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In this work, (Z)-2-((E)-(2-oxoindolin-3-ylidene)hydrazono)-3-phenylthiazolidin-4-one 7 (C17H12N4O2S) as a hybrid molecule is synthesized under an easy method and analytically ascertained by 1HNMR, 13CNMR, IR, Mass, and UV–vis. spectroscopies. The optimized geometry of the synthesized hybrid molecule 7 is acquired using DFT-assisted calculations involving B3LYP equation with 6-31G(d,p) as a basis set level. At the same level, TD-DFT calculations are performed to collect the theoretical UV–vis. spectrum of the hybrid molecule 7. The nonlinear optical (NLO) properties of the hybrid molecule 7 are studied under irradiation with a cw laser beam. The nonlinear refractive index (NLRI), n2, of the hybrid molecule 7 is estimated via diffraction patterns (DPs) and Z-scan. The all optical switching is tested for the hybrid molecule 7 using two, cw, laser beams. Both static and dynamic all-optical switching are studied. [ABSTRACT FROM AUTHOR]

4-((6-Methylbenzo[d]thiazol-2-yl)diazenyl)phenyl 4-chlorobenzoate(Azo-BE) is synthesized and characterized using 1HNMR and 13CNMR, mass spectra, differential scanning calorimetry, optimized structure and calculation of HOMO (H) and LUMO (L) and gap energy. The Azo-BE nonlinear optical properties using cw laser beam of wavelength 473 nm are studied. The nonlinear refraction index, n2, of Azo-BE is calculated using the same wavelength via the diffraction patterns and Z-scan. n2 value of 3.121 × 10–11 m2/W is obtained. It appears that Azo-BE bare no nonlinear absorption coefficient, β, at 473 nm beam and power input used. All optical switching, static and dynamic, are tested in Azo-BE using 473 and 532 nm laser beams. [ABSTRACT FROM AUTHOR]

An azo compound, T-3OCH3, is synthesized and diagnostics using 1H and 13C NMR and mass spectroscopies. The compound theoretical structure is optimized via the DFT/WB97XD approach with a 6-31+G(d,p) basis set level. The compound nonlinear optical properties are studied under irradiation with a visible CW laser beam via diffraction patterns and the Z-scan. As high as 6.739 × 10−11 m2/W of the nonlinear refraction index is obtained. Static and dynamic all-optical switching are tested in the synthesized compound using two visible CW laser beams. [ABSTRACT FROM AUTHOR]

The effects of environmental properties on the linear and nonlinear response of Bromothymol blue (BTB) were studied. The role of the optical band gap and dielectric constant, as well as thermal conductivity, on the optical properties of the BTB molecule and the BTB complex with cetyl trimethyl ammonium bromide (CTAB) were discussed using a Z-scan instrument with a wavelength of 532 nm and power of 80 mW, a spectrophotometer, and FT-IR spectra. The orders of the nonlinear absorption coefficient, β, and the nonlinear refractive index, n2, of BTB were obtained as 10−7 cm/W and 10−12 cm2/W, respectively. The main factor in the appearance of β is reverse saturable absorption. It was observed that an enhancement of up to 5 times in the dielectric constant of the environment caused a reduction of about 6 times in the nonlinear absorption and about 2 times in the nonlinear refraction coefficient of the solution. Moreover, the CTAB complex can reduce the optical band gap of BTB by 0.7 eV and also absorbs light in the 600 to 700 nm wavelength. Therefore, it is a promising candidate for photodynamic therapy. Results of DFT calculations performed via the B3LYP method and the 6-311G(d,p) basis show an enhancement of the dipole moment of BTB with an increase in the dielectric constant of the environment. [ABSTRACT FROM AUTHOR]

Solvent evaporation was used to create a novel organic Schiff-based optical crystal of Benzimidazolium gallate (BGA). The size of unit cells was determined using X-ray diffraction analysis. Fourier transform infra-red spectrum analysis revealed chemical bonds' vibrational behavior and their functional groups' existence. Optical transparency and optical bandgap (3.66 eV) were observed by the UV–visible-near infrared spectral analysis. Differential scanning calorimetry curves show that decomposition is exhibited at 215 °C. Dielectric experiments on the BGA crystal were performed at ambient temperature. High-resolution scanning electron microscope analysis shows the crystal's nature and surface shape. The Z-scan process explored the BGA crystal's nonlinearity, and the crystal is suitable for photonic, optoelectronic, and optical-limiting applications. [ABSTRACT FROM AUTHOR]

Phosphoric acid influenced the crystal structure of hexamine p-nitrophenol and their physico-chemical properties. Supermolecular assembly of hexamine, p-nitrophenol, phosphoric acid and water (HNPP) crystal was grown through slow evaporation process in acetone–water solvent. The HNPP crystal exhibits both second harmonic generation (SHG) and third order nonlinear consequences. Single crystal XRD reveals that the HNPP crystal belongs to monoclinic system with space group P21/c. To confirm structure, computational/investigational IR and UV–visible spectra were analysed. The molecular absorption, transparency and optical energy gap of HNPP was measured from experiments and compared to calculate TD-DFT quantities. The UV spectral wavenumbers of molecule were evaluated and the appropriate FMO intermolecular transitions into α (↑ ) and β(↓) offsets were assigned. The HNPP crystal is being used for the fluorescence spectral analysis. The powder SHG effect was obtained from Kurtz and Perry procedure is 0.73 times superior to standard urea. As well as, the static first hyperpolarizability value is 3.8 times superior to urea. Z-scan technique revealed that the HNPP possess third order nonlinear efficiency. The NLO and MEP, as well as Fukui functions were used to discuss the charge of the global molecule and local atoms respectively. [ABSTRACT FROM AUTHOR]

To shed the light about the effect of the linkers of the small organic molecules on their optical properties, we examine herein the linear, and nonlinear optical properties of the two easy synthesized push–pull compounds 1 and 2 bearing similar donor and acceptor moieties based on stilbene derivatives, but differ in the spacer group, namely 4-cyano-4′-(N-dihexylamino) stilbene (1), and 4-cyanobenzal-4′-(N,N-diethyl) aniline (2). The optical studies were initially examined using various spectroscopic techniques. Compounds 1 and 2 exhibited strong absorption bands in the visible spectra with maxima at 400 and 429 nm, respectively. The steady-state emission measurements of 1 with its π–π* transition showed a strong emission band at 500 nm with a fluorescence quantum yield (Φf) of 0.30, which is much higher than that of 2 with its n–π* transition (Φf = 0.004) reflecting the nature of singlet state on the optical emission properties. The cyclic voltammograms showed the oxidation potentials of 1 and 2 at 670 and 840 mV versus Ag/AgCl, respectively, confirm the effect of the inkers on their electrochemical properties. Unlike compound 2, the thin film of 1 exhibited a sharp absorption edge at 360 nm suggesting its usefulness as an excellent UV-cut optical filter. The nonlinear absorption coefficients of the examined compounds were measured using the Z-scan technique. Compounds 1 and 2 were both exposed to 100 fs laser pulses using different excitation wavelengths. The obtained positive nonlinear absorption coefficient values of 1 and 2, such positive values may be caused by reverse saturable absorption. The influence of the laser parameters (in particular, excitation wavelength, and incident peak intensity) on the nonlinear absorption coefficient of 1 and 2 has been examined. These observations suggest the significant effect of linkers on both the photophysical, linear, and nonlinear optical features of 1 (with C=C linker) compared to 2 (with C=N linker). Furthermore, the DFT/TD-DFT methods at 6-31+G(d,p) were performed to predict the geometric, electronic, and optical properties of 1 and 2. [ABSTRACT FROM AUTHOR]

The present article demonstrates the photophysical and nonlinear optical studies of the chromophore 2,2'-(hexane-1,6-diylbis(9 H-carbazole-9,3-diyl))bis(ethene-1,1,2-tricarbonitrile (HCzN). The structure and the purity of the synthesized molecule have been confirmed via Infrared (IR) and Nuclear Magnetic Resonance (NMR) spectroscopies. Absorption and emission spectroscopies have been performed to understand the photophysical properties and we have enumerated the absorption coefficient (α0), refractive index (n0), optical bandgap (Eg), and optical conductivity (σ) for this chromophore. We have also explored the third-order nonlinear optical (NLO) characteristics of HCzN at the concentrations of 1, 2, 3, and 4 mM employing both closed and open-aperture Z-scan methods at 25 mW laser power. This chromophore evinces the self-defocusing and saturable absorption nature for closed and open aperture scans respectively. The calculated NLO parameters such as the coefficients of nonlinear refraction (n2) and nonlinear absorption (β) are found to be of the order of 10−6 cm2/W and 10−3 cm/W respectively with the nonlinear optical susceptibility (χ(3)), and hyperpolarizability (γ) of the order of 10−5 esu and 10–27 esu respectively. The magnitude of NLO parameters varies linearly concerning the concentration. The enhanced values of NLO parameters of chromophore HCzN shows its potential in photonic applications. [ABSTRACT FROM AUTHOR]

Thin films of V2O5:Co nanocomposite were deposited by the thermal deposition method. Structural analyses show that all the samples had single orthorhombic phase of α-V2O5:Co. In addition, doping V2O5 with Co caused to the slightly shift of XRD peak positions to the lower angles which is due to the increase of interatomic distances. The nanoparticle size of V2−xCoxO5 (x = 0–0.2) increased with Co doping from 12 nm for x = 0.05–30 nm for x = 0.2. Moreover, the optical bandgap of samples increased from 3.08 for x = 0–3.35 eV for x = 0.2 which can be due to the surface and interface effects inducing a gap widening. The nonlinear optical properties of V2−xCoxO5 thin films were studied using the Z-scan technique. An increment has been observed in the nonlinear responses of all samples upon augmenting the laser power intensity. The nonlinear absorption (saturation absorption (SA)) and nonlinear refraction responses had the highest amount of transmittance (4.64 cmW−1 and 8.49 × 10−4 cm2W−1) for x = 0.20 and the lowest amount of transmittance (3.26 cmW−1 and 3.96 × 10−4 cm2W−1) for x = 0.00, respectively. In addition, both the self-defocusing and saturable absorption were dominant phenomena in the nonlinear refractive index and nonlinear absorption coefficient of the samples. [ABSTRACT FROM AUTHOR]

A novel azo dye compound, Ethyl (E)-4-((5-hydroxy-3,4-bis(hydroxyl methyl)-6-methyl. pyridin-2-yl)diazenyl)benzoate (EAB), have been synthesized by the coupling reaction and characterized by FT-IR, 1H-and 13C-NMR, Mass, and UV–visible spectroscopies. The nonlinear optical (NLO) properties of the EAB compound via the finding of the nonlinear refractive index (NRI) using continuous wave (cw), low power 473 nm, TEM00 mode laser beam have been studied via the diffraction patterns (DPs) and the Z-scan. Effect of power input of the laser beam, types of beam wavefront and temporal variation of the DPs are discussed. The all-optical switching (AOS) using two laser beams is proved to occur in this compound. [ABSTRACT FROM AUTHOR]

Nonlinear refractive (NLR) index ( n 2 ) and nonlinear absorption (NLA) coefficient (β ) of Fuchsine dye in the water, DMSO, surfactant solution and nano-droplets (NDs) have been measured by Z-Scan instrument. In this research fluorescence and absorbance spectra of Fuchsine have been also investigated. According to the results of this study, although nonlinear optical properties of Fuchsine dye have changed with increasing in cationic surfactant concentration, there is not any changes with the increase of anionic surfactant concentration. Moreover, the effect of size and concentration of NDs in AOT microemulsion on nonlinear optical properties of Fuchsine dye has been studied. Based on the results NLR index and NLA coefficient have been enhanced with increasing in size and concentration of NDs. [ABSTRACT FROM AUTHOR]

The present work reports the study on effect of annealing at different temperature and dissimilar Cd/Zn ratios on optical linear and nonlinear properties of Cd1-xZnxS (in x ratios of = 0.00, 0.01, 0.03, 0.05 and 0.1 wt. % of Zn) thin films deposited by spray pyrolysis (SP) technique. All the fabricated films are polycrystalline in nature and having a hexagonal crystal structure with the single phase of CdS was confirmed by Powder X-ray diffraction studies (P-XRD). The Scherer rule was used to assess the size of the crystallite and was found to be increasing with increasing annealing temperature. FESEM images display uniform grains and decrease marginally with an increase in doping content and annealing. The optical energy band gap (Eg) of the prepared films ranged from 2.40 eV to 2.64 eV. The laser-induced damage threshold (LDT) value of the annealed Cd1-xZnxS thin film is 0.1520 KW/cm2. The NLO parameters of the prepared samples were calculated at 532 nm from the Z-scan data under solid state continuous wave laser irradiation and the 3rd-order NLO components such as β, n 2 and χ(3) were found to be enhanced with the annealing temperature i.e. from 1.58 × 10−5 to 4.85 × 10−3 (cmW−1), 1.08 × 10−8 to 4.38 × 10−8 (cm2W−1) and 7.22 × 10−7 to 5.94 × 10−6 (esu) respectively. These favourable results of NLO parameters suggests, the current fabricated nanstructured films are capable material for photonic device applications. [ABSTRACT FROM AUTHOR]

In this study, Cu2ZnSnS4 nanocrystal and its constituents’ copper, zinc and tin were grown separately by pulsed laser deposition technique as thin films, and their linear and nonlinear optical properties have been investigated. Linear optical properties were analysed with UV–Vis absorption spectra. Elemental composition of Cu2ZnSnS4 thin films was analysed by scanning electron microscope–energy dispersive X-ray. The nonlinear optical properties for Cu2ZnSnS4 nanocrystal and its constituents’ copper, zinc and tin have been determined applying z-scan method with closed and open aperture measurements using femtosecond laser (90 fs) pulses which deliver fundamental wavelength at 800 nm. Furthermore, Cu2ZnSnS4 nanocrystal ultrathin films and copper, zinc and tin thin films nonlinear refractive indexes n2 were calculated about ~ 10−13 cm2/W, their nonlinear absorption coefficient β are calculated about ~ 10−12 cm/W. Third-order susceptibilities for nano-crystal ultra-thin films and copper, zinc, and tin thin films were determined to be 10−11 esu. [ABSTRACT FROM AUTHOR]

Bromophenol blue (BPB)-doped nano-droplets are recognized as a synthesis of BPB dye and transparent dispersion of nano-droplets (ND), in a continuous phase of oils. In this regard, to discover the effect of ND size on nonlinear optical properties of BPB, a solution of BPB-doped ND with heptane oil and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as a surfactant has been prepared and therefore investigated with Z-scan technique. The consequences have revealed that the nonlinear refractive (NLR) index, of the BPB-doped ND has been improved by comparison with BPB aqueous solution. The second-order hyperpolarizability of the BPB-doped ND has been also reduced subsequent a reduction in ND size owing to reducing dye aggregation. Moreover, the BPB-doped ND in the company of laser radiation has been utilized in order to study of antibacterial photodynamic therapy of Staphylococcus aureus (S. aureus) by nonlinear absorption. As a consequence, the bacteria colonies have been also exceedingly declined in the group treated with the BPB-doped ND. [ABSTRACT FROM AUTHOR]

An open-aperture Z-scan experimental technique was used to evaluate parameters of the nonlinear scattering (NLS) in the photorefractive (PR) LiNbO3 crystals. NLS is related to the photoinduced light scattering caused by the holographic amplification of the seed scattering due to PR effect. The values of the NLS coefficient, amplification gain factor and seed scattering ratio were evaluated and found to be increasing with the light intensity. [ABSTRACT FROM AUTHOR]

Ag/PVP nanocomposites were prepared by a chemical reduction process. Then, a drop-casting method was employed to deposit the Ag/PVP nanocomposite thin film on the glass substrate. To study the optical and structural properties of the prepared sample, different characterization methods including UV–Vis absorption spectroscopy, scanning electron microscopy, XPS, and Raman spectroscopy were employed. The optical nonlinearity of the prepared thin films was evaluated by the Z-scan technique using a He–Ne laser beam (632 nm). Results showed that the nonlinear refraction index (n2 ~ 10−6 cm2/w) and nonlinear absorption coefficient (β ~ 10−1 cm/w) of the prepared Ag/PVP nanocomposite thin film are higher than the previously reported values. A weak thermal optical nonlinearity was also observed and the nonlinear response dominantly resulted from the electronic origin. [ABSTRACT FROM AUTHOR]

Erythrosine B dye has found applications as photosensitizers in photodynamic therapy, fluorescent probes in chemistry and biology. In this study, we have investigated the effect of nano-droplets, concentration and size on linear and nonlinear optical characteristics of Erythrosine B (EryB) by Z-Scan, UV-Vis spectroscopy and spectrofluorometer techniques. Two-photon absorption coefficient ( β) of EryB was measured using the Z-Scan technique at two molar ratios of water to AOT surfactant (W = 3 and 8) for two types of Oil (n-decane and n-heptane) and different nano-droplet concentrations as well as nonlinear refractive index ( n ) of EryB in bulk water. Our results showed that two-photon absorption coefficient ( β) was enhanced in nano-droplet as compared with bulk water. Moreover, the fluorescence peaks of EryB was enhanced by nano-droplets (microemulsion). The excited to ground state dipole moment ratio ( μ /μ ) was calculated through quantum-mechanical second order perturbation theory for different nano-droplet concentrations. The results indicated that μ /μ of EryB in bulk water is higher than that of in water nano-droplets. It is demonstrated that for the equal concentration of EryB in the microemulsion, the peak of fluorescence intensity varied by changing the concentration of nano-droplets. Moreover, the fluorescence peak intensity enhanced when the continuous phase of microemulsion changed from n-decane to n-heptane. [ABSTRACT FROM AUTHOR]

Two-photon absorption (TPA) and fluorescence intensity have possibilities for application in photodynamic therapy and photonic devices. The nonlinear optical properties of the cationic neutral red dye (NR) encapsulated in nanodroplets were studied using the Z-scan technique. The nanodroplets were prepared with a mixture of water, oils, and anionic Bis (2-ethylhexyl) sulfosuccinate sodium salt (AOT). The TPA and nonlinear refractive (NLR) index were studied in three different systems; NR in nanodroplets, NR in AOT and water, and NR in a different solvent. The results indicated that the TPA and NLR index spectra of NR depend on the droplet size. The TPA of the NR dye in the nanodroplet is enhanced in comparison to the NR/solvent system. Moreover, the second-order hyperpolarizability and fluorescence activity of the NR are affected by the encapsulation in the nanodroplets. [ABSTRACT FROM AUTHOR]

Colloidal PbS nanocrystals have been synthesized by a developed procedure. UV-Vis absorption and Z-scan technique was also applied to study the nonlinear optical properties of prepared lead sulfide nanocrystals at 532 nm wavelength. The nonlinear refractive (n) and absorption ( β) were determined which are confirming the strong nonlinearity at 532 nm of colloidal PbS nanocrystals. The obtained results have not been reported before. In this study, only a weak thermal optical nonlinearity was observed and the dominating nonlinear response is resulted by the electronic origin. The nonlinear optical properties of prepared sample supported wide applications in nanophotonics. [ABSTRACT FROM AUTHOR]

In this research, physical properties of nickel oxide nano-structured layers doped with various amount of Cu atoms (20-60 at.%) is studied using spray pyrolysis method on the glass substrate. The FESEM images show formations of nanostructures of about 20-60 nm and the XRD patterns show layers have a polycrystalline cubic structure nature with (111) as the preferred direction that its intensity reduces as the doping density increases. Analyzing transmittance UV. Vis spectra shows the variations of optical band gap of the samples are due to occurrence of doping atoms and quantum confined effects. Optical permittivity of different doped films have been compared using new numerical method and show the prominent effect of doping percent to real and imaginary parts of electrical permittivity. Also Hall effect results shows that Cu atoms substituted by Ni atoms sites play as acceptor atoms in the crystalline lattice. Finally, thermo-optical properties of the films have been studied using Nd-YAG laser illumination. [ABSTRACT FROM AUTHOR]

The Uv-Vis, fluorescence, Raman spectroscopy and Z-scan were used to study optical properties of fluorescein sodium salt (FSS) in AOT/Oil/Water microemaulsion. The FSS-microemulsion was prepared by two types of Oil (Heptane and Hexane) at two molar ratios of water to surfactant (X = 3 and 8), different droplet concentrations at constant ratios of dye in water (Y = FSS/water). In the AOT microemulsion media, both the emission and absorption spectra of the FSS present a red shift with respect to droplet concentration and water droplet size. A change is molecular structure was observed from Anion to Dianionic by increase of droplet concentration. The Raman spectra shows, the polarity of samples doesn't change with change of droplet concentration. The ratios of the excited state to the ground state of dipole moments (μ/μ) of FSS-microemulsion were determined by perturbation theory. At the same dye concentrations in samples, the μ/μ depending on the oil type (Oil polarity) and size of water droplet (X) of the microemulsion. The dipole moment of the ground sate is decreasing by decrease of the droplet size and increase of the droplet concentration. The FSS in both microemulsion systems is localized in the interface of droplet because of the negative interface of AOT and the probabilities, the dye aggregation inside of the droplets change by the size of droplet and it can change the dipole moment of the ground state. The photophysics properties tend to bulk water with the increase of the droplet size. The nonlinear optical properties of FSS/AOT/Heptane/Water microemaulsion were investigated. The magnitude of the third-order nonlinear refractive index ( n ) and nonlinear absorption coefficient (ß) the second order hyperpolarizabilities (γ) and the real third order susceptibilities (χ) were measured using single-beam z-scan at different droplet concentration and two molar ratio. The results shows, the ratio of dipole moment (μ/μ) has behavior similar to the 1/γ. [ABSTRACT FROM AUTHOR]

The linear and nonlinear optical properties of silver nanoparticles have been investigated experimentally. Colloidal nanoparticle samples were synthesized by laser ablation at various fluences. The samples were characterized by linear absorption spectroscopy, transmission electron microscopy and dynamic light scattering methods. The behavior of nonlinear refractive index of nanoparticles was studied using the close and open Z-scan techniques by low power CW laser beam. Observation of asymmetrical configurations of the Z-scan curve indicates that nonlinear refraction occurring in the Ag samples is related to the thermo optical process. In addition, the observed optical limiting behavior is due to nonlinear refraction of samples arising from thermal lens formation under low power CW excitation. The optimum position for samples as the optical limiter based on self-defocusing effect is the valley point. When the illumination laser power is low, the self-defocusing effect is mainly dominated. Actually laser fluence variation during the ablation procedure leads to concentration variation of nanoparticles in suspensions which in turn affect the optical properties of samples. The dependence of the nonlinear properties on morphological parameters, metal concentration, and particle size have been explained by experimental results. [ABSTRACT FROM AUTHOR]

We report switch over from saturable absorption to reverse saturable absorption behavior in semiconductor doped glass (Schott-RG850) with increase in femtosecond laser excitation intensity. About ninefold increase in the normalized transmission was achieved experimentally. Two-photon absorption, saturation intensity and free carrier absorption are taken into account to analyze results obtained from Z-scan experiments. Numerical fitting to the experimental data indicates that consideration of two-photon absorption in the sample is important despite having strong linear absorption at excitation wavelength to explain large decrease in transmission at high intensity. Further, to show the applicability of such interesting nonlinear transmission behavior we have envisaged all-optical OR, AND, and XOR logic gates in parallel. [ABSTRACT FROM AUTHOR]

Effect of plasma treatment on the nonlinear optical properties of red lake doped commercial polyvinyl chloride (PVC) film is studied employing different techniques. PVC films were exposed to low pressure plasma from 5 to 15 min. Nonlinearity measurement was performed using the second harmonic of a continuous Nd-YAG laser beam at 532 nm wavelength and 50 mW power. The optical limiting behavior of samples was investigated by measuring their transmission at different beam intensities. For all pristine and plasma treated samples optical limiting started at laser beam power of 12 mW. The nonlinear refractive index and nonlinear absorption coefficient of plasma treated samples were measured using Z-scan method. Second order nonlinear refractive index of samples was measured to be in the range of $$10^{-8}\,\hbox {cm}^2/\hbox {W}$$ which was decreased after plasma treatment. Experimental results show that real and imaginary parts of nonlinear susceptibility are strongly influenced by plasma treatment. [ABSTRACT FROM AUTHOR]

The nonlinear optical properties of an azobenzene-containing ionic liquid crystalline polymer were investigated by a single beam Z-scan technique employing 38 ps and 6 ns laser pulses at 532 nm. The polymer film exhibited large nonlinear refraction and negligible nonlinear absorption under both ps and ns pulses excitation. The nonlinear refractive indices of the polymer were in the order of $$10^{-11} \hbox {cm}^{2}/\hbox {W}$$ under ps excitation and $$10^{-8}\hbox {cm}^{2}/\hbox {W}$$ under ns excitation, respectively. The mechanism accounting for the process of nonlinear refraction was discussed in terms of photoinduced trans-cis transformation and thermal effect. [ABSTRACT FROM AUTHOR]

The effect of thickness on the nonlinear optical properties of Au nanoparticles which produced by laser ablation of high purity gold bulk in distilled water were investigated by employing different optical techniques. Experiments were performed on the 0.3, 0.6, and 1 mm thickness cells of Au nanoparticles-fluid. The effect of nonlinear refractive index of samples on the laser beam broadening was observed. The optical limiting behavior of samples is investigated by measuring the transmitted intensity of the laser beam through the samples. The third order nonlinearity of Au nanoparticles-fluid was measured by using Z-scan data. Results show a positive second order refractive index and absorption coefficient for Au nanoparticles-fluid that are increased in due of increasing the thickness of the cells. The magnitudes of both real and imaginary parts of third order susceptibility of samples are increased by increasing the thickness. [ABSTRACT FROM AUTHOR]

Silver nano-colloid was prepared by chemical reduction method and its nonlinear absorption properties were investigated by using open aperture z-scan experiment with nanosecond laser pulses operating at 532 nm. Interestingly, a switch over from saturable absorption to reverse saturable absorption was observed when the input intensity is increased from 28.1 to 175.8 MW/cm. The underlying mechanism responsible for the observed switching behaviour is the interplay between ground state plasmon band bleaching and excited state absorption. Theoretical fitting was done by using a model in which nonlinear absorption coefficient as well as saturation intensity are incorporated. [ABSTRACT FROM AUTHOR]

The nonlinear optical properties in six Cr3+-doped laser crystals LiCaAlF6, LiSrGaAlF6, Gd3Ga5O12, Gd3Sc2Ga3O12, LaMgAl11O19 and Alexandrite are investigated with the help of the Z-Scan technique at λ = 532 nm in the CW regime. The data reported here include particularly the excited state absorption cross section and the third-order nonlinear susceptibilities. It is found that the three first systems only exhibit both refractive and absorptive nonlinear effects, whereas the three others have only absorptive effects. Gd3Ga5O12 shows the best nonlinear potentialities. The excited state absorption cross section corresponding mainly to the 4T2 → 4T1 transition is found to be ranging between 8.9 × 10−22 cm2 in LiSGaF and 3.1 × 10−20 cm2 in LaMgAl11O19. The calculated ratio of the third order nonlinear susceptibility to the ground state absorption coefficient is found to be largest in GGG with a value of 146 × 10−6 esu.cm and smallest in Alexandrite (0.6 × 10−6 esu.cm). [ABSTRACT FROM AUTHOR]

Nonlinear refraction, nonlinear absorption and optical limiting in photorefractive crystals Bi12SiO20(BSO) and Bi12GeO20(BGO) at the wavelengths of 1064 and 532 nm were investigated. It was shown that both BSO and BGO crystals possess by positive nonlinear refraction in two investigated spectral ranges (n2BSO=(2.5 ± 0.5)× 10-12 esu,n2BGO=(6.3 ± 1.3)× 10-12 esu at ? equals 1064 nm;n2BSO=(4.4 plusmn; 0.9)× 10-12 esu,n2BGO=(7.4 ± 1.5)× 10-12 esu at ?= 532 nm). The nonlinear absorption was due to three-photon absorption at the wavelength of 1064 nm (ß(3?)BSO=(2.5 ± 0.8)× 10-20cm3W-2,ß(3?)BSO=(4.4 ± 1.3)× 10-20cm3W-2) and two-photon absorption at the wavelength of 532 nm (ß(2?)BSO=(2 ± 0.4)× 10-9cm W-1,ß(2?)BGO=(3.7 ± 0.7)× 10-9cm W-1). [ABSTRACT FROM AUTHOR]

For the copper complex of pyrazinoporphyrazine AzaPhcCu(C(CH3)3)8 in CH2Cl2, we use nanosecond pulses to measure its third-order nonlinear optic effects at 532 nm. The results show that its effective third-order nonlinear refractive index neff 2 (−7.85 × 10−10 esu) is larger than that of the AzaPhcCu(C12H25)4 and the CuPc(OC5H11)8. The reverse saturable absorption (RSA) of AzaPhcCu-(C(CH3)3)8 is demonstrated by the ratio of effective excited state to ground state absorption cross sections. The observed intersystem crossing lifetime τisc of AzaPhcCu(C(CH3)3)8 (∼15 ns) and AzaPhcCu(C12H25)4 (∼45 ns) are longer than that of CuPc(OC5H11)8 (∼5.0 ns). The aza-substituents are suggested to form a S1(n, π*) state as their lowest excited singlet-states, and their radiationless intersystem crossing rates (1/τisc) are discussed with the spin-orbit coupling 〈ψS| HSO|ψT〉 and the vibronic coupling 〈χS|χT〉 effects between S1 and T1 states. [ABSTRACT FROM AUTHOR]

The nonlinear refractive index n2 of Yb3+:KY(WO4)2 crystal has been measured using picosecond Z-scan technique. The magnitude of n2 was found to be 8.7 × 10−16 cm2/W at wavelength of 1.08 μm. The numerical modeling based on fluctuation model showed a great potential of this crystal as active medium for Kerr-lens mode-locking. [ABSTRACT FROM AUTHOR]

The third-order susceptibility and second-order hyperpolarizability and the two-photon absorption coefficient of Eosin-B in AOT/water/Heptane were investigated by using the Z-Scan technique. The droplets were prepared with an AOT/water droplet in a continuous phase of Heptane. The droplets size changes with the amount of water and the droplet concentration decreases with the increase of Heptane concentration. To study the nonlinear optical properties of Eosin-B, the Z-scan measurements were performed by means of a laser at 532 nm and 80 mW power. The nonlinear refractive and the nonlinear absorption coefficient indices were found to be in the order of 10−12 (cm2 W−1) and 10−7 (cm W−1), respectively. The change of nonlinear optical properties of Eosin-B by droplet size and concentration is due to the change of dye aggregation and thermal conductivity and thermo-optic coefficient of samples. The absorption of Eosin-B changes with the polarity of the medium (dielectric constant and refractive index). It has been shown that the intensity of emission spectra of Eosin-B in AOT/water/Heptane is enhanced compared to that of aqueous solution. By the Bilot and Kawski theory, the ratio between the excited state and the ground state of the dipole moments (μe/μg) of Eosin-B both in water and in droplets is extracted. [ABSTRACT FROM AUTHOR]