Organic Nonlinear Optical Material Research Articles

Broadband THz Wave Generation and Detection in Organic Crystal PNPA at MHz Repetition Rates

AbstractOrganic nonlinear optical (NLO) crystals have emerged as efficient room‐temperature emitters of broadband THz radiation with high electric field strengths. Although initially confined to high‐pulse‐energy excitation in the millijoule range with kHz rates, recent efforts have focused on tailoring the physical properties of organic NLO materials for compatibility with popular MHz‐rate telecommunication wavelength lasers emitting nanojoule energy pulses. This is motivated by the large potential of such crystals for more portable and user‐safe spectroscopic systems, additionally complemented by their room‐temperature field‐sensitive THz detection capabilities. In this work, the MHz‐rate operation of the organic crystal PNPA ((E)‐4‐((4‐nitrobenzylidene)amino)‐N‐phenylaniline), which was recently discovered through data mining algorithms and reported to surpass the conversion efficiency of rivaling NLO crystals at 1 kHz repetition rate is demonstrated. Using a compact 200 mW Er:fiber laser producing 18 fs pulses at 50 MHz repetition rate, the THz field generation and detection capabilities of PNPA via performing gas phase spectroscopy in the 1.3–8.5 THz range are demonstrated. A dynamic range of 40 dB over 3.6 s and 70 dB over 2 h is obtained. The work extends the family of organic crystals compatible with telecommunication‐wavelength excitation using nJ pulses for spectroscopy beyond 5 THz.

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.

Physicochemical properties of 2-amino-5-methylpyridinium 3-carboxy-4-hydroxybenzenesulfonate single crystal: An efficient material for optoelectronic applications

A novel third-order organic nonlinear optical (NLO) material with promising excellent properties in the crucial NLO application. For the first time high NLO active 2-amino-5-methylpyridinium 5-sulfosalicylic acid (2A5MP3C4H) has been rationally designed and single crystals have been grown by the slow evaporation solution growth technique (SEST). X-ray diffraction analysis revealed that 2A5MP3C4H belongs to the category of triclinic system and has a Centro symmetric space group of P1. Remarkably, the grown crystal exhibits competitive and even superior physical properties including high thermal stability and wider transparency than the standard NLO single crystal. The morphology of the as-grown 2A5MP3C4H crystal was equivalent to the theoretically produced morphology. Fourier transform infrared spectroscopy (FTIR) was used to investigate the molecular vibrations of 2A5MP3C4H. The optical characteristics of 2A5MP3C4H recorded optical transmittance spectrum reveals that the 2A5MP3C4H crystal possesses good optical transparency in the range between ultraviolet (UV) and near-infrared (NIR) regions. Intriguingly, the short cut-off edge of the grown crystal is found to be about 345 nm which is more favourable for developing modern photonic and optoelectronic devices application. The Laser Damage Threshold (LDT), were investigated to understand its effectiveness to be utilized in the area of optoelectronics and photonics. The thermal and mechanical stability of 2A5MP3C4H was tested using Thermo gravimetric Differential Thermal Analysis (TG-DTA) and Vickers hardness test. The third-order nonlinear optical properties of 2A5MP3C4H single crystals were analyzed, which involves studying the absorption coefficient and refractive index behaviour using a continuous wave laser. Additionally, the grown crystal exhibits outstanding third-order NLO response and wide LDT, which are crucial characteristics for developing practical NLO devices. There are various 2-amino-5-methylpyridine (2A5MP) derivative single crystals available in the literature. However 2A5MP3C4H crystal has not been reported earlier. So, we have carried out our researcher on this new novel crystal. Our findings consequently open a novel path for the logical design of enormous, thermally stable and NLO-active organic complexes for true NLO applications.

Organic Electro-Optic Materials with High Electro-Optic Coefficients and Strong Stability.

The preparation of high-performance electro-optical materials is one of the key factors determining the application of optoelectronic communication technology such as 5G communication, radar detection, terahertz, and electro-optic modulators. Organic electro-optic materials have the advantage of a high electro-optic coefficient (~1000 pm/V) and could allow the utilization of photonic devices for the chip-scale integration of electronics and photonics, as compared to inorganic electro-optic materials. However, the application of organic nonlinear optical materials to commercial electro-optic modulators and other fields is also facing technical bottlenecks. Obtaining an organic electro-optic chromophore with a large electro-optic coefficient (r33 value), thermal stability, and long-term stability is still a difficulty in the industry. This brief review summarizes recent great progress and the strategies to obtain high-performance OEO materials with a high electro-optic coefficient and/or strong long-term stability. The configuration of D-π-A structure, the types of materials, and the effects of molecular engineering on the electro-optical coefficient and glass transition temperature of chromophores were summarized in detail. The difficulties and future development trends in the practical application of organic electro-optic materials was also discussed.

A Full‐Scale Analysis of Absorption Edges in Dye‐Doped Nonlinear Optical Polymers

AbstractA full‐scale analysis of the absorption edges by modified Tauc‐Lorentz models is essential in determining the optical bandgap and Urbach energy of semiconductors, transparent conductors, ionic compounds, and dielectric materials. This technique has not yet been applied to analyzing organic nonlinear optical (NLO) materials. This problem is tackled by preparing high‐quality films of guest–host NLO polymers with a wide thickness range from sub‐micron to 200 microns, allowing accurate measurement of full‐spectral absorption coefficients of NLO materials over four orders of magnitude by the UV‐VIS‐NIR spectroscopy. The Tauc model and a new Monolog–Lorentz model are used to study the optical absorption edge of guest‐host NLO polymers containing various push‐pull chromophores and the dependence of optical bandgap and Urbach edge on the structure and composition of materials is analyzed. The results reveal the critical transition of the Urbach exponential tail to a low energy tail that overlaps with vibrational overtones of materials at the telecom wavelengths. Determining the fundamental absorption region of organic NLO films in this study provides quantitative insight into the research to harness the resonance‐enhanced nonlinear coefficients of materials by operating at the wavelengths near the band edge with the control of optical loss.

Cyclodextrin-assisted supramolecular host-guest inclusion for durable and sustainable optoelectronics

Metal halide perovskites and organic nonlinear optical materials have showcased enormous potential in many kinds of optoelectronic applications, such as solar cells, light-emitting diodes, and patterned displays. However, further enhancement of optoelectronic performances has been largely limited by the intractable issues of these materials including high defect densities, unstable crystallographic structure, harsh fabrication conditions, and unfavorable biocompatibility and environmental sustainability. Encouragingly, several recent works have demonstrated an effective supramolecular host-guest inclusion strategy could ideally address abovementioned concerns by nesting optoelectronic materials within the cavities of cyclodextrin molecules and their analogs. Specifically, the supramolecule hosts embedded with multiple functional groups and/or crosslinked networks could robustly interact with those optoelectronic materials, which play multifaceted roles in terms of chemical chelation, spatial confinement, structural stabilization, defect passivation, ion immobilization and compensation, thus resulting in comprehensive enhancement of optoelectronic performances and sustainability. The current challenging issues and potential solutions are also discussed to provide a roadmap for achieving more durable and sustainable optoelectronics toward practical applications and real commercialization.

Group Contribution Method Supervised Neural Network for Precise Design of Organic Nonlinear Optical Materials.

To rationalize the design of D-π-A type organic small-molecule nonlinear optical materials, a theory guided machine learning framework is constructed. Such an approach is based on the recognition that the optical property of the molecule is predictable upon accumulating the contribution of each component, which is in line with the concept of group contribution method in thermodynamics. To realize this, a Lewis-mode group contribution method (LGC) has been developed in this work, which is combined with the multistage Bayesian neural network and the evolutionary algorithm to constitute an interactive framework (LGC-msBNN-EA). Thus, different optical properties of molecules are afforded accurately and efficiently-by using only a small data set for training. Moreover, by employing the EA model designed specifically for LGC, structural search is well achievable. The origins of the satisfying performance of the framework are discussed in detail. Considering that such a framework combines chemical principles and data-driven tools, most likely, it will be proven to be rational and efficient to complete mission regarding structure design in related fields.

Third-order nonlinear optics and optical limiting of phenanthrenone derivatives

Organic nonlinear optical materials have attracted much attention due to their large nonlinear optical coefficients and ultrafast response speeds, as well as their potential applications in optical limiting (OL). Among them, nonlinear optical materials with phenanthrenone as the backbone are consistently understudied. We have successfully realized the transformation of organic small molecules in the nonlinear optical direction by replacing the carbonyl group on the structure of phenanthrenone with a malononitrile group. The nonlinear optical properties of CN-2 were investigated under different excitation conditions at 532 nm and the kinetic process of nonlinear optics was analyzed by transient absorption spectroscopy. In addition, we also investigated the OL properties of CN-2, and the OL experiments showed that CN-2 with a lower OL threshold has superior OL properties than C60.

Synthesis, Crystal Structure and Characterization of Organic Nonlinear Optical Material Benzophenone for Spectroscopic and Optoelectronics Applications

A novel crystal benzophenone’s nonlinear optical applications are pivotal. Benzophenone is one of the promising organic nonlinear optics materials for their high energy laser photonic application. It has already been possible to generate crystals of benzophenone in various ways. In this research, the slow evaporation method at room temperature was successful in making a single crystal of benzophenone. In this paper, synthesis, growth, characterization and applications of low melting organic nonlinear optics benzophenone crystal in order to improve their structural and physical properties are reported. Different characterization methods were applied to the grown crystals. The lattice parameters of the grown material were obtained by single crystal X-ray diffraction (XRD) study. The results of the single crystal XRD analysis showed that the produced crystals are a component of an orthorhombic system with the space group P212121 and the lattice parameters are [Formula: see text] Å, [Formula: see text] Å, [Formula: see text] Å, [Formula: see text] and [Formula: see text] Å3. Ultraviolet-visible (UV–Vis) spectrum indicates that the crystal is transparent (72%) in the entire visible region with a cutoff wavelength of 258[Formula: see text]nm. The transparency of the grown crystals has been confirmed using the UV–Vis spectrum. The second harmonic generation (SHG) efficiency of the grown crystal was measured using an Nd-YAG laser and it was found to be 1.8 greater than potassium dihydrogen orthophosphate (KDP). The FT-IR spectrum was examined in order to identify the many functional groups. The formation of the material was confirmed qualitatively by FT Raman spectral analyses. Mechanical properties such as Vicker’s microhardness number, Yield strength, Fracture toughness, Brittleness index and Elastic stiffness constant values were determined using Vicker’s microhardness test. The thermal stability of the grown crystal was studied by thermal analysis.

Crystal Growth and Characterisation of Strontium on Thiourea

Thiourea, being a potential organic Non-linear optical material with high SHG efficiency having application in laser technology and photonic applications are grown as single crystals of Strontium chloride doped thioureaby slow evaporation solution growth technique (SEST), one of the best method for crystal growth at room temperature. It is furtheranalysed by single crystal XRD which infers thatthe Strontium Chloride doped thiourea crystal has monoclinicsystem. The surface morphology was studied by SEM-EDS, that confirms thepresence of Strontium in the doped specimen. FTIR reveals some slight variation in vibrational frequencies and no secondaryvibrational bandsarefoundin the doped specimen indicating the presence of some dopant

Enhanced Characterisation Studies and Synthesis of Undoped and Copper Doped-Organic Nonlinear Optical Single Crystal: L-Alanine Aluminium Nitrate

Single crystals of untreated and copper (Cu2+) metal ion-doped L-alanine aluminium nitrate (LAAN), a room-temperature slow evaporation organic nonlinear optical material. Single crystals were studied for structural, spectral, optical, hardness, secondorder non-linear optical, electrical [(alternating current (AC) and direct current (DC)], and photoconductivity properties as they grew. Crystallinity, monoclinic structure with space collection P21, and lattice specifications were deliberate using single crystal X-ray diffraction investigation. The existence of functional clusters is revealed by the spectral properties, and the means of vibration of various molecular clusters existing in LAAN were evaluated using Fourier transform infrared (FTIR). The low cut-off wavelength and transmittance properties were determined using optical analysis. The band gap energy of LAAN and Cu-doped LAAN crystals was estimated to be 3.40 eV and 2.70 eV, respectively, using the Tauc plot. It was revealed that pure crystals had a lower dielectric constant than crystals that had been doped with copper. After doping with rising temperatures, AC conductivity started to rise. With the use of the Kurtz and Perry approach, the effectiveness of the grown crystal’s second harmonic generation was computed, Cu-doped LAAN was discovered to be 3.3 times more prominent than potassium dihydrogen phosphate (KDP) and 2.2 times more prominent than pure LAAN crystals. The nonlinear optical characteristics of LAAN crystals have therefore been improved by copper doping. It is most suited for use in electro-optic applications like laser technology, telecommunications and optical signal processing because of its negative photoconductivity.

Synthesis, crystal structures, spectroscopy, and quantum chemical studies on the 4-dimethylaminopyridinium-2,4-dinitrophenolate: an organic NLO material for optoelectronics.

In this work, the 4-dimethylaminopyridinium-2,4-dinitrophenolate (4DMAP + 2,4DNP) by slow evaporation solution growth method has been presented. The Fourier transform infrared (FT-IR) (4000-400cm-1) and FT-Raman (4000-50cm-1) spectra were recorded for the grown crystal. The computational calculation has been carried out with density functional theory (DFT) in ground state with Gaussian program package. Optimized geometrical parameters (bond distances, bond angles, and dihedral angles) have been obtained and compared with X-ray crystallography data. The calculated fundamental vibrational frequencies from DFT/B3LYP with 6-311 + + G(d,p) level of theory were scaled so as to agree with the observed results, and the scaling factors were reported. Experimental and computed ultraviolet-visible (UV-Vis) spectra in acetone and methanol solvents were found comparable to each other. Furthermore, the frontier molecular orbitals (FMOs) energies, molecular electrostatic potential (MEP), nonlinear optical (NLO), hirshfeld surface (HS), and global chemical descriptors of the molecule were also calculated. The thermal stability and the melting point of the title compound were analyzed by the thermogravimetric analysis/differential thermal analysis (TGA/DTA) techniques. The mechanical behavior of the organic single crystal was measured by Vickers micro-hardness method. The third-order nonlinear optical properties such as nonlinear refractive index (n2), nonlinear absorption coefficient (β), optical nonlinear susceptibility Reχ(3), and optical nonlinear susceptibility Imχ(3) were calculated by using the open and closed aperture Z-scan technique. The theoretical and experimental NLO values clearly proposed that the nonlinearity of 4DMAP + 2,4DNP molecule could be helped as a potential candidate for optical limiting, frequency doubling, and optical switching applications.

A Review on Synthesis, Lanthanide Complexes and Biological Activites of Hydrazone Derivatives of Hydrazinecarbothioamides

Hydrazinecarbothioamides are important intermediates with biological activities in organic chemistry synthesis, especially in the synthesis of biologically active heterocyclic scaffolds and compounds. The uniqueness in of synthesis and a wild range of pharmaceutical, medicinal biological potentials and properties, their preferred application as building brick in and the synthesis of heterocyclic and other important organic compounds and nonlinear optical (NLO) materials have made them attractive derivatives of thiosemicarbazides in the recent years. In this review, a detailed account in terms of synthesis and applications of their hydrazone derivatives and their lanthanide complexes are presented .Further, the biological and analytical applications of newly reported ligands and their complexes are reported. The wide investigation of the lanthanide (III) coordination complexes with organic ligands are mainly due to their structures and strong potential biological and pharmacological properties of hydrazones as derivatives of hydrazinecarbothioamides possess sites that play important roles in the formation of heterocyclics and other biologically active scaffolds.

Structure–Property Relationships of ITIC-Based Acceptor–Donor–Acceptor Type Molecules as Novel Organic Nonlinear Optical Materials

Structure–Property Relationships of ITIC-Based Acceptor–Donor–Acceptor Type Molecules as Novel Organic Nonlinear Optical Materials

Optimization strategies for comprehensive performance of organic second-order nonlinear optical materials

Optimization strategies for comprehensive performance of organic second-order nonlinear optical materials

Durable organic nonlinear optical membranes for thermotolerant lightings and in vivo bioimaging

Organic nonlinear optical materials have potential in applications such as lightings and bioimaging, but tend to have low photoluminescent quantum yields and are prone to lose the nonlinear optical activity. Herein, we demonstrate to weave large-area, flexible organic nonlinear optical membranes composed of 4-N,N-dimethylamino-4ʹ-Nʹ-methyl-stilbazolium tosylate@cyclodextrin host-guest supramolecular complex. These membranes exhibited a record high photoluminescence quantum yield of 73.5%, and could continuously emit orange luminescence even being heated at 300 °C, thus enabling the fabrication of thermotolerant light-emitting diodes. The nonlinear optical property of these membranes can be well-preserved even in polar environment. The supramolecular assemblies with multiphoton absorption characteristics were used for in vivo real-time imaging of Escherichia coli at 1000 nm excitation. These findings demonstrate to achieve scalable fabrication of organic nonlinear optical materials with high photoluminescence quantum yields, and good stability against thermal stress and polar environment for high-performance, durable optoelectronic devices and humanized multiphoton bio-probes.

Design of the Ionic Organic Nonlinear Optical Material NH4 [LiC3 H(CH3 )O4 ] with Ultrawide Band Gap and Moderate Birefringence.

Ionic organic crystals containing organic planar π-conjugated units has become one of the hot spots as nonlinear optical (NLO) materials. However, although this type of ionic organic NLO crystals commonly have remarkable second harmonic generation (SHG) responses, they also suffer from overlarge birefringences and relatively small band gaps that be hardly beyond 6.2 eV. Herein, a flexible π-conjugated [C3 H(CH3 )O4 ]2- unit was theoretically revealed, showing great potential for designing NLO crystals with balanced optical properties. Accordingly, through the reasonable NLO-favourable layered design, a new ionic organic material, NH4 [LiC3 H(CH3 )O4 ], was successfully obtained. As expected, it achieves not only a large SHG effect (4×KDP), but also a suitable birefringence (0.06@546 nm) and an ultrawide band gap (>6.5 eV). This study provides a new flexible π-conjugated NLO-active unit, contributing to design more ionic organic NLO materials with excellent balanced optical properties.

Design of the Ionic Organic Nonlinear Optical Material NH4[LiC3H(CH3)O4] with Ultrawide Band Gap and Moderate Birefringence

AbstractIonic organic crystals containing organic planar π‐conjugated units has become one of the hot spots as nonlinear optical (NLO) materials. However, although this type of ionic organic NLO crystals commonly have remarkable second harmonic generation (SHG) responses, they also suffer from overlarge birefringences and relatively small band gaps that be hardly beyond 6.2 eV. Herein, a flexible π‐conjugated [C3H(CH3)O4]2− unit was theoretically revealed, showing great potential for designing NLO crystals with balanced optical properties. Accordingly, through the reasonable NLO‐favourable layered design, a new ionic organic material, NH4[LiC3H(CH3)O4], was successfully obtained. As expected, it achieves not only a large SHG effect (4×KDP), but also a suitable birefringence (0.06@546 nm) and an ultrawide band gap (>6.5 eV). This study provides a new flexible π‐conjugated NLO‐active unit, contributing to design more ionic organic NLO materials with excellent balanced optical properties.

Structural, Spectroscopic, Mechanical, and Nonlinear Optical Properties of 4-Dimethylaminopyridinium Picrate Single Crystal for Optoelectronic Applications

A novel organic nonlinear optical (NLO) material, 4-dimethylaminopyridinium picrate (4DMAPP) with molecular formula (C7H11N2)+.(C6H2N3O7)- has been synthesized. The single crystals have been grown from synthesized material by slow evaporation technique. The NLO behavior of the 4DMAPP has been investigated using the quantum chemical calculations with 6-311++G(d,p) basis set. The bond lengths, bond angles, and torsional angle of optimized structure of 4DMAPP are in good agreement with the X-ray diffraction experimental data. The global softness, electron affinity, global hardness, Ionization potential, electronegativity, global electrophilicity, and chemical potential have been estimated. The Meyer index is found to be 2.51 and the nature of the 4DMAPP NLO material is identified as soft. Thermodynamics and molecular parameters of 4DMAPP have been carried out with zero-point vibrational energy 186.191 and 171.908 kcal/mol using Hartree–Fock (HF) and density functional theory (DFT) methods, respectively. In optical absorption spectrum, the material 4DMAPP shows the lower cut off wavelength of 325 nm. The narrow energy gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) facilitates the intramolecular charge transfer (ICT) which makes the material to be NLO active.

Third-order nonlinear response of a novel organic acetohydrazide derivative: Experimental and theoretical approach

A novel nonlinear optical (NLO) organic material of N'-[(E)-(5-bromofuran-2-yl)methylidene]-2-(6-chloropyridin-3-yl)acetohydrazide (BCA) was synthesized by reflux method. The synthesized material was characterized using various analytical techniques, including spectroscopic methods (NMR, FTIR, PXRD). The UV–Vis absorption spectrum of BCA was recorded in different solvents. A strong absorption peak was observed in the 280–350 nm range, indicating its potential for UV-based optoelectronic applications. BCA shows good NLO responses (αCT, βCT, γCTvalues) with different solvents. The dielectric measurements were performed using impedance spectroscopy with varying temperatures as a function of frequency. Thermal stability of the material was evaluated using thermogravimetric analysis, indicating high thermal stability up to 153.28°C. The FMO, MEP, and NBO analyses were implemented using density functional theory (DFT) calculations to investigate the BCA molecule's electronic structure and charge distribution. The topology studies were carried out using the QTAIM and NCI to understand the structure's chemical bonding and intermolecular interactions and the structure's chemical bonding and intermolecular interactions. NLO properties of the BCA material were investigated using the Z-scan technique with a continuous wave (CW) laser, revealing a strong third-order nonlinear susceptibility (χ(3)) value of 2.44 × 10−6 e.s.u. and potential optical limiting behavior (OL threshold = 3.437 × 103 Wcm−2). The TD-HF method performed the calculated molecular static and dynamic of NLO parameters with frequency. The computed γ value of 6.2 × 10−36 e.s.u. was found to be consistent with the experimental value. The results of this study recommend that the synthesized hydrazide derivative material has potential NLO applications.