Z Scan

A series of double-walled carbon nanotubes (DWNTs) and multi-walled nanotubes (MWNTs) functionalized with selected organic chromophores, fluorescein 5(6)-isothiocyanate (FITC), rhodamine B isothiocyanate (RITC) and fullerene (C 60 ) were synthesized by covalently linking these electron-donor groups to the metallic nanotubes. These versatile carbon nanotube composites show remarkable nonlinear optical (NLO) performance, due to a merged effect of the complementary NLO characteristics of the moieties of the composites. The hybrids were characterized by UV-vis spectroscopy and Raman spectroscopy. Evidence suggests charge transfer species are formed between the chromophores and the nanotubes. The optical limiting performance of the DWNT, MWNT hybrids and carbon NanoBuds is found to be superior to that of single-walled nanotubes. Thermally induced light scattering from nanotube moieties is the primary mechanism dominating the NLO response. Reverse saturable absorption from fullerene moieties makes a significant contribution to the NLO response of fullerene containing hybrids and NanoBuds. Photoinduced charge transfer from the fullerenes or the organic chromophores (FITC and RITC) to nanotubes followed by absorption in the charge separated excited state may enhance the nonlinear absorption, thus an effective optical limiting response.

The nonlinear optical properties of silver nanoparticles (AgNPs) colloids in distilled water, when irradiated with 100 fs laser pulses, were investigated experimentally using the Z-scan technique. At a constant wavelength of 760 nm and different excitation powers, the nonlinear absorption coefficient and nonlinear refractive index were measured. The AgNPs colloids are synthesized by laser ablation of silver bulk in distilled water using a 532 nm Nd: YAG laser with different ablation energies fluence of 9, 15.5, and 26 ⨯10 4 (J/cm 2) over a 30min ablation time. The nanoparticle size, shape, and absorption spectra of nanoparticle colloids were determined using transmission electron microscopy and an ultraviolet-visible spectrophotometer. Spherical AgNPs are formed with an average diameter ranging from 7.5 to 12 nm. As the laser ablation energy fluence increases, the average size of the AgNPs decreases while the bandgap energy increases. As the excitation laser power and AgNPs size increase, the nonlinear absorption coefficient and nonlinear refractive index decrease. The optical limiting performance of AgNPs improves with increasing laser ablation energy fluence, with the best performance at 26⨯10 4 (J/cm 2).

We reported experimental results from investigations that employed the Z-scan method to explore the dependence of silver nanoparticles' (AgNPs) nonlinear optical properties on the excitation wavelength, AgNP concentration, and size. Using a 532 nm Nd: YAG laser beam at 100 mJ/pulse for different ablation times, AgNPs were synthesized from a silver target immersed in distilled water. UV-Vis spectroscopy and an atomic absorption spectrometer are used to characterize the optical properties of laser-synthesized AgNPs as well as their concentrations. The AgNPs' size and shape are determined using a transmission electron microscope (TEM). The laser-synthesized AgNPs are spherical, with an average particle size of 12 to 13.2 nm. Whatever the ablation time, the AgNP colloids exhibit reversed saturable absorption and a negative nonlinear refractive index (n 2). Both n 2 and the nonlinear absorption coefficient (α 3) increase as the AgNP concentration increases. As the excitation wavelength and average size of the AgNPs increase, n 2 and α 3 decrease.

Nonlinear optics has become an essential area of study for understanding and harnessing the complex light-matter interactions that occur in molecules, nanostructures, and advanced materials. This review introduces a summary of the latest advancements, with a particular focus on the nonlinear optical characteristics of noble metal nanoparticles, especially silver nanoparticles (AgNPs). These nanomaterials have gained significant interest due to their typical plasmonic features and size-dependent behavior. Silver nanoparticle colloids demonstrate enhanced light absorption at high intensities, known as reverse saturable absorption, along with a selfdefocusing optical response characterized by a negative nonlinear refractive index. It has been observed that the size of noble metal nanoparticles significantly influences their nonlinear optical properties. The thermal lens phenomenon was addressed utilizing a unique approach that considers the

Considerable efforts have been made in recent years to identify an optimal treatment method for the removal of antibiotics from wastewaters. A series of supramolecular organic-inorganic magnetic composites containing Zn-modified MgAl LDHs and Cu-phthalocyanine as photosensitizers were prepared with the aim of removing β-lactam antibiotics from aqueous solutions. The characterization of these materials confirmed the anchorage of Cu-phthalocyanine onto the edges of the LDH lamellae, with a negligible part inserted in the interlayer space. The removal of the β-lactam antibiotics occurred via concerted adsorption and photocatalytic degradation. The efficiency of the composites depended on (i) the LDH: magnetic nanoparticle (MP) ratio, which was strongly correlated with the textural properties of the catalysts, and (ii) the phthalocyanine loading in the final composite. The maximum efficiency was achieved with a removal of ~93% of the antibiotics after 2 h of reaction.

Highly porous silica nanoaerogels with low apparent density of ~0.1 g/cm3 and ~0.07 g/cm3 were synthesized through two-step sol-gel processing and low temperature  supercritical fluid drying. The nonlinear refraction (γ) of silica nanoaerogels was estimated to be ~ -3.4 x 10-16 m2/W for ~0.1 g/cm3 and ~0.07 g/cm3 apparent densities with a signal-beam femtosecond z-scan spectroscopy. The third-order nonlinear refraction coefficient of
nanostructure silica nanoaerogels was almost four orders larger than that of bulk silica materials. The large nonlinear refraction with high nonlinear figure of merit (γ/βλ, β~2×10-10 m/W for 0.07 g/cm3 apparent density, β~6×10-10 m/W for 0.1 g/cm3 apparent density, λ~0.775 μm) is an ideal optical property for nonlinear applications of homeland security, battlefield enhancement, and industrial uses.

A thin layer of Barium Strontium Titanate Ba0.15Sr0.85TiO3 (BST) was developed on a glass substrate using a sol-gel method with annealing temperatures and spin coating process at 3500 rpm for 30 seconds. The annealing temperature varied from 600 o C, 650 o C, and 700 o C. Characterization of optical properties was developed using UV-Vis spectroscopy to determine the energy bandgap. The values of the BST thin layer energy band at the annealing temperature were 3.55 eV, 3.32 eV, and 3.10 eV, respectively. The results indicate that the BST thin film was a semiconductor material.

Fundamentals and Physical concepts of optical limiting (OL) phenomenon in nanometals have been reviewed in this manuscript.Two mechanisms of OL are based on non- linear absorption and nonlinear refraction depends on the setup of the experiments. The effect of surface plasmon resonance (SPR) absorption of nanometals, as well as their size, shape, material, and concentration on their OL behavior are discussed in detail. Finally, OL phenom- enon is investigated experimentally using gold and silver nanoparticles (NPs) suspensions in water, in low intensity regime. In addition, results based on the effects of laser intensity, aperture size, concentration, and size of Au and Ag NPs are presented.

Electro optics effects are importantbranches of nonlinear optics. In thisresearch olive oil has been chosen to studyits electro optical properties. Olive oil as anorganic compound has a centro symmetricmolecular structure which means that it hasquadratic electro optical propertiesrepresented by Kerr effect. These electrooptical properties such as transmittanceversus applied voltage and birefringenceversus the square value of the appliedelectric field were measured. Theseproperties are obtained for the two types ofolive oil (virgin and refined) by analyzingof these properties, the Kerr constant andKerr coefficient for two types of olive oilhave been found at different wavelengths.

We examine the photophysics of a colloidal suspension of C60 particles in a micellar solution of Triton X-100 and water, prepared via a new synthesis which allows high-concentration suspensions. The particle sizes are characterized by transmission electron microscopy and dynamic light scattering and found to be somewhat polydisperse in the range of 10-100 nm. The suspension is characterized optically by UV-vis spectroscopy, femtosecond transient absorption spectroscopy, laser flash photolysis, and z-scan. The ground-state absorbance spectrum shows a broad absorbance feature centered near 450 nm which is indicative of colloidal C60. The transient absorption dynamics, presented for the first time with femtosecond resolution, are very similar to that of thin films of C60 and indicate a strong quenching of the singlet excited state on short time scales and evidence of little intersystem crossing to a triplet excited state. Laser flash photolysis reveals that a triplet excited-state abso...

We intend explore the possibilities offered by ultracold atoms as nanometric surface probes. The interaction between a neutral atom and the surface of a dielectric or a conductor is a subject of research around which are concentrated many experimental and theoretical efforts in recent years. The reasons are varied. On the one hand it is a fundamental problem of QED, which has open conceptual and experimental aspects, such as eg the role of thermal fluctuations of the electromagnetic field produced by the surface. On the other ...

We studied nonlinear optical properties of two different aminobenziliden-1,3-indandione derivatives-DDMABI and DMABI-OH by employing the Z-scan method. Through this we described how different donor and acceptor groups influence third-order nonlinear optical properties such as Kerr effect and two-photon absorption. During experimental measurements we used 1064 nm Nd:YAG laser with 30 ps pulse duration and 10 Hz repetition rate. From acquired values of Kerr and two-photon absorption coefficients we calculated values for real and imaginary parts of third-order susceptibility, as well as second-order hyperpolarizability. Quantum chemical calculations were carried out for secondorder hyperpolarizability to study how well calculations correlate with experimental values. Acquired data for DDMABI and DMABI-OH were compared with data for other ABI derivatives studied previously.

Cette these a pour objectif l’etude experimentale de la propagation de solitons sombres temporels aux abords de la longueur d’onde de dispersion nulle d’une fibre optique. Dans un premier temps, nous nous concentrons sur la generation d’ondes dispersives par des solitons sombres. Pour cela, plusieurs techniques de generation de solitons sont mises en oeuvre. La premiere, basee sur la collision de deux impulsions laser, permet de generer un train de quasi-solitons sombres. Ainsi, en fonction du nombre de solitons composant le train et de la puissance en entree de la fibre, nous observons l’emission d’une seule ou de plusieurs ondes dispersives ainsi que la generation de supercontinua spectraux. La deuxieme technique de generation de solitons sombres mise en place utilise un ensemble de deux faconneurs d’ondes optique. Au moyen de mesures spectrales et de correlation croisee, nous montrons que celle-ci permet la generation de solitons sombres isoles dont la longueur d’onde, la phase, ...

Cette thèse a pour objectif l’étude expérimentale de la propagation de solitons sombres temporels aux abords de la longueur d’onde de dispersion nulle d’une fibre optique. Dans un premier temps, nous nous concentrons sur la génération d’ondes dispersives par des solitons sombres. Pour cela, plusieurs techniques de génération de solitons sont mises en oeuvre. La première, basée sur la collision de deux impulsions laser, permet de générer un train de quasi-solitons sombres. Ainsi, en fonction du nombre de solitons composant le train et de la puissance en entrée de la fibre, nous observons l’émission d’une seule ou de plusieurs ondes dispersives ainsi que la génération de supercontinua spectraux. La deuxième technique de génération de solitons sombres mise en place utilise un ensemble de deux façonneurs d’ondes optique. Au moyen de mesures spectrales et de corrélation croisée, nous montrons que celle-ci permet la génération de solitons sombres isolés dont la longueur d’onde, la phase, ...

We have investigated nonlinear refraction in all-inorganic halide perovskites, the CsPbBr$_3$ and CsPbBr$_{1.5}$I$_{1.5}$ nanosheet and quantum dot colloids in toluene, by a novel beam deflection technique using near-resonant continuous wave lasers. The nonlinear refraction and its time-evolution measured here have originated from thermal lensing effect. Nonlinear behaviour of heat transport in terms of intensity dependent thermal diffusion rate has been observed. Effects of convective heat flow have been measured at high intensities. Quantum dots have higher nonlinear refraction as compared to the corresponding nanosheet samples, presumably due to reduced dimensionality. The effective values of nonlinear refractive index, estimated here for near-resonant excitations, exceed those reported in the literature for organic-inorganic hybrid perovskites in the nonresonant excitation regime, by several orders of magnitude.

We report on the observation of a large thermal nonlinearity of an organic material enhanced by the presence of gold nanoparticles. The studied system consisted of a colloid of castor oil and gold particles with average diameter of 10 nm, with filling factor of 4.0x10 -5 . Z-scan measurements were performed for an excitation wavelength tuned at 810 nm in the CW regime. It was observed that this colloidal system presents a large thermal nonlinear refractive index, which was equal to -7.4x10 -8 cm 2 /W. This value is about 41 times larger than the n 2 of the host material. The thermo-optic coefficient of the colloid was also evaluated, and a large enhancement was observed in its value owing to the presence of the gold nanoparticles in the organic material.

Delmastro, Marco (ttaly): "The ATLAS liquid Argon electromagnetic calorimeter: main features, requested physics performances and test-beam results" Doke, Tadayodhi (Japan): "Fundamental properties of liquid Ar, Kr, and Xe and their new application to calorimeters"

The ultrafast excited-state dynamics of size-dependent TiO 2-Au nanocomposites synthesized by reducing gold nanoclusters to the surface of colloidal TiO 2 nanoparticles are studied using pumpprobe transient absorption spectroscopy with 400 nm excitation pulses. The results show that the relaxation processes of the plasmon depletion band, which are described by electron-phonon and phonon-phonon scattering lifetimes, are independent of the gold nanocluster shell size surrounding the TiO 2 nanoparticle core. The dynamics corresponding to interfacial electron transfer between the gold nanoclusters and the TiO 2 bandgap are observed to spectrally overlap with the gold interband transition signal, and the electron transfer lifetimes are shown to significantly decrease as the nanocluster shell size increases. Additionally, size-dependent periodic oscillations are observed and are attributed to acoustic phonons of a porous shell composed of aggregated gold nanoclusters around the TiO 2 core, with frequencies that decrease and damping times that remain constant as the nanocluster shell size increases. These results are important for the development of improved catalytic nanomaterial applications.

Metal-substituted phthalocyanines are an important class of materials garnering attention due to their structural diversity and excellent optoelectronic properties. Herein, we comprehensively investigate the photophysical properties of a newly synthesized metal-free and metallated [Zn(II) and Cu(II)] phthalocyanines (Pcs) to explore their nonlinear optical (NLO) phenomena. Femtosecond transient absorption spectroscopy (fs-TAS) was utilized to study the excited-state relaxation dynamics of these Pcs within the visible spectral range of 430-780 nm. After photoexcitation, fs-TAS data confirmed the formation of long-lived triplet states due to intersystem crossing. The lifetimes of various intermediate excited states were retrieved from the TAS data using a target model analysis, and these lifetime values were used to fit the NLO data, which were carried out by the femtosecond Z-scan measurements. The calculated nonlinear refractive indices were (0.36-0.68) Â 10 À15 cm 2 W À1 and the values of second hyperpolarizability were (2.34-3.61) Â 10 À30 esu for these Pcs, which were verified through DFT calculations. Compared with the metal-free Pc, an enhancement of the nonlinear characteristics for the metallated Pcs was observed, and we attributed this increment to the reduction of aggregation for the metallated Pcs replaced with organic scaffolds at their peripheral locations. As a proof-of-concept application, we calculated the optical limiting onset and figure of merit. The crucial photophysical and nonlinear phenomena obtained here are believed to provide the avenues to address the critical variables involved and their correlated optoelectronic properties.

The single beam Z-Scan technique, a two beam Pulse-Delay Modulation Technique (PDMT), and a combination of these methods are implemented to measure both nonlinear absorption and nonlinear refraction in semiconductors. The laser source used is a Kerr Lens Modelocked (KLM) Ti:sapphire laser producing tunable near IR 100 femtosecond pulses of-5 nJ of energy per pulse at a 90 MHz repetition rate. Specifically we monitor two photon absorption and the bound electronic nonlinear refraction in ZnSe and this nonlinear refraction in ZnS. These techniques open the spectral range where these nonlinear optical parameters can be measured by allowing tunable high repetition rate low pulse energy lasers to be used. In the past such measurements have been made primarily with high energy low repetition rate lasers such as Q-switched or modelocked and Q-switched Nd 3 +:YAG lasers and its harmonics or Nd 3 +:YAG pumped dye lasers. Such dye lasers while tunable are difficult to use and require organic dyes and solvents which may be flammable and/or carcinogenic. Recently, the solid state KLM Ti:sapphire laser has also been used to pump broadly tunable Optical Parametric Oscillators. The techniques discussed in this thesis will also allow such sources to be used for nonlinear optical measurements. Additionally, these material measurement techniques have a great deal in common with autocorrelation pulse width measurement techniques. Therefore, this thesis also discusses the pulse width measurement techniques that we used to characterize our laser system. TABLE OF CONTENTS LIST OF FIGURES.

ZrO 2 nanoparticles were synthesized by the chemical precipitation method and coated with silica through seeded polymerization technique to form core-shell type ZrO 2 @SiO 2 nanostructures. The structural, morphological and silica coating formation of the bare and silica coated particles were studied using Transmission electron microscopy, X-ray diffraction and Fourier Transform Infrared Spectroscopy. Thermogravimetric analysis and Zeta potential measurements were performed to check the thermal and dispersion stability of the nanostructures. The optical limiting performance of these nanostructures was studied using open-aperture Z-scan technique in which nanosecond laser pulses at 532 nm have been used for optical excitation. Both bare and silica coated ZrO 2 nanoparticles exhibited good optical limiting behavior due to excited state absorption, arising from effective three photon absorption. It is observed that the optical nonlinearity is enhanced in core shell structures as compared with the bare particles.

Measurements of nonlinear optical (NLO) properties of different binary mixtures having carbon disulfide (CS2) as the common component, namely CS2-acetone, CS2-cyclopentanone, CS2-toluene, and CS2-carbon tetrachloride (CCl4), are carried out by using the z-scan technique. Open-aperture z-scan (OAZS) and close-aperture z-scan (CAZS) experiments are performed to determine the nonlinear absorption coefficient (β) and nonlinear refractive index (n2) of all binary liquid mixtures at various compositions of the components by employing a pulsed, high repetition rate (HRR) femtosecond laser. Also, we were able to use the flowing liquid to measure NLO properties in the CS2-acetone binary mixture to remove the cumulative thermal effects produced due to the pulsed HRR laser light. Nonlinear refractive index (n2) values are found to be influenced by the weak dipole-induced dipole intermolecular interactions between the nonpolar CS2 and polar acetone as well as cyclopentanone of the respective bi...

The field of guided-wave photonics (GWP) examines the phenomena associated with the confinement of light in composite structures comprising two dielectrics having distinct refractive indices. GWP has been the driving force behind landmark developments such as high-speed, longrange optical fiber communication (OFC) systems and photonic integrated circuits (PICs) for signal processing at optical frequencies. Optical fibers and photonic components have, unquestionably, revolutionized how we communicate and access information today.

Investigations have been performed to explore ultrashort laser irradiation effects on the surface topography as well as structural and nonlinear absorption properties of a polymer CR-39. For this purpose, a CR-39 target was exposed in air to 25 fs, 800 nm Ti:sapphire laser radiation at fluences ranging from 0.25 J cm −2 to 3.6 J cm −2. The surface features, structural changes and nonlinear absorption were explored by AFM, Raman Spectroscopy and a Z-scan technique, respectively. Several topographical structures like bumps, explosions and nano cavities have been observed on the irradiated surface. Raman spectroscopy reveals changes in the fundamental structure of the polymer after the irradiation. Nonlinear absorption data contained by the Z-scan technique predict the dominance of three-photon absorption in case of pristine CR-39. Furthermore, nonlinear absorption (three or two photon) increases with increasing laser fluences and is well correlated with surface and structural changes revealed by AFM and Raman spectroscopy.

The recipients of the 1993 Italgas Prizes for Research and Innovation were Manuel Cardona, Bruno Coppi and Giorgio Parisi. Established in 1987 to celebrate the 150th anniversary of Italgas, the prizes are given to acknowledge the value of scientific research and to promote closer collaboration between universities, research establishments and industry at an international level. Each year, the prizes are awarded to three researchers within the European Community who have contributed to fundamental and applied research in fields chosen for their impact on economic and social development. Manuel Cardona, MPI, Stuttgart, received the award for Technology and Materials Science. The award was presented for his contributions to the development of solid state physics, with emphasis on his experimental studies of semiconductors and superconductors as well as his theoretical interpretation of the observations. Bruno Coppi, MIT and the Torino Polytechnic, received the award for Energy Sciences for his research on the physics and engineering of thermonuclear fusion and his original approach to solving problems in the energy sciences. Giorgio Parisi, University of Rome, received the award for Physics for the development of methods which have found many applications in theoretical studies of phase transitions, spin glasses, elementary particles and neural networks.

Em primeiro lugar, agradeço a Deus que não somente me permitiu ter chegado a este ponto, mas também me sustentou ao longo de toda a minha carreira acadêmica, me dando forças e condição para continuar mesmo em meio as diversas dificuldades que eu encontrei. Agradeço a minha mãe Maria do Socorro Martins de Souza e ao meu pai Estevão Telles de Souza Filho, que me apoiaram, incentivaram nos meus estudos e me deram toda a instrução necessária para chegar até este momento com muita luta mas de forma honesta. Agradeço também ao meu irmão Jefferson Martins de Souza e ao meu amigo Renan Maciel que foram pessoas que muito me incentivaram a alcançar este grau acadêmico. Sou grato ao meu orientador Acácio Aparecido de Castro Andrade, que me aceitou como seu aluno de mestrado e me guiou ao longo de toda a minha pesquisa me ensinando e aconselhando. Também ao grupo GPOTM, que acompanhou toda a minha caminha, em especial aos professores Sergio Carlos Zilio, Viviane Pilla e Djalmir Nestor Messias que contribuiram significativamente através de longas discussões. Agradeço também aos professores Noélio Oliveira Dantas e Anielle Christine Almeida Silva pela síntese e participação nas medidas de absorção ótica respectivamente. Quero reservar esse espaço para citar alguns dos bons frutos que surgiram ao longo de todo o meu mestrado, que foram os amigos que adquiri, Adriano Queiros,

ABSTRACTThe wavelengths at which indanthrone behaves as an efficient reverse saturable absorber can be changed by chemical modification of the indanthrone chromophore. Several derivatives of indanthrone have been synthesized and they have been shown to be more efficient nonlinear optical materials than the parent chromophore. In this paper we will discuss the behavior of these indanthrone derivatives, attempt to correlate the nonlinear optical properties observed in this class of compounds to modifications in the structure of the indanthrone chromophore and suggest how these nonlinear materials may be applied to all-optical switching devices.

Zinc telluride (ZnTe) quantum dots (QDs) were synthesized by a unique supersaturation-controlled aqueous route. For a given pH, increasing the degree of initial supersaturation led to a decrease in the average diameter (davg) of the QDs and increased monodispersity. Three samples of ZnTe QDs having average sizes of 0.8, 1.7, and 2.2 nm were synthesized (hence named ZnTe_0.8, ZnTe_1.7, and ZnTe_2.2). Nonlinear absorption (NLA) and nonlinear refraction (NLR) of these colloidal ZnTe QDs of different sizes were investigated by the Z-scan technique using a continuous He–Ne laser (632.8 nm, 15 mW). Isotropic assembly of ZnTe_2.2 leads to the formation of nanoballs (hence named ZnTe_NB). The NLA profile of smaller QDs, ZnTe_1.7 and ZnTe_0.8, was found to follow a three-photon absorption (3PA) model, while relatively bigger QDs, ZnTe_2.2, followed a two-photon absorption (2PA) model. On moving from ZnTe_0.8 to ZnTe_1.7, the three-photon absorption coefficient (γ) decreases by 26% (3.00 × 10–4 → 2.21 × 10–4 cm3/MW2). The two-photon absorption coefficient (β) for ZnTe_2.2 is 0.3 cm/MW. For a 63% decrease in average diameter (2.2 → 0.8 nm), the refractive index (n2) increases by 45% (2.48 × 10–2 → 3.6 × 10–2 cm2/MW). Overall, the NLR coefficient shows a decreasing trend with size. Upon isotropic self-assembly, ZnTe_NB, there is a significant increase in the NLR coefficient by 40% (2.48 × 10–2 → 3.48 × 10–2 cm2/MW) and a simultaneous decrease in the NLA coefficient by 45% (0.3 → 0.166 cm/MW). The figure of merit was also determined for all of the samples, and it was found that ZnTe_2.2 and ZnTe_0.8 were best suited for all-optical device applications. Further, the self-assembled nanostructures are promising for making optical waveguides for supercontinuum generation (SCG).

A new series of non-aqueous phthalocyanines having 3,4,5-trimethoxy phenyl group at peripheral positions in which the central cavity possessing Cu(II), Zn(II), and without metals has been synthesized, and its absorption, fluorescence (steady-state and excited state lifetimes), electrochemical, and third-order nonlinear optical (NLO) properties were evaluated. Absorption studies data suggest that all three phthalocyanines obey Beer-Lambert's law, and the redox properties indicate that both oxidation and reduction reactions are macrocyclic centered. The singlet quantum yields were measured in different solvents and were found to be in the range of 0.2-0.5 in the case of free-base, whereas it was in the range of 0.1-0.5 in zinc derivative, while the timeresolved fluorescence data revealed lifetimes of typically a few ns. The third-order NLO properties were investigated using the Z-scan technique with kilohertz (for retrieving true electronic nonlinearities) and megahertz repetition rate femtosecond pulses at 800 nm. Intensity-dependent Z-scan studies revealed robust NLO coefficients for solutions and thin films (two-photon absorption cross-sections of 9,300-57,000 GM) of these molecules suggesting a strong potential for optical switching, imaging, and optical limiting applications.

Palavras-chave: revascularização miocárdica; circulação extracorpórea; lipoproteínas de alta densidade; paraoxonase; peroxidase endógena. ARAÚJO, Tarsila dos Santos. Impact of myocardial revascularization with cardiopulmonary bypass on high density lipoprotein (HDL) metabolism: paraoxonase and endogenous peroxidase activity. 57 f. il. Thesis (MA)

In this study, peripherally tetra-{2-[[4-((E)-{[4-(dimethylamino)phenyl]imino}methyl)phenyl](methyl)amino]ethoxy} substituted cobalt(II), manganese(III), copper(II) phthalocyanines 2a-2c and axially di-{2-[[4-((E)-{[4-(dimethylamino)phenyl]imino}methyl)phenyl](methyl)amino]ethoxy} substituted silicon phthalocyanine 3 were synthesized for the first time. These compounds were characterized by standard spectroscopy methods. Their nonlinear optical properties are evaluated with the help of z-scan technique. Both open and closed aperture configurations show clear z-scan signal in the four samples. The refractive nonlinear index n2 is found to be ranging between-4.9 and-28.1 x 10-8 cm 2 /W, and the nonlinear absorptive coefficient varied between 0.2 and 5.4 x 10-3 cm/W. The optical limiting measurements showed low threshold levels, 645 W/cm 2 in 2c and 680 W/cm 2 in 2a in full agreement with Z-scan measurements.

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The characterization of the CuInSe 2 (CIS), CuInGaSe (CIGS) and CuGaSe 2 (CGS) based semiconductor thin films are very important role for solar cell and various nonlinear optical applications. In this paper, the amorphous CuIn 0.7 Ga 0.3 (Se 1Àx Te x) 2 semiconductor thin films (0 x 1) were prepared with 60 nm thicknesses by using vacuum evaporation technique. The nonlinear absorption properties and ultrafast transient characteristics were investigated by using open aperture Z-scan and ultrafast pump-probe techniques. The energy bandgap values were calculated by using linear absorption spectra. The bandgap values are found to be varying from 0.67 eV to 1.25 eV for CuIn 0.7 Ga 0.3 Te 2 , CuIn 0.7 Ga 0.3 Se 1.6 Te 0.4 , CuIn 0.7 Ga 0.3 Se 0.4 Te 1.6 and CuIn 0.7 Ga 0.3 Se 2 thin films. The energy bandgap values decrease with increasing telluride (Te) doping ratio in mixed CuIn 0.7 Ga 0.3 (Se 1Àx Te x) 2 films. This affects nonlinear characteristics and ultrafast dynamics of amorphous thin films. Ultrafast pump-probe experiments indicated that decreasing of bandgap values with increasing the Te amount switches from the excited state absorption signals to ultrafast bleaching signals. Open aperture Z-scan experiments show that nonlinear absorption properties enhance with decreasing bandgaps values for 65 ps pulse duration at 1064 nm. Highest nonlinear absorption coefficient was found for CuIn 0.7 Ga 0.3 Te 2 thin film due to having the smallest energy bandgap.

We present our experimental results on the measurement of third-order optical nonlinearity in the ns and ps domain, in Ž. Ž. several Tetra Tolyl Porphyrin molecules TTP , using degenerate four wave mixing DFWM and Z-Scan techniques. Our results indicate a very high value of nonlinearity for these molecules in the ns domain and reasonably high values in the ps domain. They are found to exhibit a strong nonlinear absorption at both 532 nm and 600 nm. The high value of nonlinearity for ns pulses is attributed to higher excited singlet and triplet states. Time-resolved studies indicate an ultra-fast temporal evolution of the nonlinearity in these molecules.

The nonlinear optical properties of 5-Aminoindazole in Dimethyl sulfoxide (DMSO) solvent was studied using single beam Z-scan technique with a continuous-wave radiation at 473 nm of an output power of 4.6 mW. All the solution samples showed large nonlinear refractive indexice and absorption coefficient of the order of 10-8 cm 2 /W and 10-3 cm/W, respectively. The concentration-dependent nonlinear refractive index was also investigated. We presents experimental evidences of observing diffraction pattern in 5-Aminoindazole: DMSO solvent with the calculation of the refractive index change, ∆n , the relative phase shift,  , and effective nonlinear refractive index ,n 2. The solvent of spectroscopic grade and was used without further purification. All the solutions used for the study were freshly prepared.

Zn 1Àx Fe x S (x = 0.00, 0.01, 0.03, 0.05) nanospheres were synthesized by polyethylene glycol assisted hydrothermal method. XRD studies revealed that samples of all concentrations exhibited cubic structure with crystallite grain size 7-9 nm. TEM and SEM show the formation of nanospheres by dense aggregation of smaller particles. Increasing Zn/Fe ratio tune the band gap from 3.4 to 3.2 eV and also quenches the green luminescence. FTIR spectra reveal the presence of capping agent, intensity variation and shifting of LO and TO phonon modes confirm the presence of Fe ions. Nonlinear optical properties were measured using open and closed aperture z-scan techniques, employing frequency doubled 532 nm pumping sources which indicated reverse saturable absorption (RSA) process. The nonlinear optical coefficients are obtained by two photon absorption (2PA). Composition dependent nonlinear optical coefficients ''b", nonlinear refractive index, third order susceptibility and optical limiting threshold were estimated. The sample shows good nonlinear absorption and enhancement of optical limiting behavior with increasing Fe volume fraction. Contribution of RSA on optical nonlinearity of Zn 1Àx Fe x S nanospheres are also investigated using three different input energies. Zn 1Àx Fe x S with comparatively small limiting threshold value is a promising candidate for optical power limiting applications.