Crystals Of Nonlinear Optical Material Research Articles

Two Acentric Zn-Based l-Tartrates with Moderate Second Harmonic Generation Responses and Large Birefringence.

The discovery of novel organic-inorganic hybrid nonlinear optical (NLO) crystal materials holds great potential in advancing laser science and technology as they offer a wide range of benefits including easy synthesis, structural versatility, and high hyperpolarizability. Herein, the integration of l-tartaric acid (L-C4H6O6) and ZnSO4 gave rise to two acentric Zn-based organic-inorganic hybrid crystals, namely, Zn2(H2O)2(C4H4O6)2·3H2O (Zn-LT) and Zn2(H2O)(C4H4O6)(C4H6O6)(SO4)·4H2O (Zn-LTS). They both feature layered structures constructed by [ZnO6] octahedron, l-C4H6O6/l-C4H4O62-, water molecule, or [SO4] tetrahedron. Interestingly, they possess moderate second-order NLO effects of 0.28 × KH2PO4 (Zn-LT) and 0.57 × KH2PO4 (Zn-LTS), large birefringence of 0.075 (Zn-LT) and 0.069 (Zn-LTS), suggesting that the introduction of [SO4] groups with intrinsically weak polarizability and weak optical anisotropy induces the enhancement of the NLO effect while without reducing birefringence much. In addition, both of them display UV cutoff edges near 210 nm, indicating their potential as NLO crystals applied in the UV and solar-blind region.

A new benzothiazolium-based organic nonlinear optical material DABT

Second-order nonlinear optical (NLO) crystal materials are applied widely. In this work, a new benzothiazolium-based ionic organic NLO material (E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]thiazol-3-ium 4-methylbenzenesulfonate (DABT) containing strong electron donor and acceptor was designed and theoretically investigated. A simple approach that can be employed in rapidly and efficiently evaluating the second-order nonlinear properties of organic crystals based on its crystal structure information was also proposed. Results indicate that the as-designed DABT crystal possesses non-centrosymmetric structure with space group P21, and particularly, it exhibits a large static first-order hyperpolarizability of ∼117 × 10−30 esu. Moreover, the optical properties of the DABT, including its permittivity, absorption coefficient, and reflectance, were systematically investigated, revealing that the DABT crystal is an anisotropic and a new and promising material with hydrophobicity and anisotropy, holding great potential applications in nonlinear optics.

Design, synthesis and characterization of organic second-order nonlinear optical crystal materials DOBS

Recent advance of the organic nonlinear optical (NLO) crystals on the design, synthesis and characterization of 2-(3,4-Dimethoxystyryl)-3-methylbenzothiazolium-benzenesulfonate (DOBS) is reported. It is found that crystal belongs to the triclinic system, with the space group P1. The second harmonic generation efficiency is 1.8 times higher than the standard KDP. Based on density functional theory (DFT), the maximum first-order hyperpolarizability of DOBS molecule is obtained by Gaussian calculation βmax is 107.7 × 10− 30 esu. The molecular surface electrostatic potential, HOMO-LUMO orbital, ELF/LOL, Hole-electron, Hirshfeld surface and 2-D fingerprint were analyzed. The thermal stability analysis shows that DOBS crystal has a high melting point of 251 °C. In addition, UV-Vis-NIR spectra, dielectric properties and fluorescence were investigated.

Two non-centrosymmetric mixed alkali metal and alkaline earth metal scandium borate nonlinear optical materials with short ultraviolet cutoff edges.

Rare earth borates, a subset of the essential nonlinear optical (NLO) materials, have sparked a significant amount of attention in recent years. In self-fluxing systems, two non-centrosymmetric scandium borates with classical B5O10 groups, namely Rb7SrSc2B15O30 (I) and Rb7CaSc2B15O30 (II), were successfully discovered. Both I and II exhibit a short ultraviolet (UV) cutoff edge (<200 nm) and appropriate second-harmonic generation efficiency (∼0.76 × KH2PO4, ∼0.88 × KH2PO4 at 1064 nm, respectively). According to theoretical calculations, it is speculated that the band gap and NLO characteristics of these two compounds are mostly derived from the B5O10 group and the ScO6 octahedron. Due to the short cutoff edges of I and II, they may be considered as potential NLO materials in the UV and even deep UV spectral ranges. Furthermore, the advent of I and II adds to the diversity of rare earth borates.

Application of third-order nonlinear optical materials in complex crystalline chemical reactions of borates

Abstract In order to explore the application of third-order nonlinear optical (NLO) materials in complex borate crystalline chemical reactions, the laser light source with limited wavelength range can be extended to ultraviolet (UV) and deep UV region by using NLO crystal materials and frequency conversion technology, which has become a hot research direction of deep UV light source. The experimental results show that the UV cutoff edge of the grown KLi(HC3N3O3)·2H2O crystal is 237 nm. The refractive index of the crystal was measured by prism coupling technique, and the Sellmeier equation of the refractive index of the crystal was fitted. The chemical bond of the crystal is a fundamental means to understand the relationship between structure and properties. With the emergence of a large number of hybrid functional crystals, the composition and structure of crystals become more complex, and the chemical bond theory has also been greatly developed, and then the chemical bond theory of meta crystals or complex crystals has emerged. Once proposed, the theory has been widely used, such as analyzing the eligibility of luminescent crystals, NLO crystals and high-temperature superconductor crystals. NLO materials are the dominant field of China in the world. Crystals with good nonlinear behavior have more complex crystal structures, due to the theory of amorphous structure, the exploration of this aspect is particularly difficult. For the first time, the influence of the composition of rare earth-doped bismuth borate glass on the crystal precipitation and glass microstructure of NLO materials was systematically studied, which laid a theoretical foundation for further development and understanding of new bismuth borate optical systems.

A density functional study of the structural, electronic, optical and lattice dynamical properties of AgGaS2

Based on first-principles density functional theory the electronic structure, optical and lattice dynamical properties of infrared nonlinear optical crystal AgGaS2 (AGS) are calculated with four different hybrid functional (PBE0, HSE03, HSE06, B3LYP) respectively. The results show that the theoretical results obtained by PBE0 method are in good agreement with the experimental values. The geometrical structure optimization results show that the theoretical lattice parameters of AGS are in good agreement with the experimental values. The electronic structure results show that AGS is a direct wide band gap nonlinear optical crystal, and the band gap obtained by PBE0 method is 2.66 eV, which is basically in good agreement with the experimental values. The calculation results of energy band structure and density of states show that the value band edge is mainly contributed by S-3p, Ag-4d and a small amount of Ga-4p orbital electrons, while the bottom of conduction band is mainly contributed by Ag-5 s, Ga-4 s, 4p and a small amount of S-3p orbital electrons. The orbital coupling between Ga and S atoms determines the optical properties of AGS. Ag atoms contribute little to the optical properties. Especially, the results show that the crystal material has strong absorption and reflection characteristics in the ultraviolet region and strong transmittance in the infrared region. The average static dielectric constant and average static refractive index are 1.887 and 2.14, respectively, and the static birefringence is 0.02.Based on the density functional theory of linear response, the phonon dispersion curve of AGS is calculated. The results show that AGS has no virtual frequency and its dynamic performance is relatively stable. Meanwhile, the optical mode frequency of the Γpoint in the center of Brillouin region is analyzed in detail. The above results show that AGS crystal material enjoys large nonlinear optical coefficient and suitable birefringence in a wide infrared band, and AGS is an important infrared nonlinear optical crystal material.

Study of New Infrared Non-Linear Optical Crystal BaGa4Se7 Based on First Principle

The electronic structure and optical properties of BaGa4Se7 crystals were studied by generalized gradient approximation (GGA) and Heyd–Scuseria–Ernzerhof (HSE). The electronic structure results showed that BaGa4Se7 is a nonlinear optical crystal with a direct wide band gap. The band gap was calculated to be 2.36 eV using the HSE06 method, which is basically equal to the experimental value. The band structure showed that the top of the valence band was largely contributed by Ga 4s, 4p and Se 4p states, while the bottom of the conduction band was mainly comprised of Ga 4s, 4p, Se 4p, and Ba 5d states. The optical properties showed strong absorption and reflection in the ultraviolet region and strong transmittance in the infrared region. The average static refractive index of BaGa4Se7 was 2.73, and the static birefractive index was 0.04. These values indicate that the material has a good phase-matching ability and a wide laser damage threshold. The above results indicate that BaGa4Se7 is a potential infrared nonlinear optical crystal material.

Density Functional Theory Study of Infrared Nonlinear Optical Crystal ZnGeP2

The electronic structure and optical properties of ZnGeP2 crystal were studied using DFT. The electronic structure results showed that ZnGeP2 is a nonlinear optical crystal with a direct wide bandgap. The bandgap was calculated to be 1.99 eV using the HSE06 method, which is exactly equal to the experimental value. The optical properties showed strong absorption and reflection in the ultraviolet region and strong transmittance in the infrared region. The average static refractive index of ZnGeP2 was 2.73, and the static birefractive index was 0.04. The above results indicate that ZnGeP2 is a potential infrared nonlinear optical crystal material.

Investigation on the Effects of MnCl2 Doping on Structural and Optical Properties of DAST Single Crystals as Materials for Second Order Nonlinear Optics

AbstractThe intent is to explore the optoelectronic properties of metal ions doped stilbazolium derivative, 4‐N,N′‐dimethylamino‐N‐methyl‐4‐stilbazolium tosylate (MnCl2‐DAST) nonlinear optical crystal materials for the existing technological necessities. The Mn‐DAST single crystals are crystallized by adopting the slow evaporation solution technique (SEST). The structural and crystallographic dimensions of grown crystals are affirmed using single‐crystal X‐ray diffraction and powder crystal X‐ray diffraction. Fourier transform infrared spectra are performed to explicate the functional groups and energy dispersive X‐ray analysis (EDAX) spectra confirm the presence of the chemical elements of grown crystals. The UV–vis absorption spectra of DAST and Mn‐DAST crystals exhibit all possible n–π* and π–π* electronic transitions. The blue shift is observed in the doped materials due to the exchange of lone pair electrons between the metal ions and organic molecule. Tremendously, the second order harmonic generation (SHG) efficiency of Mn (0.01 mol%) doped DAST crystals has 1.68 times larger than that of DAST crystal. From the metal‐organic crystals (Mn‐DAST), all the results brought out are the promising materials in the design of nonlinear optical applications.

Cyanurates consisting of intrinsic planar π-conjugated 6-membered rings: An emerging source of optical functional materials

Optical crystalline materials, particularly for linear birefringent crystals and non-linear optical (NLO) crystal materials, play an incredible role in opto-electronics, laser industry and academic research fields. Cyanurates consisting of intrinsic coplanar π-conjugated (HxC3N3O3)x−3 (x = 0 ~ 3) 6-membered rings (6-MRs) exhibit same structural configuration, but stronger conjugacy than that of (B3O6)3− 6-MRs in borate analogues. Accordingly, cyanurates possess large linear anisotropic polarizability and microscopic second-order-generation (SHG) susceptibility, consequently resulting in great birefringence and strong SHG effects in the crystals. Moreover, they have wide band gaps and high transparency in the near infrared, visible and ultraviolet ranges. These eminent characteristics make cyanurates to be promising birefringent and NLO materials with outstanding optical properties critical for end use. In this review, we summarized the current status of crystal structures, synthetic methods, optical performances, and connections between structure and physical property of all the found cyanurates according to anion groups’ types. Then we compartmentalized the central and acentric cyanurates and discussed how to improve the probability of the acentric structures through the deprotonization and multiple cations engineering. Finally, we proposed the directions for the design and exploration of cyanurate functional materials in the future. This work presents a clear perspective to understand cyanurates with planar π-conjugated anionic groups, and speed up the exploration of unknown birefringent or NLO functional crystals for acute demands in optics technology and facilities.

The partition principles for atomic-scale structures and their physical properties: application to the nonlinear optical crystal material KBe2BO3F2.

In implementing the materials genome approach to search for new materials with interesting properties or functions, it is necessary to find the correct functional motif. To this end, it is common to partition an extended structure into various building units and then partition its properties to find the appropriate functional motif. We have developed the general principles for partitioning a structure and its properties in terms of a set of atoms and bonds by analyzing the differential cross-sections of neutron and X-ray scattering phenomena and proposed the procedures with which to partition an extended structure and its properties. We demonstrate how these procedures work by analyzing the nonlinear optical crystal KBe2BO3F2. Our partitioning analysis of KBe2BO3F2 leads to the conclusion that the second harmonic generation response of KBe2BO3F2 is dominated by the ionically bonded metal-centered groups.

Abnormal bandgap enlargement resulted in a promising mid-infrared nonlinear optical material Rb2CdBrI3with an ultrahigh laser damage threshold

An abnormal bandgap enlargement resulted in the Rb2CdBrI3material as a good candidate for mid-infrared nonlinear optical crystal materials.

Effect of Cu2+ ion on single crystal of nonlinear optical material (glycinium oxalate)

Single crystals of pure and Cu2+doped glycinium oxalate of dimensions 18 × 10 × 2 mm3 and 10 × 7 × 2 mm3 were grown by the solvent evaporation technique, respectively. Influences of Cu2+ ions on the crystalline quality of glycinium oxalate (GOX) crystal were studied. The grown pure and doped crystals were characterized by using powder X-ray diffraction, FT-IR, and FT-Raman techniques. UV–Vis–NIR spectra of GOX and Cu2+ doped GOX single crystals had transparency in the entire visible region with cut off wavelengths, 257 nm and 265 nm, respectively. Mechanical properties of pure and doped crystals were studied using Vicker’s micro-hardness test. The presence of transition metal ion has been confirmed by energy dispersive X-ray spectroscopy (EDAX) and EPR analyses. The g-value (2.4899) was calculated from EPR analysis. The TGA/DTA analysis was performed to find the thermal stability of samples. The dielectric behavior of pure and doped crystal have been reported from 102 to 106 Hz. The third-order NLO properties such as nonlinear absorption coefficient (β), third-order nonlinear susceptibility (χ(3)) and nonlinear refractive indices (n2) of pure and doped crystal were estimated in the order of 10−6 esu.

Advanced Polyphthalocyanine–Derived Electrode Materials for Energy Storage and Conversion

Metal phthalocyanine, as one of the important synthetic metal-organic compounds, is similar with the natural metal porphyrins. Thanks to its unique structure and properties, phthalocyanines are constantly refurbished and excavated from blue dyes to third-order nonlinear optical materials, supramolecular self-assemblies, photoelectric-conversion materials, and liquid crystal materials. Since the cobalt phthalocyanine has been found with the electrocatalytic activity for oxygen reduction in 1964, the extensive researches on phthalocyanine-based compounds have been carried out in electrocatalysis and beyond. As the cross-linked products of phthalocyanines, polyphthalocyanines have a unique conjugated layered morphology with the various metal-N coordinated structure, demonstrating as the rational and facile materials and/ or precursors to construct the efficient electrode for energy conversion and storage device. In this work, we will present some of our rational and scalable strategies for developing the multi-variate and multi-scale materials from polyphthalocyanine for various renewable energy applications, including fuel cells, metal-air batteries, water splitting and supercapacitors. We anticipate that our strategies and electrode materials will also be useful for other electrochemical applications. Figure Caption: Polyphthalocyanine-derived multi-functional materials for electrochemical applications. Figure 1

Theoretical Investigation on the Microscopic Mechanism of Lattice Thermal Conductivity of ZnXP2 (X = Si, Ge, and Sn).

Thermal conductivity is an important physical parameter for the application of nonlinear optical single crystal materials. The underlying science of thermal transport behavior is not well established both experimentally and theoretically. In the present work, we have studied the microscopic picture of lattice thermal conductivity of ZnXP2 (X = Si, Ge, Sn), chalcopyrite ABC2 type infrared optical crystals, by using a harmonic and anharmonic lattice dynamic method and phonon Boltzmann transport equation based on first-principle calculations. With the mass of atom X increased, the phonon frequencies and phonon group velocities of ZnXP2 (X = Si, Ge, Sn) are shown not surprisingly to be decreased. Nevertheless, the phonon lifetime of ZnXP2 is unexpectedly increased, which is the governing mechanism for the increased thermal conductivity as 12.5 W/(m·k), 31.6 W/(m·k), and 35.4 W/(m·k), for ZnSiP2, ZnGeP2, and ZnSnP2, respectively, at 300 K. The contributions of optical phonons (with the frequency below 150 cm-1) to the total thermal conductivity are remarkable, reaching 18%, 31%, and 34% for three compounds, due to the significantly increased phonon lifetime in the frequency range 50-150 cm-1. To explore the physical insights of phonon lifetime and phonon anharmonicity, three-phonon scattering phase space and electronic localization function analysis of the X-P bond are provided. The results show that the covalent nature of X-P bonds is enhanced with the increased mass of atom X = Si, Ge, Sn, which induces the reduction of three-phonon scattering phase space in the frequency range 50-150 cm-1, leading to the enhancement of the phonon lifetime and thermal conductivity of ZnXP2.

Exploration of the deep-ultraviolet nonlinear optical materials in the derivatives of KBe&lt;sub&gt;2&lt;/sub&gt;BO&lt;sub&gt;3&lt;/sub&gt;F&lt;sub&gt;2&lt;/sub&gt;

The use of nonlinear optical crystal materials to extend the limited range of laser sources to the deep-ultraviolet (deep-UV, λ &lt; 200 nm) regions by various frequency conversion techniques, has become an attractive field for generating deep-UV light. However, the lack of nonlinear optics (NLO) crystal materials capable of frequency conversion in the deep-UV light range, limits the development and application of deep-UV all-solid-state lasers. Therefore, scientists all over the world are actively exploring the new generation of deep-UV NLO crystal materials. At present, only the KBe&lt;sub&gt;2&lt;/sub&gt;BO&lt;sub&gt;3&lt;/sub&gt;F&lt;sub&gt;2&lt;/sub&gt; (KBBF) crystal is capable of generating deep-UV light through the direct sixth harmonic generation of the Nd:YAG laser. The infinite &lt;sub&gt;∞&lt;/sub&gt;[Be&lt;sub&gt;2&lt;/sub&gt;BO&lt;sub&gt;3&lt;/sub&gt;F&lt;sub&gt;2&lt;/sub&gt;]&lt;sup&gt;−&lt;/sup&gt; single layers, as the brilliant building blocks in the crystal structures of KBBF family, provide a relatively large second harmonic generation coefficient (&lt;i&gt;d&lt;/i&gt;&lt;sub&gt;11&lt;/sub&gt; = 0.47 pm/V) and a sufficient birefringence (Δ&lt;i&gt;n&lt;/i&gt; = 0.07@1064 nm). However, the KBBF crystals have insurmountable intrinsic defects, such as the usage of high toxic beryllium oxide, and the serious layer growth habit, which greatly restrict its commercialization process. Since the layered structure of the KBBF crystal is still one of the most brilliant structures for generating deep-UV laser, an effective strategy is to change the interlayer connection mode and develop new NLO materials based on KBBF with less layering growth habit. In this paper, by reviewing the development history of borate deep-UV NLO crystals and the derivatives of KBBF, the relationship between layered structure and optical properties of different interlaminar connections of crystal materials is systematically analyzed. We discuss the main contradictions and solutions of the development of deep-UV NLO crystal materials which are similar to the KBBF structure. In order to provide a reference for the innovative exploration of new materials in the future, several design strategies are also proposed.

Intrinsic sources of high thermal conductivity of CdSiP2 determined by first-principle anharmonic calculations.

CdSiP2 is an outstanding mid-infrared nonlinear optical crystal material with high thermal conductivity. However, the microscopic physics behind its thermal transport behavior is still unclear. In this study, we have investigated the source of the thermal conductivity of CdSiP2 based on anharmonicity lattice dynamics (ALD) and the first-principle calculation. The results are well accordance with the experimental measurement in a wide temperature range. Based on our results, the acoustic phonon lifetime of CdSiP2 is higher than that of the thermoelectric and semiconducting materials reported in previous studies, which is induced by the low lattice anharmonicity demonstrated by CdSiP2. The mode-dependent thermal conductivity is obtained with the contribution of optical phonons being significant (27%) above 300 K; this is mainly due to the high phonon group velocity and relatively long phonon lifetime of low-energy optical phonons (80-200 cm-1). A high lifetime of acoustic phonons and remarkable contribution of low-energy optical phonons can be responsible for the high thermal conductivity of CdSiP2.

Molecular Structures and Second-Order Nonlinear Optical Properties of Ionic Organic Crystal Materials

In recent years, there has been extensive research and continuous development on second-order nonlinear optical (NLO) crystal materials due to their potential applications in telecommunications, THz imaging and spectroscopy, optical information processing, and optical data storage. Recent progress in second-order NLO ionic organic crystal materials is reviewed in this article. Research has shown that the second-order nonlinear optical properties of organic crystal materials are closely related to their molecular structures. The basic structures of ionic organic conjugated molecules with excellent nonlinear optical properties are summarized. The effects of molecular structure, for example, conjugated π electron systems, electronic properties of donor-acceptor groups, and different counter-anion effects on second order NLO properties and crystal packing are studied.

Revealing the mechanical properties of potassium dihydrogen phosphate crystals by nanoindentation

Abstract

Synthesis and nonlinear optical properties of novel chalcone analogues of ferrocenyl biaryl derivatives

A series of structurally novel organometallic compounds (3a–g) based on 1-biaryl-3-ferrocenylprop-2-en-1-one, were synthesized by the Suzuki-Miyaura cross-coupling reaction for applications as nonlinear optical (NLO) and liquid crystal (LC) materials. Notably, a single crystal of this class of compounds was obtained for the very first time, and it was found that the two phenyl rings of the chalconyl group were nearly coplanar to one of the cyclopentadienyl rings of ferrocene. Due to the high degree of conjugation, all the chalcone analogues of ferrocenyl biaryl derivatives displayed strong second harmonic generation (SHG) response (0.45–0.60 × 10−30 esu, 3–4 times greater that of potassium dideuterophosphate (KDP)). The density functional theory (DFT) was employed to calculate the main molecular orbital energies and compositions of 3d, based on its crystallographic structure. Compound 3d was found to exhibit excellent NLO properties due to its low Egap and superior charge transfer ability within the conjugated system. This work presents a new approach for the preparation of this class of ferrocenyl biaryl derivatives, which may have potential applications as NLO materials.