Synthesis, Growth and Optical, Mechanical, Electrical and Surface Properties of an Inorganic New Nonlinear Optical Crystal: Sodium Cadmium Tetra Chloride (SCTC)

Nonlinear optical (NLO) crystal is one of the important opt-electrical functional materials that can convert laser frequency and obtain wide band tunable coherent sources, thus it possesses crucial strategic and application value in military and civil fields. On the basis of more than 30 years' efforts, the NLO crystals in visible and near infrared region, including -BaB2O4 LiB3O5 and KTiOPO4, have been basically mature. However, there are still many shortcomings for those NLO crystals used in deep ultraviolet (DUV) and mid/far-infrared (IR) regions, thus putting forward more requirements for high performance crystals. For DUV KBe2BO3F2 (KBBF) crystals, the main shortcomings are the use of toxic BeO raw materials and strong layer growth tendency. Wide transparent region and high second harmonic generation (SHG) effect are also expected in new developed DUV NLO crystals. More importantly, a large enough birefringence is highlighted to satisfy the phase-matchable condition and DUV harmonic generation capacity below 200 nm. On the other hand, the main requirement for mid/far-infrared NLO crystals is to maintain the balance between high laser damage threshold and strong SHG response. Indeed, it is a very difficult task to search for good NLO crystals through the traditional trial and error experimental methods. Theoretical studies, especially first principles calculations, can provide an efficient way to investigate and design new NLO materials with superior properties. In this paper, the recent progress of deep-UV and mid-IR NLO crystals is summarized. In addition, the crucial role of first principles calculations in new material exploration and design is highlighted by introducing several typical new NLO crystals, including defect diamond-like compound AgZnPS4, trigonal alkaline metal fluorooxoborate KB4O6F and alkaline earth fluorooxoborate SrB5O7F3. Moreover, some advanced analysis tools are introduced, such as real space atomic cutting method, SHG-weighted mapping, flexible dipole moment model, and non-bonding atomic orbitals analysis, and used to investigate the structure-property relationship in langasite La3SnGa5O14, metal cyanurate Ca3(C3N3O3)2, vanadium-carbonate K3[V(O2)2O]CO3, etc. Further, the flow chart of high-throughput first principles calculations of NLO crystal is proposed. According to the known or predicted crystal structure, we can obtain the chemical stability, band gap, NLO coefficient, birefringence and phase-matchable capacity quickly, thus easily judging the research potential of a new NLO material. On the basis of these ideas, a great blueprint for NLO crystal material genome engineering is highly put forward. Finally, the difficulties in research and challenges in NLO material investigations are discussed, and the direction of future research priorities based on first principles calculations are pointed out.

A new inorganic nonlinear optical single crystal of sodium manganese tetra chloride (SMTC) has been successfully grown form aqueous solution by the slow evaporation technique at room temperature. The crystals obtained by the above technique were subjected to different characterization analysis. The crystalline nature of the grown crystal of SMTC was analyzed by powder X-ray diffraction. Single crystal X-ray diffraction study reveals that the crystal belongs to orthorhombic system with non-centrosymmetric space group Pbam. Optical transmission study on SMTC crystal shows high transmittance in the entire UV–Vis region and the lower cutoff wavelength is found to be 240 nm. The mechanical strength of the grown crystal was estimated by Vicker’smicrohardness test. The second harmonic generation (SHG) efficiency of the crystal was measured by Kurtz’s powder technique infers that the crystal has nonlinear optical (NLO) efficiency 1.32 times that of KDP.The dielectric constant and dielectric loss of the compound were measured at different temperature with varying frequencies. Photoconductivity study confirms that the title compound possesses a negative photoconducting nature. Growth mechanism and surface features of the as grown crystals were analyzed by chemical etching analyzing.

Synthesis, growth, and structural, optical, mechanical, electrical properties of a new inorganic nonlinear optical crystal: Sodium manganese tetrachloride (SMTC)

A hot topic in materials science is to search for nonlinear optical (NLO) crystals, which are indispensable in current laser technology, future optical information, and precision measurements. In the period of the 1980s and 1990s, the anionic group theory proposed by Prof. Chuangtian Chen has greatly promoted the inventions of BaB2O4 (BBO), LiB3O5 (LBO), and KBe2BO3F2 (KBBF) which are widely applied in the ultraviolet (UV) spectral region today. From the beginning of this century, the rapid development of laser science and technology urgently demands new NLO crystals for wider application ranges. However, commercial NLO crystals in deep-UV and mid-infrared (mid-IR) regions are scarce. The challenge arises from the stringent criteria at various wavelengths and inefficient exploration strategy. As such, more comprehensive and quantitative theoretical guidance is necessary to improve and supplement the NLO structure-property understandings. Benefiting from high-performance computing resources, first-principles design and simulations came into being, which is more applicable to the understanding of mid-IR NLO mechanism and suitable for the efficient design of new NLO structures for current needs. In the past decade, a complete set of computational research programs based on first-principles simulations have been developed, which have promoted the development of NLO crystals in the deep-UV and mid-IR regions, and guided the subsequent and further experimental explorations. Based on our developed first-principles materials design system, the discoveries of NLO materials have ranged from basic theoretical design to rapid-prototyping and final experimental synthesis. In this Account, we will concisely summarize our ab initio guided and forward-looking studies on NLO crystals, which are our original contributions to this field and can be consulted by other material fields. First, we will review the development of NLO crystals and the important features of NLO materials. Second, we will summarize the important role of computer-aided design in advancing the NLO material field and our developed NLO material design system based on the first-principles simulations. Third, we will introduce the first-principles design for new deep-UV NLO crystals using two novel design proposals, i.e., interlayer cationic replacement and intralayer anionic substitution. Meanwhile, we will illustrate the hierarchical molecular engineering optimizations for mid-IR NLO crystals by illustrating an extended mid-IR NLO family pedigree, from which many promising mid-IR NLO systems were predicted theoretically and confirmed experimentally. Finally, we will give an outlook to explore new functional NLO crystals guided by our first-principles design and simulations. We believe that the computer-assisted exploration for new functional NLO materials is useful for understanding structure-property relationships and can provide researchers with a new approach to cost-effective and data-driven materials design.

Divalent Mn2+ ion-doped potassium acid phthalate (KAP), a semi-organic non-linear optical (NLO) single crystals were grown by slow evaporation solution technique (SEST) at ambient temperature. Good optical quality single crystals of size 5 × 6 × 5 mm3 were grown in a period of 1 week. The pure and Mn2+ ion-doped KAP crystals were characterised by single-crystal X-ray diffraction (XRD) analysis to study the crystal structure. Single-crystal XRD analysis confirmed that the doped KAP crystallises in orthorhombic system with the space group Pca21. Powder X-ray diffraction (XRD) has confirmed the formation of the dopant in the KAP crystal. The functional groups of the grown crystals were identified by Fourier transform infrared spectrum (FTIR). UV–Vis NIR spectrum was recorded to study the optical transparency of the grown doped KAP crystals. The mechanical strength of the crystal is estimated by Vickers microhardness test. The stiffness constant and work hardening co-efficient were also calculated. The second harmonic generation (SHG) efficiency for device application was confirmed by NLO studies.

In the past twenty years, the basic investigation of innovative Non-Linear Optical (NLO) crystals has received significant attention, which has built the crucial heritage for the use of NLO materials. Fundamental research is essential given the scarcity of materials for NLO compounds, especially in the deep ultraviolet (DUV) and middle- and far-infrared (MFIR) regions. In the present work, we synthesized high-quality MFIR SbI3·3S8 NLO crystals having a length in the range of 1–5 mm through rapid facile liquid phase ultrasonic reaction followed by the assistance of instantaneous natural evaporation phenomenon of the solvent at room temperature. X-ray diffraction (XRD) results ratify the hexagonal R3m structure of SbI3·3S8 crystal, and energy-dispersive X-ray spectroscopy (EDX) demonstrates that the elemental composition of SbI3·3S8 crystal is similar to that of its theoretical composition. The direct and indirect forbidden energy gaps of SbI3·3S8 were measured from the optical transmittance spectra and they were shown to be 2.893 eV and 1.986 eV, respectively. The green sparkling signal has been observed from the crystal during the second harmonic generation (SHG) experiment. Therefore, as inorganic adducts are often explored as NLO crystals, this work on the MFIR SbI3·3S8 NLO crystal can bring about additional investigations on this hot topic in the near future.

Crystalline materials have a variety of applications ranging from catalysis to semiconductors. One interesting and emerging application is nonlinear optics. When nonlinear optical (NLO) crystals are irradiated, the nonlinear responses of the crystals to the oscillating electric field produces light with a different frequency than the incident radiation. Using different NLO crystals, any frequency of light can be generated. For this reason, NLO crystals are in increasing demand for many photonic applications, such as the generation of terahertz radiation (THz) to investigate and utilize the vibrational frequencies of collective atom motions. To accelerate the discovery of new NLO crystals, we combine data mining and DFT calculations to find potential NLO crystals and predict their optical nonlinearity. To be a potential NLO crystal, a structure must be noncentrosymmetric as the sum of the molecular NLO responses in a centrosymmetric structure is zero due to the inversion center. Thus, X-ray structure data is the excellent starting point to identify potential NLO crystals. For this reason, our data mining efforts have focused first on searching for noncentrosymmetric materials from the Cambridge Structural Database (CSD) to be used as THz generators. Using a custom-built code, we filtered the structures for desirable properties such as a conjugated -system and then extracted the candidates’ molecular and structural information. From over 1.2 million materials in the CSD, we isolated 77,842 NLO candidates based on our selection criteria. Using DFT, we calculated the molecular hyperpolarizability of these candidates and used those values in oriented gas models to estimate the polarization values for each candidate’s crystal structure. Because crystal polarization is directly related to the strength of the nonlinear response, crystal polarization estimates should provide a means of accounting for optical nonlinearity. To verify our approach, we selected the four candidates (PNPA, ZPAN, NMBA and TMOAT), synthesized them on a large scale, and observed their THz generating ability. The structures of all crystals were characterized using single-crystal X-ray diffraction, confirming their molecular identities and noncentrosymmetric packing. Large crystals of each material (Figure 1) were grown, and all generated THz radiation during a standard electro-optic measurement (Figure 2), which is a clear indication that our method successfully discovered new NLO crystals. In addition to discovering new NLO crystals, we are endeavoring to predict the THz spectra that they generate. The frequencies and magnitudes in the THz spectum directly impacts a crystal’s potential applications, and as Figure 2 illustrates, the spectra generated from different NLO crystals vary widely because they are influenced by many factors such as molecular vibrations, phonons, crystal thickness, density, refractive index, absorption, crystal face, etc. Combining our crystal polarization values with refractive indices and absorption coefficients obtained through solid-state DFT calculation, we were able compute theoretical THz generation spectra for NMBA and PNPA. As Figure 3 shows, our calculated spectra agree with the experimental spectra reasonably well, confirming that our method can viably predict THz generation spectra.

Mid‐infrared (MIR) nonlinear optical (NLO) crystals have long been pursued, yet the realization of a balance among key performance metrics remains a formidable challenge. Herein, we propose a band‐orientation co‐anchoring strategy to precisely regulate the band structures and module spatial arrangement for the rational design of high‐performance MIR NLO crystals. Leveraging the deep‐ultraviolet NLO KBe 2 BO 3 F 2 (KBBF) as a template, a novel MIR NLO Rb 3 ZnV 4 O 12 Br (RZVB) crystal was successfully obtained through multimodule substitution. Importantly, the tailored tetrahedral hybridization mode effectively anchors the conduction band minimum—dominated by d 0 cations—at a higher energy level and suppresses d–d transitions. Concurrently, structural confinement within the KBBF‐derived lattice enforces the optimal alignment of distorted tetrahedra. Furthermore, RZVB displays an unprecedented second harmonic generation (SHG) enhancement mechanism, arising from a unique cross‐module electron transfer. Consequently, RZVB exhibits superior linear and NLO performances, including a wide bandgap (3.25 eV), high laser threshold damage (1.07 GW/cm 2 @1064 nm), broad transmission window (0.382–7.6 µm), moderate birefringence (0.06@589.3 nm) and the strongest SHG response (7.7 × KDP@1064 nm and 1.45 × AGS@2.09 µm) among vanadates with bandgap exceeding 3 eV. This work presents a high‐performance MIR NLO crystal and establishes a bottom‐up, broadly applicable design paradigm for the tailored development of next‐generation crystalline materials.

Crystal growth is an important branch of solid state physics and material science. The Growth of Nonlinear Optical (NLO) materials crystals receives much importance nowadays because NLO materials have various applications in modern technologies like Laser technology, optoelectronics, and fiber optics, etc. Potassium dihydrogen phosphate (KDP) is a well known nonlinear optical (NLO) material with different applications. Since most of the amino acids exhibit NLO property, it is of interest to dope them in KDP. In the present study, amino acid L-Phenylalanine doped KDP crystals have been grown by slow evaporation solution growth technique. In present study powder XRD analysis was carried out which show that pure and L-Phenylalanine doped KDP crystals have tetragonal symmetry. The doping of L-Phenylalanine was confirmed by FT-IR and paper chromatography. Thermal analysis has been performed on the grown crystals.The SHG efficiency of L-Phenylalanine doped KDP crystals was found to be increasing with a doping concentration of L-Phenylalanine. Introduction. The demand for high quality large size KDP single crystal increases due to its application as frequency conversion crystal in inertial confinement fusion [1, 2]. KDP belongs to scalenohedral (twelve faced) class of tetragonal crystal system [3]. With the aim of improving the second harmonic generation (SHG) efficiency of KDP, researchers have attempted to modify KDP crystals by doping different types of impurities. The non-linear optical (NLO) and other properties of the crystal have been improved by doping of organic impurities [4-9]. KDP doped with amino acids like L-glutamine acid, L-gistidine, and L-valine was reported [10]. Kumaresan et al. [11] has reported the thermal dielectric properties of amino acids such as L-glutamic acid, L-histidine and L-valine doped KDP crystals. They found improved NLO properties of the KDP crystal and modifications in the structural, optical, mechanical, and electrical properties, too. Parikh [12] has reported the SHG efficiency of L-arginine doped KDP crystal. Kumaresan et al. [13] has also reported the effect of metal ion and amino acid doping on the optical properties of KDP crystal. Muley et al. [5] has studied thermal, NLO properties of KDP crystal doped with L-arginine and L-alanine. Suresh Kumar and Rajendrababu [6] studied the effects of L-arginine, L-histidine and glycine on the growth of KDP single crystals and observed that addition of amino acid enhances transparency, thermal stability and NLO efficiency of KDP crystals. Amino acid family crystals are playing an important role in the field of non-linear optical organic molecular crystal. Among them L-Phenylalanine (LPA) with chemical formula (C6H5CH2CH(NH2)COOH) is the α-amino acid with a non-reactive hydrophobic benzyl side chain. The physical, chemical and non-linear optical properties of KDP are enhanced by adding optically active amino acids as dopants.The growth and characterization of Single crystals of KDP doped with amino acids namely glycine, arginine, alanine, tryptophan, histidine have been reported earlier [5-8]. In the present work, single crystals of Potassium dihydrogen phosphate (KDP) added

Nonlinear optical (NLO) crystals play a pivotal role in solid‐state lasers and have broad applications in both civilian and military technologies. Ideal NLO crystal materials should possess a wide transmission range, moderate birefringence, a high second‐harmonic generation (SHG) coefficient, and excellent physical and chemical stability. Recent research has highlighted that incorporating metals with stereochemically active lone pairs (SCALPs) can significantly improve the NLO performance of these materials. This review presents a comprehensive overview of the latest 20 years’ advancements in NLO crystals featuring SCALPs, with a focus on their crystal structures and optical properties, particularly their SHG responses. The article also explores how metal‐based functional units containing SCALPs influence the polarizability of these materials. It is anticipated that this review will provide valuable insights into the functional design of high‐performance NLO crystals, contributing to the discovery of new SHG materials with the desired properties to meet the growing demands of modern technologies.

Laser damage threshold (LDT) is one of the key parameters of nonlinear optical (NLO) crystals, which can seriously affect the energy output of frequency conversion laser. The traditional design of NLO crystals introduces strongly distorted structural units, which hope to obtain an enhanced second harmonic generation (SHG) coefficient. However, this approach presents a fundamental conflict with the bandgap; it inevitably induces bandgap compression, which in turn significantly degrades the LDT. Herein, we propose a highly symmetric octahedron [HfO6] to enhance the bandgap of La3Ga5SiO14 (LGS) while keeping sufficient SHG response. Incorporating Hf into the LGS framework allows us to leverage the symmetry protection of the octahedra, effectively mitigating the bandgap reduction typically associated with cation energy level splitting in the distorted octahedra. We successfully synthesized a novel NLO crystal La3Ga5HfO14 (LGHf), which possesses a wide bandgap of 5.06 eV, which leads to a significantly enhanced LDT of 1.59 GW/cm2 (@ 1064 nm), while its SHG intensity reaches 3.5 × KH2PO4 (@1064 nm) and 0.35 × AgGaS2 (@ 2090 nm). This design strategy successfully achieves the synergistic optimization between wide bandgap characteristics and balanced NLO response, offering a new material solution for high-power mid-infrared laser systems.

Linear and nonlinear optical, mechanical, electrical and surface studies of a novel nonlinear optical crystal – Manganese mercury thiocyanate (MMTC)

Nonlinear optical (NLO) crystals are the vital components of laser science and technology, as they can convert lasers in common wavelengths into new wavelength bands for ultraviolet (UV), IR, and even terahertz laser output. Known UV NLO crystals mainly focus on crystals containing cations, but covalent crystals have rarely been reported. Here we report two covalent NLO crystals, B2 O3 I and B2 O3 II. According to the first-principles calculations, B2 O3 I and II have extremely short absorption edges of about 134 nm and 141 nm, large NLO coefficients of d22 =1.38 pm/V and d24 =0.702 pm/V, as well as sufficient birefringences of 0.037 and 0.031, respectively. Notably, the absorption edges are almost the shortest among NLO crystals. Meanwhile, the NLO coefficients are evidently larger than that of another well-known covalent NLO crystal α-SiO2 and are comparable to those of the commercial UV NLO crystal LiBO3 with Li+ cation. Furthermore, the birefringences are significantly larger than that of α-SiO2 , which are favorable to the phase matching for both crystals. These results reveal that B2 O3 I and B2 O3 II are excellent candidates for UV NLO applications. In-depth calculations are carried out to reveal the origin of excellent NLO properties. These covalent crystals provide a new direction for the research of UV NLO crystals.

Exploration of nonlinear optical (NLO) crystals thatare competentin generating short-wavelength ultraviolet (UV, λ ≤ 266nm, and even deep-UV, λ ≤ 200 nm) coherent light outputby direct second harmonic generation (SHG) remains a formidable challenge.Herein, four UV/deep-UV NLO crystals, M2B4SO10 (M = K, Rb, and Cs) and Rb3B11PO19F3, were successfully synthesized by evolvingthe KBe2BO3F2 (KBBF) structure intomixed-anionic borosulfate and fluoroborophosphate systems. They displayfunctional [B4SO10]∞ or [B11PO19F3]∞ KBBF-typelayers that are composed of [BO3], [BO4], and[SO4] groups or [BO3], [BO4], [BO3F], and [PO4] groups, respectively. Experimentalcharacterization and numerical computation results indicate that thesecrystals possess exceptional NLO performance, including large SHGresponses (0.9–1.7 × KDP at 1064 nm and 0.1–0.3× β-BBO at 532 nm) and adequate birefringence to fulfillthe SHG phase-matching (PM) condition at 266 nm. In particular, theshortest type-I PM wavelength (λPM) of Rb3B11PO19F3 reaches 180 nm, whichimplies that Rb3B11PO19F3 can become a prospective deep-UV NLO crystal. In addition, singlecrystals of K2B4SO10, Rb2B4SO10, and Cs2B4SO10 are easily obtained by the high-temperature solution approach.This work will facilitate the discovery of short-wavelength PM NLOcrystals by using the KBBF structure as the template.

Starting from a general quantum-mechanical perturbation theory on the nonlinear optical (NLO) effect in crystals, this review gives a systematic presentation of the basic concepts and calculation methods of the ‘anionic group theory for the NLO effect of crystals’ and a brief discussion of the approximations involved. Calculations have been made for the second harmonic generation (SHG) coefficients of a few typical NLO crystals. Comparisions between these theoretical values and the experimental values made both on powdered crystals and on single crystals suffice to show the feasibility of the theoretical treatment and calculation methods. On this basis, borate ions of various structure types are classified and systematic calculations are carried out for the NLO susceptibilities of some typical borate crystals with good prospects of applications in opto-electronics. Through these calculations, a series of structural criteria serving as useful guidelines for searching and developing new NLO crystals in borate series are presented. These structural criteria have good prospects of wider applications in searching and developing for other new types of NLO crystal materials. The criteria are as follows. (1) The planar six-membered ring (B3O6)3- and the planar trigonal (BO3)3 group, each possessing a conjugated 7t-orbital system, are far more favourable for producing larger SHG coefficients than the non-planar tetrahedral (BO4)5- group. Moveover, in the planar group, the larger the electronic population in the conjugated 7c-orbital system, the greater the SHG effects will be. As a result, the SHG effects will decrease in the order (2) The SHG coefficients can be adjusted to a certain extent by suitable arrangement of the three-and four-coordinated B atoms, such as (BO3)3- and (BO4)5-, (B3O6)3- as opposed to(B3O7)5- and (B3O8)7-. On the basis of these structural criteria, we have been successful in developing some new high-quality NLO materials, including the LiB3O5 crystal as an excellent NLO material. Suggestions are put forward for searching for and developing other promising new NLO materials in the borate series. The recent development of two new-type NLO borate crystals, β-BaB2O4 and LiB3O5, is described.