Expanding Frontiers of Ultraviolet Nonlinear Optical Materials with Fluorophosphates

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

Linear and Nonlinear Polarizability: a Primer Second-Order Nonlinear Optical Processes in Molecules and Solids Third-Order Nonlinear Optical Effects in Molecular and Polymeric Materials Nonlinear Optical Properties of Molecules and Materials Electronic Hyperpolarizability and Chemical Structure Electrooptic Polymer Waveguide Devices: Status and Applications Waveguiding and Waveguide Applications of Nonlinear Organic Materials Nonlinear Optical Materials: The Great and Near Great Donor- and Acceptor-Substituted Organic and Organometallic Compounds: Second-Order Nonlinear Optical Properties Use of a Sulfonyl Group in Materials for Nonlinear Optical Materials: A Bifunctional Electron Acceptor Organic and Organometallic Compounds: Second-Order Molecular and Macroscopic Optical Nonlinearities Chemistry of Anomalous-Dispersion Phase-Matched Second Harmonic Generation Applications of Organic Second-Order Nonlinear Optical Materials Chromophore-Polymer Assemblies for Nonlinear Optical Materials: Routes to New Thin-Film Frequency-Doubling Materials Novel Covalently Functionalized Amorphous *y^2 Nonlinear Optical Polymer: Synthesis and Characterization Second-Order Nonlinear Optical Polyphosphazanes Molecular Design for Enhanced Electric Field Orientation of Second-Order Nonlinear Optical Chromophores Nonlinear Optical Chromophores in Photocrosslinked Matrices: Synthesis, Poling, and Second-Harmonic Generation Thermal Effects on Dopant Orientation in Poled, Doped Polymers: Use of Second Harmonic Generation Organic Polymers as Guided Wave Materials Observing High Second Harmonic Generation and Control of Molecular Alignment in One Dimension: Cyclobutenediones as a Promising New Acceptor for Nonlinear Optical Materials Strategy and Tactics in the Search for New Harmonic-Generating Crystals Development of New Nonlinear Optical Crystals in the Borate Series What is Materials Chemistry? Defect Properties and the Photorefractive Effect in Barium Titanate Defect Chemistry of Nonlinear Optical Oxide Crystals From Molecular to Supramolecular Nonlinear Optical Properties Control of Symmetry and Asymmetry in Hydrogen-Bonded Nitroaniline Materials Molecular Orbital Modeling of Monomeric Aggregates in Materials with Potentially Nonlinear Optical Properties Strategies for Design of Solids with Polar Arrangement Ferroelectric Liquid Crystals Designed For Electronic Nonlinear Optical Applications Model Polymers with Distyrylbenzene Segments for Third-Order Nonlinear Optical Properties Composites: Novel Materials for Second Harmonic Generation Clathrasils: New Materials for Nonlinear Optical Applications Inorganic Sol-Gel Glasses as Matrices for Nonlinear Optical Materials Intrazeolite Semiconductor Quantum Dots and Quantum Supralattices: New Materials for Nonlinear Optical Applications Small Semiconductor Particles: Preparation and Characterization Synthetic Approaches to Polymeric Nonlinear Optical Materials Based on Ferrocene Systems Transition Metal Acetylides for Nonlinear Optical Properties Third-Order Near-Resonance Nonlinearities in Dithiolenes and Rare Earth Metallocenes Nonlinear Optical Properties of Substituted Phthalocyanines Nonlinear Optical Properties of Substituted Polysilanes and Polygermanes Design of New Nonlinear Optic-Active Polymers: Use of Delocalized Polaronic or Bipolaronic Charge States New Polymeric Materials with Cubic Optical Nonlinearities: From Ring-Opening Metathesis Polymerization Polymers and an Unusual Molecular Crystal with Nonlinear Optical Properties Quadratic Electrooptic Effect in Small Molecules Third-Order Nonlinear Optical Properties of Organic Materials

Defect engineering of second-harmonic generation in nonlinear optical semiconductors

UV nonlinear optical materials require the simultaneous achievement of a large second harmonic generation (SHG) coefficient (≥1 × KH2PO4 (KDP), dij > 0.39 pmV−1), wide bandgap (λ < 300 nm, Eg > 4.2 eV), and moderate birefringence (0.05‐0.10@1064 nm) in a single structure. Therefore, designing UV nonlinear optical materials with excellent comprehensive performance is a challenging task. Herein, four UV transparent selenite materials are successfully obtained, namely, Al2(SeO3)3(H2O)3 (1), Ga2(SeO3)3(H2O)3 (2), NaGa3(HSeO3)6(SeO3)2 (3), and Cd5Ga4(HSeO3)2(SeO3)10 (4), through rational design and screening in the pure selenite system. Al2(SeO3)3(H2O)3 (1) and Ga2(SeO3)3(H2O)3 (2) are UV nonlinear optical materials with balanced properties, exhibiting moderate SHG responses (1.2 and 1.1 × KDP), appropriate birefringence (0.084 and 0.076@1064 nm), and wide bandgaps (5.5 and 5.3 eV). Such bandgaps are the largest in the reported pure selenite nonlinear optical (NLO) materials. This work further demonstrates that pure selenite is a good candidate for UV NLO materials.

Nonlinear optical (NLO) materials that can achieve frequency conversion and coherent light emission have garnered significant interest owing to their promising applications in laser technology and advanced photonic systems. In this study, the first-principles high-throughput screening pipeline (FHSP) was employed to systematically explore nonlinear optical materials within vanadate-based systems. A total of 204 vanadates were calculated in the Inorganic Crystal Structure Database (ICSD). Eventually, BiCa2VO6 was screened out and synthesized by a traditional high-temperature solid-state method. BiCa2VO6 exhibits an outstanding second harmonic generation (SHG) response (11.2 × KDP@1064 nm and 1.67 × AGS@2.09 μm), a wide band gap (3.25 eV), and a suitable birefringence (0.123@1064 nm). The work provides a complete perspective for vanadate as a nonlinear optical material and serves as a valuable reference for future research.

Structural, thermal, mechanical and optical properties of l-arginine diiodate crystal: A new nonlinear optical material

Second-order nonlinear optical (NLO) materials have drawn enormous academic and technological attention attributable to their indispensable role in laser frequency conversion and other greatly facilitated applications. The exploration of new NLO materials with high performances thus has long been an intriguing research field for chemists and material scientists. However, an ideal NLO material should simultaneously satisfy quite a few fundamental yet rigorous criteria including a noncentrosymmetric structure, large NLO coefficients, desired transparent range, large birefringence, high laser damage threshold, and availability of a large-size single crystal. Therefore, the identification of promising compound systems, targeted design, and experience-based syntheses are crucial to discover novel NLO materials working in the spectral region of interest. As an important family of mixed-anion compounds, versatile metal oxyhalides containing metal-centered oxyhalide functional units ([MOmXn] (X = F, Cl, Br, and I)) are becoming a marvelous branch for interesting NLO materials. Especially, when the central metals are d0/d10 transition metals or heavy post-transition metals, a number of novel NLO materials with superior functionalities are expected. Our thorough review on the recent achievements of metal oxyhalides for NLO materials are divided into the fast-growing NLO metal oxyhalides with single type halogen anions and the newly identified NLO metal oxyhalides with mixed halogen anions. Here we mainly focus on the design strategy, structural chemistry, NLO-related properties, and structure–property correlation of the metal oxyhalides with relatively large NLO responses. We hope this review can provide an insight on the rational design and future development of emerging metal oxyhalides for NLO and other applications.

Defective crystalline semiconductor plays a significant role in photocatalytic nitrogen fixation, however the rapid recombination of photoexcited electron/hole pairs largely reduces the efficiency. Spontaneous polarization of the nonlinear optical (NLO) material has emerged as a promising strategy for addressing the problem. Herein, a defects-rich NLO crystalline LiNbO3 modulated by natural nano-mineral palygorskite (LiNbO3/Pal) has been synthesized via sol–gel method. The intrinsic polarization of LiNbO3/Pal is investigated by second harmonic generation (SHG) measurements, which indicates an intensity of about 3.1 times that of typical NLO material KH2PO4 (KDP). The strong polarization can facilitate the separation of photogenerated charge carriers in the bulk phase and on the surface of LiNbO3/Pal. The existence of oxygen vacancies in LiNbO3/Pal may originate from doping of metal ions and active groups on the surface of Pal during crystallization of LiNbO3, which shortens the bandgap of LiNbO3 and facilitates the absorption and activation of N2 molecules. As a result, the polarization effect and rich oxygen vacancies make the LiNbO3/Pal an exceptional photocatalyst for N2 fixation. The 40 wt% LiNbO3/Pal composite achieves an average rate of photocatalytic NH4+ production of 52.57 μmol gcat−1 h−1 under simulated solar light, which is about sixfold higher than that of bulk LiNbO3. This work not only presents a new perspective on mineral modification of NLO material but also offers a cost-effective photocatalyst for nitrogen fixation.

Inorganic adducts are an emerging class of infrared nonlinear optical (NLO) materials. However, although the reported NLO adducts have sufficient birefringences and significant laser‐induced damage thresholds (LIDTs), they commonly suffer from weak second harmonic generation (SHG) responses. In this work, a series of polar phosphorus chalcogenide cage molecules with strong hyperpolarizabilities were theoretically screened out to enhance the SHG responses of adducts. Accordingly, (CuI)3(P4S4), (CuI)3(P4Se4), (CuBr)7(P4S3)3 and (CuBr)7(P4Se3)3 with target polar cage molecules were successfully synthesized. As expected, they exhibit enhanced SHG responses while keeping moderate birefringences and high LIDTs. Notably, (CuBr)7(P4Se3)3 possesses the largest SHG response (3.5×AGS@2.05 μm) among the known inorganic NLO adducts. Our study confirms that introducing NLO‐active cage molecules into adducts is an efficient strategy for high‐performance NLO materials.

Effective design and synthesis of second-order nonlinear optical (NLO) materials hold immense significance in driving modern science and technology advancements. In this study, we synthesized a new acentric mercury nitrate, (C5H12N2S)Hg(NO3)2, by regulating the coordination of the Hg atom through the introduction of a heteroatom. It exhibits an unprecedented [(C5H12N2S)2Hg2(NO3)4]∞ chain composed of Hg2+, NO3-, and organic molecule C5H12N2S. Notably, (C5H12N2S)Hg(NO3)2 demonstrates an unprecedented HgO3S unit and a second harmonic generation (SHG) intensity of 1.3 × KDP at 1064 nm, presenting the second-order nonlinear mercury nitrate constructed by organic molecule. Theoretical calculations suggest that the HgO3S unit and organic molecule C5H12N2S significantly contribute to the SHG effect. This study demonstrates that the incorporation of heteroatoms is an effective strategy for the development of new NLO materials.

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.

Fluorine-containing compounds have stimulated the exploration of ultraviolet/deep-ultraviolet nonlinear optical (NLO) materials. Alkali/alkaline-earth metal phosphates are one of the important potential systems as NLO materials, while the common small birefringence limits the phase-matching (PM) ability in the ultraviolet/deep-ultraviolet region. Herein, by applying a "fluorination synergy-induced enhancement of optical property" strategy, novel structures of phosphate fluoride/fluorophosphate in BePO3F with good thermodynamic/dynamic stability and promising NLO-related properties are discovered via performing crystal structure prediction combined with first-principles calculations. BePO3F-I-VI exhibit relatively large birefringence of 0.025, 0.048, 0.049, 0.049, 0.059, and 0.063 at 1064 nm, respectively. Simultaneously, BePO3F-I (Pc) is a new thermodynamically stable phosphate fluoride which possesses a wide band gap (Eg = 8.03 eV), large second-harmonic generation (SHG) coefficient (d11 = 0.67 pm/V, 1.7 × KDP), and the shortest PM wavelength of 292 nm. Other five thermodynamically metastable noncentrosymmetric (NCS) BePO3F structures (II-VI) belong to fluorophosphates and exhibit deep-ultraviolet PM wavelengths of 187, 183, 186, 188, and 196 nm. It reveals that the aligned nonbonding O 2p orbitals of [BeO2F2] and [PO4] units lead to a large SHG coefficient in the phosphate fluoride BePO3F-I. For fluorophosphates (BePO3F-II-VI), the synergy of [BeO3] planar units and [PO3F] units induces relatively large birefringence. Our research results provide an idea for exploring novel high-performance NLO materials.

Partial fluorination of oxides has positioned oxyfluorides as a promising class of nonlinear optical (NLO) materials owing to their balanced optical properties. However, effectively arranging optical chromophores to achieve strong optical nonlinearity remains challenging. In this study, we explore the structural chemistry of 1 [NbOF 4 ] ∞ chain‐based oxyfluoroniobates and establish a molecular geometric framework to quantify key structural fingerprint factors , namely, the ∠(O─Nb─O′) bond angle, χ [F,Nb,Nb′,F′] torsion angle, chain alignment, and distortion of [NbO 2 F 4 ] nodes. Theoretical calculations confirm that these factors critically influence second harmonic generation (SHG) activity. By integrating π‐conjugated biuret (C 2 H 5 N 3 O 2 ) molecules with optimally aligned 1 [NbOF 4 ] ∞ chains, we synthesized (H 3 O)(Biu) 2 (NbOF 4 ) (Biu = biuret), a crystal exhibiting a record‐breaking SHG response, reaching 10.8 times that of KH 2 PO 4 , among transition metal (TM) oxyfluorides. Its moderate birefringence (Δ n = 0.062 @1064 nm) and wide band gap ( E g = 4.50 eV) further support its potential as a high‐performance ultraviolet (UV) NLO material. These results highlight the power of structural fingerprint optimization in fully activating polar chains and offer a new strategy for designing next‐generation UV NLO crystals with enhanced SHG performance.

The semicarbazone of p-anisaldehyde (SPAS) is a novel organic nonlinear optical material. The SPAS has been synthesized and the solubility studies were carried out in the temperature range 30-60 °C. Single crystals of SPAS have been grown following the slow evaporation technique and the unit cell parameters have been evaluated by single crystal X-ray diffraction technique. The UV-Visible, FT-IR and 1HNMR spectra have been recorded to characterize the grown crystal. The thermogravimetric and differential thermal analysis of the grown crystal revealed that there is no phase transformation in SPAS, and its thermal stability was found to be good. The dielectric measurement was made as a function of frequency (50 Hz - 5 MHz). The second harmonic generation in the sample was confirmed by the Kurtz powder technique.

Fluorooxoborates have inspired investigations of deep‐ultraviolet (DUV) nonlinear optical (NLO) materials that can meet the multiple criteria. Herein, five stable structures with the composition of BaB2O3F2 (I–V) are discovered using the ab initio evolutionary algorithm. Among them, BaB2O3F2‐I has been synthesized experimentally and confirms the reliability of the method. All of the predicted structures possess extremely wide band gaps (8.1–9.0 eV). Moreover, four new structures exhibit giant second harmonic generation (SHG) coefficients (>3×KDP, d36=0.39 pm V−1). A novel type of the [BOF] layer with BO3:BO3F ratio of [1:1] is found in BaB2O3F2‐II and BaB2O3F2‐III. While BaB2O3F2‐IV and BaB2O3F2‐V are solely composed of the BO3F group and have colossal SHG coefficients (ca. 4×KDP). It gives the direct evidence that the BO3F group could generate strong SHG effect. Most importantly, the influences of BO3:BO3F ratio and their number density on band gap, birefringence and SHG effects are investigated.