Third-order Nonlinear Optical Properties Research Articles

A new class of third-order nonlinear optical materials: laser pulse-duration dependant saturable absorption and nonlinear refraction in platinum(II) diimine-dithiolate complexes.

The third-order nonlinear optical (NLO) properties of a series of platinum diimine-dithiolate complexes [Pt(N^N)(S^S)] were investigated by means of Z-scan measurements, revealing second hyperpolarizability values up to 10-29 esu, saturable absorption properties, and nonlinear refractive behaviour, which were rationalized also by means of DFT calculations.

Click reactions to prepare symmetrical and asymmetrical and broad-band near-infrared absorbing dyes

Aniline compounds, both symmetric and asymmetric, were prepared via click chemistry and Sonogashira coupling reactions, and the third-order nonlinear optical properties of these compounds were studied.

Thickness-modulated optical nonlinearity of colloidal CdSe-CdS core-shell nanoplatelets: large two-photon absorption and self-focusing effects.

As a one-dimensional quantum confined material, colloidal semiconductor nanoplatelets have been widely studied as potential nonlinear materials due to their strong exciton effect and large two-photon absorption cross-section similar to that of two-dimensional materials. In this work, CdSe-CdS core-shell nanoplatelets were synthesized and third-order nonlinear optical properties related to shell thickness were measured using the Z-scan method. Measurement revealed a monotonic increase in the imaginary part of the third-order nonlinear susceptibility (Imχ(3)) of CdSe-CdS nanoplatelets, ranging from 0.62 × 10-13 esu to 2.43 × 10-13 esu, with the growth of shell thickness. The real part of the third-order nonlinear susceptibility (Reχ(3)) shows a non-monotonic change between 4.28 × 10-13 esu and 1.99 × 10-13 esu. The trends were further elucidated by analyzing the optical properties of the nanoplatelets, such as absorption, photoluminescence, and quantum yield, and understanding the variations in defect distribution, exciton binding energy, and quantum confinement effects. The results indicated that the appropriate passivation of the CdS shell effectively enhanced the luminescent performance and third-order nonlinearity of the nanoplatelets, while the induced defects and weakened quantum confinement effects due to the continued shell growth resulted in the opposite effect.

Third-order nonlinear optical properties of the host–guest complexes formed between fullerenes and cycloparaphenylene ([n]CPP: n = 9, 10 and 11)

Among [9–11]CPPs, [10]CPP is the most ideal fullerene encapsulator. With the increase of the CPP ring size, the polarizability values and second hyperpolarizability values of [9–11]CPP⊂C60 increase gradually.

Exploration of linear and third-order nonlinear optical properties for donor-π-linker-acceptor chromophores derived from ATT-2 based non-fullerene molecule.

In the current study, seven non-fullerene compounds abbreviated as ATTD2-ATTD8 were designed through structural tailoring and their nonlinear optical (NLO) properties were reported. The objective of this study was to explore the potential for newly configured D-π-A type non-fullerene-based compounds. Quantum chemical methods were adopted and revealed the molecules as highly efficient materials with favorable NLO characteristics for use in optoelectronic devices. The M06 functional along with the 6-311G(d,p) basis set in chloroform solvent were utilized for the natural bonding orbital (NBO) analysis, absorption spectra and computational assessments of frontier molecular orbitals (FMOs), global reactivity descriptors (GRPs), transition density matrix (TDM) and nonlinear optical properties (NLO) for ATTR1 and ATTD2-ATTD8. The HOMO-LUMO energy gap was significantly reduced in all the designed moieties compared to the reference compound in the following decreasing order: ATTR1 > ATTD8 > ATTD4 > ATTD5 > ATTD2 > ATTD7 > ATTD6 > ATTD3. All of the designed molecules (ATTD2-ATTD8) showed good NLO response. Global reactivity parameters were found to be closely associated with the band gap between the HOMO and LUMO orbitals, and the compound with the smallest energy gap, ATTD3, exhibited a lower hardness value of 1.754 eV and higher softness value of 0.570 eV with outstanding NLO response. For the reference compound and ATTD2-ATTD8 derivatives, attributes like dipole moment (μtot), average polarizability 〈α〉, first hyperpolarizability (βtot), and second hyperpolarizability γtot were calculated. Out of all the derivatives, ATTD3 revealed the highest amplitude with a βtot of 8.23 × 10-27 esu, which was consistent with the reduced band gap (1.754 eV) and suggested it was the best possibility for NLO materials in the future.

Growth, characterizations and nonlinear optical studies of dimethylamine substituted anthracene chalcone single crystals

We report the structural, thermal, linear and nonlinear optical (NLO) properties of a newly grown anthracene based chalcone single crystal, (2E)-1-(anthracen-9-yl)-3-[4-(dimethylamino)phenyl]prop-2-en-1-one (abbreviated as DA-ANC). The chalcone was synthesized by Claisen-Schmidt condensation reaction and the single crystals were grown by slow evaporation of solution growth technique. Single-crystal XRD, NMR (1H & 13C), FT-IR, UV-Vis-NIR spectroscopies, TG/DTA, and computational DFT studies were performed to characterize the crystals. The intermolecular interactions were described by Hirshfeld surface analysis (HSA). The third-order NLO properties of DA-ANC were studied by Z-scan technique using CW-DPSS laser at 532 nm. Open aperture Z-scan exhibits strong two-photon assisted reverse saturation absorption (RSA) with two-photon absorption (TPA) coefficient (β) 6.9 × 10−5 cmW−1. Closed aperture Z-scan reveals the negative nonlinear refraction arising due to self-defocusing effect with nonlinear refractive index (n2) coefficient -1.31 × 10−8 cm2W−1. The optical limiting behavior based on TPA was performed and limiting-threshold was evaluated to be 6.47 kJ cm−2. The obtained one-photon and two-photon figures of merit satisfied the conditions of all-optical switching. The results show that DA-ANC can be a potential candidate for NLO applications.

Linear and nonlinear optical properties of Al2O3/Y2O3 nanolaminates fabricated by atomic layer deposition

The structure and composition of nanocomposites constitute design parameters that can be manipulated to get control over their linear and nonlinear optical response. In this work, we report the linear and nonlinear optical properties of samples consisting of multiple Al2O3/Y2O3 bilayers with a total thickness of ∼ 500 nm, fabricated through the atomic layer deposition technique onto Si and SiO2 substrates. Fabrication of the multiple layer configurations was made for four Y2O3 layer thicknesses, while maintaining a constant Al2O3 layer thickness for all the samples fabricated. Physical and chemical characterization of the samples produced was conducted by optical ellipsometry, transmission electron microscopy and XRD. Moreover, their third-order nonlinear optical properties were studied through the z-scan technique with 100 fs pulses at 800 nm from a Ti:Sapphire laser, allowing the resolution of the refractive and absorptive contributions to the response. The nonlinear parameters extracted from the experiments are discussed in terms of the fabrication thickness of the selected materials. Additionally, figures of merit relevant for the possible application of these materials in optical processing system are calculated and discussed.

Minimized thermal effects and strong two-photon absorption of aluminum, silver doped platinum bi-metal nanoparticles

Herein, for the first time, we have investigated the strong nonlinear optical (NLO) properties aided with minimal thermo-optical effects in silver-platinum (Ag-Pt) nanoparticles (NPs) using Z-scan technique with high repetition rate femtosecond pulses at 700 nm. The NPs were synthesized using ultrafast laser ablation of Ag/Al targets immersed in the Pt colloidal solutions in isopropyl alcohol (IPA). We observed reverse saturable absorption (RSA)/two-photon absorption (2PA) behavior in Ag-Pt NPs (with 0.5 mM concentration of Pt), W-shaped switching behavior in Ag-Pt NPs (with 1 mM concentration of Pt), and RSA/2PA behavior in Ag-Pt NPs (with 3 mM concentration of Pt). The multiple-stage nonlinear absorption phenomenon is attributed to the interchange of pure 2PA or excited-state absorption, and 2PA saturation effects. Additionally, the broadband third-order NLO properties of aluminum-doped Pt (Al-Pt) bi-metallic NPs were obtained using spectral-dependent Z-scan studies at 700 nm, 800 nm, and 900 nm. The results revealed that Al-Pt bi-metallic NPs exhibited strong saturable absorption (SA), 2PA, and switching from SA to RSA. It is also revealed from the closed aperture Z-scan data that Ag-Pt and Al-Pt bi-metallic NPS exceed thermal contribution with strong 2PA coefficients unprecedentedfor single metal NPs. In the case of Ag-Pt NPs, strong 2PA saturation effects are attributed to the filling of Ag-O anti-bonding states by the photo-excited electrons and then charge transfer to the Pt plane. In the case of Al-Pt NPs, strong 2PA phenomena are ascribed to the enhancement of charge carriers in the conduction band and, hence, the strong surface plasmon resonances. The 2PA coefficients were evaluated to be ∼10−7 cm/W. The superior and switching NLO effects indicate that these materials might be utilized for potential applications, including optical modulators, and all-optical switching devices.

Fine-Tuning Tridentate Ligands for the Construction of Nanotube-Based Boron Imidazolate Frameworks with High Chemical Stability

Two unusual nanotube-based boron imidazolate frameworks (BIF-134 and BIF-135) were synthesized by a dual-ligand synthetic strategy under solvothermal conditions. In the structure of BIF-134 ([Co(BH(2-mim)3)(BTC)1/3](HBH(2-mim)3)1/3(NMA); 2-mim = 2-methylimidazole, NMA = N-methylacetamide, and BTC = 1,3,5-benzene tricarboxylate), one part of boron imidazolate ligands participate in the structural skeleton coordination, while another part of boron imidazolate ligands act as guest molecules that are located between adjacent nanotubes, which enhance the stability of the framework by the host-guest interaction and the pore space partition effects. It was found to be highly stable in air, water, organic solvents, and a wide pH range (pH 0-12). However, in the structure of BIF-135 ([Zn(BH(2-mim)3)(CHTC)1/3]; CHTC = 1,3,5-cyclohexanetricarboxylate), all boron imidazolate ligands participate in the structural skeleton coordination; there is no boron imidazolate guest molecule in the pores. The topology of BIF-135 is similar to that of BIF-134 by replacing BTC with CHTC and replacing Co with Zn. Furthermore, the obtained BIFs exhibited third-order nonlinear optical properties and potential optical limiting applications demonstrated by reverse saturable absorption.

Impact of defects on the χ(3) optical nonlinearity of sputtered WSe2 thin films in the optical communication band

We present an experimental investigation on third-order nonlinear optical properties of RF-sputtered WSe2 thin films using a single-beam Z-scan technique around the optical communication window in a near-infrared spectral band. The nonlinear absorption coefficient was obtained from the open-aperture Z-scan transmission using ultrashort pulses centered at 1520nm excitation wavelength. The results show a reverse saturable absorption signature for all the WSe2 films due to two-photon absorption (TPA) mediated electronic transitions. The dependency of the TPA coefficient on film thickness is analyzed through the modification in an electronic band structure essentially caused due to defects induced in the samples. In addition, we also explored the impact of high laser intensity on the TPA process, which essentially pointed toward a significant contribution of free-carrier absorption at small laser intensities in WSe2 thin films. This investigation provides a basis for optimally tailoring the nonlinear optical properties of transition-metal-dichalcogenides via bandgap engineering for improving photonic device functionality.

Supramolecular architecture, Hirshfeld surface analysis and third-order nonlinear optical properties of crown ether with 5-nitroisophthalic acid monomethyl ester and trimesic acid

Two host-guest supramolecular complexes such as (18-crown-6)-2(5-nitroisophthalic acid monomethyl ester).2(H2O) (I) and (15-crown-6)-2(trimesic acid).2(H2O) (II), have been synthesized from ethanol-water (2:3, v/v) mixed solvent system. Crystal structures elucidated by single-crystal X-ray diffraction reveal that both belong to the triclinic system with centrosymmetric space group Pī. Inter- and intramolecular hydrogen bonding interactions and weak van der Walls forces construct the supramolecular architecture. Fingerprint plots of Hirshfeld surfaces were used to locate and analyse the percentage of hydrogen bonding interactions. The band gap energy was determined by the application of the Kubelka–Munk algorithm. The third-order nonlinear optical susceptibility (χ(3)) of the cocrystals are, 4.19 × 10−6 and 4.45 × 10−6 esu for (I) and (II) respectively.

Effect of Cerium dopant on third-order nonlinear optical properties of CdS/PEG self-standing nanocomposite films

CdS/PEG, 4 and 7 mol% Ce doped CdS/PEG nanocomposite films were synthesized by in situ method. The XRD pattern confirmed the cubic structure of the CdS and the size of the CdS nanocrystallite is found to be smaller than the Bohr exciton radius for all the samples. SEM analysis shows that CdS and Ce doped CdS nanoparticles are well mono-dispersed in PEG polymer. FTIR spectra confirm the interaction of Ce-doped CdS nanoparticles with PEG polymer. UV–Vis optical absorption studies exhibit a red-shift of CdS nanoparticle with Ce doping. The photoluminescence spectra of all the films show a red emission due to the surface defects. The third-order nonlinear optical properties of all the films have been studied using the Z-scan technique. Closed and open aperture Z-scan plots show self-focusing optical nonlinearity and reverse saturable absorption with positive nonlinear coefficients. The 7 mol% Ce doped CdS/PEG nanocomposite film exhibits the highest value of nonlinear refractive index and nonlinear absorption coefficient which are about 1.649 × 10−9 m2/W and 7.149 × 10−3 m/W. The third-order nonlinear optical susceptibility and figure of merit have also been estimated for all the films and also increase with increase in Ce dopant concentrations. The maximum value of third-order nonlinear optical susceptibility and figure merit are found for 7 mol% Ce doped CdS/PEG nanocomposite film and are about 9.882 × 10−4 esu and 5.902 × 10−8 esu m. The present study strongly recommends that the Ce doped CdS/PEG nanocomposite films are worthy candidates for fabricating the future optical limiting devices.

Synthesis of novel 2-(benzhydryloxy) phenoxy-substituted zinc phthalocyanine, third-order nonlinear optical and fluorescence properties

Synthesis of novel 2-(benzhydryloxy) phenoxy-substituted zinc phthalocyanine, third-order nonlinear optical and fluorescence properties

High-order harmonics generation in nanosecond-pulses-induced plasma containing Ni-doped CsPbBr3 perovskite nanocrystals using chirp-free and chirped femtosecond pulses

We demonstrate high-order harmonic generation in Ni-doped CsPbBr3 perovskite nanocrystals ablated by nanosecond pulses using chirp-free 35 fs, and chirped 135 fs pulses in the case of single-color pump (800 nm) and a two-color pump (800 and 400 nm). We analyzed the spectral shift, cut-off, and intensity distribution of harmonics in the case of chirped drving pulses compared to chirp-free pulses. It is shown that the presence of Ni dopants and CsPbBr3 plasma components improves the harmonics emission. Also, we measured the third-order nonlinear optical (NLO) properties of these nanocrystals using 800 nm, 60 fs, 1 kHz pulses. The variations of measured NLO parameters of CsPbBr3 perovskite nanocrystals containing different concentrations of nickel correlate with variations of generated high-order harmonics from laser induced plasmas of studied nanocrystals in terms of harmonics intensity, cut-off, and spectral shift (in case of chirped driving pulses). The spectral shift of the harmonics generated from the Ni-doped CsPbBr3 perovskite nanocrystals can be used to form tunable extreme ultraviolet sources.

Crystal structure, Hirshfeld surface analysis and third-order nonlinear optical properties of supramolecular complexes of 18-crown-6 with 6-hydrazinonicotinichydrazide and p-phenylenediamine

The crystal structures of the host-guest supramolecular complexes [2(6-HPCH)2+.3(18C6)].4[ClO4¯].2(H2O) (I) and [(PDA)2+.2(18C6)].2[Cl¯].10(H2O) (II) (18C6 = 18-crown-6; 6HPCH = 6-hydrazinylpyridine-1-ium-3-carbohydrazinium; PDA = p-phenylenediaminium) were determined by single-crystal X-ray diffraction analysis. Supramolecular assembly is constructed by NH···O, OH···O and C-H···O interactions. Both crystallize in the monoclinic system with centrosymmetric space group P21/n. The vibrational patterns in FT–IR are used to identify the functional groups. Direct band gap energy estimated by diffuse reflectance spectrum are, 3.42 eV for (I) and 4.78 eV for (II). Molecular interactions are analyzed by Hirshfeld surfaces, derived from single-crystal XRD data. Fingerprint plots of Hirshfeld surfaces were used to locate and analyze the percentage of hydrogen bonding interactions. A z-scan study was used to determine the third-order NLO response.

Molecular structure and third-order non-linear optical properties of two novel tetralone-based chalcone derivatives: Promising materials for optical limiting applications

Two novel tetralone-based chalcone derivatives (2E)-2-(3,4-dimethoxybenzylidene]-3,4-dihydro-2H-napthalen-1-one (DMDN) and (2E)-2-(3,4-dimethoxybenzylidene]-6-methoxy-3,4-dihydro-2H-napthalen-1-one (DM6MDN) have been synthesized via a Claisen–Schmidt condensation reaction. Single crystals were obtained using a slow evaporation solution growth method. Structural characterization was carried out using single crystal X-ray diffraction study. Non-centrosymmetric DMDN crystallized in the orthorhombic system with a P212121 space group. Centrosymmetric DM6MDN crystallized in the monoclinic system with a P21/c space group. Hirshfield analysis of both crystals revealed the existence of C–H···π and π···π interactions, which play an important role in creating supramolecular structures. Our TG-DSC study revealed that DM6MDN has higher thermal stability than DMDN. The linear absorption coefficient of DMDN and DM6MDN were calculated from our UV spectral analysis and their respective optical band gaps were calculated to be 2.88 and 3.05 eV, respectively. The photoluminescence spectra show emission peaks in the blue region. DMDN exhibits SHG activity and a large β value when compared to DM6MDN. The third-order NLO properties of the chalcone derivatives was investigated using the Z-scan technique. The obtained crystals show strong non-linear absorption (NLA) and negative non-linear refraction (NLR) for DMDN and a positive NLR for DM6MDN. The third-order non-linear susceptibility (χ(3)) was of the order 10−7 esu. DMDN and DM6MDN also exhibit optical limiting (OL) and optical switching behavior under continuous wave excitation. The static NLO parameters, such as dipole moment (μ), polarizability (α) and first order hyperpolarizability (β), were computed using the B3LYP/6–31++G(d,p) level of theory. The Donor-π-Acceptor-π-Donor (D-π-A-π -D) system of DMDN and DM6MDN also makes them promising materials for NLO applications.

Third-order nonlinear optical responses of Cr3+ ions on La2(WO4)3 nanoparticles for optical limiting applications

In this article, we discuss the nonlinear optical limiting characteristics of pure and Cr3+ doped La2(WO4)3nanoparticles using soft chemical method. We studied the third-order nonlinear optical properties of nanoparticle using a continuous-wave (CW) laser system pumped by a diode laser at 785 nm. The results reveal that the materials possess reverse saturable absorption (RSA) and self-defocusing in nature. Due to the presence of near-resonant excitation state, the material exhibits sequential two-photon absorption (excited state induced thermally) process. We observe a higher non-linear absorption coefficient (β) and nonlinear refractive index (n2) for 0.7 % Cr3+ doped La2(WO4)3 systems which is higher than that of pure La2(WO4)3 nanoparticles. The transmittance decreases with increased input fluence for both pure and Cr3+ doped La2(WO4)3 samples exposing the optical limiting behavior of the prepared sample. The presence of larger concentrations of more polarizable Cr3+ ions, increased density of states, and higher oxygen defects resulted in enhanced OL behaviour for 0.7 % Cr3+ doped La2(WO4)3 sample. It is found that two photon absorption (β) is increased from 0.41 to 1.16 × 10-3 and third order nonlinear susceptibility (χ(3)) enhances from 3.909 x10-6 to 6.696 × 10-6 esu on Cr doping. The optical limiting threshold of pure and CrxLa1-xWO4 nanoparticles was also studied and found to be in the range of 91.2 to 86.2 W/cm2. As a consequence of the obtained results Cr3+ doped La2(WO4)3 is likely to be an appropriate candidate for CW low-power optical limiting (OL) applications.

Two photon absorption induced optical limiting action of L-Aspartic acid monohydrate

The organic l-Aspartate Monohydrate (L-AspMH) crystal is grown by slow evaporation technique. Single crystal XRD analysis reveals that L-AspMH belongs to an orthorhombic system with P 21 21 21 space group. The inter-contacts in the crystal structure are analyzed using the Hirshfeld surface analysis. To support the experimental results, quantum chemical calculations using the density functional theory (DFT) are done. The molecular structure of L-AspMH crystal is optimized by DFT/B3LYP functional, 6–311G++(d,p) basis set. The FT-IR and FT-Raman spectra are also stimulated and validated experimentally. The blue-shift in the O–H stretching wavenumbers is due to the presence of O–H⋯O hydrogen bonding. The highest occupied molecular orbital (HOMO: −7.409 eV) energy, lowest unoccupied molecular orbital (LUMO: −0.927 eV) energy and energy gap (6.483 eV) of the AspMH crystal is calculated. The hyper conjugative and inter/intra molecular interactions have been investigated through the Natural Bond Orbital (NBO) analysis. UV–vis absorption studies shows the material exhibit absorbance maxima in the UV (204 nm) region and high transmittance in the Visible-NIR (340–900 nm) region. The predicted first order hyperpolarizability is found to be 13 times greater than that of urea. Third-order nonlinear optical property of the crystal is studied using Z-scan technique under nanopulsed Nd:YAG laser. L-AspMH exhibit intensity dependent nonlinear absorption behaviour was witnessed with M-type (2.46 × 1012 W/m2) at lower on-axis input intensity and reverse saturable absorption (4.98 × 1012 W/m2) at higher on-axis input intensity. The material demonstrates sequential two absorption induced optical limiting action. Higher two-photon absorption coefficient (0.56 × 10−10 m/W) and lower onset optical limiting threshold (5.41 × 1012 W/m2) makes AspMH a potential candidate for optical limiting devices.

Bromine Substitution Effect on Structure, Reactivity, and Linear and Third-Order Nonlinear Optical Properties of 2,3-Dimethoxybenzaldehyde.

The structural and electronic properties of 2,3-dimethoxybenzaldehyde (2,3-DMB), 5-bromo-2,3-dimethoxybenzaldehyde (5-BRB), and 6-bromo-2,3-dimethoxybenzaldehyde (6-BRB) were extensively discussed with emphasis on linear and nonlinear optical responses. The intermolecular interactions were comparatively studied by Hirshfeld surfaces, quantum theory of atoms in molecules (QTAIM), and natural bond orbitals (NBOs), indicating that bromine substitution decreases the H···H and C···H contacts and increases H···Br and Br···Br closed-shell interactions on crystalline arrangements. The frontier molecular orbitals and molecular electrostatic potential map, carried out at the CAM-B3LYP/6-311++G(d,p) level of theory, showed that the kinetic stability occurs in the increasing order 6-BRB < 5-BRB < 2.3-DMB. The bromine atom has a beneficial effect on the nonlinear third-order susceptibility of 2,3-DMB, with theoretical predictions of 89.54 ×10-22 and 83.15 ×10-22 (m/V)2 for 6-BRB and 5-BRB, respectively. These findings were favorably compared with available theoretical and experimental data of other organic crystals that may be promising as NLO materials.

Design of A-D-A-Type Organic Third-Order Nonlinear Optical Materials Based on Benzodithiophene: A DFT Study.

The acceptor-donor-acceptor (A-D-A) type conjugated organic molecule has been widely applied in the organic optoelectronics field. A total of Nine compounds (1–9) were designed under the A-D-A framework, with the electron donor benzodithiophene as the core and dicyanomethylene as the acceptor moiety, modifying the benzodithiophene with the phenyl, naphthyl, and difluorinated phenyl groups. The conjugation length can be changed by introducing a thiophene π-conjugated bridge. The geometric structures, electronic structure, excited state properties, aromaticity, and the static- and frequency-dependent second hyperpolarizabilities were investigated by employing high-precision density functional theory (DFT) calculations with an aug-cc-pVDZ basis set. As a result, the three compounds with the longest conjugation length exhibit a smaller energy gap (Egap), larger UV-vis absorption coefficient, and response range, which are the three strongest third-order nonlinear optical (NLO) response properties in this work. This work systematically explored the connection between molecular structure and NLO response, which provides a rational design strategy for high-performance organic NLO materials.