Nonlinear Optical Susceptibility Research Articles

Reversible and Tunable Second‐Order Nonlinear Optical Susceptibility in PZT Thin Films for Integrated Optics (Advanced Optical Materials 16/2021)

A laser beam passing through a thin ferroelectric lead zirconate titanate (PZT) film is transformed into a beam with doubled frequency by means of second harmonic generation. The polarization density of the PZT film and the second-order susceptibility can be controlled and reserved by means of an applied voltage. The thin film exhibits a very strong susceptibility of 128 pm/V, which opens avenues for highly efficient and tunable on-chip nonlinear devices. For further details, see article number 2100149 by Gilles F. Feutmba, Jeroen Beeckman and co-workers.

Synthesis, growth and investigation of an efficient nonlinear optical single crystal: Glycine potassium iodide

• GPI single crystals were grown by slow evaporation method. • Functional groups of the crystal were identified by FTIR spectral analysis. • The SHG efficiency is 0.89 times that of KDP. • Third-order nonlinear optical susceptibility (χ 3 ) was found to be 3.79 × 10 −6 esu. Using the slow solvent evaporation method with deionized water as the solvent, a single crystal of glycine potassium iodide (GPI) was grown at room temperature. The GPI crystal belongs with space group Cc to the monoclinic system. Functional groups present in the sample were identified by FTIR spectral analysis. The crystals were further characterized by UV-Vis NIR transmission spectrum in the range of 250–1100 nm. Second Harmonic Generation was validated in the Kurtz-Perry powder technique. The Z-scan experiment was being used to assess the nonlinear absorption coefficient, nonlinear refractive index and third-order nonlinear susceptibility to explore GPI crystal third-order NLO behavior. The photoconductivity study confirms the grown crystal is positive photoconductivity. The grown crystal suitability for nonlinear optical applications was confirmed through characterization studies.

Effect of size and composition on the third order nonlinear optical susceptibility for GaN/InxGa1-xN spherical core/shell quantum dot

In this report, we have theoretically described, analyzed, and investigated the nonlinear optical properties in the core/shell nanostructure of GaN core surrounded by InxGa1−xN shell. Taking in consideration the effective-mass formalism, electron eigenenergies and corresponding wave functions were calculated. Employing the compact density matrix method, highlight quantities namely the third-order nonlinear susceptibility associated with intersubband transition is numerically computed and discussed as a function of CSQD radii and indium (In) composition. Our simulations have revealed the tunability of the position and the magnitude of the resonance peaks by adjusting the geometrical parameters and the indium ratio. The magnitude of both real and imaginary parts of the susceptibility is remarkably aroused and the peaks are red shifted with the rise of core/shell radii.

Mode-locked fiber laser based on [formula omitted]-Fe2O3 nanosheets as saturable absorbers

With broadband saturable absorption properties and a high third-order nonlinear optical susceptibility, α-Fe2O3 exhibits potential applications in nonlinear optics. In this study, α-Fe2O3 nanosheets are embedded into polyvinyl alcohol (PVA) films to fabricate thin-film saturable absorbers (SAs) that feature an uninterrupted broad absorption band spanning over 2000 nm and a modulation depth of 16.13%. In α-Fe2O3-PVA SA-based erbium-doped fiber lasers, two stable mode-locked operations are achieved: dark-bright pulse pairs and bright solitons. The results indicate that α-Fe2O3 nanosheets are excellent candidates for two-dimensional saturable absorption materials.

Growth, characterisation and DFT investigations on 3-hydroxy-6- methyl -2- nitropyridine (3H6M2NP)-A novel third order nonlinear optical material

Single crystals of nitropyridine derivative 3-hydroxy-6-methyl-2-nitropyridine was grown by slow evaporation solution growth technique using ethanol. 3H6M2NP was crystallized in orthorhombic crystal system with centrosymmetric space group Pbca. The crystalline nature, presence of functional groups and its vibrational modes were assigned using FT-IR and FT-Raman spectroscopic techniques. The UV–Vis spectrum reveals 3H6M2NP crystal is transparent in the visible region with lower cut-off wavelength. The luminescence properties were confirmed by PL spectrum and 3H6M2NP crystal exhibited thermal stability up to 182 °C. The molecular structure of 3H6M2NP was optimised and all ab initio calculations were done theoretically. From Z-scan technique, the third order nonlinear optical susceptibility of the grown crystal was found to be χ3 = 2.616 × 10−8 esu. The hyper polarizability value was found to be 2.9 times larger than that of the urea which settles the NLO activity.

Magnetic Properties and Second Harmonic Generation of Noncentrosymmetric Cyanido-Bridged Ln(III)-W(V) Assemblies.

One-dimensional zigzag cyanido-bridged coordination polymers have been prepared as a result of self-assembly of lanthanide(III) ions with octacyanidotungstate(V) anions in the presence of N,N-dimethylacetamide (dma). All compounds crystallized in noncentrosymmetric space group P21 with a molecular formula of [LnIII(dma)5][WV(CN)8] [Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5), Tm (6), Yb (7), Lu (8), or Y (9)]. Magnetic studies revealed weak antiferromagnetic interactions through LnIII-NC-WV bridges and the formation of ferrimagnetically coupled chains at very low temperatures. Moreover, temperature dependencies of magnetic susceptibilities were fitted using the crystal field parameters for Ln(III) ions, determined by the ab initio calculations, yielding magnetic coupling constants in the range of -1 to -5 cm-1. The wide optical transparency of 1-9 has been determined using solid state absorption spectroscopy. Samples exhibited second harmonic (SH) generation properties with SH susceptibilities ranging from 4.7 × 10-12 to 9.4 × 10-11 esu due to the presence of nonlinear optical susceptibility tensor elements (χijk) χzxx, χzyy, χzzz, χzxy, χyyz, χyzx, χxyz, and χxzx, corresponding to space group P21. The determined values were also compared with the results of theoretical calculations and previous reports, indicating a potential relationship between the type of lanthanide ion and the SH intensity.

Strong near band-edge excited second-harmonic generation from multilayer 2H Tin diselenide

We report strong second-harmonic generation (SHG) from 2H polytype of multilayer Tin diselenide (SnSe2) for fundamental excitation close to the indirect band-edge in the absence of excitonic resonances. Comparison of SHG and Raman spectra from exfoliated SnSe2 flakes of different polytypes shows strong (negligible) SHG and Raman Eg mode at 109 cm−1 (119 cm−1), consistent with 2H (1T) polytypes. The difference between the A1g–Eg Raman peak positions is found to exhibit significant thickness dependent for the 1T form, which is found to be absent for the 2H form. The observed thickness dependence of SHG with rapid oscillations in signal strength for small changes in flake thickness are in good agreement with a nonlinear wave propagation model considering nonlinear polarization with alternating sign from each monolayer. The nonlinear optical susceptibility extracted from SHG signal comparison with standard quartz samples for 1040 nm excitation is found to be more than 4-times higher than that at 1550 nm. This enhanced nonlinear response at 1040 nm is attributed to the enhanced nonlinear optical response for fundamental excitation close to the indirect band-edge. We also study SHG from heterostructures of monolayer MoS2/multilayer SnSe2 which allows us to unambiguously compare the nonlinear optical response of SnSe2 with MoS2. We find the SHG signal and any interference effect in the overlap region to be dominated by the SnSe2 layer for the excitation wavelengths considered. The comparison of SHG from SnSe2 and MoS2 underscores that the choice of the 2D material for a particular nonlinear optical application is contextual on the wavelength range of interest and its optical properties at those wavelengths. The present works further highlights the usefulness of near band-edge enhancement of nonlinear processes in emerging 2D materials towards realizing useful nanophotonic devices.

Shape dependent heat transfer and nonlinear optical limiting characteristics of water stable ZnO nanofluid

In this study, we experimentally investigated the shape dependent thermal and nonlinear optical properties of water stable ZnO nanostructures. It is important to note that morphology plays a significant role in determining thermo-optic properties of ZnO. The thermal conductivity of colloidal ZnO was measured using a dual beam collinear thermal lens technique. The result shows a 23% enhancement in thermal conductivity of ZnO nanofluid compared to that of base fluid water. The nanofluid with nonspherical ZnOnanoparticles exhibit greater thermal diffusivity than a fluid with spherical nanoparticles. This enhancement in thermal conductivity was explained using the Hamilton – Crosser model based on the formation of nanolayer and interfacial thermal resistance. The third-order nonlinear optical susceptibility and optical limiting properties were investigated using a single beam Z scan technique. All samples showed two photon absorption and a negative nonlinear refractive index which varied with the nanoparticle morphology. Higher dimensional structures showed better optical nonlinearity due to their large surface area, photon scattering and exciton oscillator strength. The Z scan results reveal an increment of three orders of magnitude in third-order susceptibility for the nanoparticles compared to that of bulk ZnO. The nanofluid also exhibits a good optical limiting behaviour. The findings suggest that ZnO nanostructures can be considered as promising candidates for future optoelectronic devices.

The new pyrazoline derivative 5‐(3,4-Dimethoxy‐phenyl)‐3‐(2,5‐dimethyl‐thiophene‐3‐yl),‐4,5‐dihydro‐pyrazole‐1‐carbothioic acid amide (DDPA) as an advisable candidate for optical linearity, nonlinearity, and limiting performance

The present report provides the linear and nonlinear optical studies of a pyrazoline derivative, 5‐(3,4-Dimethoxy‐phenyl)‐3‐(2,5‐dimethyl‐thiophene‐3‐yl),‐4,5‐dihydro‐pyrazole‐1‐carbothioic acid amide (DDPA). The UV–Vis absorption and emission spectra have been recorded and analyzed to estimate the linear optical characteristics. The linear optical properties like absorption coefficient (α0), refractive index (n0), extinction coefficient (K), optical conductivity (σ opt), and optical band gap (Eg) have been evaluated. The third-order nonlinear optical (NLO) properties have been examined using the Z-scan technique employing the continuous wave (CW) diode laser of 520 nm. The third-order nonlinear refractive index (n2), nonlinear absorption coefficient (β), nonlinear optical susceptibility (χ (3)), and the second-order hyperpolarizability (γ) have been enumerated for different dye solution concentrations as well as for several laser powers. The values of β, n2, χ (3), and γ were found to be of the order of 10−3 cm/W, 10−7 cm2/W, 10−6 esu, and 10−26 esu respectively. Furthermore, the compound DDPA has been screened by the same laser excitation for the optical limiting behavior and found to be exhibiting good agreement for this nature. Hence the compound DDPA reveals its potential applications for optical switching, optical communication, and optical data storage devices.

Dielectric constant, polarizability, susceptibility and gamma ray shielding behavior of the Li2O-Li2MoO4-TiO2-P2O5 glasses

Research has been done on the effect of TiO2 on the physical and optical characteristics of Li2O-Li2MoO4-TiO2-P2O5 glasses. With an increase in concentration of TiO2, the density values drop from 3.68 g/cm3 to 3.27 g/cm3. With the inclusion of TiO2, the current glasses have smaller mean distance between Ti ions and polaron radius. Increasing non-bridging oxygens raise the refractive index, dielectric constant (ε) and optical dielectric constant. Reflection loss and transmission coefficient are found to inversely proportional. The molar refractivity increases from 24.242 to 27.817 (cm3 mol−1) which in turn increases the molar polarizability and electronic polarizability of the system from 9.616 to 11.033 (x 10−24 cm3) and 0.957 – 1.051 (x 1024). The metallization value less than unity predicts non-metallic nature of glasses. The other parameters such as optical electronegativity (χ∗), non-linear refractive index (n2) and non-linear optical susceptibility (χ3) values decrease from 0.569 to 0.363, 11.860 − 4.367 × 10−15 (esu) and 8.454 – 3.581 × 10−16 with addition of TiO2. Additionally, the shielding aspects were also explored, as well as the influence of titanium dioxide (TiO2) on attenuation factors were discussed. The linear attenuation coefficients (LAC) are at their highest values at the low energy and rapidly diminish. The effective atomic number (Zeff) decreases with the energy except at 1.333 and 2.51 MeV, where the Zeff at these two energies increases due to the pair production process. The Ti3 sample has a Zeff of 11.04 at 0.28 MeV, 10.22 at 0.83 MeV and 10.34 at 2.51 MeV.

Crystal structure, physico-chemical and third order nonlinear traits of the novel (2E)-1-(3,4-dimethoxyphenyl)-3-(4-propoxyphenyl) prop-2-en-1-one (DMPP) chalcone single crystal

Optically highly versatile novel third-order organic nonlinear single crystals of (2E)-1-(3,4-dimethoxyphenyl)-3-(4propoxyphenyl)prop-2-en-1-one (DMPP) which adapts to orthorhombic Pbca space group is crystallized by slow evaporation growth technique. Fourier transform infrared analysis affirms the presence of various functional groups in DMPP. Transparency and lower cut-off wavelength of the crystal were obtained using linear optical properties. The thermal stability without any weight loss is up to 220°C. The molecular structure of DMPP was confirmed by 1H NMR and 13C NMR analysis. From the electrical conductivity studies, the suitability of DMPP chalcone for device fabrication with a very low activation energy value of 0.04 ​at 1 ​MHz and conductivity value of 10−4 ​S/m was observed for the first time. Further B3LYP/6-31G++ level has been used to obtain static first-order and second order hyperpolarizability parameters. The calculated value of first-order hyperpolarizability was calculated to be 96 times better than that of standard urea and several orders better compared to other 3,4 dimethoxy derivatives. The experimental third order nonlinear measurements were done by continuous-wave (cw) 632.8 ​nm laser. From the Z-scan measurements, the calculated imaginary and real third-order nonlinear optical susceptibility are of the order of 10−5 e.s.u. The experimental and computational results disclose that DMPP is a novel third-order optically active single crystal and a noteworthy material for nonlinear optical applications.

Linear, non-linear optical properties and magnetic studies of spray pyrolysis nanocrystalline Sn1-xCoxO2 films for multifunctional optoelectronic and spintronic applications

Abstract In this paper, the structural, morphological, linear & non-linear optical, and magnetic properties of spray pyrolysis nanostructured Sn1-xCoxO2 thin films (0 ≤ x ≤ 0.08) were studied employing X-ray diffraction (XRD), atomic force microscope (AFM), spectrophotometric, and vibrating sample magnetometer (VSM) techniques, respectively. A tetragonal type structure was observed for films without any sign of impurities. XRD with Rietveld refinement analysis further revealed an increase in lattice parameters and unsystematic changes in crystallite size. AFM micrograph analysis shows that the surface roughness and root mean square roughness of the film are improved with increasing Co doping. Moreover, the spectrophotometry results indicate a direct optical transition for the film with an energy band gap reduces from 3.8 eV (x = 0) to 3.34 eV (x = 0.07) due to the rise in structural disorder and the increase in the density of localized states. The optical constants are calculated from the light transmission spectrum using the envelope method of Swanepoel. It is seen that the overall behavior of the refractive index n(λ) and extinction coefficient k(λ) increase with increasing of Co content. The dispersive oscillator parameters estimated from the single-oscillator Wemple–DiDomenico model were used to determine the non-linear optical parameters, such as the third-order non-linear optical susceptibility χ(3) and non-linear refractive index n2. Finally, intrinsic room temperature ferromagnetism is observed, which is interpreted based on the bound magnetic polarons model. In conclusion, Co doping in SnO2 host semiconductor nanocrystalline films enhances their optical and magnetic characteristics, making it a potential candidate for multifunctional applications like optoelectronics and spintronics devices.

Positional isomers of heterocyclic azo dyes: Investigation of NLO properties by Z-scan and correlative DFT studies

We report four azo dyes and their positional isomers having a benzothiazole-pyridone core. Selected heterocyclic emissive azo dyes in this work are analysed for their non-linear optical (NLO) properties. Non-linear absorptive coefficient (β), non-linear refractive index (ƞ2), third-order NLO susceptibility (χ3), and optical limiting (OL) in different solvents are analysed and promising results are obtained using Z-scan technique. Laser damage threshold (LDT) and thermogravimetric analysis (TGA) supports that these dyes can be a good constructive unit in laser assisted devices and several high-temperature NLO processes respectively. Molecular electrostatic potential (MEP), Frontier molecular orbitals (FMOs) are also presented using B3LYP/6–311+ G (d,p) level of theory. Global hybrid functional (GH) and Range separated hybrid functional (RSH) i.e. B3LYP, BHandHLYP and CAM-B3LYP, ωB97, ωB97X, ωB97X-D respectively used for the calculation of NLO parameters. Limits of hyperpolarizabilities and intrinsic hyperpolarizabilities are calculated and all the hyperpolarizabilities of the molecules are within estimated limits. HOMO-LUMO gap have an inverse correlation with the experimental non-linear optical susceptibility (χ3). Inverse or direct correlation with hyperpolarizability with different DFT descriptors such as electrophilicity index (ω), hyperhardness is also presented.

Enhanced optical properties of DNA-CTMA complex doped with [2.2]paracyclophane moieties

In this paper, the results of the research on linear and nonlinear optical properties of two organic molecules: 5-formyl-13-hydroxy[2.2]paracyclophane and 5-formyl-12-hydroxy[2.2]paracyclophane are presented and discussed. The studies were performed on both thin films and solutions. Thin films were obtained by spin deposition of the studied solutions molecules in DNA-CTMA matrix. Such properties like: optical absorption, fluorescence and third-order nonlinear optical (NLO) susceptibilities were determined. The molecules exhibit large transparency range in visible and an enhancement of third order NLO susceptibility at 1064.2 nm fundamental wavelength. An important χ(3) increase, ca. 50%, is observed when changing the OH substitution from para to ortho. The fluorescence measurements have shown the presence of a broad emission band in visible, well separated from the optical absorption.

Synthesis and study the influence of yttrium doping on band structure, optical, non-linear optical and dielectric results for Ca12Al14O33 (C12A7) single crystals grown using traveling-solvent floating zone (TSFZ) method

Ca12Al14O33 (C12A7) and Y0.02Ca11.98Al14O33 (Y-C12A7) single crystals were grown by using the traveling-solvent floating zone (TSFZ) method. The temperature was increased to avoid the bubbles and cracks which may be formed during the preparation of the ingot material. We have started with the flux higher than the normal to avoid the bubbles and make good treatment for the solid-liquid interface. The structures of both Ca12Al14O33 (C12A7) and Y0.02Ca11.98Al14O33 (Y-C12A7) were studied by using x-ray diffraction (XRD). Optical properties for C12A7 and Y-C12A7 single crystals have been studied in order to determine the optical parameters such as optical energy gap (E g), refractive index n, oscillating energy (E o), dispersion energy (E d), volume energy loss function (VELF), and surface energy loss function (SELF). Finally, a new result for these samples is that the third-order nonlinear optical susceptibility (χ (3)) was determined. The results have been discussed with effect of Y-doping on the C12A7 single crystals for optical and industrial applications.

Concentration effects on optical properties, DFT, crystal characterization and α-glucosidase activity studies: Novel Zn(II) complex

A novel Zn(II) complex of 6-ClpicH and picH was synthesized and its structure was determined by XRD technique. The detailed experimental optical susceptibility and band gap, refractive index, linear polarizability, optical and electrical conductivity parameters in various concentrations were investigated by means of the UV–Vis spectroscopic data. The optical band gap, refractive index (n), linear optical susceptibility (χ(1)), third-order nonlinear optical susceptibility (χ(3)), second- and third-order nonlinear optical (β and γ) parameters were examined by using DFT/M06-L and ωB97XD/6–311++G(d,p) levels. The IC50 value of Zn(II) complex against α-glucosidase was also obtained at 0.44 mM. The experimental band gap of the Zn(II) complex at 13, 33, 44 and 94 µM concentrations in ethanol were found to be 4.38, 4.37, 4.35 and 4.28 eV, respectively. The third-order NLO susceptibility χ(3) parameter at 94 µM concentration corresponding to the photon energies of 4.6 and 5.7 eV in the UV–Vis region were observed at 206.6 × 10-13 and 294.3 × 10-13 esu, respectively. Besides, the theoretical χ(3) values were obtained at 50.58 × 10−13 and 20.37 × 10−13 esu by using M06-L level. These results indicate that Zn(II) complex could be an effective third-order NLO candidate material. In brief, the detailed theoretical and experimental structural, spectral and optical properties of the Zn(II) complex were presented comparatively.

Ultrafast Third-Order Nonlinear Optical Response Excited by fs Laser Pulses at 1550 nm in GaN Crystals.

The ultrafast third-order optical nonlinearity of c-plane GaN crystal, excited by ultrashort (fs) high-repetition-rate laser pulses at 1550 nm, wavelength important for optical communications, is investigated for the first time by optical third-harmonic generation in non-phase-matching conditions. As the thermo-optic effect that can arise in the sample by cumulative thermal effects induced by high-repetition-rate laser pulses cannot be responsible for the third-harmonic generation, the ultrafast nonlinear optical effect of solely electronic origin is the only one involved in this process. The third-order nonlinear optical susceptibility of GaN crystal responsible for the third-harmonic generation process, an important indicative parameter for the potential use of this material in ultrafast photonic functionalities, is determined.

Influence of Annealing Temperatures on Nonlinear Optical, Dielectric, Semiconducting Results, and Fermi Level Position for CdP0.03Te0.97 Thin Film

CdP0.03Te0.97 thin films were deposited at room temperature using thermal evaporation and annealed at 100 and 200°C. The effect of annealing temperature Tann on both dispersion energy Ed and oscillating energy Eo were studied. The lattice dielectric constant εL and free carrier concentration/effective mass N/m* were calculated for these samples. The values of the first order of moment M-1, the third order of moment M-3, and static refractive index no were determined. Both of dielectric loss ε\ and dielectric tangent loss ε\\ for these films increased with photon energy (hν) and had the highest value higher than the energy gap Eg. All of the optical parameters such as real part of optical conductivity σ1, the imaginary part of optical conductivity σ2 and the relation between Volume Energy Loss/ Surface Energy Loss (VEL/SEL) were determined. The linear optical susceptibility χ(1) increased with Tann. The influence of annealing temperatures on all of the non-linear refractive index n2, the third-order non-linear optical susceptibility χ(3), and non-linear absorption coefficient βc were studied. Both of the electrical susceptibility χe and relative permittivity εr increased with Tann and had the highest value higher than Eg. The dependence of density valence band, conduction band, and position of Fermi level Ef were studied.

Up-conversion, energy transfer and CIE analysis of Er3+/Tm3+: MCZBP glasses

Er3+-Tm3+ ions single doped and co-doped magnesium cadmium zinc borophosphate (MCZBP) glasses were prepared with melt quenching. Their density (ρ), refractive index (n), the dielectric susceptibility (χ(1)), and the nonlinear optical susceptibility (χ(3)) etc., were articulated. Up-conversion photoluminescence spectrum of Er3+ doped glass has only a strong green emission around 550 nm assigned to 4S3/2 → 4I15/2 transition, and that of Tm3+ doped glass has only a strong NIR (near infrared) emission around 820 nm corresponding to 3H4→3H6 transition, while that of Er-Tm co-doped one has both of them, of which green emission intensity almost changed little, but NIR emission intensity nearly doubled. The latter can be attributed to the efficient energy transfer from Er3+ ions to Tm3+ ions, of which mechanism was explored. The CIE chromaticity coordinates, colour purity (CP), and correlated colour temperature (CCT) parameters were also computed for all glasses and reported.

Giant enhancement of THz-frequency optical nonlinearity by phonon polariton in ionic crystals

The field of nonlinear optics has grown substantially in past decades, leading to tremendous progress in fundamental research and revolutionized applications. Traditionally, the optical nonlinearity for a light wave at frequencies beyond near-infrared is observed with very high peak intensity, as in most materials only the electronic nonlinearity dominates while ionic contribution is negligible. However, it was shown that the ionic contribution to nonlinearity can be much larger than the electronic one in microwave experiments. In the terahertz (THz) regime, phonon polariton may assist to substantially trigger the ionic nonlinearity of the crystals, so as to enhance even more the nonlinear optical susceptibility. Here, we experimentally demonstrate a giant second-order optical nonlinearity at THz frequency, orders of magnitude higher than that in the visible and microwave regimes. Different from previous work, the phonon-light coupling is achieved under a phase-matching setting, and the dynamic process of nonlinear THz generation is directly observed in a thin-film waveguide using a time-resolved imaging technique. Furthermore, a nonlinear modification to the Huang equations is proposed to explain the observed nonlinearity enhancement. This work brings about an effective approach to achieve high nonlinearity in ionic crystals, promising for applications in THz nonlinear technologies.