Nonlinear Optical Applications Research Articles

Nucleophilic transformation of 3-substituted-6,8-dimethylchromones with phenylhydrazine under various reaction conditions: Theoretical, spectroscopic characterization and in silico ADME studies

The chemical behavior of 3-substituted-6,8-dimethylchromones 1–3 was examined towards phenylhydrazine under various reaction conditions. Under different molar ratio, reaction of aldehyde 1 with phenylhydrazine produced hydrazone 4 and pyrazole 5. Depending on the solvent used, reacting carbonitrile 2 with phenylhydrazine produced a variety of products; through ring-opening and ring-closure mechanisms. Reaction of carboxamide 3 with phenylhydrazine, afforded chromeno[4,3-c]pyrazole derivative 8. Finally, boiling carboxamide 3 in KOH solution gave 4-hydroxy-6,8-dimethylcoumarin-3-carboxaldehyde (9). Molecular geometries were examined using density functional theory, (DFT/B3LYP) with 6–311 G(d,p) basis sets, to investigate the bond lengths of certain bonds. DFT was also used to compute some global reactivity descriptors including electronegativity (χ), chemical potential (μ), electrophilicity index (ω), softness (S) and hardness (η). Compound 4 is the softest, while compound 9 is more electrophilic and more electronegative. In addition, MEP surface maps were investigated to predict the chemical reactivity of the current molecules. The chemical shifts values of 1H and 13C NMR were assessed utilizing the GIAO method, and the results were compared with those obtained experimentally. The current compounds are appropriate for non-linear optical applications, according to their first order hyperpolarizability values which found 1.5–3 times greater than those of urea. SwissADME was used to explore the features of current compounds' absorption, delivery, metabolism, and excretion (ADME).

Synthesis, SC-XRD structure, spectroscopy, intermolecular interactions, DFT/TD-DFT investigation, and (static, dynamic) NLO properties of (2E,5Z)-3-(4-fluorophenyl)-2-(4-fluorophenylimino)-5-((E)-3-(2-nitrophenyl) allyliden) thiazolidin-4-one

This paper describes the synthesis of a novel fluorine-substituted thiazolidin-4-one compound, (2E,5Z) -3-(4-fluorophenyl) -2-(4-fluorophenylimino) -5-((E)-3-(2-nitrophenyl) allyliden) thiazolidin-4-one, abbreviated as F2NTh. Its structure was subsequently characterized by Fourier transform infrared (FTIR), 1H and 13C nuclear magnetic resonance (NMR), UV–Visible, and single crystal X-ray diffraction (SC-XRD). For a better comprehension of the electronic structure of F2NTh, experimental data collected from the X-ray diffraction pattern were then compared to theoretical results computed by the density functional theory (DFT) using both B3LYP and CAM-B3LYP functionals with a 6–311 G (d, p) basis set. Theoretical results exhibited a good correlation with those established through the experimental analysis. To identify intra- and intermolecular interactions, Hirshfeld surface (HS) and reduced density gradient (RDG) analyses were performed. The results, including 2D fingerprint plots, indicated that H…H interactions played a major role, accounting for 23.6 % of the overall intermolecular contacts. To investigate the charge transfer and ascertain the electronic properties of F2NTh, frontier molecular orbitals and global and local chemical reactivity descriptors were studied. By simulating the molecular electrostatic potential (MEP) and using MPA, NPA, ESP, and MC5 atomic charges, reactive sites within the molecule responsible for electrophilic and nucleophilic attacks were identified. Some thermodynamic parameters and functions (enthalpy, heat capacity, and entropy) obtained from spectroscopic data were also examined in the temperature range of 100−1000 K. Finally, to test the title molecule in the non-linear optical (NLO) domain, the corresponding properties were predicted using B3LYP and CAM-B3LYP functionals. The predicted static NLO parameters (μ = 4.93 D, α = 56.23×10−24 esu, β = 28×10−30 esu, and γ = 244.98 × 10−36 esu) revealed highly promising outcomes, exhibiting the molecule's utility in NLO applications. This activity was confirmed by the dynamic NLO parameters showing a high third-order response.

Influence of Sm doping on the optical, mechanical, electrical, thermal and z-scan analysis of sulphamic acid single crystal for nonlinear optical device applications

Influence of Sm doping on the optical, mechanical, electrical, thermal and z-scan analysis of sulphamic acid single crystal for nonlinear optical device applications

Crystal growth, structural, Hirshfeld surface analysis, optical and laser damage threshold analysis of 2-Methylimidazolium glutarate single crystal: third-order nonlinear optical applications

Crystal growth, structural, Hirshfeld surface analysis, optical and laser damage threshold analysis of 2-Methylimidazolium glutarate single crystal: third-order nonlinear optical applications

Design of High-Performance Organic Nonlinear Optical and Terahertz Crystals by Controlling the van der Waals Volume.

In the development of new organic crystals for nonlinear optical and terahertz (THz) applications, it is very challenging to achieve the essentially required non-centrosymmetric molecular arrangement. Moreover, the resulting crystal structure is mostly unpredictable due to highly dipolar molecular components with complex functional substituents. In this work, new organic salt crystals with top-level macroscopic optical nonlinearity by controlling the van der Waals volume (VvdW ), rather than by trial and error, are logically designed. When the VvdW of molecular ionic components varies, the corresponding crystal symmetry shows an observable trend: change from centrosymmetric to non-centrosymmetric and back to centrosymmetric. All non-centrosymmetric crystals exhibit an isomorphic P1 crystal structure with an excellent macroscopic second-order nonlinear optical response. Apart from the top-level macroscopic optical nonlinearity, new organic crystals introducing highly electronegative fluorinated substituents with strong secondary bonding ability show excellent performance in efficient and broadband THz wave generation, high crystal density, high thermal stability, and good bulk crystal growth ability.

Investigating the Effect of Tuning the Metal Center in Complexes for Nonlinear Optical Application

In this study, the new transition metal complexes, ML with M = Zn (II), Ni (II), and Pd (II) based on the N,N'-Bis[O-(diphenylphosphino)benzylidene)ethylenediamine ligand were successfully synthesized with a percentage yield of between 33 – 68%. As a result of fourier transform infrared spectroscopy (FTIR), UV-vis spectroscopy (UV-vis), and 1H nuclear magnetic resonance (proton NMR) was used to design and completely describe the metal complexes properties. Moreover, for computational study, the Gaussian16 software installed in the high-performance computer (HPC) is used for NLO calculation. The method used to perform this study is Density Functional Theory (DFT) method. 6-31G(d,p) basis set is used with LANL2DZ for zinc, nickel, and palladium along with the keyword ‘GEN’. The molecular structure has been optimized and checked both bond length and bond angle before starting to run the calculation. Thus, NLO calculation had been performed. The dipole moment and the HOMO-LUMO energy gap were employed to verify the first hyperpolarizability, βtot, which can be utilized as an indication of second nonlinear optical characteristics. Transition metal-based complexes produce impressive results because they provide additional flexibility by offering charge transfer (CT) transitions between the metal and the ligands, resulting in a higher NLO response. Due to the charge transfer excitations, it was discovered that the nickel complex with 2.87 D had the largest NLO response (117215.66 x 10-30 esu), particularly in comparison with the zinc complex (2329.72 x 10-30 esu) and palladium complex (191.07 x 10-30 esu) with 6.52 D and 4.04 D values, respectively.

Nonlinear generation of an optical bottle beam in domain-engineered ferroelectric crystals.

Nonlinear wavefront shaping in periodically poled ferroelectric crystals has received great attention because it offers a convenient way to generate a structured light beam at new frequencies. In contrast to structurally uniform beams like Laguerre-Gaussian or Hermite-Gaussian modes, here we demonstrate the possibility to generate a spatially varied optical bottle beam via a frequency doubling process in a domain-engineered Sr0.61Ba0.39Nb2O6 (SBN) crystal. The nonlinear holography method was employed to design the modulation pattern of the second-order nonlinear coefficient χ(2), and the femtosecond laser poling was used to imprint the χ(2) pattern into the SBN crystal via ferroelectric domain inversion. The second harmonic bottle beam with zero intensity in its center that is surrounded in all three dimensions by light was observed with the incidence of a fundamental Gaussian beam. These results are useful for nonlinear generation and control of structured light at new frequencies, which has important applications in nonlinear photonics and quantum optics.

Impact of π-Linkers Modifications on Tuning Nonlinear Optical Amplitudes of Pyridoquinazolinone-Based Aromatic Dyes: A Rational Entry to Novel D-π-A NLO Materials

Developing efficient nonlinear optical (NLO) materials is a cutting-edge field of study. The desirability of promising NLO materials for optoelectronic applications drove us to investigate the pyridoquinazolinone-based D-π-A architectured chromophores for predicting proficient NLO compounds. Pyridoquinazolinone-based dye (WL-O) is chosen as a reference and its nine derivatives (ASH1-ASH9) are quantum chemically modeled by inserting variously reported π-linkers into the D-π-A framework. Simulations using DFT and TD-DFT provide insight into how π-linker alteration affects the NLO properties. The potential use of investigated dyes for NLO response applications is confirmed by evaluating photophysical aspects, frontier molecular orbital (FMO), natural population analysis (NPA), molecular electrostatic potential (MEP), the density of state (DOS), transition density matrix (TDM) analysis, and static, frequency-dependent NLO response properties. FMO analysis shows that all dyes’ energy gaps are lower when compared to the reference, resulting in a strong NLO response. The highest absorption wavelength of the studied dyes was found to be in the visible spectrum, as determined by UV-Vis analysis. NPA-based findings demonstrated the movement of the electrons from D to A through π-linkers resulting in the formation of a charge separation state and active NLO sensitivity of the proposed dyes. Moreover, MEP, LOL, and ELF topological investigations are performed to appraise the charge transfer inside ASH1-ASH9 and high NLO characteristics. The robust NLO response revealed the eye-catching linear polarizability(α0 ), first-hyperpolarizability (β), particularly ASH3, with the highest α0 and β0 computed to be 520.44 a.u. and 26166.79 a.u., respectively. Additionally, frequency-dependent hyperpolarizability SHG β(−2ω,ω,ω) and EOPE β(−ω,ω,0) calculations for commonly used lasers were performed at 1907.21, 532, and 1064 nm. ASH3 with terthiophene linker exhibits a striking EOPE β(−ω,ω,0) and SHG β(−2ω,ω,ω) response of 2.94 × 104 a.u. and 3.80 × 104 a.u. respectively at 1907.21 nm. This theoretical framework confirmed that the investigated dyes have fine NLO potential and are recommended for future NLO applications.

Nonlinear optical properties of methyl green investigated by the femtosecond Z-scan technique

The third-order optical nonlinearities of methyl green in aqueous solution are studied by the Z-scan technique using a femtosecond laser at 800 nm. The valley shape in the open aperture measurements reveals the presence of reverse saturable absorption effect, which is ascribed to the three-photon absorption process. The closed aperture Z-scan traces demonstrate a negative sign for the nonlinear refractive coefficient, indicating the self-defocusing optical nonlinearity. Furthermore, the magnitudes of the nonlinear refractive index n 2, the three-photon absorption coefficient α 3, and the real part of the third-order nonlinear optical susceptibility Re χ (3) are determined and found to be linearly proportional to the dye concentration within the investigated range. Our results suggest that methyl green may be a hopeful candidate for applications in nonlinear optics.

(SO3CF3)−: A Non‐π‐Conjugated Motif for Nonlinear Optical Crystals Transparent into the Deep‐Ultraviolet Region

AbstractThe search for new ultraviolet (UV) or deep‐UV nonlinear optical (NLO) crystals would greatly prompt the development of laser science and technology. As the NLO performance of these crystals is mainly determined by the anionic groups, herein the (SO3CF3)− group is highlighted as a promising non‐π‐conjugated NLO‐active motif with excellent deep‐ultraviolet (DUV) transmission and good NLO properties. First‐principles studies reveal that this group possesses the largest HUMO‐LOMO gap among the (SO4)2−‐based units, as well as a relatively large NLO response. The further experiments demonstrate that the CsSO3CF3 compound containing the (SO3CF3)− motif exhibits th UV cutoff edge below 200 nm and an NLO effect ≈0.8× KH2PO4, confirming the potentials of this new motif for UV and DUV NLO applications.

DFT molecular simulations for static, dynamic and solvent-dependent nonlinear optical properties of triphenylamine-carbazole-based organic dyes with D-D-A framework

Nonlinear optical (NLO) materials are vital for advancing cutting-edge optoelectronic technology. Herein, triphenylamine-carbazole-based organic dyes with a D-D-A framework are quantum chemically designed with acceptor modifications, and their geometric, electronic, static, dynamic, and solvent-dependent NLO properties are explored using density functional theory (DFT) simulations. The IEFPCM model is employed to investigate the solvent effect on the NLO properties of proposed compounds (BSA-1 to BSA-9). Interestingly, the dipole moment (μtot), average linear polarizability (αtot), and first hyperpolarizability (βtot) were determined for all proposed compounds in gas phase and water (ε = 78.36), DMSO (ε = 46.83), methanol (ε = 32.61), tetrahydrofuran (ε = 7.43), chloroform (ε = 4.71), and benzene (ε = 2.27) solvents. Natural population analysis (NPA), transition density matrix (TDM), UV–Vis investigation, frontier molecular orbital (FMO), and topological analysis (MEP, ELF, and LOL) were carried out to explain the NLO findings. The topological study suggests that BSA and BSA-1 to BSA-9 are chemically active and may have NLO implications. Moreover, the findings demonstrate that BSA-9 is the most promising second-order NLO candidate because of the highest λmax (418.60 nm) in dichloromethane (DMF) and the lowest energy gap (1.49 eV) among all the derivatives. It was found that BSA-2 and BSA-9 demonstrated the giant static αo (7.26 × 102) and βo (9.91 × 104) values among the proposed compounds for use in a wide range of solvent-dependent NLO applications. The solvent effect on NLO in all proposed compounds is noticeable, especially in BSA-9, which exhibited βo = 1.89 × 105 in benzene, 2.80 × 105 in THF, 3.21 × 105 in methanol, 3.25 × 105 in DMSO and 3.28 × 105 in water. Furthermore, Electro-optical Pockels effect (EOPE) β(-ω,ω,0) and the second harmonic generation (SHG) β(-2ω,ω,ω) results computed at ω = 532 nm (0.0856 au) and ω = 1064 nm (0.0428 au) frequencies confirm that all proposed compounds are excellent NLO candidates and should be targeted for future static, frequency-dependent and solvent-dependent NLO applications.

Synthesis, crystal growth and characterization of organic 1,2,4-triazole p-nitrophthalic acid (TPNP) single crystal for nonlinear optical (NLO) applications

The novel organic NLO single crystal 1,2,4-Triazole 4-nitrophthalic acid (TPNP) has been synthesised with methanol as a solvent in an equimolar ratio (1:1) by slow evaporation solution technique (SEST). The grown material was characterized for its NLO applications and reported for the first time. TPNP single crystal with the dimension of 10 mm × 5 mm × 4 mm was grown. The grown crystal was analysed through various characterization studies such as structural, optical, thermal, electrical and third harmonic generation (Z-scan) studies. The structural confirmation of the grown TPNP crystals was investigated by Single Crystal X-ray diffraction (SXRD) analysis. The Powder X-ray diffraction (PXRD) was used to identify the (h k l) planes for the purpose of drawing the morphology diagram of the original crystal image. The optical analysis carried out using UV–Vis-NIR study on TPNP crystal showed good optical transparency (80 %) and it can be used for various optical applications. To identify the structure and the functional groups, Fourier transform infrared (FTIR) study was conducted. Thermogravimetric and differential thermal analysis (TG-DTA) revealed the thermal stability of the grown TPNP crystal upto 155 °C. The surface etch pit density of TPNP crystal was carried out using chemical etching analysis. The negative photoconductive nature of title crystal was identified by photoconductivity analysis. The dielectric permittivity and dielectric loss as a function of frequency were measured for grown crystal. Intermolecular interactions and fingerprint plots of TPNP molecules are executed by Hirshfeld surface analysis. LDT of the title crystal was investigated by Q-switched Nd: YAG laser of wavelength 532 nm. Third order NLO parameters and susceptibility were determined using the Z-scan technique. It is concluded that the material can be effectively employed for various optoelectronic and photonic applications.

Breaking Through the Trade-Off Between Wide Band Gap and Large SHG Coefficient in Mercury-Based Chalcogenides for IR Nonlinear Optical Application.

It is substantially challenging for non-centrosymmetric (NCS) Hg-based chalcogenides for infrared nonlinear optical (IR-NLO) applications to realize wide band gap (Eg > 3.0eV) and sufficient phase-matching (PM) second-harmonic-generation intensity (deff > 1.0 × benchmark AgGaS2 ) simultaneously due to the inherent incompatibility. To address this issue, this work presents a diagonal synergetic substitution strategy for creating two new NCS quaternary Hg-based chalcogenides, AEHgGeS4 (AE = Sr and Ba), based on the centrosymmetric (CS) AEIn2 S4 . The derived AEHgGeS4 displays excellent NLO properties such as a wide Eg (≈3.04-3.07eV), large PM deff (≈2.2-3.0 × AgGaS2 ), ultra-high laser-induced damage threshold (≈14.8-15 × AgGaS2 ), and suitable Δn (≈0.19-0.24@2050nm), making them highly promising candidates for IR-NLO applications. Importantly, such excellent second-order NLO properties are primarily attributed to the synergistic combination of tetrahedral [HgS4 ] and [GeS4 ] functional primitives, as supported by detailed theoretical calculations. This study reports the first two NCS Hg-based materials with well-balanced comprehensive properties (i.e., Eg > 3.0eV and deff > 1.0 × benchmark AgGaS2 ) and puts forward a new design avenue for the construction of more efficient IR-NLO candidates.

A comprehensive analysis of electronic transitions in naphthalene and perylene diimide derivatives through computational methods

AbstractPerylene diimide (PDI) and naphthalene diimides (NDIs) are compounds widely used in supramolecular structures due to their versatile and functional properties. They have high absorptions and photoluminescence capabilities, which make them ideal for electronic transition studies. Reflux method, a widely employed synthetic technique, was utilized to synthesize NDI and PDI derivatives. In this method, the respective amino acids and NTDA (naphthalene‐1,4,5,8‐tetracarboxylic dianhydride) were combined in acetic acid and the resulting mixture was subjected to reflux. This study centered on a diverse set of NDI and PDI ligands, comprising L‐ala‐NDI, B‐ala‐NDI, Gly‐NDI, Imi‐NDI, Pyr‐NDI, L‐ala‐PDI, B‐ala‐PDI, Gly‐PDI, Imi‐PDI, and Pyr‐PDI ligands. Crystal structures were obtained for three NDI ligands, while the characterization of all ligands involved several analytical techniques such as NMR, IR, UV, DFT, TD‐DFT calculations, and single‐crystal x‐ray crystallography specifically for the NDI ligands. The investigation focused on studying the electron acceptor/donor behavior of the NDI and PDI ligands, identifying their potential for charge transfer applications. Furthermore, the NLO (nonlinear optical) response of all 10 NDI and PDI ligands was assessed through an analysis involving HOMO‐LUMO, TDM, EDDM, NCI, Iso‐surface, MEP, natural population, and DOS analysis. This evaluation encompassed the examination of linear polarizability, as well as first and second hyperpolarizability in the context of NLO. The findings of the study revealed that Gly‐PDI, Imi‐PDI, L‐ala‐PDI, and B‐ala‐PDI ligands displayed a higher NLO response compared with the other ligands. These results highlight the potential of these ligands for nonlinear optical applications. The comprehensive characterization and assessment of the NDI and PDI ligands contribute to a deeper understanding of their electron properties, positioning them as promising candidates for charge transfer and nonlinear optical materials.

First-principles study on AgBi(CrO4)2:An effective infrared nonlinear optical compound

The investigation of nonlinear optical (NLO) materials is critically important in developing laser technologies. The AgBi(CrO4)2 which crystallizes in the tetragonal lattice with a space group of I 4¯ is a potential candidate for the infrared (IR) region due to the large birefringence (Δn = 0.18), strong NLO response than the KDP crystal and the high electro-optical coefficients are justified their good performance NLO applications. The investigation of the elastic constant of AgBi(CrO4)2 indicates the ductile nature and the large piezoelectric coefficients make this crystal has great attention as bifunctional material.

Design of Fullerene20-thieno[2,3-c]pyrrole-4,6(5H)-dione-fullerene20 for Opto-nonlinear applications: Quantum Mechanical Study

Background:
 Many organic compounds are studied because of their nonlinear optical properties, which are crucial in photonics, optical switches, modulators, optical data storage, and other devices that use light to transport information. In experimental and theoretical researches, nonlinear optical phenomena, primarily resulting from interactions between matter and strong electric fields, have received considerable attention. Materials like these have numerous applications in science, engineering, and technology.
 Materials and Methods: Fullerene 20 has been adopted as an electron donor, which was considered an NLO molecular material, while the thieno[2,3-c]pyrrole-4,6(5H)-dione has been adopted as an electron acceptor. Fullerene20-thieno[2,3-c]pyrrole-4,6(5H)-dione-fullerene20 (FTPDF), as D-A-D, has been designed for nonlinear optical applications. Fullerene20-thieno[2,3-c]pyrrole-4,6(5H)-dione-fullerene20 (FTPDF) was studied to determine its linear and nonlinear optical properties. For FTPDF, nonlinear optical properties were calculated with DFT/B3LYP using the basis set 6-31G(d,p). Various quantum calculations determine the structural and symmetry properties of Fullerene20-thieno[2،3-c]pyrrole-4،6(5H)-dione-fullerene20.
 Results: The rotation increases the electric dipole moment µtot, average linear polarizability αo and the first hyperpolarizability βtot. And the anisotropic polarizability ∆α is smaller than the average polarizability, and the present structure has few deviations from spherical symmetry. FTPDF shows µx-switch behavior. In particular, the rotation can raise the possibility for a new type of molecular βx-switch.
 Conclusion: The Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) energies estimated by DFT for the investigated molecules have been reported here. Fullerene20-thieno[2,3-c]pyrrole-4,6(5H)-dione-fullerene20 has an increased first hyperpolarizability, making it a novel material suitable for the development of optoelectronic devices.

Growth, Structural, Spectroscopic and Thermal Analyses of Novel Organic Brucinum-3, 5 –Dihydroxybenzoate Dihydrate Single Crystals for NLO Applications

Along the line of available efficient nonlinear optical (NLO) organic single crystals in the literature, it is worthwhile to bring in a novel organic single crystal of Brucinium-3,5-dihydroxybenzoate dihydrate (B35D) which was successfully grown utilizing the technique of slow evaporation of solution at ambient conditions. As the solubility of B35D was found to be the highest in water-ethanol 1:1 mixed solvent among the conventional solvents, crystallization of B35D was accomplished by making use of the solvent. The required confirmation of the crystal structure of the crystal and its lattice parameter could be achieved by the single-crystal X-ray diffraction analysis such that B35D was found to be crystallized in the monoclinic system with the non-centrosymmetric space group C2. The recording of UV-Vis-NIR transmittance spectrum of the crystal was undertaken between the range of 300 and 900 nm whereby the lower optical cutoff wavelength was identified to be 321 nm. The spectral study of photoluminescence was carried out in the range of 300-600 nm by which the band gap energy was calculated to be about 3.8 eV (at 373 nm) indicating that B35D has a violet fluorescence spectrum. The thermal stability and melting point of the title crystal have been investigated through Thermo gravimetric and differential thermal analysis (TG-DTA) such that the thermal stability of the crystal was found to be 95.6 °C. The Nd: YAG Q-switched laser was employed so as to obtain the laser-induced surface damage threshold of the specimen which was estimated to be 3.1 GW/cm2. The Vickers microhardness test was implemented in order to arrive at the mechanical strength of the crystal. The performed non-linear optical study could reveal that the second-order harmonic generation (SHG) efficiency of B35D crystal is 2.16 times higher than KDP. So that B35D crystals are among the class of NLO materials.

Synthesis and characterization of novel thiosemicarbazide for nonlinear optical applications: combined experimental and theoretical study

(E)-4-(4-methoxyphenyl)-1-((E)-3(2nitrophenyl) allylidene) thiosemicarbazide was synthesised and screened for nonlinear optical properties. The novel compound has been characterized by infrared spectroscopy, 1H and 13C nuclear magnetic resonance. The experimental and theoretical optical gap energy is obtained using the Tauc method and density functional theory and has been estimated to be around 2.72 and 2.69 eV, respectively. The synthesized thiosemicarbazide exhibits efficiency hyper-Rayleigh scattering hyperpolarizability is calculated to be 6794.51 a.u. at the PBE0 functional. A direct relationship of the hyper-Rayleigh scattering hyperpolarizability with the optical band gap and between the hyper-Rayleigh scattering hyperpolarizability and electric field-induced second harmonic generation is found. The study showed the potential of the novel thiosemicarbazide as nonlinear optical candidates.

Vibrational Properties of the Potassium Titanyl Phosphate Crystal Family

The crystal family of potassium titanyl phosphate (KTiOPO4) is a promising material group for applications in quantum and nonlinear optics. The fabrication of low-loss optical waveguides, as well as high-grade periodically poled ferroelectric domain structures, requires a profound understanding of the material properties and crystal structure. In this regard, Raman spectroscopy offers the possibility to study and visualize domain structures, strain, defects, and the local stoichiometry, which are all factors impacting device performance. However, the accurate interpretation of Raman spectra and their changes with respect to extrinsic and intrinsic defects requires a thorough assignment of the Raman modes to their respective crystal features, which to date is only partly conducted based on phenomenological modelling. To address this issue, we calculated the phonon spectra of potassium titanyl phosphate and the related compounds rubidium titanyl phosphate (RbTiOPO4) and potassium titanyl arsenate (KTiOAsO4) based on density functional theory and compared them with experimental data. Overall, this allows us to assign various spectral features to eigenmodes of lattice substructures with improved detail compared to previous assignments. Nevertheless, the analysis also shows that not all features of the spectra can unambigiously be explained yet. A possible explanation might be that defects or long range fields not included in the modeling play a crucial rule for the resulting Raman spectrum. In conclusion, this work provides an improved foundation into the vibrational properties in the KTiOPO4 material family.

2-μm short data pulse all-optical wavelength converter based on MXene microfiber

We demonstrate the all-optical wavelength conversion of short pulse signals at 2-μm using MXene-assisted microfiber. The process involves an actively mode-locked thulium-holmium co-doped fiber laser, which is synchronously modulated by a digital signal and coupled with continuous light for the conversion process. The converted light is generated via four-wave mixing (FWM) with in the MXene-assisted microfiber. The conversion efficiency reaches −38.98 dB. For a wavelength tuning range of 6.08 nm–1.04 nm, the conversion efficiency is increased by 10.44 dB. The wavelength conversion efficiency fluctuation during 130 min is only 0.512 dB. The converter enables the successful transmission of 489 Mb/s data carried by the converted light. The results show that the MXene-assisted microfiber carrier wavelength converter has a high conversion efficiency and excellent stability. This study aligns with the development trend of all-optical wavelength conversion and explores the characteristics of highly nonlinear optical materials. The utilization of MXene-assisted microfiber enables significant advancements in all-optical wavelength conversion, particularly in the context of processing 2-μm short data pulse signals for nonlinear optics applications.