Third-order Nonlinear Susceptibility Research Articles

Strong anisotropic third-harmonic generation in layered violet phosphorus.

We demonstrate that layered violet phosphorus, an emerging 2D semiconductor, undergoes strong anisotropic third-harmonic generation (THG). Polarization dependence of in-plane THG presents a cruciate-flower-shaped curve. Through theoretical modeling of the in-plane THG response, done by considering crystalline symmetry of violet phosphorus, we successfully quantify four non-zero third-order nonlinear optical susceptibility tensor elements. From control experiments, the magnitude of third-order nonlinear optical susceptibility |χ3| is calculated to be about 4.0 × 10-19 m2 V-2, which is comparable to those of conventional 2D layered semiconductors. These results indicate that the layered violet phosphorus can serve as an ideal building block for nonlinear optical applications.

Third-order nonlinear optical properties of highly electron deficient, nonplanar push-pull porphyrins: β-nitro-hexa-substituted porphyrins bearing bromo, phenyl, and phenylethynyl groups.

β-Heptasubstituted porphyrins [MTPP(NO2)X6; M = 2H, NiII, CuII, and ZnII; X = Br, Ph, and PE] were synthesized and their third-order nonlinear optical (NLO) properties explored using the single-beam Z-scan technique with femtosecond, MHz pulses in the visible range. The three-photon absorption (γ), third-order nonlinear optical susceptibility (χ3), three-photon absorption cross-section (σ3), and nonlinear refractive index (n2) have been determined from theoretical fits with experimental results. The sign and magnitude of the nonlinear refractive index (n2) have been obtained from the closed-aperture experiment while the three-photon absorption coefficient and three-photon absorption cross-section were determined from the open-aperture experiment. The magnitudes of the 3PA and σ3 extended in the range of (2.7-3.4) × 10-23 cm3 W-2 and (5.5-7.0) × 10-78 cm6 s2, respectively. The higher magnitude of the NLO coefficients ensures their utility in optical and photonic applications.

Topography and Nonlinear Optical Properties of Thin Films Containing Iodide-Based Hybrid Perovskites.

This article covers selected properties of organic-inorganic thin films of hybrid perovskites with the summary formulas CH3NH3MI3, where M = Pb, Cd, Ge, Sn, Zn. The paper discusses not only the history, general structure, applications of perovskites and the basics of the theory of nonlinear optics, but also the results of experimental research on their structural, spectroscopic, and nonlinear optical properties. The samples used in all presented studies were prepared in the physical vapor deposition process by using co-deposition from two independent thermal sources containing the organic and inorganic parts of individual perovskites. Ultimately, thin layers with a thickness of the order of nanometers were obtained on glass and crystalline substrates. Their structural properties were characterized by atomic force microscopy imaging. Spectroscopic tests were used to confirm the tested films' transmission quality and determine previously unknown physical parameters, such as the absorption coefficient and refractive index. Experimental results of the nonlinear optical properties were obtained by studying the second and third harmonic generation processes and using initial sample polarization in the so-called Corona poling process. The obtained experimental results allowed us to determine the second- and third-order nonlinear optical susceptibility of the tested materials.

Fabrication of Two-Dimensional Homo-Bimetallic Porphyrin Framework Thin Films for Optimizing Nonlinear Optical Limiting.

Developing efficient metal-organic framework (MOF) optical devices with tunable third-order nonlinear optical (NLO) properties is an important challenge for scientific research and practical application. Herein, 2D monometallic and hetero/homo-bimetallic porphyrin MOF thin films (ZnTCPP(M) M = H2, Fe, Zn) were fabricated using the liquid-phase epitaxial (LPE) layer-by-layer (LBL) method to investigate the metal substitution dependent third-order NLO behavior. The prepared homo-bimetallic ZnTCPP(Zn) thin film exhibited enhanced third-order NLO performance with a higher third-order nonlinear susceptibility of ∼4.21 × 10-7 esu compared to monometallic and hetero-bimetallic counterparts. Additionally, theoretical calculations were performed to complement the experimental findings and revealed that the enhanced NLO effect of the ZnTCPP(Zn) thin film is mainly attributed to the enhanced local excitation. These findings not only provide a comprehensive understanding of the relationship between metal types and the NLO behavior of porphyrin MOF thin films but also offer valuable insights into the design and optimization of NLO devices.

Theoretical modeling of nonlinear optical properties in spheroidal CdTe/ZnTe core/shell quantum dot embedded in various dielectric matrices

The theoretical investigation of the electronic and nonlinear optical properties in spheroid-shaped CdTe/ZnTe core/shell quantum dots (CSQDs) embedded into two commonly adopted dielectric matrices (PVA, SiO2) is done in the framework of the Effective Mass Approximation (EMA). The discrete intra-band confined energy levels and their matching wave functions were calculated by solving the stationary Schrödinger equation taking into account the Compact Density Matrix (CDM) approach. The effect of the dielectric mismatch between the system and the capped matrix has been studied and discussed. Our numerical results revealed that the third-order nonlinear (TON) optical susceptibility χ3 is strongly influenced by the geometrical parameters and the dielectric environment.

Effects of the magnetic field and the off-center displacement on the third-order nonlinear optical susceptibility of inverted core/shell spherical one-electron quantum dots

The third order nonlinear optical susceptibility (TONOS) of an inverted ZnS/CdSe core–shell spherical quantum dot embedded in SiO 2-matrix with or without impurity, and subjected to an external magnetic field is investigated. Within the framework of effective mass approximation and using B-splines basis functions, the energy levels, the dipole matrix elements and the TONOS are computed. The dielectric mismatch in the interface dots as well as the effective mass dependence on the core and shell regions are taken into account. It is revealed that, simultaneously the shell size, magnetic field and off-center displacement have a noticeable effect on the positions and the heights of the peaks of the TONOS. Moreover, we have shown that, due to the magnetic field and the off-center displacement effects, the TONOS takes different profiles associated with the polarization direction (parallel and perpendicular). In the perpendicular polarization, two peaks of the nonlinear optical properties appear for each off-center displacement value corresponding to the two transversal allowed transitions. The shift towards higher energies of the peak position and the reduction of the intensity of the peak when the magnetic field increases are recorded in the transversal transition case. Furthermore, in the longitudinal transition, as increasing the magnetic field strength, the intensity of the peak of the TONOS grows and the position of the peak is shifted towards lower frequencies. The dielectric constant, effective mass and conduction band offset of the materials that constitute the core and shell are equally found to modify significantly the main features of the susceptibility.

Nonlinear optical properties of gold with intense femtosecond laser excitations above the damage threshold

The nonlinear optical properties of gold thin films have been studied under the irradiation of destructive laser pluses. The transmissivity and the reflectivity of a 100-nm-thick gold film are measured with femtosecond laser irradiations up to 106 J/m2 fluence, which is much higher than the damage threshold of gold. The nonlinearity is calculated with Fresnel loss equations. The real part of the complex refractive index is calculated to have a peak at ∼10 kJ/m2, which is close to the damage threshold. The complex third-order nonlinear susceptibility χ3 is estimated to be (4.95 − 2.02i) × 10−21 m2/V2, which agrees with the trend in previous reports that it decreases as the pulse duration decreases. This nonlinearity is further studied with a plasmon-photon exchange (PPE) model, where laser induced plasmons and absorbed photons are strongly correlated. The result of the simulation with the PPE model is in good agreement with the experimental transmissivity above the damage threshold. The model predicted an interaction time between photons and plasmons to be about 500 fs. This model is found to be essential in understanding such nonlinear optical processes under both extremely high and conventionally low laser irradiations.

Electrochemical synthesis of a novel hybrid nanocomposite based on Co3O4 nanoparticles embedded in PANI- camphor sulfonic Acid matrix for optoelectronic applications

In this study, we report on the preparation and characterization of Co3O4 nanoparticles (NPs) embedded in polyaniline-Camphor Sulfonic Acid (PANI-CSA) polymer matrix via electrochemical polymerization method. Developing conductive organic films with tunable optical properties are crucial for many novel optoelectronic applications. Thus, incorporation of metallic oxide nanoparticles (Co3O4 NPs) into polymer matrix (PANI-CSA) represents an alternative approach to address these desired features. As a result of careful optimization of several growth conditions, PANI-CSA/Co3O4 hybrid nanocomposites with high crystalline and homogeneous structures were successfully synthesized on ITO substrates. The impact of Co3O4 NPs concentrations on the structural and optical properties has been extensively investigated. A variety of structural and optical techniques, including FTIR, UV-VIS spectroscopy, and XRD, were employed to characterize the prepared hybrid nanocomposites. The initial findings and analysis reveal that the integration of Co3O4 NPs into PANI-CSA matrix have a trifunctional role in reducing π-polaron and Urbach energies (EU) whereas increasing π-π* band gaps. A further increase in NPs concentration up to 12 wt % results in continuous increase in the absorbance bands and absorption coefficients, indicating improved optical properties as compared to the control sample (PANI-CSA without NPs). The observed redshifts in absorbance band positions are attributed to narrowing of the optical band gap caused by interactions between PANI-CSA chains and Co3O4 NPs. FTIR spectra confirmed the exact chemical composition of PANI-CSA/Co3O4 nanocomposites, exhibiting broadened and less intense peaks compared to the control sample, indicating their interaction at the molecular levels. Additionally, XRD measurements indicate that no peaks of other phases were detected in all nanocomposites, demonstrating their purity and crystallinity. Finally, A single oscillator model by Wemple-DiDomenico (WDD) coupled with a Sellmeier dispersion relation based on one term has been utilized to model the typical electronic transition excitation energies, dispersion energies, optical conductivities, and many other optical desperation parameters for PANI-CSA and PANI-CSA/Co3O4 at various concentrations. For instance, in response to increased NPs content, linear optical susceptibility, third-order nonlinear optical susceptibility, and nonlinear refractive index decrease. In contrast, the ratio of free carriers to effective mass (N/m) increased from 4.73 × 1039 to 4.91 × 1039 m−3 kg−1 with increasing NPs concentration. Based on the observed results, these hybrid nanocomposites possess improved properties, indicating their potential use as active materials in a variety of novel optoelectronic applications.

Third-order nonlinear optical susceptibility of (Cu, Mn, Cd) doping zeolitic imidazolate framework-67 in the visible region

A set of metal–organic frameworks (MOFs), pure ZIF-67 and doped with transient metal ions (Cu, Mn, and Cd), were synthesized from Co(II) nitrate and 2-methylimidazole and completely characterized. The MOFs synthesis proceeded through a facile one-step strategy based on the aqueous solution at room temperature. The physical characterization of fabricated MOFs by FT-IR, XRD, TEM, and SEM techniques revealed a nano-crystalline structure that undergoes a negligible variation upon inserting impurities of Cu, Mn, and Cd ions. Considering the XRD pattern, values of 5.9%, 14.78%, 16.02%, and 16.40% were resulted for the crystallinity index of ZIF-67, Cu-ZIF-7, Mn-ZIF-67, and Cd-ZIF-67, respectively. The Eg for pure ZIF-67 and ZIF-67 doped with cations of Cu, Mn, and Cd was measured to be ∼3.22, 2.16, 1.96, and 1.95 eV, respectively. The nonlinear optical (NLO) features of synthesized samples were evaluated via the Z-scan method at 532 nm. The positive nonlinear refractive (NLR) index of samples demonstrated the self-defocusing effect. The nonlinear absorption coefficient (NLA) of samples dedicated to the two-photon absorption (TPA) effect. The crystallinity index, polarizability treatment, and the ionic radius of doped ions increase the NLO properties of ZIF-67.

Structural Study of alumino(boro)silicate glasses containing tin-doped indium oxide (ITO) nanocrystals with nonlinear optical and enhanced UV/ NIR-shielding properties

Transparent alumino(boro)silicate glasses containing tin-doped indium oxide nanocrystals were fabricated using conventional melt-casting and heat treatment. Structural characterization was carried out by Raman spectroscopy to study glass-forming species, coordination, type and number of oxygens, and possible connectivity of silicate, aluminate, and borate species. A changing role of indium, acting as a modifier in the glass structure, but leaving a less modified glass after clustering and crystallization was also revealed. X-ray photoelectron spectroscopy confirmed that indium was in the trivalent state only. HR-TEM provided insights into the distribution and morphology of the nanocrystals in the glass ceramic sample, yielding a mean size of 4.75 nm. The nonlinear optical behavior of aluminoborosilicate glass samples was evaluated using the Z-scan technique, demonstrating high third-order nonlinear optical susceptibility for both glass and glass ceramic samples, accompanied by a change in the signs of nonlinear refractive indices before and after crystallization from negative to positive.

Role of vacuum annealing on the structural, optical properties and Dc conductivity of titanium (IV) phthalocyanine dichloride thin films

The present work elucidates the significant alterations in several physical characteristics of thermally evaporated TiPcCl2 thin films resulting from vacuum annealing at 373 and 473 K. The structure, surface morphologies, and molecular structure of TiPcCl2 thin films were studied using x-ray Diffraction (XRD), Transmission Electron Microscope (TEM), Field-Emission Scanning Electron Microscope (FESEM), and Fourier Transform Infrared (FT-IR). Results confirmed nanostructure attributes of as-deposited and annealed films, as well as the phase transition in TiPcCl2 was observed during annealing. The optical constants of as-deposited and annealed films in the wavelength range of 200–2500 nm were determined using spectrophotometric techniques. The indirect optical energy gap was observed to diminish with increasing annealing temperature due to enhanced crystallinity of thin films. Using the single oscillator model, the dispersion of the refractive index at normal dispersion was investigated. The third-order nonlinear susceptibility, χ(3), the nonlinear refractive index n2 and the nonlinear absorption coefficient, βc, were calculated and then discussed for both the as-deposited and annealed films. The electrical conductivity of TiPcCl2 exhibited increased as the temperature increased, suggesting its characteristic as a conventional organic semiconductor. The parameters of Mott’s model were obtained and discussed under low-temperature conditions afterward. Conclusions derived from this research indicate that the unique properties of vacuum annealing TiPcCl2 have great promise for future use in optoelectronic systems.

Optimized structural, optical, and electrical properties of spin-coated Pt(II) octaethylporphyrin thin films for optoelectronic applications

Octaethylporphyrin (PtOEP) is an organic molecule that has unique optical properties, such as high fluorescence quantum yields, strong light absorption, etc. Here we investigate the structural, optical, and electrical characteristics of spin-coated PtOEP thin film. X-ray diffraction (XRD) patterns indicated an increase in the crystallite of the annealed film. Field emission-scanning electron microscope (FESEM) images clearly showed agglomeration and an increase in the nanoparticle size of the annealed film. The Raman spectra of the thin films revealed symmetrical peak positions and improved peak strength for the annealed film. UV-Vis-NIR and photoluminescence (PL) spectroscopy were used to examine optical characteristics. The findings demonstrated that energy gap and PL peak emission were significantly influenced by the grown crystallite size as well as a decrease in lattice defect concentration at the grain boundary during annealing. The optical constant and interband transition strength spectra (Jcv) were estimated and addressed. Based on the linear refractive index and optical gap, third-order nonlinear susceptibility χ(3), nonlinear refractive index n2, and two-photon absorption coefficient, βc of spin-coated PtOEP thin films were calculated and discussed. Finally, the dark current-voltage (J-V) curves were utilized to assess the diode parameters, specifically the zero-bias barrier height (ΦB) and the ideality factor (n), for the ITO/PtOEP/Al diode using thermionic emission theory. Additionally, an investigation was conducted to examine the conduction mechanism of the ITO/PtOEP/Al diode under both forward and reverse bias voltage conditions. On the basis of these findings, spin-coated PtOEP thin films were concluded to be helpful in producing cutting-edge optoelectronic devices.

Solvent-Driven Variations of Third-Order Nonlinear Thermo-Optical Features of Glutaric Acid-Directed Self-Healing Supramolecular Ni(II) Metallogels.

The generation of solvent-directed self-healing supramolecular Ni(II) metallogels of glutaric acid (i.e., Ni-Glu-DMF and Ni-Glu-DMSO) is described in this article. Polar aprotic solvents like N,N'-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are separately entrapped into the Ni(II)-acetate salt and glutaric acid-mediated networks to attain the semisolid flexible scaffolds. The gel nature of the fabricated materials is experimentally proven through different rheological tests such as amplitude sweep, frequency sweep, and thixotropic (time sweep) measurements. The self-repairing strategy and load-bearing features of the synthesized metallogel are studied in this work. The different supramolecular noncovalent interactions working within the soft scaffold are clearly explored. The formation strategy and the microstructural features of these synthesized metallogels are scrutinized through a Fourier transform infrared (FT-IR) spectroscopy study and field-emission scanning electron microscopy (FESEM) morphological analyses. The FT-IR spectroscopy observation displays a considerable amount of shifting of the infrared (IR) peaks of the xerogel samples of both the metallogels Ni-Glu-DMF and Ni-Glu-DMSO. The electrospray ionization (ESI)-mass spectroscopy result demonstrates the plausible construction of the metallogel network. In order to examine the nonlinear optical characteristics of the two synthesized self-healing metallogels Ni-Glu-DMSO and Ni-Glu-DMF, Z-scan measurements are carried out with a continuous wave (CW) diode-pumped solid-state (DPSS) laser at 532 nm. The nonlinear refractive index, nonlinear absorption coefficient, thermo-optical coefficient, and third-order susceptibility of these metallogels were evaluated by analyzing the experimental data from the Sheik-Bahae formalism. The nonlinear thermo-optical study reveals that these solvent-dependent metallogels show negative signs of nonlinear refractive index and nonlinear absorption coefficient. The figure of merit calculated for these compounds shows good agreement for their use in nonlinear photonic devices.

Effect of thickness on nonlinear optical properties of EZO thin films

In the present work, the effect of thickness on the nonlinear optical properties of Erbium-doped zinc oxide (EZO) films has been investigated. Erbium-doped zinc oxide (EZO-doping concentration of 0.4 wt%) ‘thin films’ of variable thickness were prepared by a spin coating method. The film thickness varied from 92–365 nm. EZO (0.4 wt%) samples were analyzed using Scanning Electron Microscopy (SEM), UV–vis-NIR spectroscopy, and x-ray diffraction (XRD). The z-scan method was applied to measure non-linearity for closed and open aperture configurations. The deposited films were found to have a significant growth orientation along the plane of (002). The deposited films satisfy two-photon absorption as indicated by the minus sign of n2. The values of third-order nonlinear optical susceptibility for the EZO (0.4 wt%) thin film sample were found in the range of 10–6 esu. The Erbium-doped ZnO (0.4 wt%) sample exhibited the best nonlinear behavior at a thickness of 280 nm (β = 8.90 × 10–6 cm W−1, n2 = −5.29 × 10–5 esu, (3) = 14.7 × 10–6 esu). The samples under investigation should pave the path for designing high-order optical limiter devices.

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.

Gamma irradiation-induced changes in structural, linear/nonlinear optical, and optoelectrical properties of PVB/BiVO4 nanocomposite for organic electronic devices

Herein, nanocomposite films based on polyvinyl butyral (PVB) and BiVO4 plates were synthesized through solution casting. The present study aims to investigate the impact of varying doses of gamma irradiation (0, 15, 30, 60, and 90 kGy) on the structural, dispersion, linear/nonlinear optical, and optoelectrical properties of PVB/BiVO4 nanocomposite films. The effects of gamma irradiation on various optical characteristics, such as refractive index (n), extinction coefficient (k), and other related parameters, have been observed. The study of dielectric behavior and the derivation of optoelectrical parameters, including high-frequency dielectric constant (ε∞), plasma frequency (ωP), relaxation time (τ), and optical mobility (µopt.), were conducted using the real and imaginary parts of the dielectric constants εr and εi. In addition, the linear optical susceptibility (χ(1)), the third-order nonlinear optical susceptibility (χ(3)), and the nonlinear refractive index (n2) were studied as a function of gamma irradiation doses. Furthermore, the results demonstrate that the average oscillator wavelength (λ0) values, oscillator strength (S0), and optical conductivity (σopt) vary significantly after gamma radiation treatment. Overall, the strong correlations between the linear/nonlinear optical and optoelectrical parameters of the irradiated PVB/BiVO4 nanocomposite films make them suitable for application in flexible organic electronic devices.

Supramolecular structure of bis(1-methyl-1,3,5,7-tetraazatricyclo[3.3.1.13,7]decan-1-ium)2,5-dicarboxybenzene-1,4-dicarboxylate: Synthesis, spectral, structural and third-order nonlinear optical properties

Single crystals of bis(1-methyl-1,3,5,7-tetraazatricyclo[3.3.1.13,7]decan-1-ium)2,5-dicarboxybenzene-1,4-dicarboxylate (I) were grown from an aqueous solution containing benzene-1,2,4,5-tetracarboxylic acid (BTCA) and hexamethylenetetramine (HMT) (1:4) under mild hydrothermal conditions. It was characterized by IR, 1H, 13C NMR, mass, DRS, PL, TG-DTA, powder and single crystal XRD. The characteristic peaks in HMT cation CN stretching mode appear at 1018 cm−1. 13C NMR shows the carboxylic acid carbon chemical shift is observed at 167.64 ppm. The compound is thermally stable up to ∼176 °C. Single crystal X-ray crystallography shows it crystallizes in the triclinic system with centric space group Pī. Powder X-ray diffraction scrutinizes, experimental and simulated from single-crystal diffractogram data have been matched. The existence of intramolecular (O–H•••O) and intermolecular (C–H•••O, C–H•••N) interactions helps to achieve crystal cohesion. The third-order nonlinear optical susceptibility (χ(3)) for the compound is found to be 7.67 × 10−7 esu. Hirshfeld surface analysis exposes the molecular interactions and their relative contributions.

Nonlinear optical characteristics of chemical bath-deposited pure and Cu-doped SnO2 thin films: A comparative evaluation

A chemical bath deposition method is used to grow SnO2 thin films doped with copper (0, 1, 2, and 3 wt) on glass substrates that exhibit linear and nonlinear optical properties. XRD analysis of the films verified their polycrystalline phases oriented strongly of the c-axis along the preferred (110) direction depending on the doping concentration and substrate temperature. SEM images of pure SnO2 film showed the formation of granular cubic structures. Conversely, the Cu-doped films displayed the existence of spherical granules with porosity. The transmittance spectra of the films for UV–visible light indicated large values for pure films, and that the transmittance decreased with greater doping levels. As a result of copper ions in the nanostructures, it was found that the transmittance decreased as doping levels increased. Pure SnO2 has an optical band gap of 3.63 eV; it decreases with increasing Cu doping concentrations. Wemple-Di Domenico (WDD) model for single oscillator energy was used to estimate each oscillator's optical refractive index, while the static refractive index and dispersion energy were also determined. In addition, the film's WDD parameters and nonlinear refractive index were in the range of 320–1200 nm, and the wavelength was determined. During the doping concentration increase, the nonlinear refractive index of the films increased primarily because the linear refractive index of the films at 520 nm increased. This nonlinearity of the film may arise because of the thermal effect, saturated atomic absorption, and electrostriction. For pure SnO2, third-order nonlinear susceptibility (2.77 × 10-12m2/V2) is caused by thermal effects, and for doped samples, it is caused by photorefractive effects.

Femtosecond nonlinear optical investigations of nitro chalcones-doped PMMA thin films for optical limiting and photonic applications

Herein we present the linear and third-order nonlinear optical properties of two nitro substituted chalcone derivatives [3-(4-fluorophenyl)− 1-(3-nitrophenyl) prop-2-en-1-one and (2E,4E)− 1-(3-nitrophenyl)− 5-phenylpenta-2,4-dien-1-one; abbreviated as F3NC and Ci3NC, respectively] doped PMMA polymer thin films. The chemical spray pyrolysis method was adopted to prepare the films at three different doping concentrations (5 wt%, 10 wt%, 15 wt%). The linear optical studies were performed using UV-Visible-NIR spectra, and surface roughness using AFM technique. Hirshfeld surface analysis was adopted to understand the intermolecular interactions. The third-order nonlinear optical properties were investigated using Z-scan method under Ti:Sapphire femtosecond (fs) laser pulses (∼150 fs, 80 MHz, 800 nm). Open and closed aperture Z-scan curves indicated the presence of two-photon assisted reverse saturable absorption and self-defocusing effect, respectively. The calculated nonlinear refraction (n2), nonlinear absorption (β) coefficients and third-order susceptibility [χ(3)] were found to be in the order ∼10−12 cm2 W−1, ∼10−8 cm W−1 and ∼10−11 e.s.u., respectively. We observed increase in nonlinearity of the films with increased chalcone doping concentration. Among the doped chalcones, F3NC doped films exhibit a higher nonlinearity than Ci3NC doped films. The observed results reveal that chalcone-doped PMMA thin films are possible materials for optical limiting and photonic applications.

Influence of Au on the nucleation of Ag nanoparticles in GeO2-PbO glasses and characterization of their ultrafast third-order nonlinear responses within the plasmon resonance region

Germanate (GeO2-PbO) glasses doped with AgNO3 and co-doped with AgNO3 and Au2O3 were synthesized via melting-quenching technique. Silver nanoparticles were nucleated within the sample doped only with AgNO3 and its plasmon resonance was characterized. The influence of the addition of Au2O3 on the silver nanoparticles nucleation and on the spectroscopic properties of the produced composite materials were investigated using TEM, STEM and UV–Vis spectroscopy. Using the nonlinear ellipse rotation technique, the pure electronic contribution to the samples nonlinear refraction and absorption were characterized within the visible range, including the localized surface plasmon (LSP) resonance wavelength of the metallic nanoparticles. The real and imaginary parts of the third-order nonlinear susceptibility of the glass, composite samples and of the individual nanoparticles were also obtained. In addition, all-optical switching figures of merit of the samples were also calculated. From these results, the dispersion curves of the electronic contribution to the third-order susceptibility of the metallic nanoparticles were obtained and two figures of merit for all-optical switching of the composite materials were calculated. The studied samples are potential candidates for all-optical switching applications with exception to the one with the highest volume filling factor, whose linear and nonlinear absorption coefficients associated to the local field factor deplete the material performance around the LSP resonance wavelength. As far as we know nonlinear ellipse rotation technique was not used before to evaluate the influence of metallic nanoparticles on the nonlinear optical properties of glasses.