHG response. The fully occupied d10-elements are better for SHG susceptibility than d6-elements in this study. K2CdGe3S8 is a good candidate as an infrared nonlinear optical material of high SHG response (2.1× AgGaS2, samples of particle size of 200-250 μm), type-I phase-matching capability, high laser damage threshold (6.2× AgGaS2), and good stability.

Hybrid Germanium Bromide Perovskites with Tunable Second Harmonic Generation

AbstractGe‐based hybrid perovskite materials have demonstrated great potential for second harmonic generation (SHG) due to the geometry and lone‐pair induced non‐centrosymmetric structures. Here, we report a new family of hybrid 3D Ge‐based bromide perovskitesAGeBr3,A=CH3NH3(MA), CH(NH2)2(FA), Cs and FAGe0.5Sn0.5Br3, crystallizing in polar space groups. These compounds exhibit tunable SHG responses, where MAGeBr3shows the strongest SHG intensity (5×potassium dihydrogen phosphate, KDP). Structural and theoretical analysis indicate the high SHG efficiency is attributed to the displacement of Ge2+along [111] direction and the relatively strong interactions between lone pair electrons of Ge2+and polar MA cations along thec‐axis. This work provides new structural insights for designing and fine‐tuning the SHG properties in hybrid metal halide materials.

Thermally tunable and efficient second-harmonic generation on thin-film lithium niobate with integrated micro-heater.

In this Letter, we report thermo-optic tunable and efficient second-harmonic generation (SHG) based on an X-cut periodically poled lithium niobate (PPLN) waveguide. By applying an on-chip heater with thermo-isolation trenches and combining a type-0 quasi-phase matching mechanism, we experimentally achieve a high on-chip SHG conversion efficiency of 2500-3000% W-1 cm-2 and a large tuning power efficiency of 94 pm/mW inside a single 5-mm-long straight PPLN waveguide. Our design is for energy-efficient, high-performance nonlinear applications, such as wavelength conversion, highly tunable coherent light sources, and photon-pair generation.

Reversible phase transition for switchable second harmonic generation in 2D perovskite microwires

AbstractHighly efficient second‐harmonic generation (SHG) has facilitated the development of nanophotonics and sustained promising applications, ranging from electro‐optical modulation, frequency conversion, and optical frequency combs to pulse characterization. Although controllable SHG switching has been observed in nanophotonics structures and molecule systems, the relatively small SHG switching contrast impedes its application in switchable nonlinear optics. Herein, reversible phase transitions between glassy and crystalline states without material degradation are demonstrated based on solution‐processed chiral perovskite microwire arrays. Breaking of lattice inversion symmetry and high crystallinity support efficient SHG in microwire arrays. By synergy of high‐performance SHG and reversible phase transitions between glassy and crystalline states, reversible switching of SHG is demonstrated under facile conditions. The high SHG switching performances, together with a small footprint, pave the way toward the integration of switchable nonlinear devices based on microwire arrays.

Dimethylaniline-Based Hybrid Compounds of Cadmium Diiodide: Synthesis, Crystal Structure, and Physical Properties

In this work, synthesis, crystal structure, and selected properties of two new organic–inorganic compounds based on cadmium iodide with 2,5- and 2,6-dimethylaniline: CdI2(2,5-DMA)2 1 and CdI2(2,6-DMA)2 2, respectively, were investigated. Both compounds were obtained using the same methodology, and their crystal structures were determined from powder (1) and single-crystal (2) X-ray diffraction experiments. The examined materials crystallize in the noncentrosymmetric space group Fdd2 and contain large polarizable iodine ions and electron-rich aromatic ligands. Second harmonic generation (SHG) tests performed with urea as a reference revealed high SHG efficiency of powdered samples 1 and 2. SHG signals measured for samples 1 and 2 are, respectively, around 10 and 8 times larger than the signal for urea. The experimental part was supplemented with theoretical calculations of the second-order electric susceptibility tensor components, χijk(2). Calculated values of the χ113(2) tensor component around 1.2–1.4 pm·V–1 suggest that both materials are relatively efficient second harmonic generators. Fibrous morphology of the materials was revealed by scanning electron microscopy (SEM), and the observed bending of the fibers suggested their significant flexibility. Samples 1 and 2 were also characterized by spectroscopic techniques (IR, RS, UV–Vis-DRS) and their thermal stability and decomposition rates were researched using XRPD and TG/DSC, revealing that both investigated materials are thermally stable up to around 100 °C.

High spectral contrast chiral second-harmonic generation from multilayer gallium selenide coupled to silicon holey disk metasurfaces

We present electromagnetic design and analysis of hybrid metasurfaces composed of multilayer gallium selenide (GaSe) coupled to silicon holey disk arrays for achieving high spectral contrast chiral second-harmonic generation (SHG). The silicon holey disk structures are designed to support electromagnetically induced transparency (EIT)-like optical resonances in the 1.5–1.8 µm wavelength range in the vicinity of electric and toroidal dipole scattering modes. The fundamental electric field enhancement above the silicon structures shows right-circularly polarized (RCP)- and left-circularly polarized (LCP)-like characteristics at distinct wavelengths resulting in two prominent peaks for the LCP and RCP resolved SHG from the GaSe layer above the holey disks. This results in high contrast SHG degree of circular polarization spanning − 1 to + 1 over the fundamental excitation spectral range considered. The chiral SHG response is also found to be strongly influenced by the unit-cell lattice arrangement with square or hexagonal lattice exhibiting very different chiral SHG response. This observation is consistent with the circular polarization state selection rules for the harmonic generation process considering the rotational symmetry of the underlying metasurface lattice arrangement. Two-dimensional (2D) material–dielectric resonant metasurface hybrid systems exhibit nonlinear optical polarization selection rules, which differ from the native 2D material, making them an interesting platform for realizing engineered chiral nonlinear photonic devices.

Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn): High Chemical Flexibility Resulting in Good Nonlinear-Optical Properties.

Seven acentric sulfides Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn) were grown by a high-temperature salt flux method. The crystal structures of the Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn) compounds were determined by single-crystal X-ray diffraction with the aid of solid-state NMR spectroscopy. The Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi) compounds are isostructural and crystallize in the Ba6Ag4Sn4S16 structure type. The Sn-containing compound exhibits high structural similarity to Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi) with the presence of an interstitial atomic position partially occupied by Sn atoms. The chemical bonding characteristics of Ba6(Cu2.9Sn0.4)Sn4S16 were understood with electron localization function calculations coupled with crystal orbital Hamilton population calculations. The Ba-S and Cu-S interactions are dominantly ionic, but the Sn-S interactions consist of strong covalent bonding characteristics in Ba6(Cu2.9Sn0.4)Sn4S16. The monovalent Cu atoms, mixed with certain metals with various oxidation states, significantly shift the optical properties of the Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi) compounds. This results in a good balance between the second-harmonic-generation (SHG) response and laser damage threshold (LDT). Ba6(Cu1.9Zn1.1)Sn4S16 possesses a high SHG response and a high LDT of 2.8 × AGS and 3 × AGS, respectively. A density functional theory calculation revealed that CuS4 and SnS4 tetrahedra significantly contribute to the SHG response in Ba6(Cu2Mg)Sn4S16, which also confirmed that CuS4 tetrahedra are crucial for the stability and optical properties of the Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn) compounds revealed by electronic structure analysis.

Pd and octahedra do not get along: Square planar [PdS4] units in non-centrosymmetric La6PdSi2S14

Non-linear optical (NLO) materials require a balance of high second-harmonic generation (SHG) signal and laser damage threshold (LDT), as well as phase matchable behavior. Herein, we report a new member of the (RE)6(TM)x(Tt)2Q14 family of compounds, La6PdSi2S14, which, unlike all other reported TM analogues crystallizing in hexagonal P63 space group, crystallizes in the non-centrosymmetric monoclinic P21 space group. The crystal structure contains chains of edge-sharing distorted square planar [PdS4] units. The square-planar coordination of Pd in La6PdSi2S14 exhibits remarkable NLO properties with high SHG (3.7 × AgGaS2) and LDT (3 × AgGaS2) values as well as phase matchability. This shows the promise of novel materials with distorted structural motifs for enhanced NLO properties. Upon formation of bimetallic chiral sulfides containing both Cu and Pd, Cu occupies the opposite faces of the octahedra forming [CuS3] units while Pd can be stabilized in the center of PdS6 octahedra in the hexagonal P63 crystal structure of La6Pd0.5CuSi2S14. This suggests that it is possible to form mixed metal systems which could further enhance NLO properties by incorporation of additional structural distortions.